455 Motor build opinions - Pontiac GTO Forum
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post #1 of 9 (permalink) Old 08-05-2012, 12:27 PM Thread Starter
 
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455 Motor build opinions

Ive built alot of chevy race motors but this is my first pontiac build. Im not used to building a motor that isnt meant to turn 8000 RPMs. Here is some of my ideas for a 455 for my 66 GTO Clone, im curious if it would work well, and what people think. If you think I should change something let me know since like I said its my first 455 build. I want it to be a street strip car. I would like to do 12s, but still be able to drive it on 93 octane to a show an hour away.

455 Pontiac.
96cc heads with the big valves
Edelbrock 2156 intake, 750 Holley double pumper. (I want it to fit under the stock GTO Hood.
Headers or Ram Air iv Manifolds (Opinions)

Internals
Lunati 00071LK cam and lifters
Keith Black Dome Pistons (Piston head volume 0)
Eagle Specialties 6625P3D Rods
Eagle Cast or Forged Crank (Opinions)

This should put me at 9.8 to 1 compression.

Also what rockers and pushrods should I run? Roller rockers or not?
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post #2 of 9 (permalink) Old 08-05-2012, 03:41 PM
 
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Are you dead set on the 455? In the Chevy world, I'm assuming you were more of a big block person.
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post #3 of 9 (permalink) Old 08-05-2012, 03:54 PM Thread Starter
 
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When I built race motors I built alot of 350, 383, and 400s. I built motors that could turn high rpms. As far as the 455, this 66 GTO clone is "my dream car" kind of thing. Im doing it my way from ground up, and wanted to go big with the motor. So pretty set on the 455 for this build.
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post #4 of 9 (permalink) Old 08-05-2012, 07:24 PM
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Take everything you know about chevy's and set it aside. Not much of it applies in this world. Pontiacs make mountains of torque and it's there "right now" from just above idle. They don't need much gear or a super loose converter. It's unusual to see a Pontiac street motor that turns more than 6000 rpm, or needs to. 5500 is "the norm".

First, how are you going to use the car? (street, street/strip, race only, highway cruiser, etc.)
What kind of fuel are you planning on running?

Transmission?

Which heads will you be using? (date code and casting code)
(Here's a reference: Cylinder Heads ) and have you cc'ed them yourself?

Also, which block (4 character date code on top rear near distributor hole, casting number on rear pad behind passenger side deck, and finally - 2 character code on passenger side front just below the deck)

Some thoughts:
750 cfm isn't enough for a serious Pontiac

That Edelbrock intake won't make as much power as your factory iron intake will.

That Lunati Bracket Master is a pretty mild cam in a 455. If you plan on running iron heads and pump gas, it's nowhere near enough cam to keep you out of detonation trouble at 9.8:1

cast vs. forged crank: Forged is a waste unless you're making north of 600-650 hp and/or regularly spinning the motor past 6500 rpm, and the rest of your combination isn't going to get you anywhere near either one of those figures. Forged H-beam rods are ALWAYS a good idea.

'Ram Air IV" manfolds only fit Edelbrock roundport heads and Pontiac factory round port heads (Ram Air IV, 68 1/2 Ram Air II, 71+ 455 HO, 73/4 455 SD)

And, the question I probably should have asked first --- what kind of budget are you working with?

I love talking about this stuff (and welcome) --- I'll be happy to share how I built my 461 and can also put you in touch with one of the best Pontiac engine guys there is. Here's his web site:
Central Virginia Machine Service - Home of the Injun Engine!

... and unlike many, if you consult with him he'll share honest information with you without making you spend money first.

Bear

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post #5 of 9 (permalink) Old 08-05-2012, 07:37 PM Thread Starter
 
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Street strip car. I want to run at least 12s, but I also want to be able to drive the highway to a show 2 hours away.

I want to be able to run 93 octane.

Either a Muncie wide ratio or possible a tremec tko 600.

I dont have the heads and the block yet. Heads Im planning on either a set of either 64s, 96s, or possible 7k3(I know I cant run headers with these.)
Which Year blocks would be the best? What are the differences?

the 750cfm Holley was a minimum. I can run an 850 if needed.

As far as the intake, what would be best? My only requierment is it fits under my stock GTO Hood.

That Lunati cam was something I saw listed on a pontiac post somewhere. I am fine with going bigger. What big cam would be good? I definitly want it to lope like hell at an idle

As far as the crank, how good is the stock crank? is it ok to stay with the stock or should I get the cast crank?

Budget is like this, I want to do it right, I want to do it a way that makes me happy. If I have to spend more money thats fine, might just add more time to my build. Plus I manage an aftermarket autoparts store so I get good prices!

Im in the body stages of my frame off resto right now so Im planning the drivetrain. Any help is appreciated.
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post #6 of 9 (permalink) Old 08-06-2012, 07:33 AM
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Well ok then, that helps

If you haven't bought the block yet, then instead of a 455 I'd recommend going the route I did. Take a Pontiac 400 block, have it bored + 0.035, and go with an aftermarket 4.25" stroke crank. That'll give you 461 inches. Reason: 400's (and 389's, and 350's, and 326's) have 3.000" mains as opposed to the 3.250" mains on the 455 (and 428 and 421). That makes the block stronger because there's more meat in the webs. They oil better too due to less 'surface speed' from the smaller journals. Factory Pontiac cranks are very strong because they're shorter than chevys and don't flex as much. The only reasons to replace a good factory crank with an aftermarket piece is if you want more stroke (still cast is fine - that's what I'm running in mine), Forgings are only needed at the levels I mentioned earlier. It doesn't "hurt" to have a forging if you've got the budget for it, but they aren't "required" until you get to those levels. 2-bolt mains are also just fine until you get way "up there".

My 69 GTO at 4000 lbs. went 12.72 @ 109 on its very first pass - despite my incorrect launch technique, running through the mufflers, in drive, spare tire and jack still in the trunk, and running out of gas due to insufficient fuel pressure to keep the carb filled (I had previously dialed back the pump output pressure and backed it off too much). I'm running a TH400 (3200 stall) with 3.50 gears in a Moser 9" rear, Nitto P275/r60-15 drag radials. At 70 mph I'm turning about 3100-3200 rpm.

Once I get it all sorted out, it might be capable of high 11's. It runs just fine on 93 octane, doesn't overheat even with the 105+ degree days we've been having here in the Dallas area recently, and has 10.02:1 compression (aluminum heads now - when I had iron heads it was at 9.46:1). I'm running a solid roller cam and an 800 cfm QJet, now on an early model aftermarket single plane intake ---- but only because when I switched heads my factory iron intake wasn't tall enough to cover the ports in the heads (otherwise I'd still be running it).

Here's a link to a summary along with the dyno sheet on my motor, back when it still had the iron intake and iron heads.
1-to-1 Club: Rob Garrett's 461

The heads I have on it now are probably making somewhere in the vicinity of 30-50 HP more than it was then.

I can tell you how to build one like mine or very similar to mine if you like, or you can get with Jim at CVMS for additional ideas/options. Really, he's a great guy.

Here's a link to a video walk around of my car (you can hear it run with exhaust dumps both closed and open) and also a link to the first pass it ever made - the 12.72 @ 109.

Bear

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post #7 of 9 (permalink) Old 08-08-2012, 09:46 PM Thread Starter
 
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Here is an updated engine setup possibility. What does everything think about this instead of the 455.

400 with a Butler performance 461 stroker kit rotating assembly(balanced) with Domes for zero piston head volume.
96CC Big Valve Heads
Comp Cams Thumper Cam 51-601-5
Edlebrock Performer RPM Intake
850 CFM Holley Double Pumper.
Possilby D Port Ram air 2.5" manifolds(If I end up with a set of 7K3 heads) or headers.

Should give me an RPM range of 2200 to 6200
Compression around 10:1 with a .023 compressed head gasket.

connected to a Muncie wide ratio(Maybe tremec tko 600) and rear gears between 3.23 and 3.55.
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post #8 of 9 (permalink) Old 08-09-2012, 10:33 AM
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My opinion is that 10:1 is too high with iron heads, although that cam has lots of seat timing, overlap, and a relatively late intake closing event you *might* be ok. Consider that on an engine of this size, the difference between 9.5:1 and 10.0:1 is only worth about 8 hp, so is it really worth it to take the risk?

In any case, .023" piston to head clearance is too tight. I'd like to see at least .030, .035 would be better.

Performer RPM intake with the Holley would be "ok" -- I'd tend to prefer an 800cfm QJet on a suitably port-matched and massaged factory iron intake, but the RPM/Holley can be made to work.

It's definitely going to have some attitude with that cam

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post #9 of 9 (permalink) Old 08-09-2012, 01:03 PM
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Domed pistons are definitely NOT the way to go in any angine you don't want detonating to death....at least not on a Poncho. Please listen to Mister Bear...he is running the exact combination that you seem to be after, and it works. (If he had his technique dialed his car would cut mid 11's IMO easily)... A pretty near stock 455 in sharp tune ought to break into the 12's without breaking a sweat. I had a friend long ago that ran 12.0 in a '66 GTO with a 455 and a Th400....his secret was a loose front suspension, good rear suspension, correct tire pressures, and skill. The engine had 2X4's on an Offy 360 manifold (AFB's) and it had a mild hydraulic flat tappet cam (this was waaaay before roller cams). Correctly thought out and assembled, these old Pontiacs will surprise you and put a huge grin on your face!
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