Pontiac 400 cam recommendation - Chevelle Tech
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post #1 of 17 (permalink) Old Jan 21st, 20, 7:00 PM Thread Starter
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Pontiac 400 cam recommendation

A friend of mine has a 67 Firebird with a Ram air III 400 motor. (360hp stock)

Apparently it has some rare RA III heads as well, but I don't know anything about them, trying to get some casting or code info.


The motor is torn down for a mild redo- apparently it still has the original RAIII cam in it, but the pistons were changed out years ago for low compression slugs. He's having new ones installed to bring the compression back up to around 10:1.


The shop is telling him he should reuse the stock cam, I'm suggesting him to go with something better/bigger, I advised the Poncho version of the Lunati Voodoo 03 cam I've run in my current 454 and my previous olds 455.

The shop suggested a Comp Magnum 270 if he has to change, though they recommend against it...

The car has 3.08 gears and an automatic, and RAIII reproduction manifolds, and the RAIII heads.

He is looking for this to be a street cruiser, with lots of low end for fun... not planning to ever race it.



Stock RAM AIR III Cam

Advertised Duration; 301/313

Duration @ .050; 224/236

Lift With 1.5 Rocker Arms; .408/.407

Lift With 1.65 Rocker Arms; .449/.448

Lobe Separation Angle; 115.5

Intake Centerline; 112.5





Comp Magnum 270H

Advertised duration 270/270

Intake duration @ .050 224

exhaust duration @ .050 224

Lift .476 / .476

110 LSA

1800-5800



Lunati Voodoo 03

Advertised duration 268/276

duration @ .050 227/233

Lift .489/504

LSA/ICL 110/106

1600-5800



Looking for others thoughts and suggestions. He needs to tell them what he wants to do in the next few days.

Thanks-
Ben

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post #2 of 17 (permalink) Old Jan 21st, 20, 7:22 PM
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Ram Air cams were treasured,
but not much cam from anyone
gonna work with that 3:08.

RA IV Muncie,
Enjoy !
(Check out timing &#x1f601;<img src="https://www.chevelles.com/forums/images/smilies/wink.gif" border="0" alt="" title="Wink" class="inlineimg" />

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post #3 of 17 (permalink) Old Jan 21st, 20, 7:39 PM Thread Starter
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Re: Pontiac 400 cam recommendation

Trying to get him to send me his build sheet. It "may" have the 3.23 rear gears since it was a 360hp car from the factory

Ben R.

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post #4 of 17 (permalink) Old Jan 21st, 20, 8:06 PM
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IMO needs 3:73 or 4:11
with 14” or 15” tires

350 THM with shift kit, headers and RA IV cam will be fun ! Posi is a given. (So is Holley). &#x1f601;
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post #5 of 17 (permalink) Old Jan 21st, 20, 8:44 PM
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Re: Pontiac 400 cam recommendation

That's the specs for the 744 RA2 cam.. It never worked out to well.. Those .050 nubers ar way too much for that motor and 3:08. I like the 3:08 with a turbo 400.

I'd keep the compression around 9 and run the Summit 2801.. Or raise the compression to 10 and run the 068. Nunzi had a strong version of the 068 but finding one would be hard..

Pontiacs do not like a lot of duration, the heads have excellent velocity unless somebody when grinder crazy and ruined them. They really don't need much to work well.. Just follow what Pontiac did, short duration wide lobe separation... The 288/302 always worked so nicely in them..
If you lower the compression to 9 and use the 2801 cam. You can raise the initial to 18-20, lower the mechanical to 12-14 an take the vacuum out, that 400 will haul... Just run a nice Quadrajet or even trips.. Two Carter AFBs also work well (not those cheap Edelbrock carbs)..
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post #6 of 17 (permalink) Old Jan 21st, 20, 9:10 PM
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Re: Pontiac 400 cam recommendation

I know that Pontiac's use a 30° valve seat. You could change to a 45° and pick up some top end power but you may loose it down low as a result of that change. Might help with with the camshaft change though. There was a write up over on Speedtalk about Pontiac heads that was pretty good.


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post #7 of 17 (permalink) Old Jan 21st, 20, 9:36 PM
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Re: Pontiac 400 cam recommendation

Quote:
Originally Posted by 68Chevele View Post
I know that Pontiac's use a 30° valve seat. You could change to a 45° and pick up some top end power but you may loose it down low as a result of that change. Might help with with the camshaft change though. There was a write up over on Speedtalk about Pontiac heads that was pretty good.
Yes, I would change from the 30 degree intake seat. I would change to a 38-45-60 intake seat. I don't know the shops capabilities and not much about Pontiacs but I think the stems are 3/8's. Changing the seat and keeping the valve depth should not be a problem if the shop has a Serdi or similar valve shop. He could have the guide liners put in to convert the valve to 11/32 and run a lighter, larger valve. It should not be too much trouble finding the right length with all the offerings today. The increased angle lets the engine "see" less duration at the lower lifts and has the same effect as a slightly smaller cam with better flow at the higher lifts.

I run a generic 214/224-112 summit cam in a 350 with a powerglide and stock converter. It is about the limit I would go with duration wise although the 400 deals with more cam better than a 350. I have 3.08 gears and the cam cruises great and gets very good fuel mileage. The glide doesn't have the leverage of a three speed on take off but its ok for a senior citizen to drive.
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post #8 of 17 (permalink) Old Jan 22nd, 20, 12:29 AM
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Re: Pontiac 400 cam recommendation

I hope he is getting the heads ported .
I have seen pontiac heads a few times and they could use porting to make power. those huge valves do not move the air like you would think they would.

I have ran the 270H in chevy small blocks and it will make excellent power.. more than the generic 224-234 on a 112 lsa cam.

I wonder why the low lift ..you could have that 270H ground using a SBC master and have .517" lift and duration would be about 227 @ .050.
Would make a nice one.

Buddy ran 6X heads with 2.11-1.77 valves and 8 eyebrow pistons in his 400. ran a [email protected] .050 cam .495" lift 110LSA 6 degrees advanced.
It pulled hard to 6500rpm.
But was not quick as he had a 3840 LB Trans am and 2.41 rear gears.

That same car today has a 350" chevy with flat tops .005 above the deck ported 993's and 268H cam.
It will run circles around that 400" pontiac engine.

I always told him Port the heads.

You don't want to be beat by a SBC ..Port the heads.

As far as paper specs the voodoo cam above does not look too bad.
But the added exhaust duration could cause more overlap than the 270H and hurt MPG..I could pull 15 MPG with the 270H in a 350" with spirited driving tossed in and it liked to be shifted at 6900rpm. Ported heads of course 1.94-1.50 valves.

I also think the Ram air heads in 1967 were 670 castings and the ram air heads had the 2.11-1.77 valves and screw in studs not pressed in.

Correct me if I am wrong.
You can still have 670 casting and pressed in studs but those are not "Ram Air"
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post #9 of 17 (permalink) Old Jan 22nd, 20, 12:33 AM
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Re: Pontiac 400 cam recommendation

Here is a bit of reading with castings on poncho heads.
Ron's Pontiac Page: Stock Pontiac Head Specs
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post #10 of 17 (permalink) Old Jan 22nd, 20, 12:34 AM
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Re: Pontiac 400 cam recommendation

RA III heads were from 69-70, either #48 or #12. Pontiacs used 11/32 valve stem diameter. They are essentially The same as HO D port heads from same era. Unless you rework the ports, moving from a 30 degree intake to a 45 will cost flow down below .400 lift. Unported Pontiac d port heads don’t flow much above .400 valve lift stock, the GM Pontiac engineers knew this. Pontiac always used a flattop piston and changed compression with larger combustion chamber heads. #12 or #48 d port RA III heads were really only 9.8 to 1 not the factory rated 10.5 or 10.75 compression ratio. I’d run a factory S cam equivalent in a hyd roller, just because I hate flat tappet cams.

Over camming a Pontiac is far too easy. A good strong Pontiac 400 with a factory S cam and a good q jet will pull hard from idle to 4800. Perfect for the street and your buddy’s 3.08 gears. Have your friend upgrade the valvetrain to zero lash and not the factory jambnut that is torqued to 20-25 ft lbs. just replace the stock Pontiac bottle neck 7/16 rocker studs with std BBC 7/16 studs and stock style 7/16 self locking nuts. You can reuse the stock Pontiac rocker arms, and then zero lash any hyd cam like a Chevy.
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Last edited by fr8dog; Jan 22nd, 20 at 12:51 AM.
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post #11 of 17 (permalink) Old Jan 22nd, 20, 10:55 AM
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Re: Pontiac 400 cam recommendation

Without lowering the compression, going to a modern design like Comp Xtreme Energy or Lunati Vodo is not really the right thing to do. A flat-top piston with the 72cc chamber heads is 10:1 compression on an old chamber design that likes a lot of timing. My son now has my 1969 Grand Prix that has the Ram Air III cam for an automatic trans with the stock #62 - 72 chamber heads - it requires pump premium plus Lucas Octane Boost, it runs hard and a lot of cars have a hard time keeping up on a straight road! Putting a cam in that built more cylinder pressure would be best with a dish piston lowering the compression. Rear gear is somewhere around 3.3 and the car gets high teens on the road with a TH400 if you are light on the right foot.

Pontiac had two Ram Air III cams, the 744 for manual trans applications (the specs you have above) and the 068 (or "S" stamp) which had .050" figures of 212*/225. Pontiac limited the lift to .407" because their standard heads did not flow beyond that point. Unless you step up to Ram Air IV or aftermarket heads, I would recommend the 068 cam which Crane makes a duplicate of the original.
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post #12 of 17 (permalink) Old Jan 22nd, 20, 3:51 PM
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Re: Pontiac 400 cam recommendation

Stock torque convertor? If so, Summit 2801

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post #13 of 17 (permalink) Old Jan 22nd, 20, 4:16 PM
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Re: Pontiac 400 cam recommendation

FWIW,I wouldn't use a single pattern cam in a Pontiac. There is a reason they have a split from the factory. And I don't know of anyone using a single pattern in any of the Pontiacs that run in our SuperCar class.
And these cars get street driven. And run 12's on bias ply tires with exhaust manifolds.
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post #14 of 17 (permalink) Old Jan 22nd, 20, 5:16 PM
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Put a Mac McKellar #10 in it &#x1f44d;

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post #15 of 17 (permalink) Old Jan 22nd, 20, 5:18 PM Thread Starter
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Re: Pontiac 400 cam recommendation

Some pics he took today while at the builder.

He is NOT working over the heads, and he is NOT going with performance gears.
A different converter is no big deal to add since the engine is out, but as i said this is a cruiser- not a race car, does not need to see major HP.

I suppose what he is looking for is a step or two better than stock performance wise...
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