Stock Fuel Injection and Compression Ratio

[Scott_M67]

My son just bought his first car, a '77 280 that we will be restoring together. We totally gutted and stripped it down to the shell last weekend which was a lot of fun and he learned a lot.

My question is in regards to the fuel injection system on these cars. My plans were to install a little larger cam, I think MSA calls it a Stage 1 cam along with bumping the compression using a new set of pistons, but I could not find much information on how much compression or cam the stock EFI system can handle. The engine has a freshly rebuilt N42 head but it does have the stock bottom end with the dished pistons. BTW, we do not have the budget to install an expensive aftermarket EFI system.

If anyone has experience with this I'd like to hear your comments and suggestions.

[sblake01]

You can bump the compression up somewhat, within reason as you'd want to be able to drive it without need for fuel additives or special fuels but you can't go too crazy with cams on the stock EFI. Vacuum is very important to this system and changes in lift and duration to have an effect on vacuum.

[lmcguffin]

Scott,

Congrats and good luck on the restoration. My son and I recently did the same on a 78. Both he and the Z are away at college now. Took us around 18 months from the time it was parked till he drove it back. However I was working out of town for a good bit of that.

Here's what we did:

N47 block, bored .040 over, flattop pistons

P79 head, shaved ~.030, cam towers shimmed and thicker lash pads

Estimated CR is 9.5:1; shop CC'd the head but lost results :stupid:

MSA Stage 2 cam, stock EFI/ECU, manifold, injectors, throttle, fuel system

Removed EGR and disabled BCDD (check state laws)

MSA 6 into 1 coated headers, MSA 2-1/2" exhaust/dynomax muffler

Car has a nice idle rumble, slightly lopey, starts howling/pulling around 3k rpm. Spits and snarls when you let off the gas. Haven't dyno'd the car, so can't really even guess what the rear wheel HP is. My son told me he hit 90 in 3rd gear, then had up to 136 and got scared. The car prefers 93 octane, but doesn't ping on 91 oct. He can only get 91 oct where he is.

Stock EFI works good; you can flog the car and then pull up to a light and it just idles perfectly. Starts right up, even in subfreezing weather. He wanted carbs but I wouldn't go there as long as the car is his daily driver while at school.

Good luck on reigning in the boy as far as HP goes; seems that is what really matters to them, especially when GT-Rs are 400+ from the factory. You just can't get there w/ a mostly stock L28.

[sblake01]

Car has a nice idle rumble, slightly lopey, starts howling/pulling around 3k rpm. Spits and snarls when you let off the gas. Haven't dyno'd the car, so can't really even guess what the rear wheel HP is. My son told me he hit 90 in 3rd gear, then had up to 136 and got scared. The car prefers 93 octane, but doesn't ping on 91 oct. He can only get 91 oct where he is.

The thing is, my car doesn't spit and snarl when you let off the gas, isn't 'lopey', and is prety close to the performance numbers you mention, although I don't really buy the 136 mph thing, I guess it could happen but I don't drive my car that fast on the street but it will hit 90 in third and does it on 87 octane. Stage two cams are a bit much for a stock EFI L6 engine, like I said earlier. They are vacuum sensitive (hence the 'spitting and snarling') and more cam = less manifold vacuum.

[Walter Moore]

But the spitting and snarling is part of the fun when you are young...

It doesn't get old until you do.

(Which means that for me it was old long ago...)