[pacat]

Hoping someone here can help me out with a rough running '87 Ford 460 with a 4V Holley on it.

Here's the deal - runs rough and very rich. Have spark at all 8 plugs as tested with a timing light. Can't get to all the plugs easily but of the four I can get to - the compression is good - averages 140 psi on each cylinder with no major adjacent differences.

On the left side of the engine, testing with an infrared tester, the EGTs are about 400 degrees at each exhaust port, however, on the right side only cylinder 4 has a 400 degree EGT - cylinders 3 (which has a 140 psi compression) and cylinder 2 (can't really reach 1) have an EGT of only 200 degrees. A 200 degree EGT difference just screams somethings wrong - but I can't find the problem.

There's one of those early EGR systems under the Holley but there's no real way to test it - and I don't think it would only affect cylinders 1, 2 and 3 (which are all adjacent on the right side). Is it possible that the Holley is built such that half of it supports cylinders 1, 2, 3 and 4 while the other side supports cylinders 5, 6, 7 and 8? By the way - don't know at this point exactly which Holley model is installed.

So - to summarize - have a very rich poor running 460 with no obvious problems, and 3 of the 4 cylinders on the right are running EGTs 200 degrees less than the 4 cylinders on the left side.

I'm stumped and open to any suggestions. Thanks in advance.

 

[CougarCJ]

Are you losing water?

 

[pacat]

Nope - no loss of water.

Probably should add that there's a boat load of air piping (early air injection into the exhaust manifolds) and at times air is injected into the air cleaner. Probably doesn't have a thing to do with the real problem - just thought I'd throw out some additional info.

 

[Harvey]

Not sure if it is the same. I had a 79 F250 with a 460. The EGR valve was bad. back of spacer below carb. I drove it that way but truck didn't idle well at all. Very ruff. The truck also came with California emissions. I was smart and disconnected the air pump and probably some other stuff. Gas mileage dropped to about nine miles to the gallon and truck never ran good afterward. Still got 368 thousand miles out of that truck though. Traded it in on my 97 F350. Still driving that one.

 

[Bad69cat]

Ray, I'd try the simple stuff first - Harvey may be on the right track though? Sounds like vac leak or something causing it to richen (choke/advance) or maybe even one cylinder not firing through the plug itself. Have you checked all the vac lines carefully for cracks/loose fit, spray around mating surfaces (carb/intake/etc) with carb cleaner to check for stumble...hows the fuel filter(s)? I'd swap the plugs if you havent yet ( could be one with bad/melted electrode) I know some of those mid-80's trucks are a pita to get the plugs out! (My 85 liked to melt plugs for some reason..? IDK why. Look under the cap for carbon trace/arc evidence....should look pretty clean and clean the rotor while your there. I would check that the choke is working completely too....maybe hanging up?

 

[pacat]

Guys - thanks for the replies!!!!

Harvey - agree that it could be the EGR valve but uncertain how it's constructed/if it could affect just one bank of cylinders. I did unplug it - no change but if it's stuck it's stuck - the way it's built there's no real way to see if the shaft/plunger is moving. It's gonna be a real pita to get that thing out of there. Might also not be a bad idea to unplug/disconnect some of the air piping and/or pump. By the way now that you mention it I had an '86 Pontiac with a 350 that had an EGR that would stick then 'pop' open - what a stumble at part throttle.Thanks for the great input.

Bad69cat - pretty much went the simple route first - with the exception of spraying with carb cleaner. No apparent vacuum leaks - all lines look good. Installed a new plug where one of the EGTs is low - no change. It's gonna be a dog to get to the others. Fuel filters have been recently changed, cap 'looks' good as does the rotor - no signs of cracks or arching. The Holley has an electric choke - it's closed cold and opens as the engine warm so that appears to be working OK. Also, the external coil tests good but might throw a new one at it on the off chance the plugs I can't get to (yet) are not up to par. Thanks for the great input.

I'll keep at it and let all know if I get it figured out. In the mean time any other input is welcome.

 

[cougarshaman]

If it's running rich you could have accrued a bunch of carbon in the egr system.
I'd pull the carb and check out the usual holley suspects: power valve, mating surfaces, and clogged circuits. While the carb is off, look down into the baseplate and maybe disassemble the egr system.

Gird your loins and change the spark plugs.

 

[Art]

Vacuum leak would show up as a hotter temp than normal.
Hooking a timing light to the plug wire is not a good indicator if the plug is actually firing.

Those early EGR plates (especially the aluminum ones) were notorious for burning out. You can't just remove it either because of the exhaust port.

Pull all the plugs, confirm compression on all 8 cylinders.

 

[Todd]

Start cheap. Swap the plugs and wires on the hot to the cold cylinders and check again.
If no change you ruled out ignition.

 

[pacat]

Gents - thanks for the additional ideas/input. I'm absorbing all the info and working through the input as I can get to it.

Finally got the air cleaner off - what a pita. Didn't see any obvious issues - will pull it and give it a once over as soon as I can. I did check the EGR system - two interesting observations - when applying vacuum with a hand pump the valve moves and engine operation is affected - but no vacuum was ever detected when the engine was cold - or hot for that matter - I'm thinking I could have a bad TVS but don't know how EGR issues would relate to the EGTs I have from side to side. And, according to the vacuum schematic the same EGR vacuum circuit goes to the canister purge - hummm.

Sprayed carb cleaner at the rear base of the carb - got a small reaction - looks like the gasket between the intake manifold and the EGR assembly may be distorted. Also found a check valve in the EGR loop that 'reacted' when sprayed with carb cleaner.

Back to the EGTs themselves - am I right to assume that the 400 degree readings are right - or are the 200 degree readings correct?

A local friend suggested that the air divert valves could be hosed up. It has two air pumps - one for the exhaust manifolds to burn off any left over gas and one that connects to the back of the block/heads on both sides - guess that's to pump fresh air into the crankcase? Checked the vacuum - looks pretty good and the PCV is chattering up a storm so guess it's working.

Will continue to press on towards a fix checking out all the inputs received. In the mean time all input is welcome.

 

[Harvey]

If I remember right the air pumps pump air through a silver tube manifold type system into the heads but they actually go to the exhaust side. If one of those pumps was bad and you were not getting air into that bank it would definitely be hotter on that side! Check belts to air pumps. Not sure how but check airpump output. Might even have a leak in the fresh air manifold? That stuff was all to do with lowering emissions.

 

[Bad69cat]

Mine rotted off right at the manifold before now that I think about it....I picked up a rapair kit for re-plumbing it out og the "Help" stuff they sell at parts stores...sounds like your making progress though. May have had a few things going on - she was just wanting some attention! ;>)

 

[clanceman427]

Art, I thought you could use a timing light to verify spark. How come it's not a good indicator? Is this because the timing light will flash if the voltage is present in the plug wire no matter if the plug actually fired or not? I'm curious. What would be a more definititve way? I'm guessing somehow looking for the spark on the plug with it removed from the cylinder head somehow? Thanks.

Kevin

 

[Harvey]

Pull the plug but leave it connected to the wire. lay the plug on the block and have some one turn it over, you should see the spark real easyllll

 

[clanceman427]

where do you lay the spark plug? The block is not so easily reached, depending. Does it have to be the engine block? Also, you say turn it over- do you mean run the engine for a short amount of time? Or turn it over with the starter while not supplying fuel?

 

[pacat]

Folks - an update.

Pretty sure the EGR system is good. If I forget about the wild EGTs for a minute and just think about the symptoms - it's gotta be the carb - rough idle, stumbles under acceleration (loaded or unloaded). It's an 87 Holley Motorcraft that I believe equates to a 4180 600 cfm - but it apparently has some unique environment traits - like it can't be adjusted too much - guess Ford and the Feds were trying to put us shade tree mechanics out of business . Can anyone comment on the difficulty of rebuilding a 4180, and the availability of rebuild kits? I can do 2100's and 4300's all day long but never opened a Holley.

As far as testing a firing plug with a timing light - it's never let me down but you really can't tell how adequate the spark is.

Bad69cat - think you're right there are probably several issues going on at the same time, and she really just wants some attention - LOL. She's getting plenty now.

 

[Harvey]

To test the plug ground it anywhere on the block. You are just completing a circuit. Might be the carb. Mine had a 600 holly on it too. Leaked around the butterfly rod on both sides and I was told that couldn't be fixed without replacing. Biggest issue for my ruff idle was the EGR plate was burnt. As it connected to the exhaust manifold I never took the time to fix it. Ran it with a lousy idle for years. Taking off the airpumps which I did was stupid. That along with a bad EGR plate and it idled terrible till the day I traded it in. Good luck.

 

[pacat]

Folks:

Sorry it's taken so long but I wanted to get back to you all with the results on this issue. Turns out it was a bad intake gasket - it was torn between cylinders 2 and 3 so that pretty much explains the wacky EGTs at those cylinders. Not sure exactly what the gaskets should have looked like - there was no lower gasket between the head and valley pan then there was what I'd describe as a cardboard type upper gasket between the valley pan and the intake manifold - that's the gasket that was torn. The new gasket was a soft metal on both sides of the valley pan and the whole assembly was riveted together to ensure the proper location of everything. It turned out to be quite a job but I just wanted to thank you all for your input/suggestions and let everyone know what it was.

 

[Bad69cat]

LOL - Glad you found it! Not an easy job at all if it's anything like my camper was!! Sounds like you got better quality gaskets this time.