Differance between 455 and Modified 455 hi perfomance

[fasstjim]

What exactly is the differance between the two motors? Cam, carb, distributer?? Is it a package which includes a trasmission to match, i.e. different governor for shift points?? Did it include different axle ratios like a Riviera GS??
Curios,
Jim :coffee:

[EEE]

Valves in heads for sure, the rest someone else will have to chime in on.



I used a governor from a Corvette in my car, which made it shift at 5k by pure luck, no tweaking needed..

[EEE]

Valves in heads for sure, the rest someone else will have to chime in on.



I used a governor from a Corvette in my car, which made it shift at 5k by pure luck, no tweaking needed..

[Gum,beest]

I am curious myself
Because i have a '73 with emission system and all
it is identified by the "W"in the VIN and the code "XA"on top of the block
It supposed to have 260 SAE HP
The only thing i know is a dual exhaust system
I would like to know what is different compared to other 455's so i won't order the wrong stuff (it happened before and it is expensive on this side of the puddle)
I also have a posi rear but i think that is independent of the Hi-performance engine

[dewbers]

Excellent question... I'm interested as well. There is a wealth of knowledge on here and look forward to hearing what they say on this.

[Smartin]

I have to look it up, but I know it comes with a camshaft that is in between the standard and the Stage1 cam (performance wise). As already stated, the heads are supposed to have stage1 size valves. Rolf's 71 has them, as it came with the High Perf 455 from the factory, and I know for a fact that those heads are stage1 (from the factory).

I have a feeling there was some different carb jetting and possibly a different distributor curve as well, and maybe different transmission calibration.

[Gum,beest]

any difference in compression?
and what would be involved to make it a real Stage one engine
I believe my engine is factory standard as well
Adam remember that there was a small discussion on my engine in the past because it was not mentioned in the books in 73 but in 72 or 71