[JLMounce]

Specifically 455 based. Can it be done and made durable?

The car would be a street car that also sees HPDE and possible time trials. So I'm not looking at anything incredibly exotic, but something that isn't going to puke it guts all over the track after a 20 minute high rpm session.

I've already got the 455 in the car, built by the previous owner, so I know very little about it.

XJ code 455, probably .030 over, #62's, P4B, Speed Pro Pistons. Outside of that I couldn't tell you what cam is in it, or what the bottom end components look like. I would assume it probably has forged rods, quality hardware and probably a stock crank.

I'd like to make around 500-550 hp with a powerband between 3000-6500. Moving the upper RPM limit up to 7000rpm would be ideal, but considering this is a hobby car and not something I'd be competing for every last .10th, not necessary. My main concern is having something that will survive the extended periods of high rpm use.

Can I retain the 455 I have and make necessary changes, or would I be better off going down to a block that has a 3" main?

To make the power I'm looking for, I'd be using a set of aluminum d ports, more than likely KRE.

I live in Colorado where we have significant altitude changes over short distances, so I'll be fueling with EFI of some sort. More than likely a Holley HP kit utilizing an Edelbrock Victor EFI (TII).

Thoughts? Advise?

Thanks in advance

[ho428]

Oil temps have been a problem with some people road racing with the 3.25 main. Oil containment is an even bigger problem with a stock pan, and even with the Canton pan, especially under hard braking.
HPDE and Time trials are short runs, usually 15-20 minutes. It might could handle the temps with a good oil cooler. I wouldn't run it anywhere near 7000 rpms though. More like 5800 until you know more about the cam and valve springs. I generally shift my solid flat tappet 400 at 6200, only occasionally take it to 6500. You can feel it fall off so no reason in the world to wind it up further.
I'm putting together a 7000 rpm 433, we had to put a lot of thought into the valvetrain for that, along with a splay capped 3" 400 block with forged everything.
Once you get the KRE's and new cam you might can move the RPM's up into the low 6000's.

Weight is also a big problem, I see a 69 Bird in your signature. With a steel flywheel, 11" clutch and quick time bellhousing the 455 will weigh in at over 650 lbs. Aluminum heads will help some, but the hood and front bumper assembly is well over 100 lbs if it's all steel.
You'll need some serious front springs and brakes with cooling for late braking if you want to compete in Time trials.
I've gone lightweight on everything and it's still nose dives under braking.

I'd take it out for some HPDE runs, keep it conservative, monitor everything and evaluate it after each session. Run an oil pressure light and gauge, by the time you notice a gauge it's too late. If you switch to a Canton pan they come with a bung for measuring oil temp.

[JLMounce]

Originally Posted by ho428

Oil temps have been a problem with some people road racing with the 3.25 main. Oil containment is an even bigger problem with a stock pan, and even with the Canton pan, especially under hard braking.
HPDE and Time trials are short runs, usually 15-20 minutes. It might could handle the temps with a good oil cooler. I wouldn't run it anywhere near 7000 rpms though. More like 5800 until you know more about the cam and valve springs. I generally shift my solid flat tappet 400 at 6200, only occasionally take it to 6500. You can feel it fall off so no reason in the world to wind it up further.
I'm putting together a 7000 rpm 433, we had to put a lot of thought into the valvetrain for that, along with a splay capped 3" 400 block with forged everything.
Once you get the KRE's and new cam you might can move the RPM's up into the low 6000's.

Weight is also a big problem, I see a 69 Bird in your signature. With a steel flywheel, 11" clutch and quick time bellhousing the 455 will weigh in at over 650 lbs. Aluminum heads will help some, but the hood and front bumper assembly is well over 100 lbs if it's all steel.
You'll need some serious front springs and brakes with cooling for late braking if you want to compete in Time trials.
I've gone lightweight on everything and it's still nose dives under braking.

I'd take it out for some HPDE runs, keep it conservative, monitor everything and evaluate it after each session. Run an oil pressure light and gauge, by the time you notice a gauge it's too late. If you switch to a Canton pan they come with a bung for measuring oil temp.

Yeah I'd definitely be making some upgrades before taking it out for any events. I'm honestly not sure how the engine lives right now with the #62's on top. I've never had audible pinging and the engine doesn't run hot. I'm sure the altitude here in Colorado is helping it survive on 91 pump gas.

At any rate, I'd be looking at a minimum of a head and cam change (or at least finding out what cam is in it), along with a canton pan at the least. Right now it makes about 42psi at idle when cold and drops to about 38psi at idle warm on the oil side.

The plan does include a fiberglass hood to save some additional weight off the front end.

Those things I can sort, I'm more worried about a bottom end. If I need to, I don't really have a problem with taking the engine out and rebuilding it. But if a 3" main block is desirable for this type of situation, I might as well just continue to have fun with the engine in the car and piece together a new engine on the side.

Heck I could limit my sessions for a season or two while I do that and focus on tuning the chassis and suspension.

[J.C.you]

I have a extra 2 1/2" main 400 block available. Also a complete 2 1/2" main engine available.

[JLMounce]

Granted, I'm no expert, but I wasn't even aware of those blocks existed. I guess I better pull out Jim Hand's book again!

[Jack Gifford]

They don't "exist"...

[steve25]

If there are no rules on the motor having to be NA, I would build a something in the 389 to 406 cid range with 3" mains and plunck a Paxton type supercharger on it!

[J.C.you]

Originally Posted by JLMounce

Granted, I'm no expert, but I wasn't even aware of those blocks existed. I guess I better pull out Jim Hand's book again!

sorry, let me clarify, ....modified 400 blocks w/main spacers for a 2 1/2" main crank. The crank won't be in Jim Hands book either.

[Cliff R]

"I'd like to make around 500-550 hp with a powerband between 3000-6500. Moving the upper RPM limit up to 7000rpm would be ideal, but considering this is a hobby car and not something I'd be competing for every last .10th, not necessary. My main concern is having something that will survive the extended periods of high rpm use."

That power level is relatively easy, but the rpm range is too high for the long stroke 455 to be reliable in long term use...IMHO

Those are great engines, but history has taught us that successful high rpm designs are based on oversquare designs, not big-long stroke engine with heavy internals.

The big 455 are, and always have been a bit hard on the bearings in high rpm/high HP use. Doesn't mean to shy away from one, with 3" main and lighter weight internals we've made great advances in that arena. Even so, building one specifically for sustained high rpm use just isn't a good idea, once again, IMHO......Cliff

[PunchT37]

3.25 main. I`d keep the rotating parts as light as possible with a moderate clearence on brgs. Keep the rpm`s lower than the competition and use the torque you will have, and they won`t ,in most cases. Use a taller gear and make that 455 muscle through the corners and have gears that will not need all the rpm`s in the straights.

In other words, use it like a Pontiac and not make it run in conditions like a SBC. They will last a long time IF you don`t rpm the piss out of it. Of course, oil containment and temp control.

[JLMounce]

Good information guys, this certainly helps! Looks like I need to try sourcing a 3" main 400 block if I want to keep a poncho in the car for this purpose.

Assuming I keep the rpm's down around 5800 and watch oiling, in your opinions is keeping the 455 in it now possible for a couple season?

Gearing right now is a 3.73 with a 27" tall tire so I max out at a bit shy of 120mph. Fr the majority of the courses here in Colorado, that's enough to not be up against the mechanical speed limit of the car. Save for PMI which has a half mile straight.

[Dragncar]

I wish the aftermarket blocks has a 2.75 main option.

[J.C.you]

I believe this scenario has been talked about some 50 years ago..... Smokey and Pontiac management having the big main/little main controversy back in the pontiac nascar days. Wonder who was right?

[Half-Inch Stud]

I've NEVER agreed on the 3.25" mains as an rpm, nor oil temp limiter.

Did PMD campaign 421s in the early 60's at sustained RPM on oval tracks?

[HWYSTR455]

Competing and being competitive are two different things, thought that needed to be pointed out. One costs way more than the other, that I don't think needs to be pointed out.

To have fun, use what you have, and take reasonable steps to make it live.

Good machine work, attention to detail on assembly, oiling (good pan), and cooling are key.

To be competitive, you would/should build an application-specific engine. Would think something like a 400 (3"), .060 over, long rod, light rotating component engine would be a good choice. And of course, along with all the proper support systems, dry sump would be best.

Oil cooler, PS cooler, differential cooler, good brakes and shocks go a long way in taking the extra steps.

If you look at the failures that occur in endurance racing, most of the time it's not core engine stuff that fails, it's support systems or other drivetrain items. Electrical is a biggie, believe it or not. Many run their' race engines past their' service life, and that's when you see actual engine failures.

I've beat my stuff before for more than 20 mins at a time, sometimes as long as an hour plus. I don't think it's as difficult as some may make out, common sense is a key ingredient.

ho428 - What are some of the common failures you've seen in circuit racing?

.

[sdbob]

Quality balancer.

[Cliff R]

I've never much been afraid of the 3.25" mains either. What hinders the basic Pontiac design is how heavy the crankshafts are, long strong, long/heavy rods, pistons, etc.

There are just so many far superior designs out there for sustained high rpm applications, a Pontiac 455 would be at the bottom of my list.

Not saying here it can't be done, but when it comes to high rpm's, and big displacement, it's just a LOT easier on everything when we have LESS stroke and more bore diameter to move the same amount of air if/when the engine sees sustained high rpm's to make any given amount of power.

There is a lot of "theory" involved with these things, especially when it comes to rod length for any give stroke. I don't get all caught up in that stuff, but do know that relatively heavy parts in the spinning/reciprocating part of the assembly, combined with long strokes, just isn't the best way to get this deal done.......Cliff

[HWYSTR455]

Or just do what you need to at a lower RPM.

.

[hectore3]

Also run a non-detergent oil for avoiding foaming issues.

[BruceWilkie]

I think with 3.25 main it might be a good compromise to drop down to a 4" stroke(440 ci with 4.185 bore)... Still good torque and less strain on the block... generally happier at rpm than 4.21 or longer stroke. Stock rod length is fine but BBC big end allows better radius on the journal. IMO a factory 421 or 428 crank is plenty strong. I'd upgrade to better main caps and studs though. Some(Eagle, K1) offer a 6.635 BBC rod that MIGHT help acheive zero deck as its only .010" longer than stock... The 6.7 and 6.8 BBC rods arent a bad choice though... Some builders will use a 6.535 BBC rod BUT its likely the piston gets a bit heavy...

3" main blocks have 1/8" more "meat" wrapped around the crank. Dont sound like much but when you actually look at the difference you can see it.

Still regret lettin my 440 go with a car I sold... its a good combo even with iron heads.