[Twistedpinion]

My Y88 Trans Am has done a fine job supporting all the boxes and Christmas decorations in the garage over the past four years, but it's finally time to get it moving again. I've ordered some parts, about to send the heads and block to the machine shop. Last big decision is the cam/lifters but I haven't been able to nail down a combo. I'd kinda like to go Hydraulic Roller, but I'm not set on that.

Here's where I am now

400 block
KB flat top 455 std bore pistons
I-beam forged rods
400 cast crank, 250 stroke

6x-8 heads - ports cleaned up and gasket matched going to have the heads slightly milled.
new SS valves
Crower 68404 springs

Q-Jet carb

Still need to pick an intake.

Goal is weekend driver with a strip visit maybe twice a year. Any help or advice much appreciated!

-Sean

[1971WARBIRD]

not sure what you mean by: 400 cast crank, 250 stroke.

do you main; a crank for a 400 block(3 inch mains) with 4.250 stroke?

make sure you add in what type trans and what rear gear you are going to run.these will effect what cam will work the best.it's about the whole combo of parts and how they work together.

[Twistedpinion]

Yes, that's what I intended to say, but was typing to fast

It's a 400 crank with a 4.250 stroke.

I have a TH350 transmission (several actually) that will be rebuilt by a transmission guy I trust.

I have 3.42 gears right now. I *think* they should be good for what I'm trying to do.

[1971WARBIRD]

if you haven't opened the ports up very much,the stock pontiac intake is hard to beat.they are heavy,which is why alot of people go with the alum intakes.if i went with alum,i think i would go with the RPM intake.using that on a TA and still keeping the shaker,you need the air pan sold by Navarro.http://forums.maxperformanceinc.com/...d.php?t=618982

try this link.http://forums.maxperformanceinc.com/...d.php?t=637533

they are talking about a heavier car,but they are talking about the cams that would work for you.I would contact Pontiac Dude,Cliff,or SDPerformance,they are the ones using and selling alot of hydro cam.depending on what head work is done,500hp is not out of the question,with well over 500lbs torque.the butcher special,or stump puller would work real nice with a 9/9.5-1 compression 455 set up like you are talking about.

[Twistedpinion]

I didn't pull a lot of metal out of the heads. I did fill the heat cross overs and smooth those back out.

Looking through that thread I saw a few different cams I'll look into. I think I need to talk to Cliff about my carb as well.

Brings up another question though, will I need to open up the pushrod holes for ALL roller lifters or only certain ones?

[rad400]

Not for roller lifters, but for 1.65 roller rockers.

[Twistedpinion]

ugh, thanks.

I've been reading so much lately it's all blending together.

[screamingchief]

Uhhh,there are a few flaws to point out here.

That 4.25" stroke crank is'nt gonna work with the pistons your talking about here.

I say that for two reasons:
1. The CH for the pistons is wrong.
2. The rods for the stroker crank use a different wrist pin size than the std. bore 455 pistons use.

The 4.25" stroke cranks come with the 2.200" BBC rod journals,as opposed to the pontiacs 2.250" rod journals,so they require BBC style rods to match that rod journal.

And the BBC rods (6.535",6.635",6.7",6.8" lengths) all use a .990" pin bore vs. the 6.625" long pontiac rods .980" pin bore.

So the std. bore pontiac 455 pistons will have the wrong compression height for sure,as well as the wrong pin bore size for the rods needed to mate with the stroker crank.

The CH for the 4.25" stroke will typically need to be appx. .020" shorter than the CH of the 455 pistons.
(that's 1/2 the difference in stroke:ie 4.25" - 4.21" = .040" difference ÷ 2 = .020")

So almost certainly those 455 pistons are gonna be sticking outta the hole with that 4.25" stroke crank,that is if you find a "work around" for the other "rod problem" here.

I dunno,you need to stop and think this over for a second or two and figure out exactly what bottom end pieces are gonna be needed here.

What you really need is a 3.0" main (400 cid) 4.21" stroke/2.250" (pontiac) rod journal stroker crank to work with the stock rod length and the KB 455 pistons,IIRC Ohio crank has those,so I suppose other places might have them as well.

That,or you need a complete 4.25" stroker reciprocating assembly,that includes the correct pistons & rods.

Then there is the plan of using the Crower #68404-16 springs with a HR cam.

Those springs are a little "light" in the seat pressure needed for a HR cam.

And they'll be pushing their limits with the lift most HR cams have as well.

A much better plan would be to use the Crower #68405-16 springs and install them @ 1.650" or so IH,as that set-up would do better in both those areas.

But that would require either milling the 6X heads spring seats .050",or using + height locks and/or retainers.

We're here to help,but dont get too far ahead of yourself on this sorta deal,take your time,and be sure to watch out for mismatches and such.

HTH

Bret P.

[Johnny406]

Are you saying that you are making a 455 out of a 400?

What year/casting# is the block? If you have a 557 block, you would be wise to find a better one to stroke it or keep it a 400. I've been racing my "557" block for quite awhile and it has held up fine with heavy TRW pistons and stock rods, but I attribute that to first class machining, luck, and keeping the RPM's down.

If you go the 455 route, the Tomahawk intake would also work well for you and gives you the option to change and experiment with carbs as it's made for both spreadbore and square bore carbs.

If you are going to go with a Q-jet by Cliff, which is a good choice, you need to order it soon or atleast get your initial order in as he always has a waiting list/period.

[Twistedpinion]

Bret-
Kind of embarrassing typing this since I'm asking for input and I'm causing the confusion since I can't read part specs.

The crank is in fact the Ohio 4.21" stroke with 3" mains. I checked the part on the living room floor. I just read the wrong description yesterday when reading the website yesterday.

I had the same concern with those springs yesterday after reading through a bunch of the threads I found here on the site. Funny thing is though, they aren't too far off what Comp Cams calls for with their HR cams. I'd rather worry about getting the right cam though rather since I do have another motor these springs will work in, so I won't be "out" anything if I end up buying another set of springs.

Again, thank you for the input.

Johnny,
This is a 557 block. From what I've been reading though, it would take a good amount more power than I'll be making to split it. As you said, you've been racing yours with out incident for some time and I know of a few others that are making similar horsepower to my goal and have been for years.

I do also have my W72 'XX' block that is numbers matching for the car, but I was planning on tucking that one away in case I ever wanted to do a factory correct build. Thoughts?

Thanks again

-Sean

[74Grandville]

use the XX block and get rid of the 557.

not sure the 557 is going to like the longer stroke.


If i was going to use the 557 I would keep it a 400 and keep the power below 375hp as experts have stated in other posts.

[tom s]

if you are going to do any serious racing then dont use the 557 block.With just street driving and RPMs under 5500 you should have no problems.SHOULD is the word.I built a street motor with the samr block,crank and light weight pistons and rods and made 585 HP at 6200 on the dyno.When it goes in the car it wont see 3000 more than a couple times a year.Tom

[PONTIAC DUDE]

Keep the hp in the 375/390 or so hp and you should be OK with the 557 block. But bottom fill it. stud it and have it align honed. Also make sure it has solid dowels in the main saddles.

[Johnny406]

Originally Posted by Twistedpinion

Johnny,
This is a 557 block. From what I've been reading though, it would take a good amount more power than I'll be making to split it. As you said, you've been racing yours with out incident for some time and I know of a few others that are making similar horsepower to my goal and have been for years.

I do also have my W72 'XX' block that is numbers matching for the car, but I was planning on tucking that one away in case I ever wanted to do a factory correct build. Thoughts?

Thanks again

-Sean

-Sean,

If I knew then what I know now, that 557 block wouldn't be in my car and it will be out in a couple of weeks for the new 455. I'm going to tear it down and inspect it real hard. If it checks out, that motor will then become the spare or will go in the red 81 as a street driver.

For peace of mind, I wouldn't do it.

[steve]

I'll get back to you guys on the 557 deal. Just put a 500+HP 557 into service.

[1971WARBIRD]

for a couple hundred dollars you can find a 70-75 400 that will be stronger and bolt right in your TA.

[screamingchief]

Hands down I'd use the XX block for this.

I dont touch the 557 blocks at all.

Never have,never will.

I have 4 400 cid engines/blocks around here,not a single 557 among them,1- 9799914 (70 YS),2- 481988 (73 XN/74 YH),1-481988 (74 YF).

Have 1 455 cid engine that's in my '72 bird (that's a 485428 casting,'71 or '72 YC code).

Me personally,I'd build a 3" main 4" stroker 350 cid block combo before I'd build a 557 block/stroker combo.

Matter of fact I have a '72 350 cid shortblock that's just sitting around here doing nothing,that one came outta the '72 bird (IIRC this one is 481990 casting,with YR code).

This just so happens to be one of the earliest things I learned about building "fast" pontiacs,that info was not so much about the webbing issue itself,just that the mid '70 up blocks were weaker in many ways than the earlier blocks were,and since then I have always avoided the later blocks as SOP.

Yeah,there's been some heated debate on this here,I really dont care what anyone else has to say on that deal,I build my stuff as I see fit,not how someone else tells me to build 'em,so I also try not to tell other folks how to build their own stuff,rather I just tell them what I would do,and leave the rest to the other fella to decide for themselves.

Me,I just cant afford to throw good money after bad,it's that simple.

That and I've never had even the slightest bit of trouble finding plenty of the earlier 400 cid blocks/cores to build.

More than once I've had them given to me just to get them outta someone else's way.



Bret P.

[bnorris_74]

That and I've never had even the slightest bit of trouble finding plenty of the earlier 400 cid blocks/cores to build.

More than once I've had them given to me just to get them outta someone else's way

Count your lucky stars. I live in the Sahara Desert of Pontiac Land.

[steve]

I Actually don't recommend doing it. My case was a little different. If I was starting from scratch I would not use the 557 either.

[screamingchief]

Yeah,you & I talked alot about that when you were posting about that deal Steve,and I totally agree your deal was sorta a "forced" decision,and like I told you then,I'd run it and not sweat it too much at all,pretty much said "let the chips fall where they may",for you,the money was already spent,and you did get a decent value for that money spent,so really there was no turning back for your deal,and spending more to address that issue would have been a big problem for you @ that time.

Though for anyone who has'nt got a fully prepped block sitting there waiting to be used,well they indeed would be in a different position,they do have the chance to ponder the pros & cons,and make changes before any real $$ is spent.

It does'nt cost any more (or less) to machine either block.



Bret P.