Kurt G.

65` VERT, Freshly rebuilt 327/365. Solid lifters, pertronix ignition, stock Holley 2818-1 carb, 3:55 rear end...This thing doesnt sound just right to me...I really have to rev her up and slip the clutch away from a stop ( some have said that is a characteristic of this motor) and the only way I can describe the sound from the side exhaust is -The sound a tailpipe would make if it was partially submerged under water (does that make sense??)
Already checked the spark plugs, and they indicated I was running a little lean so I adjusted the air/fuel screws about 1/2 a turn. Maybe I need to re-jet this thing....Could it be starving for fuel?
Also, if I sit in stop and go traffic for too long, she starts to heat up, 220+...new clutch fan, Dewitts alum rad new water pump, 160 degree thermostat, etc... Maybe the temp thing is carb related..?? I just want to get this thing done ! ANY SUGGESTIONS?? THANKS.

Bill Irwin

Kurt. That is not a character of the 365. I would look at the timing if I were you. What's the timing set at with can disc & line pluged> Bill

stingrayl76

:i agree: I'm running the same engine and axle ratio with a close ratio trans (2.20:1 first gear) and had the same problem until I went through the ignition timing. Now it will launch without excessive RPM. Check your initial timing, centrifugal advance and vacuum advance.

How low can you set you idle speed before the engine stalls out? The centrifugal advance curve in a 365 normally starts advancing the timing at around 800 RPM. If you can't get it to idle at around 800-850 RPM but idles fine at 1000 RPM and above, the increased RPM advances the timing via the centrifugal mechanism giving the engine enough timing to idle. When you let the clutch out and loose RPM, you are simultaneously retarding the timing via the centrifugal mechanism. Therefore, to compensate for the loss of RPM and timing at launch you must increase the RPM.
Anyway, make sure you have your initial timing set properly to spec.

Dave

P.S. Retarded timing will cause the engine to run hotter.

L78racer

sounds very possibly like a spark timing issue.
but also put a vacuum gage on it and check manifold vacuum at idle.
it should be steady. if not your valve lash may be too tight or incorrectly done.

Kurt G.

Thanks guys- Where do I hook up the vacuum gauge on my manifold??

Also, I need to buy a timing light, vac gauge etc...I left it to my local shop to dial in. I don't think its right. He said the total timing is 36...I think about 12 at idle.

Bill Irwin

Kurt, unplug the vac line at the carb, put vac guage hose there. As far as what you said about the timing, that you think it is. That's right in the ballpark. But verify to make sure. Bill.

redred65cpe

Kurt,
A timing light with dial back and a tach would be the thing to get. And most all vacuum gauges come with adapters and such which make hook up easy. Also, reading up and understanding timing, vacuum, and vacuum advance is a must. Barry's site has the good docs for this: http://lbfun.com/Corvette/Tech/vettetech.html.

larry

BarryK

hook up the vacuum gauge to a full manifold vacuum source. On your 2818 carb the easiest way is to "tee" off the vacuum line that goes to the vac adv can on the distributor.
make sure it's idling at correct idle speed (800-900rpm on an L76).
Turn the idle mixture screw all the way in until it just lightly touches the seat than back it out 1.5 turns as a starting point.
Now, adjust the idle mixture screw slowly, no more than 1/4 turn at a time and let the motor stablize for 15-30 seconds before reading the gauge. Your goal is to get the adjustment to achieve the highest steady vacuum reading. Make an adjustment, let it stabilize, read the gauge, than repeat. keep doing this until you get the best reading.

For the timing, make sure dwell is set at 30, than with the dialback timing light confirm the timing readings the shop told you. total timing with the Vac Adv hose disconnected and plugged should be 36º all in by 3,000rpm. Depending on the fuel you can get in your area you may be able to bring in the timing a bit sooner, somewhere between 2500-3,000rpm. The factory curve on the L76 had the total timing all in by 2,350rpm but on most fuels available today it's doubtful you will be able to bring in the timing that quickly without getting some detonation.
If the shops set up is really 12º initial, 36º total with the Vac Adv can disconnected and plugged and the timing is all in somewhere around the 3,000rpm range, give or take, than it's set up fine.

BTW, if the sound from the exhaust is like a fluttering sound (you said sounds like underwater) it may be the intake gaskets they used when reinstalling the intake manifold. A few years ago when I took my intake off to clean it I reinstalled it with gaskets that closed off the internal intake crossover ports (don't drive the car in the winter so didn't need the crossovers to help warm up the motor - I also replaced the heat riser valve with the spacer unit for the same reason).
Doing that created a big "fluttering" sound thru the exhaust that I hated. No affect on performance but i hated the sound so I ended up pulling the intake off again and replacing the gaskets with the original style with the open crossover ports and the annoying fluttering sound went away.
You may want to check with the shop that rebuilt your motor and ask what type of gaskets they used.
Here are images showing the differences in the two styles of gaskets:

open crossover port gaskets:


closed crossover port gaskets:

Kurt G.

Thanks again for ALL the great info......I'll see if I can give it a go....

Frankie the Fink

If the sound created by blocking off the intake crossover ports bothers you that much (sometimes described as two Harleys chasing each other down the street); you can install a crossover pipe to reestablish the harmonics and restore the classic vette sound - that is what I did:

BarryK

yep, definitely a good option there to solve that problem. I'm not sure how difficult, or even possible it would have been in my case with sidepipes though.
I just found it easier to reinstall the gaskets with the open ports

jimgessner

Start from the beginning. The timing advice is all very correct and should be performed. Your distributor ADVANCE may be not set up correctly, especially with the PORTRONIX.

Your camshaft 'may' be installed incorrectly and valve lash not set to correct specs.

You engine rebuilder should have all those specs.

Don't be affraid to take the car to a POWER TUNE UP SHOP, that can put the car on a their Dyno where they can check everything, including emmisions.

Hate to say it, but if the wrong oil was used in the engine, you may have wiped out a lobe on the camshaft. Not uncommon these days with the new oils for new cars DON'T meet old car specs.

365HP engines run like naked apes ! They were the strongest of the 65 solid lifter engines.......even more than fuel injection. And I love fuel injection

toddalin

They brachiate?

Kurt G.

Thanks again.. Penn Grade Zinc Phosphate break in oil was used to break in the cam on initial start up, that real runny stuff. What should my vacuum be and what is the CORRECT valve lash? or does that vary with the cam? Thanks...

BarryK

if you are running the factory 30-30 cam the vacuum level should be approx 11"-13"Hg range.

for adjusting the valves, see this tech article:
http://www.lbfun.com/warehouse/tech_...n/SBvlvadj.pdf

GCD1962

If you have a heat riser make sure that it is not stuck in the closed position.

Kurt G.

Thanks all.

Kensmith

Kurt,

If you have the true 327/365 motor with dome pistons be careful with 36 degree advance. You are in California and you are restricted to probably 91 octane. You might get some pinging/detonation. My mechanic had to back off my timing to 34 degrees due to pinging under load.