So I recently bought a 1977 Firebird Formula, with a 1974 pontiac 400 big block (got the year off the rear engine code). It ran okay okay when I bought it and now it wont start.
The engine has HEI, a edlebrock performer pontiac Intake, and stock carb (for now).
The engine fires a bit then the starter disengages (really annoying), but just does not want to run,
I checked the timing and spark plug wire configuration, that is good. Gaped the sparkplugs to .04". The distrubutor cap is new, wires are yellow accell and look in good shape..
Does anyone have any experiance with these engines and some sugestions? Thanks
That might be the saddest looking engine compartment I've ever seen. If that's indicative of how you run your operation, it's no wonder to me that the motor doesn't want to run. When's the last time the motor got new spark plugs? How long have those plug wires been on there? Have you monitored the fuel pressure at the carb? Cleaned and/or replaced the fuel filter? Set the carb float? Have you ever done a compression test on the motor or had a vacuum gauge hooked up to the intake manifold? Sad lookin' deal Jo-Jo.
Did you take the plugs out and verify the sparkl at the trode?
Then with a finger in the hole bump the engine and cinfirm compression? Better yet compression gauge, shrader valve in.
Then look for fuel cranking into a bucket.
Connect the carb and swab to see if the needle coming off the seat. Look for accelerator pump function and the pump shot in the primary/front carb barrel.
Did not verify spark on electrodes, i'll try that tonight with new plugs,
and a compression test!
Ya did the timing by takin out #1 plug, saw the piston was at highest point, timing mark on balencer was at 0.. ect
Thanks for the ideas! I'll give them a try tonight.
Ya I just bought the car... It has never been restored or refinished, you can't expect a old car from 1977 to look new under the hood lol.
The plugs looked okay when I gapped them, but I'll try some new ones in there.
No compression test or vacume test done yet, maybe I'll do that tonight.
Also, there is no such thing as a Pontiac "big block". All Pontiac blocks are the same. The 265 and 301 just had shorter decks along with the Ram Air 5, that were special built race engines.
Hi
Just looking at spark plug wires won't tell you anything
you need to check them with a ohm meter. Or stick your finger
in the end of the wire while someone cranks it. just kidding
Another thing. I'd look for a shroud before summer get's here.
Rich
should be a 4 speed car.
its kind of apperent that the carb is leaking on your new bright shiny intake manifold.
im no professional, but i would start there. you know, with the obvious things.
just remember, it only takes a roll of 1200 grit to polish a turd!
How long has it been since it last ran ?? Could the gas have gotten stale ? Moisture under the cap from temp changes ? I would find a better starter so it will turn over beyond a couple fires before the bendix kicks out.
Well got a new fuel filter and spark plugs in last night and did a cold compression test (really cold, -10 degrees, no heat where the car is!) they were all around 115 psi.
It kinda ran for about 20 seconds. Sounded like not firing on all cylinders! I checked the rotor cap and there are white powder burns on the inside (dont know what that is about).
Im gonna check the wires like suggested or get new wires . Also getting a good carb on friday, so hopefully some progress can be made friday night!
That white powder is from moisture corrosion. It is blocking some of the current to the plugs. Scrape it off. Also, check the center carbon button. When the powder blocks the voltage, it backfeeds into the button and can burn it off in the cap. There is a silicone washer and a spring under a cover that the button comes out of. Remove the rotor too and see if the backfeed has burned thru to the shaft.
AND while you have the cap off, check the 2 little wires coming out of the pick up coil. They get brittle and break when the advance moves. They cause intermittent running issues and false starts.
Ditto to what TMP has just said.
HEI are infamous for burning a hole right through the rotor, so the spark goes directly from the coil to the distributor shaft.
Why?
It takes the path of least resistance. If there is corrosion build-up on the dist cap terminals, or bad wires, or bad plugs.
I'd also recommend the better quality cap and rotor with BRASS rather than aluminum contacts.
If the cap and rotor don't fix your problem, and you still have intermittent or no spark ... the ignition module is a fairly common culprit.
If you replace that, be sure to use the dielectric compound which is (or should be) supplied with a new module.
Alright so I got it running tonight! The weird thing is that the timing Haas to be retarded 15 to 30 degrees for it to run (that's without the vacuum advance hooked up). And it does not idle very well I have to keep giving it gas to run but its runs nice with good thotlle responded when I'm on the gas.
I bought a holly 750 Carb off a guy that used it for a dyno run on a smc stroked so I don't know if that is why it won't idle well?
Has anyone come across that timing issue before?
No, I had the timing light on it, its 15 - 30 before 0. I wonder if someone before me did a timing chain and set it one notch off? I had the valve covers off, spun the engine over slowly and the #1 exhaust valve opens and closes a fair amount before the #1 piston reaches TDC.
all the pictures floating around and we missed this car?jk.start by cleaning up everything. replace whats needed,maybe even that fuel stained carb,,,maybe visit fbird88 in ontario,he can set your timing for you
as already mentioned,check for spark,check for fuel,check compression.
make sure the fuel is good quality.
clean up everything so you can work on the car.check all the top screws on the carb(for now)
When this is all done let us know what happened
Ya thats all been done, new spark plugs, fuel hose and filter, distrubutor all cleaned, spark wires all good, and I got a good holly carb on it now, I'll be takeing some new pics in a day or so.
IDK about the 74, but these old Pontiacs had nylon teeth molded over the steel on the crankshaft timing gear. The teeth would strip off or jump a tooth. Often it would happen when you try to start the engine. It would be a good idea to check that your camshaft timing is correct.
It's premature to worry what's wrong with the engine when it has such old wiring, distributor cap, dirty (and wrong) carb and so forth. Restore these to good condition first.
distrubutor cap and rotor before cleaning off contacts, Holly 750 carb, a look under the valve covers and such.
So the engine runs now, but it still needs a lot of work to get it cleaned up and tuned. That will come later the rest of the car needs alot of attention first.
I'll create a album for the car soon if anyone wants to check it out.
The center pin in the cap doesn't look right. It appears to be recessed in the cap. It should protrude out of the cap about 3/16ths to ride on the spring of the rotor. If the spark has to jump that gap, it will affect the timing and strength of the spark at the plugs. If the cam is stock in that engine, about 4-8 degrees advanced is all they required '74 to run smoooth.
Maybe it's just an illusion from the angle of the pic, but check that. I see the pickup coil has already been replaced with a Borg Warner. That should be good.
In picture #1 I see the center connector is not sticking down through the distributor cap as it should, causing an issue captured in picture 5....Massive carbon tracking and shorting across the rotor.
Replace the rotor with a new one and take the coil out of the cap, get the center conductor issue corrected, be sure the carbon button goes back in FIRST, then the insulator, then some dielectric grease then the coil. Be sure to use the little grounding fork on the coil frame unless it has the wire with the eyelet for the coil. I would also replace the cap in the process as well.
Thank you Vinnie.
One thing for the OP... the borg warner device is the ignition module.The pickup coil is the piece that has the green and white (yellowed with age) wires on it that hook to the end on the right. I mention this because the 2 wires are supposed to be in a connector so they dont get plugged in wrong. Looks like the white wire is on the correct terminal, but If they get plugged in backwards, the car wont run. Just an FYI
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