[TimBW]

Hello from the UK!

I've got a 68 firebird with a 1970 455, and a new set of round port eheads waiting on a shelf.

The 455 had a full rebuild 10 years ago, has:
- a HFT comp cams 280h 230/230
- 4x heads
- performer intake
- 750cfm edelbrock carb (carter)
- stock pan
- stock bottom end (nothing trick)
- Mallory HEI ignition.
- Comp roller rockers.
- Rusty old 1 3/4 headers.

Has been running great with a m20 muncie since the rebuild.

Right now the engine is out the car for a clutch and engine bay repaint. I've been collecting new speed parts (as everyone does I'm sure) and was thinking of throwing on:

- MSD ignition + 6AL box
- Performer RPM intake
- 750HP double pumper
- MLS .068 cometic head gaskets.
- APR Head studs
- round port eheads
- dougs 1 7/8 ceramic headers.

If I turn the RPM limit down to 4k for example do you reckon it'll be okay to run for the meantime to get the car back on the road?

Street only car, no track work.

Am I being crazy? happy to hear your thoughts!

[78w72]

a good but stock rebuilt bottom end will do fine on the street with E-heads or any other head. keeping the RPM lower within the range of the smaller cam will ensure it will live a long life.

forged rods etc are great & probably needed for high HP or race type builds, but guys used stock cast rods & cranks for decades making pretty big power & turning well above 6000 rpms.

i had a stock bottom end 455 for almost 10 years in a 78 t/a as a kid in highschool & into my 20's, i beat the living crap out of that car on a daily basis, countless 6000rpm runs racing anything that would race, pulled the engine after crashing the car & the internals looked very good still.

if the rebuild was done right, it should be fine, even above 4000 rpm.

[JLMounce]

I have KRE D ports on top of a basic build 455. Stock crank, rods and Speed Pro pistons. Nothing crazy about it.

I beat the snot out of this thing and I haven't had a lick of problems with the rotating assembly.

[ta man]

I had 2 stock bottom end 455 shortblock's (other then rebuilt with new pistons). Zero issues for years, many dragstrip passes. Even ran into the 10's with one.
Make sure you have a rev limiter! My engine was saved many times with one.
Especially first time out with new heads and cam I was up over 100 hp.
On the street for cruising you will be fine.

[nas t eh]

Oil starvation to the connecting rods is likely your biggest enemy, so 5000-5200rpm is your cut off on a stock oil pump, stock oil pan. The cam will not be making great power by then anyway.

How many miles on the bottom end? If you have ~70,000 miles or more, you may find the new heads pull oil past the old rings making the motor smoke a bit. If it has that many miles I’d be tempted to do rings and bearings.
If the mileage on the motor is rather low, there should be no issues.

[25stevem]

It's been printed that for a Pontiac V8 to go into production the motor had to pass a test of running at 4500 rpm for 100 hours consecutively and then during a tare down only finding what the Engineers considered normal ware.

So, yes your motor will be fine if the rebuild was of a guality equal to factory stock.

[72projectbird]

It'll be fine. The stock bottom ends are plenty strong for what you want to do with it.

Hell I've been dailying a 77 400 4speed TA that's been sitting in the woods for 27 years. I've been power shifting the thing at 5k rpm the whole time lol

[NeighborsComplaint]

If you set a 4K rev limit, you might as well go back to stock and top it with a 2bbl carb. A 5200 rev limit is where you want to be with stock rods and it'll last forever. Your heads are capable of more but you need to protect the bottom end.

[hurryinhoosier62]

The stock cast steel rods will work fine at the power level you are aiming for. If you are planning on going through the engine in the future that would be the time to replace the cast steel rods with forged rods and the cast OE pistons with forged pistons.

[ta man]

Originally Posted by NeighborsComplaint

If you set a 4K rev limit, you might as well go back to stock and top it with a 2bbl carb. A 5200 rev limit is where you want to be with stock rods and it'll last forever. Your heads are capable of more but you need to protect the bottom end.

I set my rev limiter at 5500 no issues..I believe later I had it at 5800

[Skip Fix]

I had a good stock bottom end TRW short block under my RAIV heads that spun 6500 all the time autcrossing and drag racing.

[nas t eh]

Originally Posted by Skip Fix

I had a good stock bottom end TRW short block under my RAIV heads that spun 6500 all the time autcrossing and drag racing.

3” or 3.25” mains?

I’ve lost rod bearings in two original stock 455 engines, just by taking them a few times to 5800-6000rpm.

[25stevem]

Just keep in mind that with cast pistons and how much hotter they run that you do not want to be full throttling on them for too long on highway blast if your motor is built and Cam’ed up like yours is with it making over 400 hp.

Remember that Pontiacs first production usage of forged pistons was in the 69 370 hp RA400 motors !

[JLMounce]

Originally Posted by nas t eh

3” or 3.25” mains?

I’ve lost rod bearings in two original stock 455 engines, just by taking them a few times to 5800-6000rpm.

Just a couple times?

my 3.25" main KRE headed 455 sees 5700-6000 rpm a couple times every time I drive it...a couple times a week.

mostly stockish bottom end. Just a set of Speed Pro pistons on stock rods and the N crank. 60 psi pump

[25stevem]

Loosing rod bearing in 455 motors in which the rods did not break is mainly a oil supply issue, or a detonation issue, especially if it was rod bearings at the front of the motor which get fed oil last.

[Skip Fix]

3.25 main 70 big car short block. Same one with E heads but a dish piston and forged rods in my 78 now. Cast rods did have new bolts and a good balance job. Peak HP on dyno with RAIV head motor was 6100.

[nas t eh]

Originally Posted by JLMounce

Just a couple times?

my 3.25" main KRE headed 455 sees 5700-6000 rpm a couple times every time I drive it...a couple times a week.

mostly stockish bottom end. Just a set of Speed Pro pistons on stock rods and the N crank. 60 psi pump

If you have a good 60psi oil pump, that will make the difference between needing to stop at 5200rpm and being able to go to 6000.

Most or all of the d-port 455s don’t get a very good oil pump from the factory.

[Dragncar]

Most stock type 455s will have the main bearing with a round oil hole. For any kind of abuse, like you might see with a set of E heads and RAIV cam I would want the main bearings with the oil slot at least.
There are 3 holes that intersect in the block and the one on the tab side of the bearing has the shot of oil,
I drill a hole right through my main bearings to give this hole a straight shot. If you do not do this the oil has to hit the back of the bearing, move over and go through the hole in the middle of the bearing.
This equals oil starvation at high RPM to the rods.
Seen a few 455s raced blown up because of this.
A 60 or even 80lb pump will not fix this. Need to drill the hole in the right spot.

[nas t eh]

Originally Posted by Dragncar

Most stock type 455s will have the main bearing with a round oil hole. For any kind of abuse, like you might see with a set of E heads and RAIV cam I would want the main bearings with the oil slot at least.
There are 3 holes that intersect in the block and the one on the tab side of the bearing has the shot of oil,
I drill a hole right through my main bearings to give this hole a straight shot. If you do not do this the oil has to hit the back of the bearing, move over and go through the hole in the middle of the bearing.
This equals oil starvation at high RPM to the rods.
Seen a few 455s raced blown up because of this.
A 60 or even 80lb pump will not fix this. Need to drill the hole in the right spot.

Excellent advice, simple fix, too bad it’s not built into more of the stock 455s in the first place.

[Dragncar]

Originally Posted by nas t eh

Excellent advice, simple fix, too bad it’s not built into more of the stock 455s in the first place.

Thanks, all Pontiac V8s have the issue. Some blocks, aftermarket too you need to grind down the material between the intersecting holes as its too close to the saddle surface blocking oil flow.
Cr@* oiling system like a old Mopar 318-340-360 engine. Whitmore gave me these tips back in the day. He had a book on modifying 340s for NASSCAR racing and applied the info to Pontiacs.