[locomotivebreath]

What chip said is certainly something to think about . How do you intend to use the car ? Race , cruise ? I did a numbers matching resto on my GTO , I don’t race or drive hard so in the end , a stroker engine didn’t seem to fit my purpose even though I could’ve done it for about the same price . I wanted to use my original Muncie and not kill it or the rear . I know , I know , ya can store the original parts - I’ve been storing the original parts for years and it takes up space ! What I ended up with was a 420hp / 485 ftlb 406 that’s not temperamental , sounds killer , runs cool ,pulls good vacuum, will through ya back in the seat and is getting around 14mpg with 3.90 gears and a 4speed . It’ll light the tires off easily with 485 pounds of torque - what would I possibly do with 600 ?

[Jay S]

With the 4 speed and stock heads it would overall like the 4” crank and 433 cid better than the 467. But as long as the compression is fairly low the bigger cubes won’t care all that much running that smaller cam and stock d ports. The 467 and small HR roller cam combo combo is fine as long as the compression is held to about 9:1.

I believe Tom S had that cam in a 455 with stock iron heads and made 430 HP or so. He had dished pistons, I don’t recall reading about any loss in efficiency, but I don’t recall the exact numbers.

The biggest mistake people make with that cam in 455s is too much compression. It does not want or need much more compression than 9:1 on pump gas. On the bigger cubes combos it does not like much advance either, should install it on 108 ICL instead of the factory 106.

Here is an old Motortrend article with that small HR cam in a 4.25” crank with 9:1 compression and some ported iron heads. It made 487 HP at 5100.

https://www.motortrend.com/how-to/hp...uska-dyno/amp/

[Jay S]

I think Tom had stock 48 heads when he ran that small 423 cam with bigger cubes. Seems like at some point he did a cam swap to a little bigger cam also. Tom already commented, so, if you have questions about how it ran. Ask Tom. I think it was even a 4 speed car?

[tom s]

made 432 with the XE276 which was pulled for the SP II.Tom

[Pontiakerr]

Originally Posted by jhein

If you post your location maybe someone here knows a local builder they could recommend.

I am in SW FL but willing to travel within the state, any recommended builders in FL?

[Pontiakerr]

Originally Posted by Jay S

With the 4 speed and stock heads it would overall like the 4” crank and 433 cid better than the 467. But as long as the compression is fairly low the bigger cubes won’t care all that much running that smaller cam and stock d ports. The 467 and small HR roller cam combo combo is fine as long as the compression is held to about 9:1.

I believe Tom S had that cam in a 455 with stock iron heads and made 430 HP or so. He had dished pistons, I don’t recall reading about any loss in efficiency, but I don’t recall the exact numbers.

The biggest mistake people make with that cam in 455s is too much compression. It does not want or need much more compression than 9:1 on pump gas. On the bigger cubes combos it does not like much advance either, should install it on 108 ICL instead of the factory 106.

Here is an old Motortrend article with that small HR cam in a 4.25” crank with 9:1 compression and some ported iron heads. It made 487 HP at 5100.

https://www.motortrend.com/how-to/hp...uska-dyno/amp/

The heads have all the comp parts installed already, springs valves retainers etc. They were not ported but they was cleaned up for better flow. Would you recommend a set up like this, and what would I be looking at roughly for horsepower?

4" crank
bigger cam? (recommendations?) or use current cam
Forged pistons and rods

I would be happy with somewhere between 450-500 hp
I want it to sound amazing, and perform but still be street worthy/cruiser. I do live in SWFL so temperature is a factor, I dont want it to run super hot.

[Pontiakerr]

Originally Posted by locomotivebreath

What chip said is certainly something to think about . How do you intend to use the car ? Race , cruise ? I did a numbers matching resto on my GTO , I don’t race or drive hard so in the end , a stroker engine didn’t seem to fit my purpose even though I could’ve done it for about the same price . I wanted to use my original Muncie and not kill it or the rear . I know , I know , ya can store the original parts - I’ve been storing the original parts for years and it takes up space ! What I ended up with was a 420hp / 485 ftlb 406 that’s not temperamental , sounds killer , runs cool ,pulls good vacuum, will through ya back in the seat and is getting around 14mpg with 3.90 gears and a 4speed . It’ll light the tires off easily with 485 pounds of torque - what would I possibly do with 600 ?

This sounds like a perfect build.
I do not plan to race it at all. Id like between 450-500 and fun to drive but very street worthy and dependable. After reading chips post I think I am leaning away from the stroker.

Would you mind sending me the info on your build?

[Pontiakerr]

Originally Posted by chiphead

Running a 4.25" crank and a roller cam changes the calculus when choosing heads. The 62 heads are no longer a good match for that. The small chambers will require a large piston dish, which hurts efficiency and quench. That makes the motor more fuel hungry and harder to tune. Also, the 62s can't flow enough air to support a 468 with a roller cam.

When going stroker crank and roller cam, aftermarket aluminum heads start making more sense. A box stock E-head or KRE D-port is much better than a set of fully reworked 62 irons. It costs the same, maybe less once you factor in roller cam mods and the porting the 62s would need, to even approach the performance of an aftermarket head. The aluminum heads are available with 72 or 87CC chambers, and can easily run pump gas with flattop pistons. A 468 with an Old Faithful II or stump puller cam (well documented aftermarket roller grinds), ported AL heads at 10.5 would make 560 horses, easy.

The other thing about big power is, a healthy 468 will easily hurt the 4-speed and rear end with a few good clutch dumps. That BOP 8.2 is made outta glass, it'll twist axles if you look at it hard.

Thanks, this post is definitely helpful. Im reconsidering the stroker now. The trans was rebuilt with hardened gears and an iron mid plate 1000 miles ago, and the rear end was redone with 3.55 gears and limited slip differential added. If I went the stroker route with the Edel heads, do you think the trans and RE will support it? If I dont go the stroker route, can you recommend a set up for my trans and rear end? I just want a decent running street machine that doesnt need a lot of work but has decent hp.

[Jay S]

Originally Posted by Pontiakerr

The heads have all the comp parts installed already, springs valves retainers etc. They were not ported but they was cleaned up for better flow. Would you recommend a set up like this, and what would I be looking at roughly for horsepower?

4" crank
bigger cam? (recommendations?) or use current cam
Forged pistons and rods

I would be happy with somewhere between 450-500 hp
I want it to sound amazing, and perform but still be street worthy/cruiser. I do live in SWFL so temperature is a factor, I dont want it to run super hot.

With the camshaft you have (276/282 comp) it would have around 420 to 430 HP with stock 62 heads. Like the other guys said, it is a small cam using the bigger stroke combinations. With that camshaft in a stock d port pump gas combo will make pretty much the same power whether it is stock 3.75” stroke, 4” or 4.25” stroke. The longer stroke requires less compression to make the power than the 3.75” stroke. My choice for a 4 speed combo would be the 4” crank with the cam you have, I think it best combination of torque and higher RPM HP with the stock heads.

With more head flow, whether that is from aftermarket heads or some porting on the 62s, you could get between 450 to 500 HP with the 276/282 camshaft, like the Motortrend article I linked in the earlier post.


With a cam swap to a bigger cam I would be more inclined to do the bigger 4.25” crank, and that would put the engine around 440- 450HP with the stock 62 heads. The camshaft specs would like look similar to this camshaft from Butler performance. https://butlerperformance.com/i-3164...tegory:1459686

A better choice would be Camshaft similar to a SD performance Old faithful cam (slightly bigger)). Personally I would do a camshaft from Bullet racing cams that would let the engine run some extra compression to increase the top power up a bit more, and lower the tq some so the drivetrain isn’t abused quite as much.

[chiphead]

Originally Posted by Pontiakerr

This sounds like a perfect build.
I do not plan to race it at all. Id like between 450-500 and fun to drive but very street worthy and dependable. After reading chips post I think I am leaning away from the stroker.

Would you mind sending me the info on your build?

You can make whatever power you want, it just depends on the constraints and how you plan on using the car. Are you married to the iron heads? A 60s GTO or Firebird car can't effectively make use of more than about 425-450 HP without significant upgrades to the rear end, steering, suspension, brakes, fuel system, tires and wheels. So what are you going to DO with 500 HP? Often, the answer is: "wreck the car" or break parts. That much power makes it very easy to outrun the stock suspension and brakes.

A BOP 10 bolt 3.55/Muncie 4 speed is a good fit for a 389-428 sized engine. A larger engine doesn't need the 3.55s. The stoplight performance is fun, highway cruising, not so much. I had 3.89s in my first LeMans, Once I got over the "gee-whiz its a hot rod" factor, the high engine RPMs on the highway are a real bummer. That's why Pontiac and other MFGs went to the very large engines in the first place. A 455 will drag a 5500lb Grand Prix around with 3.08 gears pretty good. If you build a really big engine, it would let you gear down the rear end and cruise on the highway at a lower RPM. You could also install a 5-speed for the OD, lots of ways to skin the cat. A bigger engine is going to be more street friendly at lower RPMs. The downside is the need to upgrade the rest of the car to effectively use it.

I agree with Jay. A set of iron heads is a good match to a performance engine, up to 4" stroke (433). The 62s could allow a 433 to spin to 5400 RPM without any porting. The stock 62s on a 468 are going to limit the power-making RPM to 5000 or less. Yes, stock iron heads were used on lots of 455s, but the stock TH400 transmissions were set to shift at 4600 RPM at WOT.

I went through a very similar thought process. I had a lot of money into a set of ported 670s. The compression would be too high on a 468, so I built a forged roller 433 that could take a 200 hit of nitrous. The plan is to grow into a set of Edelbrocks or KRE D-ports when the 670s become the limiting factor. I've done the drivetrain and suspension upgrades to keep the shiny side of the car up.