KRE aluminum heads + cam ?? - Pontiac GTO Forum
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post #1 of 22 (permalink) Old 09-15-2019, 08:59 AM Thread Starter
 
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KRE aluminum heads + cam ??

I am looking for a bit more power out of my 400 ci motor. I am running low compression (#14 ? IIRC) heads and have been considering upgrading to KRE aluminum heads and a new camshaft. A friend is suggesting just adding a flat tappet camshaft and waiting until I build the motor and go all out. Thoughts?

1965 GTO Convertible 3 speed tri-power drum brakes originally

Current setup:
400 cu in with tri-power
4 speed Muncie
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post #2 of 22 (permalink) Old 09-15-2019, 10:03 AM
 
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Depends on how much money you have to spend on your car.

I you have plenty, buy the heads & cam now, then worry about the future build when that time comes.

If you don't have a big budget, you might consider buying the alum heads ONLY if they are also the heads you'll use on the new future build.

You can always sell the alum heads. BUT, most of the time you won't get more than half your money back. Pontiac guys who can't afford new alum heads, usually can't afford more than half price for used heads.

Most HFT cam set-ups don't cost that much, unless you buy Crower cam & springs. If you can settle for a Summit 2802 cam & Jegs lifters, you can save a few bucks. That's what I did for my super low budget 455 bracket project.

Obviously, the guys here will need all the engine & car specs, as well as your power goals, in order to make a specific cam recommendation.
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post #3 of 22 (permalink) Old 09-15-2019, 12:21 PM
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Famous quote from A.J. Foyt: "Speed costs money. How fast do you want to go?"

It's no secret that building a Pontiac is very often more expensive than building a bowtie -- owing to parts availability, parts cost, and difficulty in finding people who actually know what they're doing. Balancing the money side of things is the hardest part and there are tradeoffs always. For example: building a flat tappet engine is a crap shoot these days because it's now literally been decades since any "new" cars had flat tappet valve trains, so the quality of parts, especially the "affordable" ones has declined. You can do everything right including using high zinc content oil (if you can find it) and still just be unlucky and wipe out a lobe, causing you to have to start over. The obvious answer is to go with a roller system, but those are more expensive in terms of parts cost and also indirect cost (different valve springs, different installed heights that require machining the spring seats in the heads, different pushrod lengths, etc.) -- and they too come with their own dangers. If a roller bearing or bushing goes a way or a link bar fails and allows the lifter to turn sideways... the results ain't pretty.

Building an "all out" Pontiac and doing it right with the best quality parts can easily cost you north of $10k. I"m not trying to discourage you from doing that, in fact quite the opposite --- however it's sad when someone starts down that road without realizing what they're getting into and then have to stop without ever getting it finished because it got too expensive. The result is another permanently dead Pontiac - and no one here wants that.

So, back to your question: First be honest with yourself about just how far you want to take it and realistically how much you're able to fund the project to get it there. Details like gear ratio, transmission type, rear axle type, how you plan to use the car (street machine, race car, highway cruiser, etc.) all influence your other choices. An all out race engine that doesn't even begin to make significant power until it's north of 4000 rpm is going to be a miserable experience in a car that spends most of the time cruising the streets down to the local hangout, and it's also not going to be very successful in "stop light wars" - or anywhere else except the drap strip.

Ok --- heads. Just about any of the popular aluminum aftermarket heads are going to outperform all of the Pontiac factory heads, except MAYBE the rare as unicorns Ram Air V's. I personally have a set of ported Ram Air IV #722's that I had flow tested, and even those don't flow as well as my Edebrocks that have been treated to a basic entry level street porting. The tip on aftermarket heads is to buy them bare - i.e. without valves or springs. There's a reason that the price difference between bare heads and so called "ready to run" heads isn't that much. Check out the videos:


No, buy the heads bare and have them sent to an expert "head guy" to have them outfitted with high quality valves, springs (to match the cam you've selected), retainers, locks, etc. If you can afford it, spend a little extra to have him work the ports a little.

Camshaft: The most significant criterion for selection is expected RPM range. Where is the engine going to live most of the time? Pontiacs aren't chevys so we don't have to fret so much about killing bottom end torque, but still you can't ignore that completely. An engine that has a torque peak well within the RPM range where it spends most of its time is going to be the most fun to drive. Don't go chasing horsepower to the exclusion of all else. Remember HP is really just a mathematical formula: HP = (torque X RPM) / 5252. (That's why on every honest dyno sheet the torque and HP plots will *always* cross at exactly 5252 RPM). Take an engine that makes say 450 lb ft at 2500 rpm vs an engine that makes the same 450 lb ft but at 5000 rpm ---- the second engine is making TWICE as much horsepower (because of the formula) even thought it's not pulling one ounce harder. Furthermore, on the street and everywhere else except maybe the drag strip, that first engine is going to eat it alive (because at normal street rpm, engine #2 is going to be a dog). Pick a cam that's going to put the torque peak in a reasonable spot, then work "outward" from there.

Compression: You can get away with more with aluminum because the material doesn't retain heat as well as iron, and heat is one of the main contributors to detonation. In fact, because of this you really NEED to up compression when you swap to aluminum. This is an area where you'll find passionate opinions all over the map about how much is acceptable, "dynamic" vs. "static" compression, ad-inifinitum. I have my opinions too. However consider this: On a very healthy Pontiac 461 with good aluminum heads and a moderately aggressive (for the street) solid roller valve train, raising the compression from 10.5:1 a full "number" to 11.5:1 makes very little difference. How little? About +15 in both torque and HP -- in an engine that was already making north of 560 in both torque and HP. Taking it from a safe on 93 octane (for aluminum) 10.5:1 to a risky for detonation 11.5:1 was good for about a 2% increase, and that's ASSUMING that you can keep it out of detonation at 11.5:1. Worth the risk? Your choice, but personally, not for me, not on the street... not unless I'm trying to milk every last bit out of an engine for race purposes - but in that case I'd be building it to run on race gas anyway. For iron heads, knock off "a number" - on 93 octane pump gas personally I wouldn't push above 9.3:1-9.5:1 tops.

My .02 - your mileage may vary - void where prohibited by law - slippery when wet - past performance is not an indication of future return.

Bear
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post #4 of 22 (permalink) Old 09-15-2019, 01:16 PM
 
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If you’re spending the money on that setup then spend the extra, get a hydraulic roller cam and a set of link bar roller lifters. You can buy the heads fully assembled and get hydraulic roller springs for roughly the same price. The real question is do you want to spend all that money on updated heads and have 40+ year old cam technology?

2006 GTO M6

Motor - Stock with Vararam
Bunch of suspension
Bunch of brakes
Stock tune

365/368 std
12.81 @ 110.6 2.03 60'
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post #5 of 22 (permalink) Old 09-15-2019, 06:01 PM
 
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If you’re spending the money on that setup then spend the extra, get a hydraulic roller cam and a set of link bar roller lifters. You can buy the heads fully assembled and get hydraulic roller springs for roughly the same price. The real question is do you want to spend all that money on updated heads and have 40+ year old cam technology?


40+ year old technology still works! https://www.gtoforum.com/f170/flat-t...ler-bs-135559/
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post #6 of 22 (permalink) Old 09-16-2019, 07:17 AM Thread Starter
 
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Wow guys thanks so much for the feedback, guidance, and help!

The question re the cam vs. cam + heads was really based upon the fact that I know at some point I will build the bottom end (currently a 400 and it will become a forged 455 - 461). No idea when I will build the bottom end as it appears to be working just fine for now (no smoking or bearing noises). From my experience the heads and cam selection make all the power, so I thought about slapping the beautiful KRE aluminum ported heads + roller cam on and calling it a day. I am not sure if doing this will cause issues with the bottom end. That said, I would hate to install expensive heads and then have an engine failure and do damage to the heads.....

My plan was to run 10.5:1 with the aluminum heads. And I guess now I will spend the extra money and just get the roller cam. I was hoping to get some feedback on KRE. From what I have read they seem to really be the benchmark in the Pontiac world, but I was hoping to hear from others that have used their heads.

Specifications on the car:
(1) 400 ci
(2) Muncie 4 speed
(3) 3.55 rear, but I will be swapping this for either a 12 bolt or a Ford 9" with a limited slip differential (probably keep the ratio close to 3.55)

Specifications on me:
(1) old road racer

In terms of goals, I really would like to be north of 400+ ft lbs of torque and 400+ whp (measured at the wheels) or put otherwise a 12 second 1/4 mile car. Redline is ~5000 rpm (ok maybe 5500) and with 400 ci and 3.55 rear, I really think the optimal rpm range to tweak / maximize is ~2500 - 5000, otherwise putting the power to the ground will become an exercise / impossible.

1965 GTO Convertible 3 speed tri-power drum brakes originally

Current setup:
400 cu in with tri-power
4 speed Muncie
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post #7 of 22 (permalink) Old 09-16-2019, 07:40 AM
 
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If you’re spending the money on that setup then spend the extra, get a hydraulic roller cam and a set of link bar roller lifters. You can buy the heads fully assembled and get hydraulic roller springs for roughly the same price. The real question is do you want to spend all that money on updated heads and have 40+ year old cam technology?

40+ year old technology still works! https://www.gtoforum.com/f170/flat-t...ler-bs-135559/
Never said it doesnt work. Fact of the matter is flat tappet is old tech and there are much better options out there if your wallet is deep enough 🙂

2006 GTO M6

Motor - Stock with Vararam
Bunch of suspension
Bunch of brakes
Stock tune

365/368 std
12.81 @ 110.6 2.03 60'
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post #8 of 22 (permalink) Old 09-16-2019, 01:26 PM
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FWIW, stock GTO 400's make about 430-440 foot pounds of torque bone stock. 389's, same deal. With the right tune, very basic, very stock engines can be made to perform quite respectively for not a large amount of coin. It's all in the details.
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post #9 of 22 (permalink) Old 09-16-2019, 04:14 PM
 
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"...400+ whp (measured at the wheels) or put otherwise a 12 second 1/4 mile car. Redline is ~5000 rpm (ok maybe 5500) and with 400 ci and 3.55 rear..."

Don't need 400hp, at the rear wheels, to run 12.90's.

BUT, the rear tires will have to hook up to the track. Got my '69 RA3 GTO into the 12's. But I had 4.56 gears & 9" slicks.

Now, with a 455/TH400/3.73 gears, it was no problem at all running 12's, in that same GTO. The long stroke torque makes all the difference. I ran 13" slicks to keep it hooked up on slippery tracks.

Now a 400 with alum heads & HR cam that will make good power to say about 5800rpm, might run 12's, with 3.55's & a good clutch. Still needs to hook up. Hard to run 12's if the rear tires spin a lot. With sticky tires, you'll need a stronger rear end. I used 12-bolts. I think 9" Fords are cheaper now.

"...KRE...seem to really be the benchmark in the Pontiac world..."

If this car will be driven a lot on the street, you might wanna consider some Edelbrock D-port heads. They are the only alum heads that have the exhaust heat riser, that will heat the exhaust crossover of the intake manifold. This will be helpful, especially in cold weather.

https://butlerperformance.com/i-2445...tegory:1287735

Here's an example of an alum head 400 that should run 12's, even with a HFT cam.

http://lenwilliamsautomachine.com/40...ock_Heads.html

Put some alum heads on this stroker shortblock, and you've got well over 400hp/500 torque. Main problems would be traction & driveline breakage.

http://lenwilliamsautomachine.com/455_Short_Block.html

Upgrades would be forged crank & H-beam rods. Pretty easy to get near 500hp, with the right cam.

Butler sells ready-to-assemble shortblocks, for a fairly reasonable price.

https://butlerperformance.com/i-2445...tegory:1234783
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Last edited by bigD; 09-16-2019 at 04:51 PM.
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post #10 of 22 (permalink) Old 09-16-2019, 05:32 PM
 
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Wow guys thanks so much for the feedback, guidance, and help!

The question re the cam vs. cam + heads was really based upon the fact that I know at some point I will build the bottom end (currently a 400 and it will become a forged 455 - 461). No idea when I will build the bottom end as it appears to be working just fine for now (no smoking or bearing noises). From my experience the heads and cam selection make all the power, so I thought about slapping the beautiful KRE aluminum ported heads + roller cam on and calling it a day. I am not sure if doing this will cause issues with the bottom end. That said, I would hate to install expensive heads and then have an engine failure and do damage to the heads.....

My plan was to run 10.5:1 with the aluminum heads. And I guess now I will spend the extra money and just get the roller cam. I was hoping to get some feedback on KRE. From what I have read they seem to really be the benchmark in the Pontiac world, but I was hoping to hear from others that have used their heads.

Specifications on the car:
(1) 400 ci
(2) Muncie 4 speed
(3) 3.55 rear, but I will be swapping this for either a 12 bolt or a Ford 9" with a limited slip differential (probably keep the ratio close to 3.55)

Specifications on me:
(1) old road racer

In terms of goals, I really would like to be north of 400+ ft lbs of torque and 400+ whp (measured at the wheels) or put otherwise a 12 second 1/4 mile car. Redline is ~5000 rpm (ok maybe 5500) and with 400 ci and 3.55 rear, I really think the optimal rpm range to tweak / maximize is ~2500 - 5000, otherwise putting the power to the ground will become an exercise / impossible.


If you have the deep pockets, then go all out, go big. Here is one of our forum members build with the parts used and dyno results.

I just dynoíd my engine today. Itís a 490 CI stroker, 10:1 compression, KRE D-port heads out of the box, edelbrock performer intake with a mild hydraulic Roller cam, 850 vac secondary carb MSD Billet distributor, and Ram air exhaust manifolds. It made 616 HP and 703 ft/lb of torque on pump gas. I was very happy. I was hoping for 550 HP so this was great. The monster torque numbers were really a bonus. This will def make driving my big heavy 70 GTO a lot of fun! Thanks for all the help you guys have provided me over the last year while I assembled this motor, my first build.


Here's the info on the build:
Ohio Crank forged 4.50/3.00
KB Pistons 943-30 4.5 stroke
Eagle Rods 6.700
KRE Heads 85 cc stock heads
MSD Dist. 8528
RPM Performer intake
Comp cam 235/241HR14+4
Trend pushrods 8.800

Peek HP was at 5,400 RPM, peek torque was at 3,600. One question I had was about the oil pressure. It was recorded by the Dyno throughout the run. It started at 60 psi at 3,500 RPM (the lowest RPM the Dyno recorded data) on one run it went down to 42 psi and on the other it went dwin to 32 psi at 5,800 rpm. Is this a reasonable pressure for a Pontiac engine? This is my first Pontiac build. Thanks for your input. (Turned out the oil was low, filled up, and oil pressure came back)

Mike
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