Like the title says -- say you took a completely stock LT1 and slapped on some heads with decent flow (say 280cfm@.500 lift for arguments sake). What sort of things would you be giving up from the stock performance level -- i was thinking maybe some sort of loss of fuel economy or maybe low end torque. Any ideas?

 

you wont give up anything unless the porter doesnt know what he's doing in terms of target port cross section. you would really need a more aggressive cam with the heads to pick up a lot tho.

 

Right, i understand that the stock cam wouldnt really make good use of the heads.

But what sort of things would you give up?

 

if the heads are done right nothing. if they are to big in terms of port cross section for the displacement youll give up some torque. there are enough good porters out there that can make an LT1 head flow 280 w/o giving up anything.

 

Wouldn't it increase MPG since the engine would be more efficient? A good CAI, and exhaust can increase MPG.

 

Put some 1.6RR's on it and let it fly and a thin gasket. Ya might be surprised at the increase in power up high.

 

I think you need the whole package to make the heads work properly. Like headers, cam and exhaust. If you don't have that you have restrictions of flow of your air/fuel going into and coming out of your engine. Those stock lt1 manifolds are more of a problem on the lt1's than say ls1's.

 

Neg, with bigger ports you'd have less air velocity down in the lower RPM's, therefore less power...therefore crappy MPG

 

if it had less port velocity then the ports are too big. and you can actually have a big port and have port velocity. but i dont want to divulge any secrets.

 

On a basically stock Lt4 with the exception of long tube headers and dual 3" exhaust, I went from 331 rwhp to 363 rwhp by just adding a set of GTP LT4 heads that flowed 282 @ .600. Still stock cam, etc.

Should of left the damn thing alone after that.

 

i hear ya!!

 

what do you mean???? whats wrong with it now..... did you ever get any track #'s with just the heads.......

 

Way too much of a story to post. Let’s just say my wallet would be thicker and I’d look 10 years younger if I had left it alone.

With the car making 331 rwhp I ran a 12.65@ 112 mph with a 8.19 1/8th on street tires. Now this is with a 96 Vette and they tend to hook better with street tires. After the heads and the additional 30 hp, I only picked up another 10th in the eighth. Should have been a little more of an improvement and I didn’t make it to the 1/4th mile as we started redoing it. So……… whatever?

With an additional 46 cubic inches, solid roller cam, 125 hp nitrous and a set of Street Et’s it ran a 6.83 @ 105 mph.