[wakawu]

Hey, new here looking for some advice on my 79 Camaro with a SB 350. It has an ACCEL HEI type distributor that seems to fire up fine. Spark plugs and wires replaced with new A/C Delco's and Moroso Ultra 40's. Fuel filter just replaced, oil changed and I have checked for any vacuum leaks but I still get this somewhat hesitation/brick wall when revving or driving the car. It will not pass 1500-1600rpm.

The engine was first flooded out when I bought it, I replaced the spark plugs and wires and it was great, revved to 5500rpm no problem. I test drove the car and noticed it bogging and wouldn't increase rpms.. it was stuck around 1600rpm while driving normally. It would backfire if I gave it any more gas. I tuned the idle/fuel mixture screws and the curb idle speed is set fine. It's clearly getting gas and spark, I'm not exactly sure what else could be the problem. I was thinking about throwing out the distributor and replacing with an MSD but not before I got some advice.. so any help would be appreciated.

 

[gizmo-1948]

Check for plugged exhaust system. If it still has a cat, its probably the culprit.

 

[wakawu]

Heh.. a cat is probably the least of my worries. It's got open headers into glasspacks

 

[airboat]

Wires on the pickup coil inside the HEI? pull off the vacuum advance line and see if it revs up. Little wires will break and when they move will create an intermitant open circuit killing the ignition.

 

[T-bucket23]

I would start by checking your fuel pressure and float levels. It is possible you are running out of fuel. It could be ignition but I would look at fuel first. Will it rev in neutral ?

 

[wakawu]

Problem is in Park and neutral as well as driving the car. Checking fuel pressure will be a little more complicated as I don't have the right tools yet but definitely something I'll confirm. If anything it seems a little too rich somehow. I'll pull the HEI coil tomorrow and check it as well as the spark plugs.

 

[riesman20]

I had that problem once when I was in high school (15 years ago) What it ended up being was the fuel filter on the side of the carb was plugged. The only reason I offer this was that I was driving a 79 Camaro......

 

[wakawu]

Ah, well hey any advice is appreciated. The car has had a few problems so it helps to hear other perspectives when I'm racking my brain. I just replaced the filter and it doesn't seem to be a problem at all. The old filter I replaced was able to revv freely to the limit anyway so that's not an issue.

 

[airboat]

You don't have a clue what i'm talking about do you? :drool:

 

[Blazin72]

Check to see if you have a plugged jet. I had this problem with the 351 in my boat. In the water it wouldn't rev past 1400 but on the trailer without a load on the prop it would rev fine. I pulled the float bowl off than a piece of o-ring was stuck in one of the jets.

 

[wakawu]

Wires on the pickup coil inside the HEI? pull off the vacuum advance line and see if it revs up. Little wires will break and when they move will create an intermitant open circuit killing the ignition.

Well this is getting more and more difficult to diagnose. I now have a transmission problem at the same time that is allowing all gears (P, R, N, D, 1 and 2) to act like drive gears so I'll have to either fix the tranny problem or jack the rear to revv the car freely to diagnose and test this. I tried pulling the spark plugs, cyl # 1 and 2 are clean, look the way they are supposed to. Cleaned out the carb with carb cleaner and pulled the hei and distributor cap to clean them off, all look fine, no loose wires. I'll take a look at the tranny and jack the rear tomorrow and see if it can revv freely. I did try to pull the vacuum off the distributor advance and the rpms lowered maybe 1-200. It sounded a little rough but somewhat better, but again I wasn't really able to test it because of the tranny so I'll know more tomorrow.

 

[MrChevy]

You don't have a clue what i'm talking about do you? :drool:

I LOVE it! Hahahaha. Yep, that IS the way it IS with people. No hope either.

Reminds me of a pretty girl in June of 1982 if I remember correctly. Had a Pontiac V8, just a girls car. Ran GREAT. Get a few blocks and it would start running at maybe 1,500 RPM then.

It had a vacuum-thermoswitch on the thermostat housing. YEP! Soon as it got warm and that thermoswitch opened the vacuum line... BINGO.

Easy to fix. Just replaced the module. The parts store didn't have one so I plugged the vacuum line so she could drive her car that weekend.

I've found that problem another time or two also. Sounds like you have too.

People say "Looks good." You ask them "Did you use a VOM to see with?" and they go "HUH???"

I think you are correct, it went right over somebodies head! Soon as the vacuum plate moved. I was just a dumb kid back then, only 34 years old, thought I knew something. Now I know I don't know anything. Makes life much easier.

How many times you caught that? Three times for me that I can remember, but I quit working on cars 26 years ago when I moved into this house I am in now.

Easy to check too, just pull the line and wham, the engine revved right up since it was getting juice again.

Have you noticed, experience doesn't seem to count for much on most of these boards.

A guy sort of has to look at it as entertainment.

The odds are good that that IS what it is.

Thanks for the laugh, airboat!

 

[wakawu]

A vacuum-thermoswitch on the thermostat housing?? I don't see any sort of thing on my motor. By the way, I'm not sure if this is the original 79 Camaro 350 motor that was rebuilt and bored out. The guy I bought it from had a friend with a shop do all the work for him.

The vacuum thermoswitch would connect the vacuum advance, tranny vacuum and carb port if I'm not mistaken? My vacuum advance on the distributor is connected to a port toward the front of the engine on the carb. The transmission vacuum line is connected to what looks like the intake manifold itself. Is there another place I should be looking for a thermoswitch?

 

[MrChevy]

No one was saying you have a thermo-vacuum switch on YOUR car. What a few of us were saying is: We HAVE seen BROKEN module wires that HAVE caused the problem you are talking about WHEN the plate the module is mounted on is MOVED by the vacuum advance moving it.

It WAS said that if you remove the vacuum LINE and PLUG it, then the PLATE does NOT/will not move and the engine should rev fine.

That is just part of common sense trouble shooting. Remove the vacuum advance hose and plug it to start with, then you KNOW it can't be caused by the plate in the distributor moving and causing a broken wire to open/close causing the miss.

It COULD even be caused by sparkplugs gapped to CLOSE together. I think I have ran into that a couple of times, too.

IF I bought a car that way, NOT running, and put plugs in it and it DID run okay for a very short time and THEN it DID start backfiring through the carb when I gave it too much gas, the FIRST thing I would do is pull the valve covers and LOOSEN all the valves a half turn or so.

It sounds like the lifters were bled off and as soon as you got it running for a bit it pumped them up and could cause a problem like you have because someone TIGHTENED them too tight.

It is something to check.

Ken

 

[sbchevfreak]

Never mind, re read OP, and saw it had been done.
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