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Old 03-31-2022, 08:57 AM
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Default Jay’s 77 Trans am W72 build thread

I am going to start a thread for my W72 4 speed build. I had a lot of pictures at one point but can’t seem to find them now. But I have some pictures I will share, with more to come, including performance numbers, and show some of the mods I have done to the car. The car retains all it’s original drivetrain, which was a 200 HP W72 400 engine package with a ST-10 4 speed and 3.23s. It has fairly standard options for T/A’s in my area, PS, PB, A/C, rear defrost, firethorn red deluxe interior, and sterling silver exterior. Overall it is still in nice shape, with about 94,000 miles on it now. It has been repainted once, to a charcoal gray with black graphics. We do all of our own repairs, and paint and body work at our own shop. If the thread last long enough it will likely catch the repaint back to the factory silver.

Back when I first bought the car it hadn’t seen much love for awhile. It took a lot of little repairs to get the car so it was a dependable driver. Still have some things to do, such as the dash lights still don’t work and it is missing some ducting on the A/C. It ran pretty well though, my wife even drove it to work for a month while I worked on her daily driver. It was not particularly economical to drive, took some cranking after it set to get the qjet fired up, and 12- 14 mph was about what it averaged for fuel milage. It seemed to be dependable, at least until the heat core started leaking. I bypassed the heater and some how got an coolant air lock up in engine and it overheated, was pinging rather badly and hammered out a rod bearing. It happened after 20 miles of driving, with even a cool down in between before hand, I thought it was in the clear. So I had the stereo cranking and didn’t hear anything except the radio, until the noise was loud enough I heard it over the radio. About a mile from home I heard the rattling, and I looked down at the gauges and noticed it was overheating, I pulled off the road and shut it down….But it was too late. Funny thing was after it cooled down it still was not very low on coolant. I let it cool down, added a 2 qts of coolant, and drove it home.

Anyway, that is a little of the back story to what led me to these engine mod’s I did, and now have. My goal has been to retain all the original parts on the outside, including the 6x heads and factory egr intake, and only modify the engine on the inside. I will add the specs in my next post. I have and have had quite a few pretty fast street and drag cars, several low 11 second cars, a couple in the 10s. A couple turbocharged combos, but most the combo’s are fairly high compression (10-12:1 scr) naturally aspirated pump gas combos. I don’t beat on this one a terrible amount, it is more a fun cruiser. If it can run in the mid to upper 11s I am pretty content. I may have over shot that here initially with 550+ hp, but I would like nothing more than have to take off the headers and run log manifolds to slow it down. Hopefully by the end of this thread the car run deep into the 11s with it’s glorious (I am being sarcastic) egr goodies and looks something like this:
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Last edited by Jay S; 03-31-2022 at 09:24 AM.
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Old 03-31-2022, 09:36 AM
TAKerry TAKerry is offline
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Looking forward to your build. I have the same motor in my 79. It has been in the shop for a rebuild going on 15 months now. I have been told its almost finished. He did some upgrades to boost the h/p as well. Curious to see what you do with yours.

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Old 03-31-2022, 10:28 AM
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Looking forward to hearing more and seeing some photos!

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Old 03-31-2022, 10:28 AM
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After 15 months I am sure you will be ready to get your car going again. I worked on this off and on for 2 years to get it how I wanted it.

Engine specs: with all the secret squirrel stuff

Compression is 11.1 SCR, 91 octane pump gas
4.155” x 4.25” stroke,
Factory 455 N crank, surface imperfections removed, and balanced
Offset ground to 4.25” stroke
RJ resized to 2.20” BBC
MJ cut to 3”, shimmed Olds thrust bearing
Clevite full groove H series bearings, oil hole opened up for full oil flow
Main girdle that connects to pan rails
Milidon 7 qt pan
King rod bearings
Scat 6.8” H beam rods
Bored with a tq plate

JE, ceramic coated, gas port 12cc domed pistons, .043”, .043”, 3/16” rings
Block is squared, decked, and line honed for ARP main studs
60 psi pump with Teflon coated gears, milidon pickup

piston to deck height is .015”
.039” felpro gaskets.

6X-4 heads, fully ported 192-194 cc port volume (stock was measured between 148-152 cc), New exhaust seats and 5.11” length 1.77” ferrea’s SS valves, Manley 2.125” x 5.12” race SS intake valves.

I will post the flows numbers for the full range, but Max flow is 292 cfm @ 28” intake and 224 cfm @ 28” on the exhaust all it by .6” lift. Center exh ports are raised .5” at the head bolts.

Bullet SolId Roller Cam, 300* 308* @.006”, 245* 253* @.050”, .3823” lobes, ICL is 111* . Cam LSA is 114*.

Morel solid roller lifters with pin oiling, .003” lash intake, .005” lash exh, Compcam 928 valve springs, 170 seat pressure, 1.85” installed height, 10 degree locks and steel retainers.

Crane gold 1.65 rockers, .631” lift max net lift.
Comp cams hi tech 5/16” pushrods
BP 7/16” rocker studs

Factory 850 cfm qjet, Cliff R mods and jetting done by me. Ported stock egr intake (in progress) I have been running a ported torker in the mean time.

DOUG’s 1 3/4” headers, 2.5” X pipe with exh cut outs

Trans: stock ST10 with a billet midplate, dual friction clutch


Last edited by Jay S; 03-31-2022 at 10:50 AM.
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Old 03-31-2022, 06:37 PM
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Nice build Jay! Following as well. I like it with the Honeycombs!

Dennis

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Old 03-31-2022, 08:49 PM
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Hey Jay sounds like a kewl thread! How many Firebirds you got anyway? Did you ever have time to see what was up with the heads on the one you had out at Great Bend?

I put A.C. on the wife’s car over the winter & some other small projects. I hope to get some miles on the Rhoads lifter setup & see how they work out.

Look forward to your posts!

Murf

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Old 03-31-2022, 09:26 PM
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I would have preferred a silver TA, but am glad for my black car. For whatever reasons, silver paint on GM. Cars back then, always had problems.
Did 77’s come with honeycomb’s? I’m guessing that’s how you ought it....

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Old 03-31-2022, 09:52 PM
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Hi Murf. A/C in the convertible, that will be sweat. Your wife is going to want to drive that ALL the time!

This thread is for the same car I had at Great Bend. That first photo in post 1 is what I want to get the car back too.

I did some brazing on one of the intake ports and got in a hurry and didn’t take time to pressure check it. It was the only place I did any brazing in the head, I ended up removing all the brazing and redid it with a cast iron welding. The cast iron rod I use has a really high modulus of elasticity, higher that the factory iron, it is really resilient to cracking. I thought at the time that brazing would be a good fix, but where there is a thin area right next to a thick area it is tough to get the brazing to stick to the thicker iron. Brazing doesn’t mix well with other welding right next to it. I had to start over. I attached a photo of pressure checking.

I am switching back to the factory intake right now. The T/A is in the back of our race trailer. I have been looking and I have partial picture of my car. But no full photo’s. I think they were in my old phone . Lol

For Pontiacs we have a 68 GTO 400 HO with ported 16s (314 cfm) stroked to 455 cid, it is getting the Rhoads hyd roller cam set up we have. Our 71 T37 has a 455 and 280 cfm 96 heads, it is 10:1 and a big sff cam. The GTO is build similarly to my T/A, it is a high compression 11:1 pump gas build also. We are working on those, just went thi both engines. We also have a Super Stock 400 HO engine for the GTO we have been rounding up part for it. Not sure when we will get to play with that though, the GTO is going to be in street clothing most of the time. My brother and I just bought the GTO last year.
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Last edited by Jay S; 03-31-2022 at 10:42 PM.
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Old 03-31-2022, 10:55 PM
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Quote:
Originally Posted by 77 TRASHCAN View Post
I would have preferred a silver TA, but am glad for my black car. For whatever reasons, silver paint on GM. Cars back then, always had problems.
Did 77’s come with honeycomb’s? I’m guessing that’s how you ought it....
IRC, 76 was the last year for honey comb’s. I like swapping rims for different looks though, it will likely have an assortment of wheels on it. I am not sure what the car had when it was new, I am guessing it had 7” snow flakes. I suppose it could have had rally 2’s though. I wouldn’t mind some 17” snow flakes, but if I spend that much on new wheels it wouldn’t be as fun to do wheels swaps, the big snow flakes wouldn’t look quite as good on any of my other cars….

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Old 03-31-2022, 11:29 PM
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Ha! Murf that was suppose to be Sweet..not sweat. Sweat is what you had without the A/C!

First photo is of the main bearing oiling opened up.

Bottom Intake Port view, I think I had the 2.11s yet in that photo. That was around 275 cfm flow. 2.125” came later…


Bare short block weighted in at only 154 lbs!

And a random shot of one of our other past cars. I will through those in now and then so you don’t get to bored wandering thru this thread.
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Old 04-01-2022, 02:06 AM
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That silver T/A in the first photo was a low milage survivor car I took photo’s of to help document what my car originally looked like. My car has been that dark grey ever since I had it. It had dark tinted glass, kind of a darker color theme to it with the black bird, stickers and dark tint. It probably looked mean back when it was fresh, but scraping the glue left over from the crappy job someone did on the tint was not fun at all!

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Old 04-01-2022, 06:33 AM
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Ha! Murf that was suppose to be Sweet..not sweat. Sweat is what you had without the A/C!

Could go either way. I haven’t got it working yet! ��

Sounds like you got a lot of irons in the fire!

Will be interesting to see what you can get out of that combo in “stealth mode”.

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Old 04-01-2022, 09:57 AM
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silver/red 77/78 t/a's are my favorite color combo for these later year cars, but im kind of biased since that was my first T/A back in high school & into my mid 20s, was a WS6 W72 T top car with no power options.

sounds like a nice build, couple of questions on the specs posted- 11:1 with iron heads on pump gas? that seems rather high, does the cam & tuning combo allow you to do that without pushing the limits of major detonation? & is this the original 557 block that is stroked & plans to go mid 11's? isnt that way past the "safe" power limits of these thinner blocks based on what ive read over the years.

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Old 04-01-2022, 10:28 AM
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Love cool build threads like this one.
Seems like a really wicked motor build, and the cyl head porting looks spot on - reminds me of when I ported mine. Messy and time consuming.

And your "firethorn red deluxe interior" - My Bro had the same in his '76 455 T/A, and I still have a brand new full set of Firethorn Red seat covers in my basement for the last 40 years that he never installed

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Old 04-01-2022, 10:47 AM
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Murf if you get feeling overwhelmed by to many projects talk to me, I can make you feel better!

A silver and red tee top T/A for a high school ride. That is Awesome!

For thoughts on what is normal and to much for compression with iron heads and how much power you “should” push the 500557’s too, I think what you said is generally very CORRECT!

I did a bunch of stuff to this engine too prepare it for the power and the compression. Give me some time and I will detail some of that. My brother and I both have engineering degree’s in machine design. I have an Agricultural Engineering degree, similar to a Mechanical Engineering degree for machine design. There is usually (not always, sometimes I am just flat nut’s ) some reasoning to the madness.

Our high compression pump gas ventures started back when we turbo charged one of our cars in the 1990’s. We were running that cuda drag car , and had a turbo charged street engine in another car. We started to contemplate that if we could run an effective boosted compression of nearly 12:1 on pump gas, then why was it not possible to do that N/A? We started looking at what makes each engine different for how it reacts to pump gas.

Probably one of my best example’s for what is possible for compression is our 69 Dodge Charger, which has a 510 CID engine with iron heads. A TON of people struggle to run 91 octane with mid 9s compression with 440s, open chamber heads, no quench at all, pistons way down in the deck, fast rate cams, tons of different issues. Big cid’s with the same component’s as smaller cid’s generally make some of that worse. In theory that 510, which is based off of a 440, should not be super friendly for pump gas. Our engine is 10.5 SCR and we run it on 87 octane, it is roughly 550 HP. It isn’t like it “barely” works either. It has full timing, doesn’t ping anywhere ever, we shift at 6000-6200 rpm. We built it more than 20 years ago, I drove it to town last night. It is a blast. Basically we took some of what we were doing with other makes for boost and high compression, and started applying it to Pontiac’s. It isn’t just one thing, it is a bunch of things.

I do like the firethorn red. My son thought it was Kool. This photo was back when I just brought the car home for the first time
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Old 04-02-2022, 02:50 PM
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I've learned here about the proper quench distance. Makes sense, the tight quench super mixing the mixture trapped between the head and piston...

SD455SJ built a mild 400 with a seemingly smallish cam (cam was perfect for THAT engine!!!)excellent quench, excellent power, excellent build!!!

Chief used to post some hre. One time he was looking for some relatively thick head gaskets, like .080 inch. Using them on a turbo'd engine. I don't have the knowledge why a turbo engine would not like tight quench, like a NA engine. May have to do with heat, already super mixed mixture, I don't know...

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Old 04-03-2022, 08:39 PM
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When the compression is 11 or more with older chamber designs the quench is usually not quite as important as 10 and below. Quench will force the air and fuel mixture toward the spark plug, and makes the mixture burn more homogenous. Raising the compression tends to do some similar things. Most engine builders have a good grasp on a tight quench allowing the engine to want less timing for max power, but it seems like it still get overlooked often on builds. Quench brings all good things no matter what the compression.

We prefer to set the timing up so it comes in fairly late with higher compression, the timing curve’s are set up pretty much like factory curves on high output engines. Nothing really special. This engine has a modest .054” quench, it has some quench with the piston domes also.

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Old 04-03-2022, 08:44 PM
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Over the winter there was a guy here in central Nebraska that built a turbo charged 400 using a 500557 block. I don’t know much about who did the engine, but they clearly had no clue what they were doing with Pontiacs. It didn’t even have main studs. They broke one of the main bulkheads out tuning it on a wheel dyno.

Even so….It broke at 860+HP….AT THE WHEELS!


Last edited by Jay S; 04-03-2022 at 09:09 PM.
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Old 04-05-2022, 09:25 AM
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I did a lot of research on the 500557 blocks. I don’t know of ANY mods to that guys turbo engine that would have ended much different, that was over 1000 HP! It will even be asking a lot out of an earlier heavier block if he doesn’t step up and add 4 bolt caps, preferably splayed.

For smaller HP builds, all the weak blocks I have seen that broke the main webbing out had dowel pins. The first year of production there was a lot of trouble with a crack starting at the dowel hole. The holes are drilled all the way thru, once a crack starts it will grow until the webbed breaks out. But, there have been a couple effective methods to stop a crack from starting.

The best modification I have seen, at least more most moderate street builds, is to increase the dowel size to 5/16”, and use a longer dowel the goes the FULL length of the dowel hole. That mod along with main studs using up to a 4” crank the block can take a good amount of HP.

I have found some builds machine the block to use 4 bolt main. The outside bolt’s are pretty short, it is pretty expensive for not a lot of improvement in strength. But it is probably a little stronger than the 2 bolt, it still needs the longer dowels.

Pontiac’s solution was to use roll pins or spring pins instead of solid dowels to index the main caps. The springs put an equal force on the drilled hole. This stopped the cracks that started at the dowels. But the problem they had is it didn’t index the caps enough. Those engines, with a good amount of abuse, have a tendency to spin main bearings.

For this engine I used a main girdle to support the main caps. It lowers the stock pan a 1/4”, but it uses a stock aftermarket oil pan. It adds another level of indexing to the mains. I kept the roll pins and it has ARP studs clamping the main caps on. I have another build similar to this one that has solid dowels and the full girdle.

This is my thoughts on power output on the weaker late 500557 400 blocks.

400 HP -Stock
500 HP—ARP studs, line honed, longer and enlarged dowels, 3.75” or 4” crank
600 HP, strokers, Full girdle, halos and pan rail supports, ARP’s, line honed
ARP main studs, line honed, full main girdle with
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Last edited by Jay S; 04-05-2022 at 09:42 AM.
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Old 04-05-2022, 09:44 AM
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I will post the head flows next. But here is some explanation on compression.


There is not much special tuning like jetting or special ignition curve’s on this engine. It isn’t hard to tune. At least NOT YET. The massively ported single plane intake and headers I have on it right now put peak power well past 6000 RPM. I expect there could be some tuning challenges as I make changes that tend to narrow back up the power band, like a dual plane intake, or possibly exhaust manifolds. Right now I don’t even know how many RPM’s it can run…It buries the Tach. 6000 is a good place to stop for now.

For the ignition the distributer and curves are original. The initial timing is 14, with 38* total. It is running NGK plugs with a 7 for heat range, pretty cold plugs. I like to keep the operating heat range for spark plugs on the cold side if possible.

Porting heads for more flow, bigger port CSA’s, big inductions, big headers and exhaust, combined with the right cam, can work at pulling more air into the engine. More air pulled into the engine from those things can cool the air&fuel charge, and make it more dense and less prone to preignition.

The cam on this engine has an LSA of 114, but the way it is ground with the long closing ramps it acts like it is a 116 LSA. To reinforce that, the heads are ported in such a way the LSA acts quite a bit wider also. The heads are ported to shift some of the air flow from scavenging to cylinder fill. When the heads flow a great at low lifts it has a similar effect of narrowing up the LSA of the cam. If you left the compression low, and lost the low head flows from porting, the porting would be hurting power. The compression helps the top end power a lot, off setting the loss of power from less flow at during scavenging. The camshaft and the head flow are matched up to the compression. The end result is a smooth long power band, that is not very picky on carb settings or shift points. Cranking it over when starting your would never guess it has that much compression. I have done some cams in engines that by the way they act you would guess the engine to have 11:1 compression, but are only in the 9s. This combo is opposite of that, it is at 11 and it’s manors act like it only has 9:1.


Last edited by Jay S; 04-05-2022 at 09:55 AM.
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