79corvette

After I installed a new camshaft I am having some trouble tuning my engine. It hesitates on acceleration at all rpm’s, from idle to 5000rpm, idle is slightly rough. It also feels low on power. I do not have any of the vacuum accessories hooked up, unless I am sure they are not leaking. I was able to get the engine to idle at 14* advanced. The float level is set according to Lars’ specs. The cam is a Summit Racing cam, specs are: lift .465in both intake and exhaust, duration is 224 for intake and exhaust. The primary jets are size 74 and the rods are stock 40. I also replaced all the ignition components (coil, wires, cap, rotor, plugs). The spark plugs are AC Delco R45TS. I pulled the plugs to take a look and maybe tell if it is running rich or lean. Numbers 4 and 8 appear as though they are very rich, and every other plug looks fine. 2 and 6 looked a little whiter than the others. There doesn’t seem to be any smoke coming out of the exhaust. I also adjusted the valves and checked them 3 times to make sure everything was adjusted, they seem fine. When I drove it, about 15minutes into driving, on deceleration, there would be a very loud popping noise in the passenger exhaust. If I held the gas up while braking and gently brought the revs down, it would not pop. I did notice a huge leak from the head to the headers coming from cylinders 4and 6. I have Vortec heads, Edelbrock Performer intake manifold, 1 5/8in headers, dual exhaust, and the stock Q-jet. I really can’t figure out how to fix it, any help would be very appreciated. If I have left a crucial piece of information out, please tell me. Thanks for the help.

Pete79L82

From the descrption you give, the first thing I would look at is a vaccum leak.

Recheck the carb base gaskets to make sure they are sealing properly.
With the engine running, spray carb cleaner along the top of the intake runners to see it there is a possible vaccum leak there.

Give us a little more backround. Did you just change the cam? Or did you also do the heads and intake and headers? Was it runnung fine before you made these changes?

79corvette

Already changed the carb base gasket. I also changed the intake manifold gaskets. I was really hoping it was a vacuum leak.


I also reinstalled the heads. I had the heads machined to fit the new cam. It was running alright. It would have a slight hesitation sometimes, not what it is now. The previous cam had the exhaust lobe wiped down on the number 1 cylinder. The cam is the only item that isn't the same. Tommorrow I will check to see if the intake manifold is sealed up properly, forgot to check that today.

[Modified by 79corvette, 7:59 PM 3/20/2004]


[Modified by 79corvette, 1:52 AM 3/21/2004]