Hello All,
I bought a SP383 crate engine directly from the Chevrolet Performance parts center 4 years ago and installed it in a 1970 chevelle. I’ve had nothing but problems with the new EFI and functioning of the engine (backfire, rough idle etc). I’ve had it to a few shops and got the efi tuned directly from holley twice. Nothing like new wires, plugs etc helped fully.

After sitting on and off for long periods of time with no solutions I found another shop who found a vacuum leak from the factory installed manifold and upon removal found that the wrong gaskets were used when chevrolet installed the manifold.

I’ll be calling them tomorrow but has anyone ever dealt with anything similar to this? Or know what sort of action could be taken?

 

Did you contact Chevrolet Performance about this like you said you were going to? I'd be curious if they gave you any kind of answer or help? I purchased a new engine from Blueprint a 350-365 HP completely built with everything. All except the flywheel. They dynode it at 381 HP. When I put it in my 85 Choo Choo El Camino SS it ran good but I didn't care for the carburetor they used. I took the hit buying a Holley EFI converting everything to fuel injection. The engine ran good before, but the Holley woke it up.

I've used Chevrolet Performance engines before putting one in my 77 Corvette. It was a 350-300 HP. I can't remember if I installed the intake or not? But one thing I seem to remember is the engine was assembled in Mexico? Luckily I didn't have any issues with several Chevrolet Performance engines I've used in the past throughout the years. But I know it's disheartening to find out a simple mistake by whom ever assembled your engine caused you so much grief!

If you can let us know what came out of your conversation with Chevrolet Performance. Hopefully they didn't say, well you bought the engine 4 years ago?

Good Luck! Now you know what the cause was. Go out and have some fun.