This is inspired by another thread on a sputtering enigne in a 65....

Setup is: C2, 327-365HP, Holley 4150, 4speed, 3,08 rear

Got thte following problem:
My engine runs ok in low revs....as soon as I now go into revs at about 3800 it starts sputtering. I cannot go beyond 4000 right now...just can´t get there.
It really starts blowing black smoke out the exhaust.

Should be a clear sign for running too rich (so I do not believe something is wrong with the pump).

So...got new coil, new points, new cap, new rotor, new cables, new sparks.
Ignition was adjusted.

The orgingal 65nozzle of the first stage of my Holley was replaced with a smaller one. Haven´t looked yet at the plate of the 2nd stage.

The crankshaft balancer is a non finned version (so it has been replaced at some point in time...). Could the ignition marking on that be incorrect ?

Any other ideas ?


[Modified by Mikey1, 3:52 AM 6/11/2003]


[Modified by Mikey1, 2:56 PM 7/19/2003]

 

I had the same problem with my 365hp when I bought it last year. I pulled my spark plugs and they were all fouled. After I cleaned I could rev the car again. I then checked the timing and it was 8 deg ABTC which wasn't correct for a 365hp I guess the previous owner thought it was a 350hp car? I advanced the timing to 12 deg ABTC and leaned out the carb mixture alittle. Ever since I did that my car has been running 95% better. I do not have the right holley carb I do know that, mine is a 4160 600cfm which could be some of my continuing problems under sudden acceleration. It will sputter and backfire though the carb. I'm not sure about my whole engine is far as it goes. I know its not the original, but was told it was right for the car. The intake has a GM P.N. on it but does not have the a vacuum connection for the air cleaner? So inother words I really am unsure of what I actually have. I do know that I can rev it over 3500 RPM now. I'm not sure this is going to help with your problem, but it feels good to talk about and at least be able to compare my car to another one of its like.

 

Don't know if your car is new (to you) and you got it with this problem or this problem just manifested itself (was ok yesterday). Here are my thoughts in order of importance.
(1) Exhaust system restriction.....happened to me and would not rev until I got rid of the glas-paks.
(2) Worn points or bushings in distributor shaft.....causes poor timing control at speed.
(3) Oil fouled plugs........I do not like 'cleaning' plugs, they just do not work for me once they're fouled out.
(4) Cracked dist cap or plug wires arcing.
(5) Carb float level or needle seat leaking, as a last resort. :cheers:

 

Well, spark plugs are ok and new. Old ones did not look too bad. Have the car for more than one year and the problem exists ever since to me.

All ignition stuff except the distributer itself is new. I was told that ignition advance could not be the problem as in that particulart engine mode the vacuum would be close to zero anyway...

My initial thought was that the vacuum advance coudl be the reason but apperrantely not.

I have got a Holley 4150 with the correct 365HP intake manifold. The carb is dry and doesn´t have leaks to the outside. The main seals have been replaced.

 

In that case check the mechanical advance (suck on the vac line as it's hooked to the vac can) and with the cap off make sure the point plate rotates easily and stays until you release pressue. Also check your weights to see if they easily rotate out and back. I still see a restricted exhaust as a culprit though.

 

I've seen that problem exsist in situations where the air cleaner is incorrect for the carb. If the air cleaner is sitting too low relative to the top of the carb, the turbulence created by the air flow at higher rpm will make the engine starve for air. Try running it with no air cleaner or a different one. Good luck

 

Can you post the GM P.N. on your intake manifold for my information?

 

check how close the carb bowl vents are to the top of the air cleaner. corvette carbs have to have the bowl vents cut at a 45 degree angle to prevent pressure buildup in the float bowls. the top of the vents must be 1/2" from the air cleaner top. :chevy

 

Clem,
I always wondered why they were cut like that. Those suckers are sharp! Why does a 45 degree angle stop pressure build up?

Thanks
Brian

 

@ MasterDave.....exhaust restrictions...no way...got 2,5" manifolds, heat riser removed...and Sidepipes....think that´s possibly the neatest way to have less restrictions... :D

The engine also carries the original Hi-performance Aircleaner Housing..and an aircleaner that fits.

I am really :confused: :confused:

@cjgemm ....intake manifold carries 3844461 and is aluminium

I am missing the orignial thermostat housing..which is hard to find and should carry 3827370...this one is cast iron and was originally painted silver....my car carries an aftermarket housing....


[Modified by Mikey1, 1:39 PM 6/11/2003]


[Modified by Mikey1, 1:44 PM 6/11/2003]

 

it is just more area for the pressure to escape and makes the exit farther from the air cleaner lid

 

Well then, let's go back to your symptoms. Runs fine below 3800 rpm, will not rev past 3800 and smokes black like mad. Been this way since you got it. Can you unhook the rear barrels on your carb? You should be able to disable them and then give it a shot. Heck, as unusual as it sounds you may have a couple rear main jets out of their holes. Just a shot in the dark. :cheers:

 

Nice idea...will try even if the secondaries are operated through vacuum....

 

Thanks for the post mikey1, Those are the same #'s that are on my intake. I guess that it is what the I was told after all. Where does the crankcase vent come from that connects to the air cleaner? What size is your carb? Do you think that my carb could be my problem under sudden acceleration (It only happens some times)? My car will scream all the way to 6000RPM. I haven't revved it hire though. Not brave enough I guess.

 

I also have a 365 64 convert, all org x the block. I had your problem until I jammed the vacum advance to the intake manifold, 12 TDC, where it should be. I am 90% satisfied with the results. I am in the mile high city and can't get any better. frank

 

I had the same problem with my 65 327/365 SHP.

It turned out to be the cannon plug on the back of the fuse block. The Ignition harness was not making proper contact and at high speeds the vibration or bumps would weaken an already poor conection.

If the car just quits, it is most likely an electrical problem. If it is booging down and sputtering then it is most likely fuel or ignition.

I replaced the ignition harness with a new M&H harness and problem solved.

I also had a Hgh RPM cut-out or "miss" Turned out to be my alternator at extreem Revs was not charging and the amperage would drop to -40.

Had alternator rebuild and back to 7000 RPM reving :hurray:

Mark

 

@cjgemm

crankcase vent is kinda black tube that is screwed down to the block left from the distributor (not to the intake...directly to block !)

..as it should be for a 327....


[Modified by Mikey1, 3:14 AM 7/7/2003]

 

Quote
"crankcase vent is konda black tube that is screwed down to the block left from the distributor (not to the intake...directly to block !)

..as it should be for a 327....

It should be secured by a 3/8" bolt to the intake thought. I am not sure if the intake is taped all the way into the plenum.

With all this black smoke it sounds like fuel. The original 2818-1 carb had some unique designs for the 365-shp motor, bleed air holes for one. You should have #65 jets in the front, and #76 in the rear. You could also have a blown power valve but I think that would effect all circuits of the carb and driveability. Power Valve should be a 6.5 or a #65.

Do you have another carb to swap on there?

Have you mapped out the distributor and it's functions?

Is there any popping out the carb or exhaust?

Mark

 

That´s the way the crankcase vent is mounted.

Had #65 jet in front and got it replaced with a smaller one....helped for some more 200 revs before problem comes...but no solution.

Nothing to swap...got an old Holley 600 cfm but don´t even knwo if the thing works...not a good point to start.

Haven´t got time this week to check that all...but defintely next week. Will let you know the outcome.

Thanks for the ideas.

 

I had same problem. I installed Pertronic ignition. Problem is gone! Guess something was awry in the dist.