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I know Army has a thread like this going, but I don't like to hijack threads so I will start a new one.

I am always looking 2 or 3 projects into the future, and since I finished my wheel well saga, I thought it would be fun to pull my tripower setup out of storage and think about what to do with it. I spoke with John at pontiactripower.com and asked him what parts he thought I would need to rebuild the carbs. He said that the parts that he would recommend would depend entirely on my plan for the motor, such as cam choice and heads. Which led me to this...

I have a good magnafluxed 1973 400 block that I was planning on building with a stroker kit from Butler. I also have a set of magged 6X-4 heads. Id like to see 500 torque and 400+HP out of the motor. I am keeping the 4 speed, although I may opt for the M22Z with 2.98 1st gear. My rear is a 3.23 posi 8.5 from a 71 Olds.

Where would you start with this? Work on the heads first? Decide on the stroker kit and then do the heads? Cam choice first?

Thanks
Drew
 

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I would start by really, really thinking hard about how the car is going to be used and where and what for. With a 3.23 Posi, you do not need the 2.98 low gear and the gear spacing of the M22Z is not optimal for high performance compared to an M20-M21 or M22. It's a compromise trans to run a 2.75-3.08 rear gear without an overdrive.
I have 2 tripowers, a '66 unit I've had for 45 years, and a '65 unit that's been on my '65 GTO for 58 years. I rebuilt both of them about 35 years ago and still no issues. Beware the tripower restoration guys that say you need to replace the throttle shaft bushings, do a full restoration, etc. That's bunk, in my experience. Just get three kits that are ethanol compatible and go through thte carbs per manual. Nothing simpler than a Rochester 2GC carb. You want heads with a chamber volume of 85-90 for street use if you use flat top pistons. Do your homework and research before breaking open your wallet. There is a lot of misinformation out there. "Upgraded" and "Improved" aren't necessarily so.
I run flat tappet cams, factory points distributors, and carbs on all my old cars and they are reliable and efficient.
 

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I know Army has a thread like this going, but I don't like to hijack threads so I will start a new one.

I am always looking 2 or 3 projects into the future, and since I finished my wheel well saga, I thought it would be fun to pull my tripower setup out of storage and think about what to do with it. I spoke with John at pontiactripower.com and asked him what parts he thought I would need to rebuild the carbs. He said that the parts that he would recommend would depend entirely on my plan for the motor, such as cam choice and heads. Which led me to this...

I have a good magnafluxed 1973 400 block that I was planning on building with a stroker kit from Butler. I also have a set of magged 6X-4 heads. Id like to see 500 torque and 400+HP out of the motor. I am keeping the 4 speed, although I may opt for the M22Z with 2.98 1st gear. My rear is a 3.23 posi 8.5 from a 71 Olds.

Where would you start with this? Work on the heads first? Decide on the stroker kit and then do the heads? Cam choice first?

Thanks
Drew
sounds like a good start. i guess i would cc the heads to see what i had then order the stroker kit for a good 9.2 compression then a cam to match. this is my opinion.
 

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I know Army has a thread like this going, but I don't like to hijack threads so I will start a new one.

I am always looking 2 or 3 projects into the future, and since I finished my wheel well saga, I thought it would be fun to pull my tripower setup out of storage and think about what to do with it. I spoke with John at pontiactripower.com and asked him what parts he thought I would need to rebuild the carbs. He said that the parts that he would recommend would depend entirely on my plan for the motor, such as cam choice and heads. Which led me to this...

I have a good magnafluxed 1973 400 block that I was planning on building with a stroker kit from Butler. I also have a set of magged 6X-4 heads. Id like to see 500 torque and 400+HP out of the motor. I am keeping the 4 speed, although I may opt for the M22Z with 2.98 1st gear. My rear is a 3.23 posi 8.5 from a 71 Olds.

Where would you start with this? Work on the heads first? Decide on the stroker kit and then do the heads? Cam choice first?

Thanks
Drew
I just might have an M23Z with low miles for sale next year if I need overdrive after I install the 3.73 ;)
 

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Discussion Starter · #6 ·
Don't worry about my thread. If anything yours will help me. I'm going to do a step-by-step build like I did with the Tremec. It will have machine work and assembly tips that are a collaboration of everyone here
Im following your thread too, Im sure Ill pick up something useful there also.
 

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Back to rocket scientists again. As geeteeohguy pointed out, Rochesters are very simple carbs. However, a few fie points. I don't think head choice has much to do with it, never heard that one.

Going bigger cubes/stroke will mean going up on jetting. You don't want the engine running lean on you or it will be running hot - so that is the first thing.

Second consideration is the cam choice and manifold vacuum. The Rochester has a "power valve" of sorts. There is a spring (like AFB carb's') that add more fuel when vacuum drops, ie wide open throttle. If you have low vacuum (stock is around 18"-20" Hg) the factory spring rate will be too strong for the lower vacuum signal and not pull the "power valve" down to seat it. Basically you willbe dumping extra, and unneeded gas into the intake - and then you may have issues you will be chasing trying to figure why you have the issues. You can purchase different spring rates, ie a lighter spring that the lower vacuum can pull to close off the extra fuel enrichment.

Third, if the throttle shafts are not sloppy, ie up/down, not so much in/out, then I would install new bushings because it'll mean the round hole for the shaft is somewhat oblong. Too much slop and you will actually be creating a slight vacuum leak of sorts - and more issues. If they seem good, don't go messing with removing the throttle blades and get yourself in trouble is the little screws break - fixable, but not fun.

Fourth, close the throttle blades and hold the bases up to a nice bright light. You don't want to see any light shining through. If you do, try to figure out the cause. Pontiac used a special black sealer on the blades to help get a 100% seal out of them. I do believe this product is available through one of the tri-power rebuilders. So if nothing is bent/deformed and you see a ray of light at the blades where they seat, it just might need some sealer. Again, another vacuum leak source that may elude you once on the car.

There are assorted needle/seat sizes. The larger ones are better and this may be where the lower 3.5-4 lbs of fuel pressure comes in (since factory was 5.5-6 and was lower at idle) as you will move more volume and don't need the higher pressure. Personally, if you don't have this, I would install a !/4" return line as this will also drop pressure slightly and help with vapor lock.

Have a Service Manual on hand as they go through the rebuild process for a Rochester. I would get one for the year of your carb set-up so you have the correct rebuilding info. Get one of those manual on CD.

You may want to pick up this DVD from Pontiac Tripower. Probably well worth the $25.00. Have not added it yet to my collection, so can't comment on it. Trouble Shooting guide itself may be worth the price. (y)


Of course YouTube can be helpful as well.

DO THE HEADS FIRST, as pointed out, so you can CC a chamber and know what piston to order.
 

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Getting 400 hp and 500 tq out of a 461 is probably just a matter of putting the thing together with whatever parts you have lying around. :)

If you want to be more precise than that (and why wouldn't you?) the most important thing is getting compression "right" for the fuel you have available and the head TYPE you're going to use. For iron heads, on 93 octane, shoot for 9.3:1 maybe 9.5:1 tops. In a "standard" 461 (4.155 bore, 4.25 stroke) and assuming "the usual" Pontiac piston height of about 0.015 "down", standard 0.045 (compressed) head gaskets, 92 cc's of clearance volume puts you at 9.468:1 compression. 94 cc's puts you at 9.318 compression. (Yes, just 2 cc's makes that much difference). If you're going to run aluminum heads, then your target for compression should be a full number higher - 10.3-10.5:1

The engine won't care much how you get to 92-94 cc's. You can get it from the chamber volume in the heads, you can get it from dishes in the pistons, or a combination of the two. If you go with dished pistons (and that's probably the best option since you're ordering a stroker kit anyway), make SURE you get D-shaped dishes that still have a standard height quench pad and not fully round, circular dishes. Also do NOT cheat and get that additional volume from running fat/thick head gaskets. That kills your quench properties which can actually make it more likely to get into detonation.

So, first thing: CC your heads, or have them cc'ed. You need to know exactly how much volume is in each of all 8 chambers (don't do just one) so you'll know how much dish volume you need in the pistons to bring the total to 92-94 cc's. Don't rely on factory specs for this. Pontiac heads have been known to vary from factory values enough to make a difference and besides, unless the heads have been in your possession since they were knew, who knows if they may have already been milled some in the past?

Truth be told, on a street engine I just don't think it's worth twisting the dragon's tail by trying to push compression to the limit. On a 461 like you're building, the difference between 9.3:1 and 10.3:1 (iron heads) will only amount to measly 5-8 hp, all else held equal. If you're already at 400+, is it really worth taking that chance? I don't think so, but it's your choice.

Next thing. Decide if you're going to run bolts or studs on the main caps. Either way, I recommend having the main bores at least checked for roundness and alignment and honed to get them 'perfect' if needed. The reason you want to decide that now is because if you switch from bolts to studs (or vice versa) some time in the future you'll have to have the block align honed AGAIN, and each time that operation is done, a few thousandths gets shaved off the main caps before the operation. Why does that matter? because if you have it done multiple times it can affect both the rear main seal groove (it will get further and further out of round) and also the outer shape of the rear cap where it seals to the oil pan and make it a lot harder to keep those areas from leaking. And it's hard enough already to seal the rear of a Pontiac anyway.

The goal here is to have all the machining done on the block exactly one time.

If you're handy with tools, replace the two front and driver side rear oil gallery plugs with tapped, screw in pipe plugs. Make sure to get the 'shallow' ones so that the ones in the front don't obstruct the oil passages the exit towards the inside. (The 'hidden' plug that's in front of the distributor is already a screw in pipe plug).

Get and run a good windage tray. I really like the ones that Paul Spotts makes. I'm also using his oil scraper.

Cam choice. Hoo boy that's a topic. The best advice I can give you there is to be brutally honest with yourself about how and where you're going to be driving the car 90% of the time. Those cubic inches will tend to 'tame' any cam. Even the RA IV profile which was pretty nasty in a 400, so much so that you couldn't order a IV with A/C from Pontiac, will be a lot more docile in a 461. I'm not necessarily recommending that cam (modern computer designed cam profiles are significantly better), just using it as an example of how inches affects them. Think about getting a cam that's going to place the meat of the torque curve at the RPM where you're going to be spending most of your time. I'd consider talking with the tech guys at Bullet cams and Butler to get their opinions.
If the car has power brakes, make sure the cam you choose will generate sufficient manifold vacuum to operate them - or get ready to spend money on modifying the brake system with a vacuum pump or a hydroboost system. I personally like rollers, but they're quite a bit more expensive and they also have their drawbacks. What I like about them is that you can get a lot more duration out of a roller profile without also murdering the overlap (which kills low end torque if it gets out of control), but getting quality lifters and also keeping an eye on them is of extreme importance. If one fails "in the wrong way" it can destroy the block. Something worth looking into which has come around since I built mine, is running LS roller lifters in a Pontiac. Supposedly it's not all that hard to pull off, and since you're using lifters from GM that they put in production cars that are intended these days to last multiple hundreds of thousands of miles... the idea has merit I think.

Other stuff, just don't cheap out on any of the ancillary parts, and don't let yourself get excited so that you rush and get in a hurry. That will always come back to bite you. I've got the teeth marks to prove it.

Bear
 

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Getting 400 hp and 500 tq out of a 461 is probably just a matter of putting the thing together with whatever parts you have lying around. :)

If you want to be more precise than that (and why wouldn't you?) the most important thing is getting compression "right" for the fuel you have available and the head TYPE you're going to use. For iron heads, on 93 octane, shoot for 9.3:1 maybe 9.5:1 tops. In a "standard" 461 (4.155 bore, 4.25 stroke) and assuming "the usual" Pontiac piston height of about 0.015 "down", standard 0.045 (compressed) head gaskets, 92 cc's of clearance volume puts you at 9.468:1 compression. 94 cc's puts you at 9.318 compression. (Yes, just 2 cc's makes that much difference). If you're going to run aluminum heads, then your target for compression should be a full number higher - 10.3-10.5:1

The engine won't care much how you get to 92-94 cc's. You can get it from the chamber volume in the heads, you can get it from dishes in the pistons, or a combination of the two. If you go with dished pistons (and that's probably the best option since you're ordering a stroker kit anyway), make SURE you get D-shaped dishes that still have a standard height quench pad and not fully round, circular dishes. Also do NOT cheat and get that additional volume from running fat/thick head gaskets. That kills your quench properties which can actually make it more likely to get into detonation.

So, first thing: CC your heads, or have them cc'ed. You need to know exactly how much volume is in each of all 8 chambers (don't do just one) so you'll know how much dish volume you need in the pistons to bring the total to 92-94 cc's. Don't rely on factory specs for this. Pontiac heads have been known to vary from factory values enough to make a difference and besides, unless the heads have been in your possession since they were knew, who knows if they may have already been milled some in the past?

Truth be told, on a street engine I just don't think it's worth twisting the dragon's tail by trying to push compression to the limit. On a 461 like you're building, the difference between 9.3:1 and 10.3:1 (iron heads) will only amount to measly 5-8 hp, all else held equal. If you're already at 400+, is it really worth taking that chance? I don't think so, but it's your choice.

Next thing. Decide if you're going to run bolts or studs on the main caps. Either way, I recommend having the main bores at least checked for roundness and alignment and honed to get them 'perfect' if needed. The reason you want to decide that now is because if you switch from bolts to studs (or vice versa) some time in the future you'll have to have the block align honed AGAIN, and each time that operation is done, a few thousandths gets shaved off the main caps before the operation. Why does that matter? because if you have it done multiple times it can affect both the rear main seal groove (it will get further and further out of round) and also the outer shape of the rear cap where it seals to the oil pan and make it a lot harder to keep those areas from leaking. And it's hard enough already to seal the rear of a Pontiac anyway.

The goal here is to have all the machining done on the block exactly one time.

If you're handy with tools, replace the two front and driver side rear oil gallery plugs with tapped, screw in pipe plugs. Make sure to get the 'shallow' ones so that the ones in the front don't obstruct the oil passages the exit towards the inside. (The 'hidden' plug that's in front of the distributor is already a screw in pipe plug).

Get and run a good windage tray. I really like the ones that Paul Spotts makes. I'm also using his oil scraper.

Cam choice. Hoo boy that's a topic. The best advice I can give you there is to be brutally honest with yourself about how and where you're going to be driving the car 90% of the time. Those cubic inches will tend to 'tame' any cam. Even the RA IV profile which was pretty nasty in a 400, so much so that you couldn't order a IV with A/C from Pontiac, will be a lot more docile in a 461. I'm not necessarily recommending that cam (modern computer designed cam profiles are significantly better), just using it as an example of how inches affects them. Think about getting a cam that's going to place the meat of the torque curve at the RPM where you're going to be spending most of your time. I'd consider talking with the tech guys at Bullet cams and Butler to get their opinions.
If the car has power brakes, make sure the cam you choose will generate sufficient manifold vacuum to operate them - or get ready to spend money on modifying the brake system with a vacuum pump or a hydroboost system. I personally like rollers, but they're quite a bit more expensive and they also have their drawbacks. What I like about them is that you can get a lot more duration out of a roller profile without also murdering the overlap (which kills low end torque if it gets out of control), but getting quality lifters and also keeping an eye on them is of extreme importance. If one fails "in the wrong way" it can destroy the block. Something worth looking into which has come around since I built mine, is running LS roller lifters in a Pontiac. Supposedly it's not all that hard to pull off, and since you're using lifters from GM that they put in production cars that are intended these days to last multiple hundreds of thousands of miles... the idea has merit I think.

Other stuff, just don't cheap out on any of the ancillary parts, and don't let yourself get excited so that you rush and get in a hurry. That will always come back to bite you. I've got the teeth marks to prove it.

Bear
i was looking at the ls lifter option. do you think it would work? it looks like it would but has many people had success?
 

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Anyone have the Jim Hand Pontiac book? Someone is selling a copy near me, but for a bit more than the original cover price. Is it worth it?
those books go for about 100.00 to 125.00. i have the rocky rotella book. it does not have the porting info. i have the max performance version.may be in the how to rebuild a pontiac version. but the jim hand book is better from what i read.
 

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The Jim Hand book is more detailed as I mentioned before, and I imagine is for for the person who will be racing their car and looking for every bit of horsepower.
If you visit the DAPA website there's a series of articles from Jim Hand regarding how he set up his wagon for the strip


Pete McCarthy has a book too, but not as detailed as Jim's.

Then the booklets from H.O. Racing which do have porting guides. I bought these back in the eighties. The HD parts guide is available on Ebay, the Engine Design and blueprinting is difficult to find.

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