Sluggish take off power

[prayers1 153]

I finally threw in the towel. I've been battling this scenario for the past year and now it's making me frustrated.

From a stand still it's a dog, but once above 2000 it fly's.

At this point, I've tried tuning so many ways that now I think I've over done it.

 

Things I've done:

Changed Quick Fuel SS 735 Carb. Vac Squirter to 35, Changed air bleeds from 70 to 74, Changed main jet from 68 to 70.

Changed from Mallory Unilte Dist to MSD 8577 added a MSD 6 box (this changed made a noticeable difference on top end)

Changed gears from 3:55 to 4:11.

 

Played up & down with timing, now it's set at Initial 16, advance 21

Below is the MSD advance chart, I'm set now with (D) Blue bushing & 2 lite blue springs.

 

Tried Quickfuel tech line but I think the guys don't understand the nature of the Cleveland heads.

Above carb adjustments is their recommendation.

 

I have been told Pos & Neg of having a 2600 stall. One person said, since I have an AOD to  be careful with the advance curve. You don't want it coming in super fast as it will be easy to lug the engine down.

 

Tried countless times to adjust the 4 corner idle screws, always wound up at 3/4 turned out, highest vac is 12.

 

Taken intake off 2x's in the past and made sure it is sealed correctly.

 

I think I'm missing something or doing something wrong with the carb adjustments. I did check the transfer slot on the secondaries (Might need to check it again).

Factory carb secondary adjustment is 1/2 out, I tried a closing a 1/4 to see if they were opening too soon. I couldn't tell so I set it back to 1/2.

 

Here's what I have-

351 4v Iron Closed Chamber 63cc heads, SS valves
Scorpion Pedestal roller rockers
Bullet Custom grind 541/559, 270/283, 50@ 220/231, lsa 110
Springs #145@1.800 & #350@1.200
RobbMc Mech Fuel Pump.
Blue Thunder Intake
Carb- Quick Fuel 735 Vac Sec
Sandersons Shorty headers
FlowMaster 40 out to tail pipe
4 speed AOD, 12" 2600 stall non locking
MSD 8577, MSD 6 box

ProMaster E-Coil 41000 volts
4:11 trac-lok 9" rear

 

 

MSD Advance Curve.pdf

[afret 37]

Are you sure you have a 2600 stall converter?   I would think it would flash at least to the stall speed at launch and be where your engine is starting to make power.  I don't know anything about AODs but with a C4 or C6 a performance converter is usually smaller than 12".

[blueblood 26]

Are you sure the converter is working correctly? My first thought was seized converter stator or something not allowing the converter to slip enough to get you into the power band

[prayers1 153]

I had a well respected trans builder, Dan Gilsdord aka Silver Fox Trans, built the trans and pick which converter to use based upon my cam profile.

I can't confirm now since it's in the car but he did reconfirm that it is a 12" non locking 2600 stall converter.

 

How can you tell if I have a seized converter stator?

 

I've have conflicting advise:

Engine builder-  You need something with around a 2000 rpm stall. The stall rpm is the rpm where the converter stops free-wheeling and starts to lock up. So if you were to power-brake the car, you should see the car start trying to overcome the brakes at 2600 (in your case). Up until that point, it's not efficient and is not transmitting power.

 

PTC (Performance Torque Converters)-  Our 10" will do great with your setup and will stall around 3500 RPM for you. You'll no longer have to worry about being slow off the line on the street.

 

IMO, I'm still thinking the carb tuning, advance curve and the 2600 stall need to be in line somehow........

[ray1970 88]

Not much help here.

My pre-stoker motor was not to far off from yours..What was different?

 

1.750 QF mec secndery 

2.4 speed

3. 3.50 gears

4. 24in tires

5. OEM rockers.

6.LUNATI cam.07112

.560-.560 285-285 @.50 235-235......110 

 

IT WAS A PIG till 2600 rpms

Spent 100s of hours and $$$ trying to get this thing to make the bottom end I was told about.

Never saw it...Or felt it.

The fact I could side step the clutch to were I needed it to be made it usable..

The only time it made good bottom end was when i had a RV cam in it...( 1 of 5 cams)

 

This doesn't  mean something not right(Or wrong) with yours.or mine.....I gave up and went up..(chi-roller-408)

 

Gives you that warm and fuzzy feeling dont it?

[ray1970 88]

Let me add if you did the blue thunder intake mod. GIVE UP NOW..... 

[1969_Mach1 333]

Not much help here.  I'm not a Cleveland person.  I've only known 4 people with 351 Cleveland motors.  All with 4 barrel heads.  One absolutly stock, two street performance, and one for bracket racing.  But they all had one thing in common.  Very little low end power.  Not saying it cannot be sorted out.  But is seems to be more common than not with 4 barrel head Clevelands.

 

Aside from a really messed up timing curve (doesn't seem to your case), typically no low end power is associated with either low intake runner and port velocity at low RPM or low cylinder pressure at low RPM.  I guess the cylinders don't charge as well with a new A/F mixture with a low velocity condition. And low cylinder pressure at low RPM is usually accompanied by cams with large valve overlap and/or late intake valve closing.  From your specs that doesn't appear to be the condition.

[prayers1 153]

I took the Carb off today to check the transition slot.  I believe I'm getting myself confused on transition slot adjustment on both primaries and secondaries.

 

I always thought to get a better adjustment on the mixture screws, that I needed to make an adjustment to the secondaries transition slot, making it a nice square opening roughly 0.15 - 0.20, by using the set screw near the bottom side of the carb near the Vac diaphragm.

 

I don't know why I didn't see the Primary transition slot.  By adjusting the primary idle screw the throttle plate position negotiates that adjustment

 

Then how do I make that perfect square in the primaries if I'm always adjusting idle.

 

What confuses me is that I read idle is controlled by the secondly butterfly w/ the transition slot showing between 0.15-0.20

 

Someone Please explain the procedure for both transition slot adjustments on both primaries and secondary!

[prayers1 153]

The attached photos are taken w/o any adjustments made when taking the Carb off, this is how it was on the engine.

 

Here's the Primaries, the transition slot is too exposed. 

 

 

 

Here's the Secondaries, I think I might have it too tight or maybe not?

[larryc94 38]

I have a similar setup  351C, 66cc Closed camber heads, RPM Air gap, roller rockers, Sanderson Shorty headers, Flowmaster Delta 50's and 2 1/4 tail pipes out the rear.

 

I see you have a custom cam, who came up with those specs.  I have a Crane H-278-2 which is 222/234 duration @ 0.50, .534/539 lift and 114 LSA,

 

Clevelands don't do well with overlap, hurts the low end.  My cam has 56* of overlap.  Mine has great throttle response and low end.

 

Everybody blames the 4v heads, if you use a cam spec'd for Windsor or chevy it will be a dog.  There is a good source of info a http://pantera.infopop.cc/eve/forums/a/tpc/f/5650045562/m/319104265   Followed the info there and very happy with the results.

 

I don't have an auto, have a 5 speed with a 2.95 first and 370 rear with 25.8 tall tires.  I can lug it down to 1000 rpm in 4th and lay into and it just starts pullin

 

I had a Summit 750 vs which ran good but suffer from crap ethanol fuel we have, hot soak restarts.  Now have a FiTech which runs great, even better throttle response and better idle

 

Larry

[ray1970 88]

What your looking for P1 is not going to be found in air screws or throttle plate adj no mater how long you spend at it.

Timing my help but I think you have been down that road to the end..

As Larry was saying its time for a cam change....This one is not working for you and has not for far to long.

Getting the cam that works for you is not always easy... I had one I pulled out after 20 miles I hated it so much..

The time you have spent on the internet trying to fix this problem you could have changed out 2 or 3 cams by now..

[prayers1 153]

Sad to say but I agree with you Ray.  Growing up in the late 70's all I can remember was how Bad Ass Cleveland's were.  When putting this motor together I never heard any complaints about the low end bog that I'm constantly seeing now on the web. It's time to tear her apart!!!!!!!!!!!!!!!!!!!!!!!!

 

When building this motor the Trans builder, Bullet Cams and another well know Ford builder got together and designed the cam, the rest is history.

 

larryc94, I'd like to visit with you at another time, not much time to blog today.

 

I been in contact with a Cleveland Guru, Brent Lykins who's gonna tailor me a cam.

[1969_Mach1 333]

The attached photos are taken w/o any adjustments made when taking the Carb off, this is how it was on the engine.

 

Here's the Primaries, the transition slot is too exposed. 

DSC03893.JPG

 

 

 

Here's the Secondaries, I think I might have it too tight or maybe not?

DSC03894.JPG

 

I don't know if it will affect your sluggish low end power.  But, it looks like the primary throttle plates are open too far exposing too much transfer slot.  The secondaries look correct.  At this point might you might need a bleed hole in each throttle plate to allow the primaries to be closed some.  If you go that route Holley sells throttle plate kits with predrilled holes.  I think 0.093" diameter is the smallest predrilled holes offered.  At least if you purchase the throttle plates you still have the option of going back to original.

 

Myself and many others position the primary throttle plate for about 0.030" of the transition slot exposed when the carb is off the car.  Then get an idea of how much adjustment can be made with the idle speed screw.  Additional idle speed adjustments are made using the secondaries.  But, like I mentioned, your secondaries cannot be opened any more so throttle plates with holes in them might be needed.  Are you certain there are no vacuum leaks anywhere? 

 

Honestly, I don't care what others say, I've never had any luck with QFT carb parts.  I know the QFT carbs have more adjustment features than the lower and mid range Holley's.  But, every time I use QFT base plates or metering blocks I fight and fight and fight tuning the carb.  Eventually I switch back to Holley parts and everything falls into place.  On a Holley carb's base plate the secondary transfer slot seems to be up higher allowing the secondaries to be open farther at idle.  Thus, less need for holes in throttle plates.

[barnett468 418]

I been in contact with a Cleveland Guru, Brent Lykins who's gonna tailor me a cam.

 

There are other people that are extremely knowledgeable about Cevelands, therefore, I would talk to them also then decide whom you want to go with, but for starters I suggest you call Chris Straub and tell him barnett from this forum suggested you call . He has designed cams for many race winning vehicles including a 2 time National boat title winner and Ed Morel maker of Morel lifters, and most recently, a cam he designed was in a car that won the overall at Drag Weekend.

 

Chris Straub

 

http://www.straubtechnologies.com/

 

 

Scott Main, mult time NHRA record holder

 

http://www.camresearchcorp.com/quick-links/news/

 

 

Keith Craft

 

http://www.keithcraft.com/

.

[1969_Mach1 333]

I will add, if prayers1 is thinking about another custom grind cam.  Take time to research and be realistic on how you drive the car most of the time.  Also, some custom grinders are realistic and more conservative with how the car will be used.  Some look at how the car will be used and try to squeeze every horsepower they can out the motor for that application.  The latter can sometimes cause drivability issues that are difficult and sometimes impossible to overcome.  

[ray1970 88]

Brad put to gather a very nice cam for my 408 after i spent 300.00+ on a off the shelf one that i didn't care for..

Always in a rush I am...... and it cost me...time and money...

 

For me his cam has done all i asked for.....

[fordguy69 24]

May want to check with Scotty J as well. 

 

http://www.reincarnation-automotive.com/custom_camshafts

 

He ground a cam for me that absolutely hit every goal I wanted.  Dude really knows his Fords.

[prayers1 153]

Guys thanks for the above info. I'll check into it.

 

1969_Mach1- The pictures above is how I've been running the car, the picture shows the primary slot 1/8" exposed.

The most I can turn it out is 3/4" on the mixture screws before vacuum drops (this is on all 4). 

 

I never really paid any attention to the primary transition slot because I thought, how could I adjust it if I'm always adjusting the main idle screw, that will always throw off the transition slot setting.

 

It was my understanding that I was to adjust the secondaries transition slot 1st by exposing it in a box shape or 0.15- 0.20, in order to adjust the primary throttle blade.

 

I called Quickfuel today and for some reason I always get the same Tech, he sounds like a Cowboy from the deep south.  I told him my concerns and while on the phone he told me to take the Secondary Transition Slot set screw and turn it in until it softly seats, then turn it out 1/8 - 1/4 of a turn. 

 

I told the Guy that an 1/8th seemed not enough, so I turned it out a 1/4, I can just barely see the top of the transition slot, he said leave it at that.

Next he said to turn the (4) idle mixture screws 3/4 to 1 full turn out, next start the car and adjust idle the mixture screws. DOES THIS MAKE SENCE?

[ray1970 88]

I dont know if I ever had the fuel screws all set the same and it ran rite .3 different new carbs and some old ones..

I think having it idle rite over rides having them all being set the same. 

 

Some my be as little as a half turn or as much as two turns...Dont seem right some days..

I think having a duel plane intact with a divider my have something to do with it?? 

[larryc94 38]

 

 

I called Quickfuel today and for some reason I always get the same Tech, he sounds like a Cowboy from the deep south.  I told him my concerns and while on the phone he told me to take the secondary transition slot set screw and turn it in until it softly seats, then turn it out 1/8 - 1/4 of a turn. 

 

I thought you back out the screw, then turn  till it just touches , then turn screw to open secondary 1/4 turn

 

Larry

[1969_Mach1 333]

Guys thanks for the above info. I'll check into it.

 

1969_Mach1- The pictures above is how I've been running the car, the picture shows the primary slot 1/8" exposed.

The most I can turn it out is 3/4" on the mixture screws before vacuum drops (this is on all 4). 

 

I never really paid any attention to the primary transition slot because I thought, how could I adjust it if I'm always adjusting the main idle screw, that will always throw off the transition slot setting.

 

It was my understanding that I was to adjust the secondaries transition slot 1st by exposing it in a box shape or 0.15- 0.20, in order to adjust the primary throttle blade.

 

I called Quickfuel today and for some reason I always get the same Tech, he sounds like a Cowboy from the deep south.  I told him my concerns and while on the phone he told me to take the Secondary Transition Slot set screw and turn it in until it softly seats, then turn it out 1/8 - 1/4 of a turn. 

 

I told the Guy that an 1/8th seemed not enough, so I turned it out a 1/4, I can just barely see the top of the transition slot, he said leave it at that.

Next he said to turn the (4) idle mixture screws 3/4 to 1 full turn out, next start the car and adjust idle the mixture screws. DOES THIS MAKE SENCE?

 

Yes his instructions make sense.  Preliminary adjustments:

 

1)  For the secondary's position I typically end up at 1/4 to 3/8 turn of the screw off seat.  If at 3/8" off seat only exposes about 0.030" of the transfer slot that is good.  Start at 1/4 turn.  Difficult to do, but if needed you can reset it to 3/8 turn.  Now is the time to get an ideal of how much you can turn the adjustment screw and maintain about 0.020" to 0.040" of the transfer slot exposed.

 

2)  Then set the primary throttle plates to expose the same amount of transfer slot, about 0.030".  Get an ideal of how much you can turn the adjustment screw and maintain about 0.020" to 0.040" of the transfer slot exposed.  For me, it's always been about 1/4 turn each way.

 

3)  Set the idle air fuel mixture screws at 1 turn off seat.

 

After starting the car:

 

1)  Make the idle air fuel mixture adjustments.  With 4 to adjust go slowly, maybe 1/8 turn max at a time.

 

2)  When adjusting the idle speed screw be mindful of the amount you can turn the adjustment screw.  At this point you'll find out if you need to readjust the secondaries a little.

 

3)  You might have to recheck the A/F screws if the idle speed changes much from where you initially started.

 

Don't go nuts watching the vacuum gauge, listen to the motor as well.  As a matter of fact, after reaching that best idle, or highest vacuum reading on the gauge, many people will richen the mixture very slightly. Maybe 1/16 turn on each A/F screw when there are 4 A/F screws.  Idle mixtures that are too lean can cause off idle stumbles as you slowly tip open the throttle.  Like when driving through a parking lot.

 

If you get the idle A/F mixture screws and idle speed screws adjusted without needing to turn the idle speed screws more than the allowable amount you estimated, there is nothing more to do for idle adjustments.  In the future you'll know X-turns off seat for A/F screws and X-turns off seat for idle speed screws and adjustments will be simple.

 

If you have to turn the idle speed screws more than allowable to get the idle speed needed, it's time to think about different throttle plates with a bleed hole in each one.  I'd say possible vacuum leaks but only needing to adjust the A/F mixture screws about 3/4 turn off seat rules that out.

 

Let us know what happens. 

 

---This is probably not your case, but if the baseplate is removed from the carb you can also check to make certain the throttle plates are centered in the bores.  With the adjustment screw backed out so the throttle plates are seated shine a flashlight from the bottom side.  It will reveal a small gap between the throttle plates and throttle bores.  Just make certain it's fairly even from side to side, etc.

[prayers1 153]

1969-_Mach1- Thanks for the detailed explanation!

 

I have read the same and will do what you suggest, but I have a question regarding you statement "If at 3/8" off seat only exposes about 0.030" of the transfer slot that is good".

 

When I adjust the Sec Transition slot set screw to an 1/8, I don't see the transition slot at all. If I turn it out a 1/4, I only start to see the very beginning of it.

I get the square opening (or 0.30) at  5/8's of a turn ( a little less than 3/4's a little more than 1/2.)

 

When I spoke to Quickfuel, I turned it out a 1/4 and didn't see the transition slot, he said that was OK. (Whats with that?)

 

When adjusting the idle speed screw, I have it turned out all the way and I still see the primary transition slot exposed 0.45-0.50.

Is there another adjustment that is causing this to not close any further??

 

Do I want to be in error of more or less of the square opening?

 

THANK YOU!

[1969_Mach1 333]

Too little of the secondary transfer slot being exposed at idle is not as critical.  My reasoning is because engine speed and air velocity through the carb is high when the secondaries start to open.  Thus the main circuit will start more emmidiately negating some need for fuel through the transition slots.

 

Sorry about the statement of 3/8" turn off seat.  Typo, should be 3/8 turn off seat.  I was initially going to suggest starting at 3/8 turn off seat for the secondaries.  And now maybe I should have.  For what you have I would open the secondaties a little more maybe to 3/8 turn off seat or slightly more.  Then you can close the primaries some.  I know it's a pain if you cannot easily get to the screw for the secondaries.

 

As far as not being able to close the primaries so less of the transfer slot is exposed.  Make certain the choke fast idle screw is not holding the throttle open.  Also, make certain the link connecting the primary to secondary throttle shafts is not preventing the primaries from closing any more.  If those are okay, I would double check and make certain the throttle plates are centered in the bores.  I've seen many carbs, new and used with throttle plates not centered, thus, not allowing them to close enough.  To do this you will have to remove the carb and more than likely remove the base plate from the carb.  It's an easy operation but you should get another gasket.  https://www.holley.com/products/gaskets/carburetor_gaskets/parts/108-5 Summit and Jegs carries them.  QFT uses red Lok-tite on the throttle plate screws so you would need that if you remove any throttle plate screws.

[prayers1 153]

I was able to close the gap on the primary transition slot by backing off the choke fast idle screw. Actually I took that screw off because as much as I had it turned out, it was hitting the secondary vacuum arm. The primary transition slot exposure did not disappear, but I was able to get it closed to with in 0.15, so now I can open both Prim & Sec transitions slots to 0.30.

 

I have read numerous times to have the Sec transition slot exposed no more than a perfect square or 0.20, why use 0,30?

 

On this Carb there is a screw on top of the dash pot for Vac Sec, called Secondary Adjustment.  The screw is turned out a 1/2 to Quickfuel specs. If turned more in the Secondaries will kick in sooner. As in my case with Cleveland heads, should I just leave it alone or turn it in a 1/4?

 

Thanks!

[LSG 15]

   P1, not sure WHO designed the camshaft......but they weren't thinking largeport Cleveland when they did it. I'd look for a smaller cam, something like 210-214 @ 050 intake and 220-225 @ 050 exhaust on AT LEAST a 112 LDA, maybe 114.  Lots of lift is fine. And dump the MSD dizzy, and get a Duraspark, AND run a vacuum advance, plumbed to full manifold vacuum.  Yes, you'll need an adjustable can, but it will be worth it. You'll completely change the low speed manners, and the big ports will still breath just fine when the rpm is up. Everything else is just nibbling around the edges. BTDT   LSG