I'm trying to figure out where the 45hp comes from.

Heads, cam, intake, timing set...what else is different?

 

Here the flow info http://www.malcams.com/legacy/misc/headflow.htm plus at the bottom is more LT1 - LT4 compare info.

 

The extra power comes from heads, intake, cam, timing set like you said. Also, the Knock Module and the programming of the computer are different. the LT-1 block is a 2-bolt main, the LT-4 is 4-bolt main, but that has got more to do with the strength of the block than hp. If you are talking about LT4s in Vettes, then some of the extra power also comes from the true duals that the vettes have.

 

I would be port-matching the intake to any heads I do, and I am doing a Hot Cam.

Can I get as good or better numbers from a well-ported set of LT1 heads over a well-ported set of LT4 heads?

 

If you do a good job at it, I don't see any reason why you shouldn't get as good numbers from the LT1 heads. With the hot cam + ported polished heads, you are looking at about a 100hp gain.

 

the pcms are the the km is not going to give you anymore hp power unless you do headers and the hotcam and lt4 heads will not give you a hundred hp. it would take ported heads lt1 0r lt4 and a bigger cam (bigger than the hot cam.

ported lt1s are better than stock lt4s but ported lt4s are alot better the ported lt1s and there are alot of differences in the heads just as stock.

 

The main difference between the LT-1 and LT-4 heads are the LT-4's have raised intake runners and "D" port exhaust. This is why you need the LT-4 intake manifold to match the heads.
If you haven't purchased the parts yet both GM Parts Direct and PACE have LT-4 conversion kits at resonable prices.

 

I don't know about the whole LT4 conversion, I don't think it is worth the price. For the same money, get your LT1 heads ported and polished, get the HotCam (or something bigger if you want to) w/1.6rr, and you will see very nice gains. I did the HOtCam w/1.6rr / ported+polished heads combo to my 1997 Z28 M6, and it is like day and night. Incredible gains for the money. Now if only I can find a way to get better traction.....

1997 Z28 M6 30th Ann. Ed. White/Orange Stripes
Moroso CAI, POrted and polished heads, LT4 HOtCAm w/1.6rr, Heavy Duty Timing Chain, LT4 KM, SLP Headers, !Cats.

 

Actually the LT4 has 10.8-1 cr where LT1 has 10.4-1 the LT4 heads have 2.0/1.56 valves and flow 250@.500 I/185@.500 E and LT1 has 1.9/1.5 valves and flows 215@.450 I/170@.450 E plus LT4 has bigger cam and 1.6 roller rockers.
So it's a combination of more compression, cam and head flow that gives it the extra power over the LT1.

 

Well, I gotta ask:

Money is no object, and you are doing a 355 s/c. Ported LT4 heads?

 

Here's a link to LT1 vs. LT4 comparison. . IT will give you some more accurate info on head flow, valve sizes, etc.

 

Thanks for the link injuneer, lots of great info.