Richard Cooper

I put a new crate motor in my 81. I also eliminated the computer so I put in a new distributer and carburator. When installed the new motor started right up, but had what I called a "miss". So I checked all the usual causes. I also had a little problem where the car stalled when put in gear.
I finally had enough and brought the car to the local mechanic. He re-adjusted the carburator and this stopped the stalling problem. He said that he could not get rid of the "miss" and it would always be there because it was being caused by the 'mild cam" I had in the new motor.
The new crate motor is a 350/300HP crate motor from Pace Performance. The cam is: Hydraulic Flat Tappet camshaft Intake, lift-443", Exhaust Lift-465", Intake Duration@.050"-214, Exhaust duration@ .050-224, Lobe Seperation-112. From this information can someone tell me if the mechanic was right? Will there always be this "miss"? Thanks in advance and sorry this was so long.

Crash80

When you say "miss" do you mean just at idle, or through the entire RPM range?

Ganey

It’s called a loping idle & normal with more cam, as the intake & exhaust duration is increased the overlap when both valves are open is increased resulting in the loping idle.

A large cam has more.

http://forums.corvetteforum.com/c3-t...t-rodders.html

Richard Cooper

I only feel it at idle. When I give the car more gas it takes off like a rocket and I do not feel any miss.

Richard Cooper

Ganey,
Thanks, I never used this mechanic before and I was wondering if he was B'sing me. I feel better now with the info coming from you and Crash80. Thank you very much for you time and information. Have a great day.

Crash80

Ganey beat me to it but yep, that is normal of your "mild" cam. I put a cam in my 80 and I call it the $1000 idle, since that was about what I sunk into it with the cam and head upgrades. It lopes along nicely but clears right up once the RPM's come up.

Richard Cooper

Guys,
Thank you both VERY much. I have been driving myself crazy for the past 4 weeks trying to get rid of the "miss". Again, thank you.

Ralphbf

That's funny

I just built the 350 in my 75.
I loved the way it loped at idle.
I even lowered the idle so it would lope more.

I got rid of the Q-jet and put on a new Edelbrock carb and my lope all but went away.

Ralph

cardo0

The 260hp crate motor in my vette when i bought it had a tiny miss that i could not tune out. But this was a miss - not a lope. My idle was smooth except for the tiny miss. And it would go away with higher rpm. But i would not say a lope could be mistaken for a miss. A lope will not be smooth at idle but sounds like the engine is laboring to continue to run.
Anyways it proved to be a wiped lobe on #4 exh. And this was a very low time (<30K mi) GM crate motor.

Sorry if this hurts,
cardo0