Power difference between stock 1969 396 vs 1972 402?

[jumpsoffrock]

I'm just asking this as a random curiosity.
Because they had EPA regulations and changed from Gross ratings to Net ratings, is there a real tangible power or performance difference in these two engines if they were factory stock, hot off the assembly line? Was the 1972 version actually detuned?

Could a 1969 truck be able to pull more weight and faster than a 1972 truck with the 402?

[72c20customcamper]

Object of going to 402 was to avoid detuning and emissions . All engines over 400 ci had less requirements. I dont think you would notice a difference between the two. Even AMC made the 390 into a 401 .

[davischevy]

Mark is right, and there is no way to get either of them to run like a big block Chevy should without changing heads.

[jimijam00]

Originally Posted by davischevy

there is no way to get either of them to run like a big block Chevy should without changing heads.

500hp was easy to achieve on the L78 with just a cam, manifold, headers, and a carb tune.

[davischevy]

Originally Posted by jimijam00

500hp was easy to achieve on the L78 with just a cam, manifold, headers, and a carb tune.

Yep, one of my favorite engines, but those square port heads weren't really ideal for everyday driving in a truck. They were designed for higher RPM.


I used to watch a 69 Chevelle SS with the setup you speak of, running a class called showroom option, pull the left front wheel off the ground one every run.

That Chevelle is still around with the original engine in it.

[72c20customcamper]

Originally Posted by davischevy

Yep, one of my favorite engines, but those square port heads weren't really ideal for everyday driving in a truck. They were designed for higher RPM.


I used to watch a 69 Chevelle SS with the setup you speak of, running a class called showroom option, pull the left front wheel off the ground one every run.

That Chevelle is still around with the original engine in it.

Ya they didnt run like this stock
https://m.facebook.com/story.php?sto...09713&sfnsn=mo

[special-K]

The light truck 402 was an L-47, rated at 310hp 70-72. The '69 396 was an L-66 also rated at 310hp

[davischevy]

The 402 in my Longhorn got tired. I could have built the 402, but it costs the same to build a 454.

We bored the 454 .040, used 781 heads and installed a full roller valve train. It idles smooth and has tons of torque. Now it breathes free. It no longer feels "smothered".

[jumpsoffrock]

^^^^.....And see, how will that much power be if my truck has an sm465 and 4.10 gears(she's a 1 ton) and I plan on daily driving it in the rain.
Would your kind of torque be usable in that situation, or a hazard?

I bought this truck to use as a work truck that I can/will daily drive.

I'm afraid of spending 2-3k on building an engine and ending up with a useless "work" truck that won't keep traction without a ton in the bed.
I was hoping to build a 502 if I decided against reusing my 402.

[kwmech]

Originally Posted by jumpsoffrock

^^^^.....And see, how will that much power be if my truck has an sm465 and 4.10 gears(she's a 1 ton) and I plan on daily driving it in the rain.
Would your kind of torque be usable in that situation, or a hazard?

I bought this truck to use as a work truck that I can/will daily drive.

I'm afraid of spending 2-3k on building an engine and ending up with a useless "work" truck that won't keep traction without a ton in the bed.
I was hoping to build a 502 if I decided against reusing my 402.

I'm running a 465 with an AA Ranger Overdrive, 3.73 gearing and a power-loc. does not feel like it wants to get away from me unless I want it to. I am actually restricting it some with a 650 edelbrock. I have a 750 on my flatbed and it will lite up the duals from a standing stop with a T400 and gear vendor

[Accelo]

"is there a real tangible power or performance difference in these two engines if they were factory stock?"

Max is 6hp, if they made 1ph per cubic inch which they didn't .
So I'll give it 4 to 5hp difference. Or 1.3% if you use the 310hp rating.
Withing the margin of error on most dynamos.

[davischevy]

Because I didn't want to run a stall converter in the 700R4, I didn't put a lopey cam in mine. It idles smooth as silk. Running 3.73 gears, it doesn't feel finicky at all.

If you stand on it it will get out of the way.

[geezer#99]

Buddy of mine had his ‘74 Chevy ugly truck’ (his name for it) set up with a 12.5 to 1 454 with rectangular port heads and the old LS7 cam. Ran a turbo 400 and 4.10 gear. It got on the cam and really started to haul the mail at 3500. Pulled his fifth wheel holiday trailer.
Surprised a lot of folks when he’d pull out to pass uphill.

[davischevy]

My Longhorn has a 454, now it needs a posi trac.

[davischevy]

We have a late 69 dated 412 LS6 block in the storeroom. I don't know what happened to the heads.

A friend of mine bought a new 70 El Camino LS6. This engine came out of it. I wish I had the car. He special ordered it hugger orange.

[jgr]

basically, it is the same motor you would not notice any difference between the two. both are awesome motors. There is nothing like a BBC you will never go back to a small black LOL