Help me make a build a 455ho
 

I have a 1972 yb code 455ho. Its the original engine to a 72 gto coupled to a th400. I want it to retain the factory heads, and appear from the outside to be stock, even valve covers, except for the fact it will have black long tube headers. It will have a full 3", rear exit exhaust.
My gut says put a modern rotating assembly instead of reconditioning the rods, and using a oem crank. Stroker kits worth it? I would like to hear whats good in 2021. Eagle, Butler?? I need to Pick out roller cam that will work with the iron heads and oem aluminum intake. Head wise, i am looking to leave them mostly alone except a clean up cut, valve job, and recommended springs retainers. Perhaps some crower enduro rockers. Would prefer to keep it on premium pump gas if i can.
Also an opinion on the converter. Rear gear will be a 12 bolt, somewhere around a 3.42 gear. 27" tall tire. This car will be used as an aggressive weekend cruiser. Maybe 2000 miles per season. I want it to straight up snap your neck. Chime in if you have any opinions. This kinda is a blank canvas. I am willing to spend some coin. This is a one time deal. I want it to run. Thanks

Given your parameters, I'd actually use a flat tappet cam, hyd or solid.
Voodoo, Ultradyne or Jones Cams.
Hy-Lift Johnson lifters.
I'd save the money, not go roller.

Harland Sharp 1.65 rockers, I'd clearance heads for pushrods.
Factory crank, Molnar rods and a nice forged piston.
Zero deck the block.

PTC Torque converter - ptcrace.com

455HO suggestions
 

A 1972 455HO, like any factory Pontiac 455, combines a large journal (3.25") with 4.21" stroke.

Swapping in a modern, better-quality reciprocating assembly is imperative.

You may de-stroke to 4", or stroke to 4.5"

Butler has a range of options:

https://butlerperformance.com/c-1234...55-blocks.html

Closet in size is the 4.25" option.

Eagle may be the most widely used, but Scat is superior.

The best bang per buck for crankshafts and rods are SCAT and Molnar. For rods definitely go with MOLNAR. With the 2.20 crankshaft rod journal, use the BBC 6.8" or 6.7" Molnars.

use the stock crank. get some aftermrket 4340 rods. Use some more modern pistons with 1/16" rings.
There will be zero advantage to a aftermarket crank for what you are doing. You could have it offset ground to 4.25 BBC rod if you wanted to but no real reason to do that.
Carefully pick a camshaft. Run a flat tappet.
I run a 71 455 HO.

Here's a 72 455 HO I built for another member on the forum here. Stock crank, H-beam rods, custom pistons, 7F6 heads and stock HO intake and Q-jet. Custom hydraulic roller spec'd by Paul C. that is very docile and runs the AC and Power brakes perfectly. With the stock RA manifolds in place it dyno'd 507hp at 5700 and 571tq. If you read through the thread you'll find head flow numbers, cam specs, dyno sheets etc... and probably some videos of the engine running on the dyno and in the car.

Ended up doing a custom TSP converter that flashes around 35-3600 but drives around really nice, and it has a 12 bolt Moser rear with 3.42's.



https://forums.maxperformanceinc.com...d.php?t=827701

The factory crank is fine,you can still find Pontiac length rods and you can use aftermarket 455 pin height pistons.Your heads have large chambers so getting up close too 9.5 CR could require custom piston.As said a FTC can be used and will save a lot of money.Tom

You may have to go stroke kit just to gather up enough good pieces
Availability might be your guide

Even a stock well tuned D port 455 can provide so called neck snapping performance IF you can hook it!

Don't spend all your time and funds on building a level of power that you don't need or can't apply, also work on the rear suspension and getting sticky drag radials on the ass end.

Build your short block nice and strong with light Pistons and wrist pins, good I beam Rods and Cam that can make you 450 hp, and then down the road when you have tapped that out for all it's worth with the car hooking well you can swap Cams and maybe even get some head work done to get to the 540 hp level with the heads ported to into 275 cfm land, up from the stock 222 cfm.

Spending adds up quick!!!!! I'm building one as we speak....oh I am helping my sons build mine....simple 455. As I am noticing about prices. A balanced rotating assembly CAN be worthwhile $$$$. 1st step is evaluating what you have to work with. Does the motor currently run well? Your limiting factor is going to be those 115 cc heads as that kills your compression. For a simple motor a roller cam is WAY more expense vs result. Sad part is you will have $600-700 in a set of cast iron anchors just to ensure it actuall lives because if you have them off...your instantly looking at $200 for valves, $230 valve job, $150 for guides (and mods for cam lift) THEN you still got to cut n clean.
Now there are so many performance OPTIONS your wallet is the only limiting factor of what power level you want to be at.

Ok. So here it is as i see it anyways. I am not seeking an absolute max effort build, but currently my other pontiacs represent themselves nicely. My 06 gto is an all motor 6 speed, ls2 makes 485hp to tire. My 1970 firebird is a numbers matching car that i had the original wt shortblock rebuilt to a 406, full arp hardware, using the cast crank, h beam rods, trw forged pistons, ect. Balanced rotating assembly. Had the #12 heads done by sd performance. It runs a crower flat tappet cam. Which wiped a cam lobe on break in. 😝 After ironing it all out, its a 430hp engine.
So the point i am making is, i am used to higher hp cars. This 72 is heavier than my 70 formula and my 06 gto. Though i do know it cannot be held in the same category as either car, i do wish for it to uphold the Pontiac name with attitude and style the company was eventually noted upon. I wish for the car to be something different, and not have an ls engine swapped in. Even though those are cool, but i like "as built" with modernizing.
So with that in mind, some of you may laugh at me, but i would like in excess of 5-550 hp at the flywheel. I would like the engine to spin past 6500 rpm without breaking or distorting the crank, a rod or two, or losing a bearing. I only figured a roller cam since its less rotational drag, and i don't have to wonder if another cam lobe will be wiped out and my new engine gets a belly full of glitter upon break in.

Thanks for that link. I am reading through it. Awesome build and car. 👍

that sums up alot. Your not looking at a simple build. A 455 spinning 6500+ rpm...get your wallet out and dig deep cause this aint no 400. Sounds like you already know whats needed. Rotating assembly, serious head work then pick a cam. The 600 hp mark is doable with iron heads good bottom end and proper cam. That 6500+ rpm mark changes most everythng about the build as you are pushing into BIG WORK. You do not need that kind of rpm on a 455 to get 600 hp/torque. Those numbers can be had at 5500 rpm without getting dramatic.

6500 rpm is not a set rpm the engine will live at. I just know i tend to get a bit to excited with the skinny pedal
from time to time. In my formula, it has 3.55 gears and a aluminum flywheel, and that car will go right past 6000 if you let it. I guess i would rather over build it.

600hp/ tq. @5500?!! Lets hear it!

Yeah I'd like to see some examples of that with stock type iron heads. I don't see that happening without a bunch of other things getting on the wild side. Especially at 5500 rpm in a 455. That must be a really happy dyno. I'd like to see an engine like that go in a typical 36-3800 lbs. car and make some track passes to back that up.

First of all the iron heads would have to flow nearly 300 cfm. You would need a pretty rambunctious camshaft to take advantage, and it would need a fair amount of compression too.

All those things would add up to a not so friendly street engine that may or may not run on pump gas, that again, depending on other variables. That starts to take the "street car" idea out of the equation.

I've seen a lot of these 455's on the dyno that make 500 to 550 HP on pump gas and be very street friendly with very well ported iron heads, but usually the higher side of that needs a pretty good aluminum head with some compression and a healthy roller camshaft to get near or top 600, and they generally won't do that at 5500.

Totally agree...Pontiacs have great torque, build for it. If you are doing any kind of crank work or boring I would go ahead and stroke it. Use good rods and light forged pistons like Ross.

Reading the expectations for the build I think I would stroke the engine to 4.5”. More so to meet the goals with the stock heads versus ported, ported I would leave the 4.21 crank. Stockish head flow I would go for all the TQ and average power you can find. Plus… the forged crank isn’t a bad idea on a number matching combo, and the extra cid would make it easier to get the compression to a more reasonable range with the massive round port chambers and still use a flat top piston. Running a 6.7” rod with a 4.5” crank you should be able to get away from more expensive domed pistons. Most of the pistons for the 4.25” stroked combos with 6.8” rods use the same piston as a 4.5” and 6.7” rod, but the 4.5” stroke will put the piston up closer to zero deck and will take less machining for zero deck. As is 480 HP would be doable with stock head flow and pump gas, but higher that that and naturally aspirated I think you would need to port the heads. 500 + with stock heads on pump gas is possible, but going to take a good sized cam that will eat away at the drivability, and the head flow would need to be above average.

Mock up a set of built E heads to look like your factory HO's...to achieve what you want for hp goals I can't see using your cast heads unless the bottom end is stroked and major work done to the heads. Its just easier to build a pump gas friendly big horsepower street friendly combo with newer heads.

Does anyone make a large journal 4.5" stroke crank??? If so, THose low compression HO heads would likely have a good comp ratio with flat top pistons...My non expert thought for the day

I was trying to do exactly what you are years ago. Here is the problem and people can say what they want, but since my 455 HO is quicker than any pump gas 455 HO I know of I think you should at least listen. If someone has been quicker with a pump gas HO feel free to chime in.
The cam required to get 550-600 HP out of HO heads even at 9-1 CR is not streetable. You have zero chance without real port work.
I have HO 197s done by one of the best, Dan Whitmore. Bunch of money in them. The cam is a nasty solid roller close to .700 lift. Open exhaust with a ported Warrior and my GTO runs 10.80s. the heads were milled something like .060 to get the CR up to just over 9-1. I would not do that to yours in this day of age when you can just buy aluminum which was not available when I started.
You have zero chance of getting a HO head 455 to pull to 6500 RPM because you simply can not get enough air in the cylinder to push the piston with that long of stroke at that RPM. But there is noting wrong with making your bottom end stay alive up there as mine has been there many times, when I make a mistake shifting after 5500 RPM.
If you really want 550-600 HP get some aluminum heads and you will get it done without cutting up your HOs and spending almost what it would take to buy some E heads. Even your E heads might need port work as the more they flow the less cam you need to make the power you are after which = more streetable.
If you are dead set on your HO heads go for 500 streetable HP and be done with it.
The worse heads flow and all Pontiac iron heads flow like crap , the more nasty the cam you need to make power. There are very few real H0 head 455s that make a true 600 HP. I do not know of any unless big bucks are spent and its not worth is because the chambers are so deep.
There are no Pontiac HO heads that flow 300cfm unless they are full of brass/weld/epoxy. There are RAIV that flow than much but they have a smaller chamber, that is the reason.
These day I would not mess with a hyd roller, too many problems. Spend the bucks on bushed solid rollers and do not worry about little needle bearings flying around.
If you are dead set on using your HO heads Paul Carter is a good one to send them to.