[racerboy]

Hi Jay
I don’t know how much power. I was hoping to get on Paul’s list to have him do my #12 heads. As I mentioned already, it will have a 4.00 stroker crank. I am having the block done again with a torque plate and I think the bore will be 4.156 (I think Paul can source me custom pistons for that bore). I haven’t decided on a cam yet, and will definitely be asking the team here for input, but was initially leaning towards SD Performance Stump Puller HR cam. My carb was done by one of Cliff’s former employees, and he also opened up the plenum on a stock ‘70 intake for me. For exhaust, I have the factory RAIII manifolds. I was thinking maybe 425-450 hp with this combo? No idea how accurate or far fetched that number might be.


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[Jack Ferris]

Off the subject a little but, what are you going to use for a crank? I want to do the same thing with my 70.

[jhein]

Seems like 425-450 hp should be pretty easy. There's an old article out there that I'm sure everyone has seen which I recall demonstrates that a totally stock RA III build will get you 400 hp and a stock RA IV will get you 425 hp. I find that really interesting because the main differences would be the cam and the better flowing heads in the RA IV. Seems like a pretty small increase in power to me for those changes. Regardless...

If you're going with a 4 inch stroke, ported #12 heads, then all you need is at least a RA IV-ish cam and you're there.

[Ramairnacho]

Originally Posted by jhein

Seems like 425-450 hp should be pretty easy. There's an old article out there that I'm sure everyone has seen which I recall demonstrates that a totally stock RA III build will get you 400 hp and a stock RA IV will get you 425 hp. I find that really interesting because the main differences would be the cam and the better flowing heads in the RA IV. Seems like a pretty small increase in power to me for those changes. Regardless...

If you're going with a 4 inch stroke, ported #12 heads, then all you need is at least a RA IV-ish cam and you're there.

When I take my engine out I hope you guys will help me too. I just want stock.yz with 12 and lower compression ratio to run on today's has. All stock components. I hope there's a trick to get close to 400hp.with 68 style cam. And bored over .20

[jhein]

Originally Posted by Ramairnacho

When I take my engine out I hope you guys will help me too. I just want stock.yz with 12 and lower compression ratio to run on today's has. All stock components. I hope there's a trick to get close to 400hp.with 68 style cam. And bored over .20

Well, that's above my pay grade. Now you're talking about a 400 cid motor with iron heads, pump gas friendly compression and a 068 cam that will still make 400 hp.

Don't know about that.

[Formulajones]

Originally Posted by jhein

Well, that's above my pay grade. Now you're talking about a 400 cid motor with iron heads, pump gas friendly compression and a 068 cam that will still make 400 hp.

Don't know about that.

I'd have to guess that mine is close to that and I haven't done any fancy port work on the heads or intake.

I built mine to run on pump gas and still fit within the PS rules some 25+ years ago. Stock 400 RAIII .030 over with an old set of TRW forged flat tops that I dished slightly to keep compression at 10.13:1 with the stock #12 heads, unported. Today I would have used a more modern ring package, the old 5/64 stuff in the engine now gives up a little power.

It is zero decked, 068 cam, stock manifolds. The rest of it is just years of tuning and racing the car to dial it in. On a chassis dyno it made 301/355 through a 400 turbo and 12 bolt rear using the legal limit 2 1/2" exhaust per PS rules, stock RA air cleaner in place etc.....

It's trapped as high as 106 mph at a 3890 race weight with just a 3.31 gear so it is likely making something very close to 400hp at the flywheel.

If I had to do it over again, I'd run an aftermarket rod in it, preferably lighter weight, and a lighter piston setup with a better ring package. I could probably find a pinch more power in it.

[jhein]

Originally Posted by Formulajones

I'd have to guess that mine is close to that and I haven't done any fancy port work on the heads or intake.

I built mine to run on pump gas and still fit within the PS rules some 25+ years ago. Stock 400 RAIII .030 over with an old set of TRW forged flat tops that I dished slightly to keep compression at 10.13:1 with the stock #12 heads, unported. Today I would have used a more modern ring package, the old 5/64 stuff in the engine now gives up a little power.

It is zero decked, 068 cam, stock manifolds. The rest of it is just years of tuning and racing the car to dial it in. On a chassis dyno it made 301/355 through a 400 turbo and 12 bolt rear using the legal limit 2 1/2" exhaust per PS rules, stock RA air cleaner in place etc.....

It's trapped as high as 106 mph at a 3890 race weight with just a 3.31 gear so it is likely making something very close to 400hp at the flywheel.

If I had to do it over again, I'd run an aftermarket rod in it, preferably lighter weight, and a lighter piston setup with a better ring package. I could probably find a pinch more power in it.

That's pretty darn good. Shows you what I know. I'd have thought you'd have to bring the CR down more than that to keep it happy on pump gas.

[Formulajones]

Originally Posted by jhein

That's pretty darn good. Shows you what I know. I'd have thought you'd have to bring the CR down more than that to keep it happy on pump gas.

Good quench, degree the cam for a certain intake/exhaust lobe relationship, and a sharp tune has allowed it to work on pump gas for years.

I'd say it's not a combination that can just be thrown together without having some things right and then expect it to work. The details are important.

[unruhjonny]

I think this thread is worth mentioning.

LINK

Now, pure stock permits blue printing, and raising compression;
I would think that to achieve 400 hp on a “stock” 70-RAIII (read: 068 cam) that a compression bump would be in order.
(but a not-legal-for-pure-stock displacement increase should negate the need for bumped compression)

I would also guess that if you were running the 67-69 (D-port) “Ram Air” camshaft (744), that you might more easily hit the mark.
It’s my opinion that a 744 cammed Pontiac 400 (with heads along the lines of 31/48/12), is quite possibly the best sounding Pontiac period.

You also may hit the mark easier if you use a more modern camshaft - while not raising attention with the lope of a larger duration camshaft, since members here have achieved this with seemingly “mild” builds, with just strict attention to detail.

[Formulajones]

Originally Posted by unruhjonny

I think this thread is worth mentioning.

LINK

Now, pure stock permits blue printing, and raising compression;
I would think that to achieve 400 hp on a “stock” 70-RAIII (read: 068 cam) that a compression bump would be in order.
(but a not-legal-for-pure-stock displacement increase should negate the need for bumped compression)

I would also guess that if you were running the 67-69 (D-port) “Ram Air” camshaft (744), that you might more easily hit the mark.
It’s my opinion that a 744 cammed Pontiac 400 (with heads along the lines of 31/48/12), is quite possibly the best sounding Pontiac period.

You also may hit the mark easier if you use a more modern camshaft - while not raising attention with the lope of a larger duration camshaft, since members here have achieved this with seemingly “mild” builds, with just strict attention to detail.

I think it could be done without the compression bump that PS allows in the rules. I know I'm close to that HP mark and I didn't use the allowed bump in compression. Mainly because I knew running 1 1/2 points above advertised compression was not going to work with pump gas and an 068 camshaft, not even close. Pump gas was my primary goal with the car so I didn't take every advantage of the PS rules.

So for sure 400hp would be doable with a RAIII 400 using all the PS rules allowed.

It should also be worth mentioning, that these 400's really didn't have the compression they were advertised with. Mine was virgin before it's first rebuild and it wasn't even close to the advertised 10.5:1, it was closer to 10:1 near as I can remember when I tore it down 25 years ago. In fact I've found several different brands of virgin engines since then that weren't close to advertised compression. So actually building them to the advertised compression is a bump in power without even using the allowed 1.5 bump per the PS rules.
That's been my experience anyway.

As far as the 744 cam, that isn't allowed as far as I'm aware, certainly not for the 70 model year so I used the Melling version of the 068 as that one at the time was said to have the most accurate valve events vs other blueprint versions.

The rules do allow, last time I checked, something like a 1% to 2% variation in lift and duration so there is some trickery that can be done if one desired, but the 068 is such a small camshaft, those percentages really don't amount to much of anything anyway. It would become more advantageous starting with an engine that actually had some sort of camshaft to start with if you know what I mean, as those percentages increase exponentially.

You can also do things like play with valve job angles to help flow, or do things like install valves with smaller valve stems etc.... The rules just say "no porting allowed" Lots of little tricks to find a few HP here and there

Even just a good solid basic rebuild with a squared up block and paying attention to little details will make a nice running RAIII to start with, better than the OEM had without any fancy work.

[unruhjonny]

I only mentioned pure stock, because it had been recently mentioned, but since the OP's query was about a numbers 'stock' engine being build for more fun, and then 'Nacho got in on the discussion wanting 400hp while still being pump gas friendly (so no bump in compression, and presumably with a stock crank) then any cam would be fair game.

At least one PS guy has a 067 cam (wink-wink) car beyond 400hp - but if my memory serves me, it's most definitely NOT pump gas friendly;
Smaller cam, better low end torque and higher dynamic compression (I believe that's the correct term)...
Bigger cam, higher (rpm band) peak numbers, lower dynamic compression...

[jhein]

I thought I had read that some very early 70 RA III 4 spds may have gotten 744 cams, don't know if that's true. If so wouldn't that make it semi-legit to use in a restoration type build, at least for a 4spd? Not saying for the purpose of PS drag rules.

[unruhjonny]

Originally Posted by jhein

I thought I had read that some very early 70 RA III 4 spds may have gotten 744 cams, don't know if that's true. If so wouldn't that make it semi-legit to use in a restoration type build, at least for a 4spd? Not saying for the purpose of PS drag rules.

no, early 1969 model year;
Part way through the 1969 model year, all L74/RAIII started receiving the 068;
I believe that I too read that some 1970's received the 744 - but that is just not true.

[jhein]

Originally Posted by unruhjonny

no, early 1969 model year;
Part way through the 1969 model year, all L74/RAIII started receiving the 068;
I believe that I too read that some 1970's received the 744 - but that is just not true.

Ah, early 69, not early 70. Got it. But if you really wanted to make sure you get to 400 hp, then...

[Formulajones]

I mentioned the PS thing because that's what mine was built for, and it nearly meets the HP goal as is, without high compression and using the stock heads/intake/camshaft.

For a purely fun engine, at that point it's fair game. It's easy to far exceed 400hp with a 400 Pontiac, with some mildly ported heads, any cam you want, intake etc... pick your poison.

[jhein]

So I looked around a little and it appears that the 744 cam was used from 66-early 69 then phased out?

Seems like it's the Rodney Dangerfield of cams. Seems underrated and underused?

Also, unless I'm misunderstanding things, a bigger cam will decrease dynamic compression and decrease likelihood of detonation, yes? So a bigger cam allows you to run a higher static CR safely. So if a person was going to run small chamber iron heads then having a bigger cam would help it run on pump gas, yes or no?

[tom s]

We put bigger cams in our engines to make more HP,it comes from loading the cyc better.True it can bleed off compression at low RPMs but will increase it as it goes up so unless your going to idle around dont get into the detonation level in your build.JMHO,Tom

[unruhjonny]

Originally Posted by jhein

So I looked around a little and it appears that the 744 cam was used from 66-early 69 then phased out?

Seems like it's the Rodney Dangerfield of cams. Seems underrated and underused?
...

I wouldn't call it the 'Rodney Dangerfield of OE Pontiac grinds;
It was the biggest hydraulic lifter cam before the 041 came out.

May people smarter than myself say it's just not worth it - they cite the nearly flat lobes, and something to do with the valve just hanging up or something...

But, it's sounds just wonderful.

Originally Posted by jhein

...
Also, unless I'm misunderstanding things, a bigger cam will decrease dynamic compression and decrease likelihood of detonation, yes?
So a bigger cam allows you to run a higher static CR safely.
So if a person was going to run small chamber iron heads then having a bigger cam would help it run on pump gas, yes or no?

That is precisely my understanding.

When I got my car, the engine had previously been rebuilt;
0.030 over, TRW slugs, and an OE "A" cam!!?!
My car ran great, but did run out of steam earlier than I would have thought - this made me feel all the better when I was mid-rebuild (and TOTALLY broke) and looking at getting a better cam for it;
I wanted an OE grind, and nearly bought a 068, but after reading some discussion on the 'Classical Pontiac' discussion board (anyone here remember that one!?; it still exists, but after a couple crashes(?hacks?) this site took over all the traffic) about the 744 grind, I ended up finding one, from a cam grinder that recently closed it's doors (or so the guy who found it for me said).

When I rebuilt my engine I did not port anything, I bought another set of TRW's, and many people said I shouldn't have been able to run on pump gas... but it did - and just fine too.
But the idles would smooth out if I could get a tank of 110 octane aviation gas.

[Jay S]

Originally Posted by jhein

So I looked around a little and it appears that the 744 cam was used from 66-early 69 then phased out?

Seems like it's the Rodney Dangerfield of cams. Seems underrated and underused?

Also, unless I'm misunderstanding things, a bigger cam will decrease dynamic compression and decrease likelihood of detonation, yes? So a bigger cam allows you to run a higher static CR safely. So if a person was going to run small chamber iron heads then having a bigger cam would help it run on pump gas, yes or no?

If you make the cam bigger with more overlap, and at the same time lowering the dynamic compression, (which is what most bigger cams do) you basically are not changing the safe place for detonation. If you want to run more compression you have to move the cam events further apart, opening the exhaust valve sooner, and the intake later, with LESS overlap. The overlap build cylinder pressure. Pure stock you can move the LSA where ever you want, the wider LSA with more compression and less overlap out runs the less compression and narrower LSA most of the time with exhaust manifolds. Not always though.

[jhein]

Originally Posted by Jay S

If you make the cam bigger with more overlap, and at the same time lowering the dynamic compression, (which is what most bigger cams do) you basically are not changing the safe place for detonation. If you want to run more compression you have to move the cam events further apart, opening the exhaust valve sooner, and the intake later, with LESS overlap. The overlap build cylinder pressure. Pure stock you can move the LSA where ever you want, the wider LSA with more compression and less overlap out runs the less compression and narrower LSA most of the time with exhaust manifolds. Not always though.

Thanks for the excellent explanation. Trying to learn...