bundy

I have been reading all I can on this forum and it is great. question I have is:


On my 1971 SX 455 if I have to go thru the motor can I make like it was in 1970 with 365 HP? And if so what would it take?


Thanks for your help.

RROLDSX

I'm curious as to what is wrong with it? If everything is working normally you should be pretty close now?

RROLDSX

Sorry I miss read your post, the biggest difference would be the pistons being a lower compression. Love those SX's.

vette442

If nothing's wrong, it's putting out 320 gross hp / 250 net hp now.

Other guys will know more on the specifics, but compression/pistons are probably the biggest difference in output between the L31 "big car" 365 hp of 1970 and your L32 1971 455. If you want the equivalent of the "base 442" 365 hp found in W32 SXes, then a cam change and a few other upgrades would be in order. You'd want to upgrade the trans to OG specs from OD specs as well to take advantage of the power.

Terry

Fun71

Exactly.

The big difference between the '70 365 HP and the '71 250 HP is the rating system itself. '70 and older used the Gross rating system (blueprinted engine with no exhaust or accessories (alternator, water pump, etc) and running on propane? - anyway a cheater high octane fuel) vs. the later NET rating in which the engine had all accessories installed and ran through the exhaust system. As you can imagine, the later system would give a more realistic, although lower, power rating.

bundy

So are we saying that the 71 is not that much of a dog?


Should I just rebuild it as close to what it was?

oldstata

I am currently getting ready for a rebuild, my advise is if it runs good enjoy it! if it needs work then by all means upgrade pistons rods and cam in the end it's really up to you and what funds you have.
a basic rebuild is around 3k and a performance up grade range from 6k and up as more performance is produced

MDchanic

And, with 1971 as the transition year, they gave both for all of their engines that year, so you can actually compare the different rating scales directly.

According to the SPECS Guide, the L32 455 with dual exhausts made 320 SAE Gross HP at 4,400 RPM and 250 SAE Net HP at 4,300 RPM.

- Eric

Fun71

Here's a story from my past that may help:

I had a '70 Supreme with a 350-4bbl (310 hp) and 2.56 rear gears that ran really well. My friend had a '71 Supreme 350-4bbl (200 HP) with 2.56 gears. So essentially we had the same thing, except I had 110 HP on him, right? From a dead stop, the cars would run side-by-side until the top of first gear, where I pulled away slightly.

So yeah, the '71 lacks a bit of compression vs. the '70 but everything else is so close I would call it the same.

Yes and no. If you are doing a rebuild then DO NOT build it with deep dish 8.5:1 pistons and the lame cam those factory engines had. Those two things are all you really need to change, though.

507OLDS

If you rebuilt it,it would be hard to not make more power with it.Even a mild build will give you more power than it ever had.

bundy

Thanks Everyone !


I'm pretty sure I'm going to have in rebuilt. It has been setting in the desert for 15-20 years, frost plug is out and the distributor was popped up.


Should be getting to a shop by Monday and then I will know more.