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Discussion Starter · #1 ·
Just installed the following:
Edlebrock Performer heads
FMS 1.6 roller rockers
FMS 24# injectors
70mm Throtle body and EGR
75mm MAF
Sheet metal aluminum valve covers

But now I have a problem that seems timing related. What the....?

Checked and set the TPS to .98V. Then set the timing to 14 degrees BTDC as it was before (w/spout out). Plugs are gapped to .45. Triple checked the firing order (and yes I used anti-seize on the plug threads). Even tried backing the timing down to 12 degrees BTDC but no help.

Symptoms-
Car runs rich and a little rough at idle, which I have bumped up to almost 1000RPM. At cruising speed the car stutters with a pretty bad miss and even sounded like it backfired once or twice. At idle I'm only getting about 12# of vacuum.

What's different?
1) The pasenger valve cover is not venting to the throttle body. Rather it's venting to open air and the connection at the throttle body is plugged. Could this contribute to the vacuum leak?

2) The engine ground is now bolted to aluminum heads rather than cast iron. Could this cause a ground issue?

I'm hoping someone out there can give me a few pointers.

Thanks
 

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FFCobra Craftsman
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1,975 Posts
Jeff - three things come quickly to mind.

1. Check for a vacuum leak around the intake manifold. Use a can of spray on brake cleaner and just spray it around the base. If the engine smooths out or picks up rpm, that is where your leak is. BTW, there is about a 1/2 threaded port under the intake on the Performer on the driver's side that is easy to froget to put a plug in (don't ask how I know).

2. Check your fuel pressure, may be too high, esp if you put in a bigger pump with the original pressure regulator.

3. Is your Mass Air calibrated for 24 lb injectors?

Frank.
 

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Premium Member
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7,237 Posts
If you're running a PCV valve, you've got a big vacuum leak with that vented valve cover. Are you saying it's rich because you see black smoke, or because it burns your eyes? A really lean condition will burn your eyes more than a rich condition. If you're not seeing black smoke or fouled plugs, the vacuum leak/lean condition makes more sense, and would also cause your popping under cruise conditions. A quick check would be to plug the PCV line (or the vented cover), reset the computer, and fire it back up.

BTW - I doubt the aluminum ground is your problem, but it wouldn't be a bad idea to change that too.

Keep us posted! :D
 

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FFCobra Fanatic
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2,578 Posts
Wade has a good point. Plug the PCV valve and then check your vacuum reading. I doubt it will be much better than what you have if you're running a healthy cam. However, you could get closer to 14"HG. Unless you're using a MSD type ignition, your plugs only need to be gapped to .035. As for the ground, make sure you have a good engine to frame and battery to frame connection, but I doubt that is your problem.
 

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Jeff,

What everybody else said and one question. What kind of Mass Air Meter are you using? Is it calibrated for 24 pounders? I had a similiar problem and mine had to do with fuel pressure. Also, some of us (Rick Williams and myself) have had bad luck with C&L meters and switched to ProM. Just a thought.

Sean
 

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Discussion Starter · #6 ·
Fantastic input guys. You've given me many things to check as a process of elimination continues. That's what makes this forum so awesome.

I'll get started on this stuff. It's just never easy, is it?

To answer a couple of questions:
Frank and Wade, I'll continue checking for vacuum leaks and start with pluging the PCV and valve cover vents seperately to see if that makes a difference.

Frank, Fuel pressure is 40psi with just the stock pump in place but I have a 190lp/h that I'm going to install.

Frank and Sean, Mass air is calibrated to 24# injectors but it is the C&L that everone warned me about. Jack @ Muscle Motors talked me into it, so I'm trying to make it work. I have a Pro-M Bullet that I can swap on with a little work.

Wade, No black smoke, but it definitely burns your eyes. Are you saying this could mean lean?

Running the e-cam Ween, so there is some loss of vacuum, but 10 - 12 still semed low.

And of course I'm gonna try and find a new engine ground to cast iron on the block just to eliminate that as a possibility.

Thanks everyone, and if you think of anything else please respond or email me.
 

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FFCobra Fanatic
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929 Posts
Jeff, its not uncommon for the Edelbrock to leak around the top gasket (the one for the plate). Wrap electrical tape all the way around it and see if that helps. Also, remember, with the pvc, the lower the vacuum, the more the valve is open. With good idle vacuum, the pvc valve does not contribute a vacuum leak of any consequence. With poor vacuum, it will contribute more of a leak, cause less vacuum and you are into a postive feedback loop which is not good. Matt
 

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Discussion Starter · #8 ·
Good point Matt. I had to use a plenum spacer from Summit because the valve covers from Muscle Motors are so tall. A word of caution about this is that the throttle body is now touching the under side of the hood on the brass colored elbow at the top. Need to do some adjusting there.

I think the plenum spacer sealed up nicely, but I'll double check.
 

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Premium Member
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7,237 Posts
Ugghhhh. C&L :(

Guarantee you're running super lean. You can pull the codes from the computer to confirm it. I spent 3 months fighting with a 76mm C&L, then a 73mm C&L. Had the same issues. Eyes burning, wouldn't idle, stumbled, popped under load, etc. The lean calibration of the C&L coupled with at least one confirmed vac leak (breather), and you're in REALLY lean territory.

Plug the breather, swap in the ProM, and be happy! ;) ;) ;)
 
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