69 351W running issues

[1969Fstback 58]

I picked up a 68 Cougar project last November for my son.  It came with a 351W half put together. I know the guy and his uncle had blown the car apart it's still apart.  He was in the middle of putting the motor together and passed away.  I got the car for next to nothing.  The the block had the crank and pistons and that was it.  Everything else in boxes.  I put it all together.  Stand started it and it sounded good.  Granted I didn't let it sit on the stand running for 30 mins.  I pulled my 302 dropped it in and fired up. The more it warms up the less well it runs.  Oil pressure is good and it  hold 160-165 temp. 

At initial start up I can run about 18 degrees timing and get around 10 vacuum and the motor is very responsive. With dist unplugged.  As it warms to keep it running I have to add more timing.  Eventually vacuum drops to 5.5ish and the motor becomes less responsive. If you put it in gear it dies immediately, but it also dawned on me I tried that without the vacuum hooked to distributor.  But I am not sure if that would make a difference or not.  The only vacuum hooked to the motor is the trans and vacuum gauge. It acts like a vacuum leak to me, but I checked 2 or 3 times spraying around intake and carb base.  When warm adjusting the idle fuel air ratio does little unless you screw them all the way in.  

So 351W 60 over

comp 292H cam.  

Heads are original cast with double valve springs.

Crane roller rockers 1.6

For now I cannibalized the summit 500 carb off my 302.

Has new HEI dist.

I am going to perform a compression test this week.  

Looking for suggestions on diagnosing the issue.  

thanks

 

[LoneWolf2U 136]

Start with basics first, Check the valve settings and timing marks.

Loss of vac with heat shows a leak is present at temps and could be internal like intake mounting.

[1969Fstback 58]

I pulled the intake once and remounted it with new gaskets.  I may need to check the torque on it again or take it back off and do it again.  

But yeah I was leaning that away to, but was stumped.

[DocWok 30]

3 hours ago, 1969Fstback said:

  When warm adjusting the idle fuel air ratio does little unless you screw them all the way in.  

It would seem that something in making your engine run richer as it warms up if you need to screw your idle mixture screws all the way in as it heats up.

This symptom would seem to be the opposite of what a vacuum leak would cause, which would cause it to run lean.

Maybe your carb floats are leaking and as the engine warms the float(s) leaks and sinks, causing the fuel level to rise?

Did the engine have the same issues when you tried a different carb on it?

[1969Fstback 58]

The few level in the eye glass is right below midway. I tried a Holley 570 with no change.  The 500 came of my 302 I had been running but then again it was mostly stock 302. 

[1969_Mach1 333]

Check basic stuff like others mentioned, vacuum leaks, etc.  Keep in mind that is a fairly aggressive cam, especially in a 351W for street driving.  It doesn't surprise me that the vacuum drops off the way you describe.  If your car has vacuum assist power brakes, they won't work.  If you have a larger carb, it might be worth a try, 650-700-750 cfm.  Maybe a mechanical secondary carb.  The 500 and 570 are a little small for a mild 351W, but, that cam will make matters worse and they might have too lean of an idle circuit for it.  If your 500 and 570 carbs have an operating choke, that would explain why it runs better cold (richer A/F mixture).

When you do get it running with that cam, you'll need a fairly low rear axle gear ratio.  Plus, if it's an auto trans car, the stock torque converter will not work.  After you obtain a good neutral idle, it will likely die when you drop it into gear.  Or you will have to turn the idle speed up fairly high and it will lung hard and creep when you put it into gear.

Again, check the basic stuff first.  If all is okay, maybe consider a less aggressive cam or do more work to tune the motor for that cam.  

[1969Fstback 58]

I had planned on picking up a 700 or 750 once I had the motor going and driving, but may anyway and try it.  The chokes where both open.  I am running a 2000 stall converter, but it calls for a 3k. 

And honestly, I was thinking about doing just that with the cam.  

[1969_Mach1 333]

I'm curious to see if you can get it tuned and running good with the current combination or ultimately a cam change will be needed.

A Holley 700 CFM mechanical secondary carb Holley list 4778-8 runs good on my mild 351W motor.  A 650 CFM Holley mechanical secondary carb, list 4777, is a little more crisp but it seems to pull harder in mid-range with the 700. 

[dcm0123 15]

Spray WD40 or carb cleaner in areas you think you have a leak. If engine changes speed, you have a leak.

You will have a problem with your power brakes at 10" vacuum. You may have to install an electric vacuum pump kit as we did to provide the assist for the brakes. We have about 12" due to cam design.

If your carburetor has a vacuum operated power valve, you need to find out what vacuum it opens up at otherwise you may flood your engine. The rating of the valve must be for vacuum lower than the vacuum your engine runs at. If you valve is rated 10.5" vacuum then it will be open and pouring in gas when it should not be.

Holley carbs typically have power valves. We had to change ours. You probably want one rated for 3-4" vacuum. They are less than $10.

Not sure if the low vacuum will affect the transmission shift quality or how to fix it.

https://www.summitracing.com/parts/hly-125-35?rrec=true

 

[1969Fstback 58]

13 hours ago, dcm0123 said:

Spray WD40 or carb cleaner in areas you think you have a leak. If engine changes speed, you have a leak.

You will have a problem with your power brakes at 10" vacuum. You may have to install an electric vacuum pump kit as we did to provide the assist for the brakes. We have about 12" due to cam design.

If your carburetor has a vacuum operated power valve, you need to find out what vacuum it opens up at otherwise you may flood your engine. The rating of the valve must be for vacuum lower than the vacuum your engine runs at. If you valve is rated 10.5" vacuum then it will be open and pouring in gas when it should not be.

Holley carbs typically have power valves. We had to change ours. You probably want one rated for 3-4" vacuum. They are less than $10.

Not sure if the low vacuum will affect the transmission shift quality or how to fix it.

https://www.summitracing.com/parts/hly-125-35?rrec=true

 

Thanks, I put a 3.5 power valve in.  Have manual brakes. I am going to redo the valve lash.  I do not have a lot of experience with setting it.  After some research and speaking with a buddy we are leaning towards that being an issue.  

[dcm0123 15]

If you have conventional hydraulic lifters and adjustable pedestals with self locking nuts- heat up the engine, remove the valve cover, with the engine running back the nut off until it just starts clicking, then tighten 1/2 a turn. Some folks say tighten 3/4 a turn or more but I typically set it at 1/2.

If you have Comp Cam brand lifters, refer to their documentation for how many turns to tighten- this may be between 3/4 and 1.5 turns..

You may want to make a baffle the length of the head from aluminum flashing to keep the oil inside the head if it splashes over the headers and fenders.

If you have non adjustable rockers like they use on later model engines, let me know and I will explain how to shim them.

 

[1969Fstback 58]

Thanks. I have comp cam roller rockers with poly locks. The pedestals and guides were already installed and seem to be correctly aligned. 

[1969_Mach1 333]

If you don't have much experience adjusting the valves I'd suggest go to Comp Cams website and look for the instructions they offer.  It's a tedious method of one valve at a time and rotate the crank each time.  But, it assures the lifter for the valve you are adjusting is where it's supposed to be, on the heel of the cam lobe, and the lifter gets preloaded correctly.

[dcm0123 15]

5 hours ago, 1969_Mach1 said:

If you don't have much experience adjusting the valves I'd suggest go to Comp Cams website and look for the instructions they offer.  It's a tedious method of one valve at a time and rotate the crank each time.  But, it assures the lifter for the valve you are adjusting is where it's supposed to be, on the heel of the cam lobe, and the lifter gets preloaded correctly.

Is there an advantage on setting rollers like this vs while the engine is running?  How about non-roller?

Reason I ask is it is easy to set it wrong using the above method (I have done it). Some cars such as those with rocker shafts leave you no choice but set to a gap, not turns of the nut. .

If you have comp can lifters I suggest you call them, explain what you have and ask for the correct preload to use. My son has them in his 390. We set to a preload equivalent (measured the gap) of 3/4 turn which was on one set of instructions from their website but he had ticking. We then found another set of instructions of a later date for the same lifter series which said to set for 1 turn. This eliminated the ticking. These were not roller lifters. They came with the Comp Cam camshaft kit.

Not enough preload causes ticking but should run decent. To much preload causes valves not to close which results in poor idle etc.

When I initially started the 351w after rebuild it idled poor. This was because a valve was not fully closing even when set to 1/2 turn (not Comp Cam). I knew this was the problem because I measured the compression. I backed the rocker nut off more and the compression went  up. I am not sure if this was because of a lifter problem or I put moly grease on the face of the lifter and may have accidentally put some in the bore which ended up inside the lifter hydraulic system.

[1969Fstback 58]

I educated myself more and followed some of the advice on this thread and readjusted the valves.  That seems to have been the issue. Haven't driven it yet, but the idle is now smoother and consistent, vacuum does not drop, and best of all I can put it in gear and it doesn't die.