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Old 03-18-2013, 07:32 AM
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Pontiac 400 Assistance

I am new to Pontiacs but this is what I have and I am trying to find the best heads , cam and such to use on the car.

Car: 72 Pontiac Ventura 2 door
Gears: 3.73 Posi
Trans: TH350 Super Street fighter & B & M 3500 Stahl., trans cooler.
Engine: 1969 Pontiac 400 , heads # 62 1 step up cam ( not sure on duration) Was told motor is bored 0.030 over. Running 104/ 92 octane mix.
1.65 roller rockers, 750cfm Dual Feed Double pump Holly Carb,
Holly Blue elect. fuel pump, High flow water pump, new timing chain
gear, worn out HEI with super coil, Had Victor Intake and car ran
13.01 @ 101 mph, with 2 1/4in full exhaust off header.... previous
owner had exhaust off, torker II intake Running 12.70 @ 107mph ,
using 9"x28" M/T slicks, Drive shaft loop, Battery in trunk, sump in
gas tank.
Was told with the 1.65 roller rockers/cam set up lift is around 0.510

Just installed new leaf springs w/extra leaf, shackles, rear shocks

Purchased Upgrades to install: Performer RPM dual plane intake, Aluminum 3 pass radiator, MSD billet Dist., MSD 6 Digital Box, blaster 3 coil, purple hornies off the headers. New control arm bushings (car has worn out originals), aluminum trans pan.

Looking for Options on head and Cam upgrades? What kind of time difference will this give and is it worth the money for the upgrades for a street/strip car?
Thank you ahead of time

Quick image preview of car and my new design layout here

https://www.facebook.com/photo.php?f...type=3&theater



Dave

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Old 03-18-2013, 11:11 AM
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pontiac 400

What are the casting #'s on your current heads? The hard part is that pontiac heads are so varied and inconsistent. 6X or 4X can be worked with. Aftermarket heads for pontiacs are very pricey...but you can achieve the same effect by taking the heads you have to a good machine shop, have some milling done and get a serious port job done and some good valves. You'll notice it will really come to life. Choices in the aftermarket are limited sadly. With a pontiac try to concentrate on a low RPM torque monster and not a high revving HP beast. Horsepower is overrated. Torque wins races! A good set of heads can bring that cam to life. Those engines like to breathe, so perhaps a larger set of headers would be helpful as well.
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Old 03-18-2013, 12:23 PM
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# 62 heads show to be 72 CCs by the charts , however i suspect they are closer to 80 ish. If they were any smaller say 72 CCs compression would be 9.88 to one, Static, which may be OK if the cam is up near 298 duration or more as it will bleed some compression off to keep detonation in check.I would say that may be the case , evidenced by the 3500 stall converter you say it has.
I would have to say you are at the limit when it comes to streetable. If you put a larger cam in, the stall should be OK but it will make it less manageble on the street. Also a dual plane is not what you want on a strip motor that obviously churns some RPMs as yours must as it has a 3500 stall.A dual plane will make it a tad more streetable but may limit top end a tad. No free lunch you know.
You could venture into hydaulic rollers.You could gain some in both areas by doing that.
Really need more info on your engine , do you know if the bottom end has forged rods and pistons?
How about actual cam specs?
Are you sure you have 1.65 ratio rockers.
Kaufmann racing and edelbrock, make good heads for pontiacs. I think there are a few others but I had a brain fart and dont recall at the moment.
There is tons of stuff for pontiacs.Prices are not bad either.
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Old 03-18-2013, 12:24 PM
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Pontiac 400

Sorry,
I mentioned in the descrip..... they are # 62 heads , the block and heads are from a 1969 GP The only head work I seen done was new springs and retainers. not sure on anything else. I haven't tore into the motor that far yet. Just doing what I can to get it running again.... car was running 13.60's when I got it, after tweaking and such got to 13.10 then I pulled the Victor intake off and put the RPM on and haven't been back to a track yet. I noticed a coolant leak on the back of the block behind the flex plate, so I am going to pull the trans and check the soft plugs, I think one is leaking from the looks of it... very slow drip.
The Headers are Hooker, The collector is 3" and the kid I got the car from downsized to 2 1/4 exhaust out... really restricting the exhaust, so need some changes, new headers seems a goal also.
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Old 03-18-2013, 12:36 PM
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Pontiac 400

Sorry, All I know is the block was bored 0.030 over and had the stock compression of 10:1, cam was a summit cam, almost equal to a ram lV, the Roller rockers I put on are the Crane Gold 1.65, The torque conv. was what the guy put in the car before I bought it. The trans and conv. had 2000 miles on it when I got the car. Total engine work is not known. They put a early 60's timing cover and water pump on it and wondered why it ran hot, I went to a never timing cover and a high flow pump. Still need to do the radiator swap, dist. & module when the weather warms up, car runs strong to 5900 rpm is where I have my trans programmer set at (gov. weight kit)
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Old 03-18-2013, 12:48 PM
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As you've found, the high compression D-port 62 heads require more octane than you can normally get from a pump. Not the best scenario for a vehicle that's driven a lot.

You do have some choices, though. On the cheap end are 6X-4 heads, milled to give you 9.5:1 static compression ratio (SCR). The exact amount to mill depends on what the chambers measure, they are advertised to be 96cc, 94cc, 92cc, etc. depending on where you look. FWIW the 6X-4 heads I had that were off an original, un-rebuilt engine measured exactly 95cc. This would lead me to believe the nominal size is either 94 or 96cc, as most production heads measure some amount over the nominal size. These heads ported and w/a 1.77" exhaust valve can make decent power, but the more you spend on a production head, the better the aftermarket heads begin to look.

And there are D-cup dished pistons that will give you a pump gas friendly SCR.

Aftermarket heads. Nothing wrong w/a set of Edelbrock D-port or even Performer/RPM aluminum heads, but the pushrod holes need opening up for the 1.65 ratio rocker arms. They come in 87cc and 72cc chambers as well as a smaller size (something like 64cc in the D-port version). 87cc will get you about 9.2:1 w/a 0.040" quench distance and a flat top piston (-5cc valve reliefs), less depending on the piston deck clearance (how far the piston is down the bore at TDC). 72cc = about 10.6:1 static CR. The piston deck clearance also needs to be measured; there's no way to know if the block has been milled some time in the past unless you measure. This can be done w/nothing more complicated than a straight edge and feeler gauges if you don't have precision measuring tools handy.

Do you have (or can you get) the specs on the cam? Having only the lift doesn't tell much, although the RA IV cam specs out near 0.510" lift w/1.65 rockers (actually the lift is 0.516", and this was a popular cam- although it's now dated; better cams are available.

You will notice almost all the factory cams are split pattern, favoring the intake side by 9-13 degrees duration. That's a good thing to keep in mind when looking for a cam, especially if you're using production heads. Pontiac often used a wide lobe separation angle, something that's fallen out of favor in modern cam grinds. IMO there's little need to go any wider than 112 degrees, and 110-112 degree LSA is a common spec for aftermarket cams.

If you can deal w/the idea of doing a small amount of routine maintenance, you should consider a solid lifter cam. A roller cam would be nice, too- but not a 'must-do'. But if you go w/a cam that has a power peak over 6K rpm, you should look into some forged rods. The chinese have seen to it that cheap forged rods are available. Used to be only poor quality factory forged rods or aluminum rods were available for the Pontiac, or BBC rods were used on a reworked Pontiac crank.

And before the thread is done, someone will be along to fill you in on a stroker crank.

A couple pages w/some info if you're in the mood:

Info/sites
Pontiac engine info
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Old 03-18-2013, 12:59 PM
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Those Pontiacs are awesome. That long stroke hits me in the gut every time.

I grew up with my neighbor and his poncho. No matter what anybody sez, it is a GTO. Pic, you can see my cuda's tail in the garage.

Nice car there.
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Old 03-18-2013, 12:59 PM
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A NON RUNNING ENGINE.......!
Better pull it and put it on a stand and pull the pan and have a look at the bottom end.
Might as well pull the heads too. If you can...before you pull it..do a compression test first.
Be sure to pull the pan and have a look BEFORE you roll the engine upside down on a stand.
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Old 03-18-2013, 01:09 PM
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Nothing wrong w/the RPM intake, IMHO. It would be the intake I would have bought if it was me.

To really know what to do, you need to know the actual compression ratio and the cam specs. Measuring the depth of the pistons in the bore at TDC is easy. "CC'ing" the chambers (measuring their volume) is a little more involved, but well within the average guy's ability. Or you can have a shop do it for you.

Once the CR is known, the cam can be compared to the rest of the combo to see if it's a good match.

The potential problem is too much static CR w/the heads you have. If they're 72cc (~10.6:1), or even 75cc (~10.3:1). BTW, 75cc is closer to what most nominal 72cc heads measure in my experience, like some #16, #12, #13, etc. Problem is, w/o measuring, you just cannot say. And when you're dealing w/parts that are as old as these are, there's no telling how many times they may have been rebuilt, or if the block has been decked.

Note- the CR figures I've given here are derived using a 0.040" quench distance, a head gasket bore diameter of 4.2", and a -5cc valve relief volume. This is to eliminate having to type all the possibilities involved w/different head gasket bores, thicknesses, different deck heights, etc. That means the figures I have given will be the MAX CR you're likely to see. The downside is anything lower means a less-than-optimum quench distance.

Last edited by cobalt327; 03-18-2013 at 01:18 PM. Reason: Typo.
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Old 03-18-2013, 01:16 PM
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I agree to pull it. No way I would run it w/o a thorough going over.

Pay particular attention to the bearings. If it was detonating, the rod bearings are going to be hammered- I can assure you. Whether that means the crank needs turning remains to be seen; the stock Pontiac cranks are tough but that doesn't mean it will not need turning- everything has a limit, plus there could be normal wear from mileage. Also check the fit of the rings in the ring lands. Detonation can close down the clearance, sometimes to the point of pinching the rings, causing blowby in massive quantities. The condition of the plugs will show this if it was bad.

Last edited by cobalt327; 03-18-2013 at 01:38 PM.
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