Tuning question

[SA69mach 39]

Please explain. You kept asking where the hose from the distributor was hooked up to. I never had a hose hooked up to the Dist. so I figured when he hooked it up and it started running better that was a good step towards fixing the issue. We played with the timing by ear since I'm waiting on a pointer to arrive via mail and nothing was working. It kept dieseling. Then, once we hooked the hose up and put the timing near the best running position (where it was before) it didn't diesel and it didn't hesitate anymore. So, those 2 issues being gone...I was under the impression that is a great thing. 

It is a great thing.  Glad you got your engine running nicely with such a simple fix.

 

I would guess that from Barnetts viewpoint, he was leading you step by step through the process of setting timing and carburetor together, in the correct way.  To be sure, that would teach you things that would make all future adjustments better for you.  Because you would know what the adjustment do, and how they affect other parts.

Remember, the distributor and the carburetor  have two totally different function, but they rely on each other.  fuel, spark, timing, vacuum.

 

Now it is running, you will be able to establish your base timing, set your advance curve in the distributor, and get to a point where you can make adjustments with confidence.  In addition, once you have your timing set by light, you use the vacuum gauge to make slight adjustments to achieve the HIGHEST vacuum reading. 

 

Understanding how the distributor works to advance the timing is pretty interesting too.

 

Hopefully you still have the desire to learn about this stuff, and Barnett has the interest to walk you through it.  Knowledge you will use over and over.

[barnett468 418]

.

1969 mach 1 summed it up very well, but there is also more to it and it get quite technical but one thing connecting the vacuum to manifold vac does, is advance the timing once the car starts and it can advance it as you are trying to start it.

 

even most gm cars used ported vacuum contrary to a report that is online which is partially inaccurate and somewhat misleading and the only reason your friend would connect the distributor vac to manifold vac instead of ported vac is because either someone said it is better this way or he read that it is better this way but in fact it is not but chevy guys and some ford guys will continue to claim that it is and most have never even did any type of test to actually see if it i better . . their ignition timing was too low at idle so instead of fixing it properly, they simply connected their vacuum line to manifold vac and it increased the rm so because it increased the rpm, they automatically think it is a good thing.

 

one problem with doing it this is that when y step on the gas, the engine vacuum drops and when the engine vacuum drops, the timing the vacuum can was providing drops top ZERO so your timing is really right back where it was before they connected the hose which was probably too low which is why they connected the hose to manifold vac in the first place.

 

if you advance the timing at idle by moving the distributor and your rpm goes up, you can close the throttle plat which will often stop the dieseling but it can sometimes cause the engine to detonate some . . if it detonates, you simply change the advance curve . . this is the PROPER way to set timing and it will in fact give you the optimum amount of power.

 

yes your car no longer diesels, but no, it does not run as well as it could.

[Mach1 Driver 560]

Hopefully when he gets the timing pointer he will come back so barnett468 and 1969_Mach1 can continue with this thoughtful and measured approach. It makes very good reading and is interesting to see the process from the eyes of a novice and actually get detailed instructions from experts. The problem with connecting to manifold vacuum instead of the proper carb port was very instructive...and insightful. This is great stuff.  

 

My first car was a 64 Chevy with a 283 and it always had vacuum at idle to the dizzy. You had to disconnect and plug the line to set timing. I never really noticed my Ford was different.

[nickjames138 15]

So here is where I hooked up the vacuum hose from the distributor. If this isn't right I'm totally open to hearing why and the correct way as soon as I get the pointer. But I'm

Telling you it's running GREAT all the time now! Every little mechanical problem has been fixed. So, if you're saying it'll run even better after your steps....IM IN!!! Just happy it's not dieseling or hesitating! And it's not as sluggish when I put it into drive.

[1969_Mach1 333]

The vacuum advance doesn't connect there.  That is a manifold vacuum source.  The vacuum advance connects to a ported vacuum source on the carb.  A ported vacuum source has no vacuum at idle.  On Holley's, it is the vacuum port on the right side of the front metering block.  Again, for the reasons mentioned previously, the vacuum advance is connected to a ported vacuum source.  Thus, the vacuum advance does not operate at idle.

 

Also, keep in mind, vacuum advances originated as a devise to increase fuel economy at highway speeds.  They were not to improve idle quality or other drivability issues.

 

The base timing must be pretty far off for that to fix all the issues.  I would still suggest after the pointer is installed to go through and set up everything correctly.

[barnett468 418]

yup just what he said and unless you car has a huge cam it will absolutely run at least a little better if you follow our suggestions . its really easy to do and will take maybe just 10 minutes or so to get us all the info we need to determine a course of actioon . . any changes that need to be made are also easy to do and should require nothing more than a blade and phillips screwdriver a 1n2 inch wrench to loosen the distriubtor and needle nose or regular pliers . . and small allen wrench . you may have to buy a 5.00 spring and new vacuum advance can for 20.00. . dont forget to look at the lower timing cover bolt on the drivers side . it it does not have threads sticking out of the top of it you need to buy a special bolt.

[nickjames138 15]

I'm not sure if I mentioned this at the beginning, but to be specific I have a 351 (obviously) with 302 heads. The heads are so big they knock on the sidewalls of the engine bay. I'm not sure what kind of Cam it has in it, but it's definitely a big cam. I also have a Vintage Air conditioning unit hooked up. I ordered the pointer and vacuum advance can today. So, hopefully I'll get it soon. Oh and my cam is set at 0. So, I just got the normal pointer. I'll let you know as soon as I get the parts and I'll get at it!!

[nickjames138 15]

yup just what he said and unless you car has a huge cam it will absolutely run at least a little better if you follow our suggestions . its really easy to do and will take maybe just 10 minutes or so to get us all the info we need to determine a course of actioon . . any changes that need to be made are also easy to do and should require nothing more than a blade and phillips screwdriver a 1n2 inch wrench to loosen the distriubtor and needle nose or regular pliers . . and small allen wrench . you may have to buy a 5.00 spring and new vacuum advance can for 20.00. . dont forget to look at the lower timing cover bolt on the drivers side . it it does not have threads sticking out of the top of it you need to buy a special bolt.

 

Being that I have a big cam...should I get a more expensive vacuum canister? Like this one? http://www.summitracing.com/parts/cca-5201

[barnett468 418]

why are you buying a brake booster can?

 

what do you mean yuor cam is big ad set at 0?

[nickjames138 15]

why are you buying a brake booster can?

 

what do you mean yuor cam is big ad set at 0?

The guy who I bought the car from put a big cam in it, but I'm not sure what cam it is. It sounds big. It cuts up. As far as it being set to 0. I'm not sure how to say it, but the timing markers that you can adjust to different marks if your cam is set top dead center or 4 marks to the left or right....a friend tried to explain it to me.

 

Wrong canister....I can't find a vacuum advance canister in summitracing's site.

[barnett468 418]

The guy who I bought the car from put a big cam in it, but I'm not sure what cam it is. It sounds big. It cuts up. As far as it being set to 0. I'm not sure how to say it, but the timing markers that you can adjust to different marks if your cam is set top dead center or 4 marks to the left or right....a friend tried to explain it to me.

 

Wrong canister....I can't find a vacuum advance canister in summitracing's site.

 

What vacuum canister do you want?

 

Almost every cam has 4 degrees of advance ground into it so when the timing marks on the gear are lined up, the cam is advanced 4 degrees which is how they are designed to be installed.

[SA69mach 39]

You said in your first post you are running MSD ignition and distributor.,  So, that is the start point and raises some questions.

 

What model "ignition" and distributor do you have installed?

Is it new?  Do you have the spring and bushing kit that comes with?

Can you post a picture of the ignition and the distributor please?

 

Did you or the shop remove a canister from the distributor? 

 

Where exactly did the fellow stick the hose into the MSD distributor you have? 

Do you have a canister or not?

 

There is something basically wrong with your set up.  I predicted low advance way back page 1, and I think that is proven out.  The problem is-  how did it leave a shop in that state?  I don't think the tuning and timing will take long to get a base line and stock setting, however, keep in mind the cam may turn out to be incorrectly "degreed".  Wait out on that for now,

 

You will need the stock vacuum canister for the distributor you have, so please get that information and pictures. 

 

And Barnett - please, stop with the cryptic stuff  "What canister do you want?"  You know he wants the right canister for his car and distributor.  I think you are teasing this guy or making him look foolish.  If you can help him, please get on with it.  I have faith you can.

 

nickjames- please watch this video on msd timing and learn something about timing, distributors, and how it all works.  Hopefully this will save you and everyone else a lot of time, posts and effort.  AND get the details and pics of your ignition and distributor as soon as you can.  5 pages of post to be at this point is a bit long winded, right? 

 

http://setyourtiming.com/video.html

 

edit - this link might help you identify your ignition unit and distributor if you don't know.

 

https://msdignition.com/products/distributors/

[nickjames138 15]

As you can see I have the vacuum can on the distributor, the coil, and then there's a pic to show where the hose from the distrib vacuum connects to the spot behind the carb and to show the vacuum port on the carb is plugged. Honestly, I've heard so many different theories from everyone and they all contradict what the next person says. So, I'm up to my eyes in opinions. The guy who helped restore the car said the cam is set at 0 degrees dot to dot from cam to crank sprocket. Oh and a friend had showed me a little backup vacuum cam that's linked to his vacuum hose that looks similar to that break booster can I sent a link to, so I'm just floating in it all.

[nickjames138 15]

I should also add I used to have power brakes that wouldn't stop on a dime because of very poor vacuum and I had someone set my timing to where it was pulling the highest vacuum, but it still wasn't enough to stop my brakes on a dime. So, now I switched over to manual brakes. All of it has been really frustrating because like I said I have so many people telling me different things. This is why I want to learn to do it all myself or find a shop that's spot on (so far finding a shop has failed me).

[SA69mach 39]

Fair enough.  Opinions are like backsides - everyone's got one, and they all stink.....haha

 

Right - some basics that should clarify a few things and get you providing the best information  so "we" can offer better advice.

 

Cams - it is common to grind a cam with advance already built in.  Say 4 degrees advance.  So when installed 'dot to dot' - what you call zero, it has some small advance on the stick.  The reason is it is easy to line up the dots on installation.  Trying to set 4 or 6 degrees is fiddly   Most cars will never sit on zero advance at top dead center, it is just too low.  And when firing first time, you want a little advance, so they build it in to the grind.

Do you have the spec sheet for your cam?  (I think you already said no)  That spec will have those details.  If not, you need to consider getting some vacuum readings from the manifold while the engine is idling and running so we can see what numbers you have, and take a better guess at what the cam is doing. 

 

Distributor - You have two methods of increasing the advance of the spark timing as the engine revs increase.  You want this.  and you want to keep within limits.  Basically you want about 12 degrees advance at idle, and you want the distributor to increase advance to about 32 degrees by 2500-3000 revs, and NO MORE.  that is called the "curve" of the advance.  the rate, if you like.

The vacuum can "pulls" some advance for you, and the mechanical weights inside the distributor pull some more as revs get higher.  Little weights spin with centrifugal force as revs build, and pull an arm out.  So, two separate systems working to make the 'advance curve' 

 

Vacuum source - There is always lively debate about whether to use ported or manifold source for the distributor.   At idle, you don't need either vacuum or mechanical advance.  it is set at idle by adjusting the distributor - twisting it clockwise or anti-clockwise, and then locked down tight.  Lets say you set your 'initial timing' at 12 degrees BTDC.  You don't want any vacuum pulling more.  If you have a leak in your vacuum line your idle will go to crap, because your initial timing is not properly set, it is being affected by the vacuum from the little can.  Follow me???

 

So, the conventional source of vacuum for your distributor can is from the "ported" vacuum  port on your carburetor.  Look at the second picture above, that you posted - there is a small rubber plug up the side.  Above the level of the butterflies of the carburetor.  That is what ported means.  So at idle, the butterflies are basically closed, so there is little to no vacuum being pulled through that port (or your distributor.)  When you rev, the butterflies open and vacuum is pulled, and pulled at the distributor too, now.  

that is exactly how the whole system was designed to work.

 

Manifold vacuum is always pulling.  That is what your distributor is connected to at the moment.  and it has solved your poor idle and dieseling.  That is because your initial timing was so low, so very low, and now your vacuum advance has pulled in some advance.  it is working, but it is not the fix you need.  I hope you can understand my rambling and see why you need to keep working on this problem.  it is not 'fixed" properly.

 

You need to set your initial timing to 12* BTDC and then plug your line into ported vacuum.  And then tune and adjust as necessary.  Barnett was getting around to all this, and he is probably pi$$ed at me, but it is just taking so long, and you don't seem to understand the basics. 

 

Hope this helps. 

[SA69mach 39]

I should also add I used to have power brakes that wouldn't stop on a dime because of very poor vacuum and I had someone set my timing to where it was pulling the highest vacuum, but it still wasn't enough to stop my brakes on a dime. So, now I switched over to manual brakes. All of it has been really frustrating because like I said I have so many people telling me different things. This is why I want to learn to do it all myself or find a shop that's spot on (so far finding a shop has failed me).

 

OK, well, the vacuum can you had up before might be a fix for brakes.  It is a reservoir to hold additional vacuum, specifically to power your brake booster when you have low manifold vacuum available.  But I don't think it will be any use with your distributor vacuum can. 

 

If you have very poor vacuum, then you use the mechanical advance inside the distributor to do the work.  Another option is a dedicated spark advance and timing box.  As you might assume, this electronic box completely replaces the vacuum AND mechanical weights to achieve advance curve.  The magic box.  You lock out your mechanical advance and remove the vacuum can (or block it off) and let the box advance the timing. 

 

Please get your vacuum readings as soon as you can so we can see what is going on there.  18 inches is GOOD  12 inches is normal,  5-7 inches is LOW and needs help.  See what you have so we can make an informed guess what your cam is doing. 

[Mach1 Driver 560]

 All of it has been really frustrating because like I said I have so many people telling me different things. This is why I want to learn to do it all myself or find a shop that's spot on (so far finding a shop has failed me).

 You can trust what barnett468 and 1969_Mach1 are saying. From previous posts 1969_Mach1 has stated he is a service tech, barnett may also be a service tech because he is very knowledgeable and presents the solution in a easy to follow step by step manner. If you do this stuff as steady work and get trained properly you become competent, and only 25% of any profession is competent at their job. Everything I've read that these guys say is spot on. SA69mach is good too, and has an excellent "bedside manner". My 2 cents worth.

 

PS, I don't think the 5 pages are long winded. You learn more by making mistakes, see the result and then correcting the problem. You probably wouldn't have gotten the link to MSD's timing video otherwise. Go at your own pace and LEARN. You're going great!

[barnett468 418]

Did you or the shop remove a canister from the distributor? 

 

Where exactly did the fellow stick the hose into the MSD distributor you have? 

 

Do you have a canister or not?

 

You will need the stock vacuum canister for the distributor you have, so please get that information and pictures. 

 

And Barnett - please, stop with the cryptic stuff  "What canister do you want?"  You know he wants the right canister for his car and distributor.  I think you are teasing this guy or making him look foolish.  If you can help him, please get on with it.  I have faith you can.

 

If you read all the posts before posting, you would know that his distributor has a vacuum can because I asked him where his friend connected it and he posted a photo of where it was connected in post 79.

 

So here is where I hooked up the vacuum hose from the distributor.

 

 

 

Please stop telling people what to do . . I will ask questions any way I want to and try to help people in a way that I want to . . Since unlike you, I and others like 1969 Mach actually read ALL the posts, we knew he had a vacuum can which is why I was simply asking what vacuum can he was looking for . . Pretty simple isn't it?

 

I don't tease people . . I and others like 1969 Mach put in an enormous amount of time trying to help them which many people know, and which some like nickjames greatly appreciate as evidenced by his kind words to us in the quote below.

 

 

FROM POST 72

 

Ok, update. I stopped by my friends who built his own 73 vette. He helped me tune and we could not stop the dieseling. Then, he grabbed a hose and connected it from the distributor to the vacuum advance and immediately my car started running night and day better!

 

Barnett and 1969_Mach1, thank you so much for your help! you guys are really awesome for teaching me some things!

 

.

[barnett468 418]

I should also add I used to have power brakes that wouldn't stop on a dime because of very poor vacuum and I had someone set my timing to where it was pulling the highest vacuum, but it still wasn't enough to stop my brakes on a dime. So, now I switched over to manual brakes. All of it has been really frustrating because like I said I have so many people telling me different things. This is why I want to learn to do it all myself or find a shop that's spot on (so far finding a shop has failed me).

 

DISTRIBUTOR VACUUM ADVANCE MODULE [CAN]

 

We know that it is working because your rpm increased when your friend connected it . . There are adjustable cans and non adjustable cans . . Most aftermarket distributors have adjustable cans . . You can easily tell if yours is adjustable be removing the vacuum hose from the can itself, then take the long end of an allen wrench that just barely fits inside the vacuum fitting and push it in until it stops, then turn it whille still trying lightly to push it in . . If the wrench does not lock into a screw and then get harder to turn, try the next size smaller wrench, if this one does not lock into a screw, your can is not adjustable . . You may or may not need an adjustable can if you want to get your timing set to its optimum level . . We will just need to have you do a simple test once you get your timing pointer installed to determine exactly how many degree of timing it provides.

 

 

BRAKES

 

Ok, when an engine has low vacuum at idle on a car with power brakes, your brakes will typically operate normally the first time you push the pedal because the brake booster quickly gets filled with the proper amount of vacuum as soon as you start driving.

 

In general, the faster the engine turns, the more vacuum it will make up to a certain point, so the faster the power booster reservoir will fill up.

 

All engines make the most vacuum when you remove your foot from the gas pedal with the engine still in gear . . If you have a manual trans and put it in neutral when you slow down, the engine goes back down to idle speed where it will have low vacuum if it has a big cam.

 

If you put an engine with a big cam in neutral as you slow down, the first time you push on the brake pedal, they will work perfectly fine PROVIDING, there is nothing wrong with them.

 

After you push the pedal once, you have depleted a lot of the vacuum that was stored in the brake booster, therefore, the next time you push the brake pedal, it will require more force to slow the car because there is less vacuum remaining in the booster.

 

If you put your car in neutral as you come to a stop then push on the pedal 3 separate times, there will basically be no vacuum left in the booster so the brakes will then be manual instead of power and require a LOT of force to slow the car.

 

If you are driving in stop and go traffic, and never get over maybe 10 mph, the engine with a big cam will not make enough vacuum to work properly because it doesn't get up to enough rpm . . Driving in heavy traffic with a car with power brakes and a big cam is dangerous.

 

To improve the brakes on a car with a big cam, you can buy an additional vacuum storage can just like the aluminum one you posted, however, even these will run out of vacuum if the brakes are used a lot at low speed . . If you have a vacuum can and this occurs, you can step up to a vacuum pump . . If the pump is big enough, it will supply enough vacuum that power brakes will work well under almost all conditions . . Summit Racing has them along with virtually everything else under the sun.

 

Now, if the brakes on your car sucked under all conditions, there is a problem other than low vacuum which we can also help you with, however, brakes are far more complicated and difficult to work on, and in your case, it would probably be better if an expert looks at them, however, you can test your brake booster on your own to see if that is bad . . You can also check your brake fluid level and remove the rear wheels and check the brake shoes, brake drums, and the wheel cylinders . . If you have not checked the brakes, I would do it asap because in my experience, most people that are selling their car do not check or rebuild the brakes before they sell it and in many cases I have personally seem, the brakes need some type of repair.

.

[nickjames138 15]

BRAKES

 

Ok, when an engine has low vacuum at idle on a car with power brakes, your brakes will typically operate normally the first time you push the pedal because the brake booster quickly gets filled with the proper amount of vacuum as soon as you start driving.

 

In general, the faster the engine turns, the more vacuum it will make up to a certain point, so the faster the power booster reservoir will fill up.

 

All engines make the most vacuum when you remove your foot from the gas pedal with the engine still in gear . . If you have a manual trans and put it in neutral when you slow down, the engine goes back down to idle speed where it will have low vacuum if it has a big cam.

 

If you put an engine with a big cam in neutral as you slow down, the first time you push on the brake pedal, they will work perfectly fine PROVIDING, there is nothing wrong with them.

 

After you push the pedal once, you have depleted a lot of the vacuum that was stored in the brake booster, therefore, the next time you push the brake pedal, it will require more force to slow the car because there is less vacuum remaining in the booster.

 

If you put your car in neutral as you come to a stop then push on the pedal 3 separate times, there will basically be no vacuum left in the booster so the brakes will then be manual instead of power and require a LOT of force to slow the car.

 

If you are driving in stop and go traffic, and never get over maybe 10 mph, the engine with a big cam will not make enough vacuum to work properly because it doesn't get up to enough rpm . . Driving in heavy traffic with a car with power brakes and a big cam is dangerous.

 

To improve the brakes on a car with a big cam, you can buy an additional vacuum storage can just like the aluminum one you posted, however, even these will run out of vacuum if the brakes are used a lot at low speed . . If you have a vacuum can and this occurs, you can step up to a vacuum pump . . If the pump is big enough, it will supply enough vacuum that power brakes will work well under almost all conditions . . Summit Racing has them along with virtually everything else under the sun.

 

Now, if the brakes on your car sucked under all conditions, there is a problem other than low vacuum which we can also help you with, however, brakes are far more complicated and difficult to work on, and in your case, it would probably be better if an expert looks at them, however, you can test your brake booster on your own to see if that is bad . . You can also check your brake fluid level and remove the rear wheels and check the brake shoes, brake drums, and the wheel cylinders . . If you have not checked the brakes, I would do it asap because in my experience, most people that are selling their car do not check or rebuild the brakes before they sell it and in many cases I have personally seem, the brakes need some type of repair.

.

As far as the brakes go, I replaced all the brakes as soon as I bought the car. I'm in Los Angeles, so that's a big "Check" on the stop and go traffic. I didn't try a can or pump, but it's too late because a shop suggested I take the brake booster off and put a manual wilwood master on there. I just mentioned the brakes to add that the vacuum was not supplying enough pressure to the brakes. And if I recall correctly when I punched it down the road the brakes would be considerably worse than if I just went slow. 

 

SA69 helped me understand why I need to hook up the vacuum hose from the can to the carb instead of the advance. I've been reading a lot on timing, watching vids, and he helped bridge the gap to understand why. So thank you for the explanation. 

 

So, like I said the pointer is in the mail. I have a good idea on how to set the initial timing from all your help, Barnett. Thinking ahead, my RPM gauge stopped working ever since I put the new Distributor and coil in. So, will I need additional tools or gauges for readings? I don't have a vacuum gauge or RPM gauge to know where I need to set the advanced timing?

[barnett468 418]

As far as the brakes go, I replaced all the brakes as soon as I bought the car. I'm in Los Angeles, so that's a big "Check" on the stop and go traffic. I didn't try a can or pump, but it's too late because a shop suggested I take the brake booster off and put a manual wilwood master on there. I just mentioned the brakes to add that the vacuum was not supplying enough pressure to the brakes. And if I recall correctly when I punched it down the road the brakes would be considerably worse than if I just went slow. 

 

So, like I said the pointer is in the mail. I have a good idea on how to set the initial timing from all your help, Barnett. Thinking ahead, my RPM gauge stopped working ever since I put the new Distributor and coil in. So, will I need additional tools or gauges for readings? I don't have a vacuum gauge or RPM gauge to know where I need to set the advanced timing? 

 

As far as the brakes go, i can almost guarantee you that your brake lite switch valve is off center . . If it is, it can adversely affect brake performance so I would check that.

 

As far as needing a vacuum gauge or tachometer, you do not need either of those if you are able to hear a small change of rpm in your engine . . With your engine idling, you can turn your idle set screw in 1/4 turn . . If you can hear the small increase in rpm, you do not need a vacuum gauge or tach, however, it would still be easier with either item.

 

The best tool for inexperienced people that are doing this is a digital tach because it is more sensitive than an analog tach [which is one with a needle] and it is more sensitive than a vacuum gauge . . Some timing lites have a digital tach.

 

The reason a vacuum gauge isn't needed if you have a tach is because the higher the engine rpm is, the higher the vacuum will be and the higher the vacuum is, the higher the rpm will be, so they are both interconnected.

 

The tricky part is that there is a threshold where you reach a point where the more you advance the timing, the less the engine increases in rpm for every degree the timing is advanced . . If you were to plot rpm for every degree of advance, you would easily see this point because the line on the graph would initially go up sharply/quickly, and after you reached the "ideal" amount of timing, the line would go up less sharply until it basically leveled off.

 

The higher your compression, the rougher the engine will run when the timing is too far advanced . . For example, if you have 10.0:1 compression, you engine might run rough if you advance the timing to maybe 20 degrees at idle, however, if your engine has low compression like maybe 8.5:1, you can advance the timing much further before it begins to tn rough and when it does run rough, it will typically not run as rough as the engine with the higher compression.

 

The reason it wll start to run rough with too much timing is because the fuel mix is ignited sooner the more advance the engine has and at some point, it is ignited so soon that the cylinder builds up pressure early enough that it tries to run backwards and the more compression it has, the more cylinder pressure it will have which creates more power, so the more power it has, the harder it will try to force the piston down which is why the engine with higher compression will run rougher than one with lower compression.

[Mach1 Driver 560]

Thinking ahead, my RPM gauge stopped working ever since I put the new Distributor and coil in. 

I don't want to get off topic here, but if I may offer a guess here, you also installed a MSD ignition box? I say that because in one of the pictures you seem to have a MSD brand Blaster coil. If you confirm the use of a MSD ignition box then I think I can offer an explanation as to why the tach isn't working.

[barnett468 418]

I'm not sure if I mentioned this at the beginning, but to be specific I have a 351 (obviously) with 302 heads. The heads are so big they knock on the sidewalls of the engine bay.

 

Exactly what year are the heads off of?

 

They don't look like any head I remember.

 

The 302 and 351 heads are the same size and they will not hit the shock towers unless your shock towers have been pushed in at least 2".

[barnett468 418]

I don't want to get off topic here, but if I may offer a guess here, you also installed a MSD ignition box? I say that because in one of the pictures you seem to have a MSD brand Blaster coil. If you confirm the use of a MSD ignition box then I think I can offer an explanation as to why the tach isn't working.

 

xlnt!

[nickjames138 15]

I don't want to get off topic here, but if I may offer a guess here, you also installed a MSD ignition box? I say that because in one of the pictures you seem to have a MSD brand Blaster coil. If you confirm the use of a MSD ignition box then I think I can offer an explanation as to why the tach isn't working.

Yes! The mechanic took out the old one and said it wasn't necessary anymore.