Corvette Forum : DigitalCorvettes.com Corvette Forums banner

1 - 7 of 7 Posts

·
Registered
Joined
·
5 Posts
Discussion Starter #1
So here is my problem. I have a 1970 4-speed with the middle hp motor 350/350. I blew up the original motor, but happen to have a almost exact same thing engine in a old truck of mine. The truck motor was originally out of a 70 full size car (can't remember model) but it had double hump heads so we had the engine rebuilt with a lt1 cam installed 10.5 pistons at 30 over. Anyway this motor in the truck ran great and it was a big truck! So blew the origninal vette engine swapped in this motor that was fairly fresh (less thank 10K on it) I used my original vette intake carb, exhaust mans and all the assesories so everything looked right and fit.

So here is my prob. The thing just doesn't run like it did in the truck. In the truck it would pull all the way up to 5500 or better, but in the vette it seems like it dogs out at 3-3500rpm. The only difference between when it was in the truck and now the vette is the intake, they used the same carb, and ignition. In the truck it had electronic distributor, and in the vette it has the old points dist.

O my question is whats the best way to go to upgrade my ignition? It kills me that I think it ran harder in a lifted 83 3/4 ton truck than it does my little 1970 vette with a close ratio 4-speed.

Thanks ahead of time guys!
 

·
Registered
Joined
·
3,808 Posts
I would put the original intake and distributor back on the engine.
It ran great with the original parts, but not with the old corvette parts.
 

·
Registered
Joined
·
1,845 Posts
You need to make sure everything is right with this engine. Swapping intakes isn't going to help if the timing chain is not set up correctly, the cam is not installed at the correct location (degree-wise) or the timing is wrong, the point gap is negligable, etc. Something is not right. Did the truck engine have a solid-lifter LT-1 cam in it?

I would check the timing (initial and total) first. A points-type distributor should work fine, they just need more attention. I would check the dwell angle/point gap. Basic troubleshooting is needed first.
 

·
Registered
Joined
·
3,100 Posts
:agree:

If there's a problem with the advance curve, that will cause the performance to be down. (Could even be the reason the original engine in the Vette let go!)
 

·
Registered
Joined
·
5 Posts
Discussion Starter #5
Dad is looking for the dist out of the truck we have it somewhere, its been a few years since this swap took place. But that was what I was thinking of trying first.

The truck motor does have the lt1 with solid lifters. But the cam and timing chain were never removed when we swapped motors so that shouldn't be an issue.

My guess is its not advancing like it should hence the loss of performance at higher rpm.

And the reason or at least what happened to the original vette motor was a connecting rod end cap broke in two and then the end of that rod went out the side of the pan and also knocked a hole in the block water jacket!

I was heading to town and it started knocking, so I turned around and tried to limp home. Should have just shut her down! Lessons learned at 18 are hard ones when your baby breaks! That was 11 years ago!
 

·
Registered
Joined
·
3,100 Posts
Good place to start..

Also check the valve adjustment- if that's off it could also cause your low power. The LT-1 was pretty strong if all is right.

I adjust my valves- Fully warmed up, shut off, the pull one rocker cover. Set the intake as the exhaust opens, exhaust as the intake closes. I've set them from .024 to .030 and can't really tell much difference. Put that rocker cover back on, warm it up again and do the other side. It takes 2 people (one to adjust and one to bump the starter) or a remote start button. (I have one permanently wired in).

Also set your timing so you have 36* at 3000 RPM, mechanical and initial, no vacuum. Get to the 36* at 3000, and just let the intiial fall where it wants to at first, then see how it cranks when it's hot. IF it cranks OK, leave it there, if not, back it up a little and try again. Then work the mechanical stop to get back to 36.
 

·
Registered
Joined
·
1,845 Posts
You answered (eliminated) alot of questions with your last post. Could be that the advance mechanism is bound up and not moving or only moving a few degrees worth and you are just way down on the timing.
 
1 - 7 of 7 Posts
Top