[ck67goat]

Technically this will be a street engine, however posting in race and not street to avoid any judgement over what I'm planning to build on a number matching car.

The car is the 67 GP convertible (heavy car, with power windows and top, plus plan to add A/C). Goal is to keep the car very street-able, use little or no stall converter with the original TH400, however very respectable in the E.T. category. I plan to retain the original 3.55 limited slip rear.

The original '67 block is already .030 over, so plan to go .040, The original Armasteel crank will be kept in storage if I ever choose to make this all factory original again, as will the heads, intake and carb.

CRANK choices - In place of original, trying to choose between a factory 455 crank and an Eagle 4.25 stroke. The 4 cubic inches gained by the Eagle is not a primary considering factor as is strength/durability. The 455 crank I have is cast #496453 with no date stamp and no N stamp. It is unused and is a factory Service Replacement crank I obtained in a somewhat disintegrated GM box. It appears to weigh out at standard crank weight (not lightened version of later Pontiac cranks). This source here http://pontiacpower.org/PontiacCranks.htm
states this is an N crank and does not differentiate it to be a thin counterweight crank. Others sources online seem to have conflicting information. Best I can tell, it should be an N crank even though stamp not on it and be the equivalent of all other earlier 455 N cranks in terms of strength. Question for this forum - can anyone with the background and knowledge confirm this is a good crank to use? If yes, I'm leaning toward this crank vs. the Eagle.

RODS - Though I have a set of unused 455 SD Rods I could use, I'm not sure would be right to use for this build however. I'm leaning toward either the Crower I-beam 6.8 inch Pontiac sized or the Eagle H-beam 6.8 inch (If wind up going with an Eagle crank seems no choice but Eagle rods). Thoughts on which rods to use?

OTHER - The new heart shape combustion chambers seem too nice an upgrade to pass up, so the iron heads will go on a shelf. Likely Kauffman, but have not picked CFM yet. Cam will be a hydraulic roller somewhere in the 230@.050 duration range. Goal will be to get close to 550 squared for gross torque/hp, confidently turn up to 6000 RPM but keep mild enough for all accessories to run. Any "non-car person" should be able to start and drive this car without exhibiting any problems or odd behaviors (new car mentality).

Would appreciate thoughts/feedback primarily on the crank and rod selection for this build - thanks!

[ponyakr]

"...Would appreciate thoughts/feedback primarily on the crank and rod selection for this build..."

455 crank & Eagle 6.625 H-beam rods. Some say the RPM H-beams are just as good & cheaper.

Another option is to cut the rod journals down to BBC size & go with 6.635 Eagle BBC rods. They're cheaper than Eagle 6.625 rods, and the .990 BBC pins are probably cheaper and available in several lighter weights.

I'd go with Auto Tec pistons, with the pins moved to the correct location for zero deck height, so that no extra machining will be required to achieve zero deck height. Ross can make 'em too, but are probably $300 higher.


"...Cam will be a hydraulic roller somewhere in the 230@.050 duration range. Goal will be to get close to 550 squared for gross torque/hp..."

You'll need a bigger cam than mentioned to reach your power goal, IMO. Most of the Pro builders here say that a 230 HR cam is too small for a 455. The OF cam appears to make the power you want.

http://www.sdperformance.com/viewPro...productID=1816

For mostly all street driving under 5500rpm, you might wanna go with less lift. A KRE HR236 might give you the power you want, with less lift. I suppose you can use less spring pressure with this cam. With all the talk about broken HR lifters, less spring pressure may be a good thing.

"...use little or no stall converter..."

Might need some stall, in order to have a decent in gear idle, if you go with a cam big enuff to make 550hp.


"...Likely Kauffman, but have not picked CFM yet..."

They say 10.5 CR is plenty safe, for pump gas, with alum heads.

http://www.wallaceracing.com/cr_test2.php

But, I'm interested in what the pros here say about this build.

[ck67goat]

Thanks Ponyakr - Cam choice will come later - with this thread want to pick out the crank and rods. My gut tells me the Pontiac SR crank should be fine but want to hear from others. +/- HP is not as much concern as is the foundation and strength for the build.

[ponyakr]

Yeah, you have a choice of stock, Chinese forged, or high dollar USA custom, such as a Moldex. I reckin your budget will have to determine that for you.

https://butlerperformance.com/i-2445...ef=brand:99990

I think several here have posted that 455 cranks can make 600hp safely. And some have probably survived more.

[Johnny406]

I recently picked up a 990 forged 421 S/D crank that I will be using in my upcoming 428 build. With that said, the cast 428 crank I was planning on using is available, all machine work completed. Greg Merrick (Pontiac Gregg) had it turned for me to use with 6.625 Eagle rods and Venolia custom pistons.

Another option, Shaker455 here has a Pontiac 990 forged S/D crank for sale. I think he was looking for $1500 for it but it's a real deal American made forged Pontiac crank.

[mysticmissle]

I would not hesitate to us the 455 crank some scat rods and auto tec pistons
Mine are making 600 no prob. I have eheads though. Gd set of kre sports from Sd and you’re going to smile all day long

[hurryinhoosier62]

Just make sure the machinist who grinds your crank KNOWS what he's doing. He SHOULD equalize the strokes and ensure journal taper is kept to .0002 or less. The stock cast nodular Pontiac crank is one tough piece of work that can easily survive 600hp. With the hp numbers you're hoping to obtain, good rods are a must. Crower Sportsman rods are my first choice with Molnar rods a close second. CP/Carillo seems to be producing the best pistons at the point in time. I'd contact them with your specs and see what they recommend.

[ANDYA]

If it were my motor I would go with the GM crank. With the money you save you can get the Crower rods. Try and use a light piston/pin combo. With quality machine work that engine should last forever in a street car.

[ponyakr]

The Eagle H-beam rods weigh 760 grams & are rated to 750hp & 7500rpm. So, for engines making less than 700hp, I'm just wondering why so many think the Crower rods are worth more than twice the cost of RPM H-beams, and nearly twice the cost of Eagle H-beams. Have there been reports of Chinese H-beam rod failures, in engines under 700hp ?

https://www.summitracing.com/parts/e...xoCuKkQAvD_BwE

http://www.racingpartsmaximum.com/sa...elhbeam-2.html

https://www.summitracing.com/parts/c...w/make/pontiac

I understand that guys building high dollar high rpm race only engines might wanna buy all the insurance they can get. But, for a 500-600hp street or street/strip engine, are the Chinese H-beams just not up to the task ? There seem to have been thousands of Pontiac engines built with Chinese rods. Just wondering what percentage of these engines have experienced rod failures.

[tom s]

FWI,John Angeles runs Eagles rods in his 428 SS engine.Tom

[slowbird]

I ran h-beam Eagle rods in my 496. Never had an issue made upper 800hp and spun it to 8000rpm. We did put good bolts in them but that was it.

[Tom Vaught]

What series of 455 SD rods do you have?
Some are better vs others.

Tom V.

[ck67goat]

Thank you all. So seems consensus is no concerns the N stamp missing from crank? My machinist (a Pontiac guy) quoted a prep price about 100 less than a new Eagle but I'll confirm tolerances. Thanks for advice.

[Dragncar]

SD rods are gamble. Some have snapped just under the pin at 5000 RPMs in a burnout. Longtime Pontiac builders have told me "sometimes all you have to do is look at them sideways" for them to go.
Your 455 crank is more than fine. Just get it done right.
Rods, Molnar is the best rod you can buy for the money, period. They far exceed the strength you need and are cheaper than the Crowers. stronger too, stronger than Eagles and Scats. They are a billet H beam rod with priority ARP bolts and have a better cross section than Eagles or Scat. All machining done here. That said, the other H beams are more than strong enough too.
You put that 455 crank in your block and you will need to get a pretty good head/intake/cam to get it to pull to 6000RPMs. Not the most streetable cam either. Might want to keep your RPMs a little lower for a 455.
Just find another non numbers matching 428 crank, not hard to find. Cheap. Then to 6000 RPM engine is a lot easier.

[ck67goat]

Originally Posted by Tom Vaught

What series of 455 SD rods do you have?
Some are better vs others.

Tom V.

I have 7 of the D forgings and 1 F forging. Odd 1 is not from same series but they were all originally shipped together in the same box from GM.

[slowbird]

Originally Posted by Dragncar

Rods, Molnar is the best rod you can buy for the money, period.

Can you prove this? Do you know anyone running them?

[ponyakr]

Looks like maybe those are the ONLY rods for that money. Priced between RPM/Eagle/Scat and Crower.

http://www.molnartechnologies.com/rods-dom-pontiac.html

" Technically this will be a street engine..."

Are the cheaper H-beams with 8740 bolts not strong enuff for a street engine ?

The cheaper Chinese rods are sold with bolt upgrade options.

http://www.racingpartsmaximum.com/sa...elhbeam-2.html

These are rated to 1300hp & 9000rpm. Apparently the rods are stronger than the 8740 bolts.

https://www.summitracing.com/parts/e...2000/overview/

These are rated to 1500hp. Will these work for a street engine ?

https://www.summitracing.com/parts/e...dl19/overview/

RPM also has I-beams with 8740 or 2000 bolts.

http://www.racingpartsmaximum.com/sae4340ibeam-3.html

[ck67goat]

To clarify, goal is not to spin to 6000 RPM, just want it safe to there and beyond. Definitely going with 4.21 stroke to get torque and vacuum numbers to move heavy car and to "tame" down whatever cam I go with - also reason why likely going with the hydraulic roller.

[Dragncar]

Originally Posted by slowbird

Can you prove this? Do you know anyone running them?

Its my opinion Brian. I pretty well informed opinion, but a opinion.
Had some long conversations with Tom, he sold me on them. sure, he owns the company. You go and show me some people who know more about steel racing rods in this country. Thats a very short list, very. (Oliver went to $h!t after he left)
Their ARP bolts have a slight interference fit when tightening. But mate perfectly at right torque/stretch. I want that kind of detail on my stuff. They are a machined H beam billet rod. The "H" part of the rod is much thicker than a Scat/Eagle and have large radius in the middle. Night and day better.

And some of the Street Outlaw guys are running them on 2000HP NO2 engines with success. Rod bearings have came back perfect.
Good enough for me. The Power Adder rods are a nice option. Not that much more money.

[ck67goat]

Dragncar - I've never heard of Molnar. Per their webpage looks like a newer company in Michigan. They say they do all machine work locally but source of forging is unknown. Their 6.625 length price certainly is competitive with Crower. (though I prefer a 6.8 rod). Has anyone had first hand experience with quality of their rods?

Regarding your quote below about SD rods -

"sometimes all you have to do is look at them sideways" for them to go.

I have not heard of any such issues except for the time period when aftermarket rods were unavailable and they were the best available for full race applications. Were those issues in greater than 600 hp applications? Also, I can see where 2nd hand rods with an unknown history could have issues or a bad wrist pin fit could cause a break you describe, but the ones I have are unused and I don't plan to cut any corners on machine and prep work.