1975 400 Pontiac 461ci stroker - Performance Modifications - Firebird Nation

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1975 400 Pontiac 461ci stroker


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7 replies to this topic

#1 Mclo

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  • Transmission: m 20

Posted 4 weeks ago

hey guys i got lots of question so bare with me.

To start Ive always wanted to build an old car and finaly got an 81 trans am(not the prettiest but can change that haha).

So now i got a 400 pontiac 1975 with 6x-4 heads and block #481988 and want to build a 461 stroker. Streetable,occasional track. I live in canada so ill only use it 4months or so a year. Here we only have 91 as the highest oct at station.Keep in mine i can buy octane booster if i need to reach a little bit higher octane!!

So i was hoping of maybe getting roughly 450hp and 550ft-lbs of torque. Am i unrealistic?

I would love to keep my iron heads. i know they arent the best but i could always port them up a bit myself. I am a machinist and aint afraid to take my time. I just have no way of testing the heads so not sure if it's a great idea.

As far as the stroker i was thinking a butler kit? BUT now with there calculator on there site im just not sure about piston deck heigh. do i have to use the stock height i will measure or do i need to figure out what i will have with the stroker? if so how to do so?

Im pretty good in mechanics. i can rebuild an engine no problem and check for the specs if i got the numbers. BUT i no nothing about CAMS. can anyone help me?

If anyone wanna share there builds(aprox engine numbers,what you used,where you bought..would love to encourage canadian if anyone is from here if not not afraid to buy state side.)

Any books recomended buying before doing so?

#2 tjs

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Posted 4 weeks ago

I would talk to Butler and buy a complete rotating assm.They can spec a piston and cam for your requirements.450 HP with that kind of CI will be no issue with your heads.Tom



#3 Mclo

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  • Engine: 400
  • Transmission: m 20

Posted 4 weeks ago

i will get in touch with them. and i did mean a 461 not 472.. but also you see i was talking with a machine shop here in ontario and they seem to say that butler and eagle arent the best but yet i only seem to find good reviews with them.

Edited by Mclo, 4 weeks ago.


#4 tjs

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  • Engine: RA III stroker(455)
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Posted 4 weeks ago

Just make sure your machinist checks all clearance on anything supplied.Butler also use SCAT cranks and rods.I have used both SCAT and Ohio cranks but not Eagle.Tom



#5 Injuneer

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Posted 4 weeks ago

........ i did mean a 461 not 472............. 

 

 

Would you like me to edit the topic of this thread?



#6 Mclo

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Posted 4 weeks ago

yes please! i did not know how or if i could. much appriciated and might have more people coming to chip in!!

#7 ponyakr

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Posted 3 weeks ago

Haven't checked this site in a few days. So I just saw this thread. Added my 2 cents last night. Took me over an hour to look up & post all the links. Then I made the same mistake I've been making for years now. I DIDN'T copy the entire post, so that I could simply paste it back in, just in case something went wrong with posting. 

 

Well, when I hit post, the screen said no internet connection. That was NOT the problem. I suppose maybe the site kicked it out because I'd taken so long to compose it. Don't have a clue. Anyhow, I'll post a few of my thoughts, on this subject. May be too late for, or may not help the OP. But, it may help somebody who reads it. 

 

"...they seem to say that butler and eagle arent the best..."

 

I suppose that depends on what a person means by the "best".

 

What some people call the best parts are only those that are made completely in the USA. Well, that makes the Pontiac stroker parts far more expensive than most average Pontiac guys can afford. We're talkin about rods & cranks that cost thousands, rather than hundreds. 

 

But, rods & cranks that were forged in China, but finish machined in the USA, are MUCH cheaper than those that are totally USA made. But, for those who have plenty of money & don't mind spending it, USA made Pontiac stroker parts ARE available. 

 

There have been LOTS of Pontiac stroker engines built using Eagle cranks & rods. Cliff Ruggles has posted several times that he has found most all the Chinese H-BEAM rods to be very close on the tolerances, even when machined in China. 

 

But, if someone prefers to avoid Eagle products, as mentioned, there are others, such as Scat. Molnar is another brand that some like. Higher priced. But not as high as the USA only parts.  

 

https://www.molnartechnologies.com/

 

And about Butler. Butler has a rep of being one of the very best Pontiac engine builders. I suppose that because of their rep, they also have very high prices for their complete engines. Now, for someone wanting a really competitive Stock or Super Stock racing engine, their are better Pontiac engine builders. In fact, Butler told me that they don't even build NHRA class racing engines. It's not their segment of the market. They build engines for street, street/strip, & bracket racing. 

 

But, they have very competitive prices on Pontiac stroker parts. Therefore, they can sell a complete, balanced stroker assembly for very little, if any, more than many of their competitors. 

 

For those who have a good machine shop/engine builder, who prefers to measure & buy their own stroker assembly parts, all the parts can be purchased separately. Not much money to be saved. BUT, the pistons can be custom ordered, so that you can get the exact pin height you need, AFTER machining the block deck. Many like to do it this way in order to get zero deck height, or very near it, WITHOUT having to cut extra material off the block deck. 

 

But, some shops don't seem to care how much they have to cut off the block. They just order the commonly available stroker assembly & machine the block more, depending on what is needed. 

 

Another consideration is whether to go with a 4.21" stroke or a 4.25" stroke. Most DO agree to go with a FORGED crank, even if you go with the 4.25" stroke. 

 

If you go with the 4.21 stroke, you can use Pontiac size rods & pistons meant for a 455. In other words, you'd basically have a small journal 455, with whatever bore size you need. 

 

https://www.summitra...s/uem-ic888-std

 

https://www.cnc-moto...4-160-bore.html

 

If you go with the 4.25" stroke, you'll have to use rods that are BBC size on both ends. The popular stroker lengths are 6.7" & 6.8". The pistons will use the BBC .990 dia pins, and will have a shorter pin height(compression distance), because of the longer stroke & rods.   

 

You can choose either the cheaper 5140 I-beam rods, or stronger, lighter 4340 H-beam rods. 

 

You can choose pistons made of either the 2618 material, like racing pistons are made of, OR the 4032 material, like most of the street/strip forged pistons are made of. The 4032 material expands less with heat, therefore requiring less piston-to-cyl-wall clearance. The popular SP pistons are made of this 4032 material. Auto Tec brand pistons are also made of 4032. They make Pontiac stroker pistons, & will make custom pistons, using shelf blanks in common bore sizes. They will put the pin holes wherever you need them, in order to achieve zero deck height. That's one of the best things about custom pistons. 

 

I've been told that on these listed pistons, there is no extra charge to put the pin holes in a different location than what's listed. 

 

https://shanonsengin...lat-top-pistons

 

Besides Butler, there are several other Pontiac shops where you can probably buy stroker assemblies and/or separate components. 

 

http://www.krepower....tating Kits.htm

 

http://www.spottsperformance.com/

 

https://www.facebook...nsMuscleMotors/

 

http://www.dcimotors...engine-builder/

 

http://lenwilliamsau...hort_Block.html

 

Some of these parts are also available thru Summit, Jegs, & even from Ebay stores.

 

The Scat balanced assembly is part #1-41660BI. The pistons are Icon brand, with 4.30cc valve reliefs. 

 

https://www.ebay.com...7YAAOSwOyJX7rmL

 

if you want 10.60cc dish Icon pistons, the part number is 1-41661BI. 

 

https://www.ebay.com...0YAAOSwzaJX7rmc


Edited by ponyakr, 3 weeks ago.

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#8 Mclo

Mclo

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  • Model: trans am
  • Engine: 400
  • Transmission: m 20

Posted A week ago

wow..thanks for all that info! had nt been on for a little while now.




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