77 400 Pontiac rebuild
 

Hello All,

I'm new to the forum and want to say hello.

I own a 1977 Grand Prix LJ. I looked for this car for over 20 years. Finally I found the one I was wanting!! It had all the options I was looking for. So happy to have found her. Anyway I am in the process of making it truly mine. I will be taking out the engine soon for a rebuild, and painting the car. I have a plan in mind for the way I want it to perform.

I know for a fact that the Pontiac 400 is a different animal. My frame of reference has always been Chevy engines. I would appreciate any advice for this rebuild. I want to get this right the first time, if you know what I mean. Does anyone know the best headers to fit this engine with D port 72 cc aluminum heads? Also just good solid advice on parts that work and perform well together? I have a Edelbrock performer RPM intake and 800 cfm carb installed now.

Appreciate any info..........

Thanks Gregg

Welcome to the PY forum !

If you have a casting number 500557 or 568557 block, I would not spend that much money on it. Those "557" blocks have thin, weak main webs, which have failed in numerous engines.

Since you plan on alum heads, you obviously want more power. So, I recommend putting larger chamber alum heads, on either a 455 or a 400 block stroker shortblock.

Here's an example.

http://lenwilliamsautomachine.com/455_Short_Block.html

If you go with a 400 block stroker, I'd go with a FORGED crank upgrade, which will cost $300-$400 extra.

A 400 block storker, with 87cc Edlelbrock D-ports, would make a nice streetable pump gas GP engine.

https://butlerperformance.com/i-2445...tegory:1287735

KRE has 85cc D-ports, but do not have the exhaust crossover hole. They are a little cheaper than the Butler/E-heads.

http://www.krepower.com/Pontiac%20Al...er%20Heads.htm

I wouldn't go overboard with the cam.

The Summit 2802 is a decent & cheap 455 cam.

https://www.summitracing.com/parts/s...RoCJdgQAvD_BwE

Here's a few more.

Crane 283951

https://www.summitracing.com/parts/c...IaAusEEALw_wcB

Crower 60243.

https://www.crower.com/camshafts/pon...m-284-hdp.html

Voodoo 268.

http://www.lunatipower.com/Product.aspx?id=1776&gid=287

Howards 410051-14.

https://www.summitracing.com/parts/h...w/make/pontiac

Well, you'll get lots of different opinions on cam choice, depending on what cubic inch you choose, how much power you want, and your budget.

But, I think we can all agree that you need to have it built by somebody who knows & has experience building Pontiac engines. Some Chevy guys can really mess up a Pontiac build.

Good luck with your build !

Welcome! I remember when my schoolmate and next door neighbor got a one year old '77 GP after we graduated high school. Pretty car, pale metallic green with white vinyl top and interior.
He raised the hood and there sat a Buick engine! That blew my mind..lol, so if that's the original engine, count yourself lucky to have gotten one of the last Poncho V8s.
https://www.nytimes.com/1977/03/15/a...sinful-to.html

Thanks guys....... Yes I do have the original Pontiac 400 in mine. I have read a lot about all the screw ups by GM back in that era.... I would have been upset to find a different engine than was supposed to be in the car as well. I have been researching the paint color for my block....... around 1976 / 19 77 years it seems GM abandoned the "Pontiac Blue" color and painted blocks in what they call Corporate GM Blue........

http://forums.maxperformanceinc.com/...1&d=1520366998

Picture of my Pontiac

Nice Grandprix :3gears:

I'm looking to have a good solid 450 HP or so when I'm done with this rebuild. I want it to run on 89 octane....... I'm not looking for it to be an everyday driver...... just want to be able to drive it to car shows and around town every once in a while. I have an engine builder to help me but as I mentioned before, I know you all probably know some things that work well and not so well........

I just got back from tooling around the country side and drove through town........ this car renews my soul every time I take it out..... Nothing IMHO duplicates the feel of it!!

But, I think we can all agree that you need to have it built by somebody who knows & has experience building Pontiac engines. Some Chevy guys can really mess up a Pontiac build.

Good luck with your build ![/QUOTE]


For Sure...................

For Sure...................[/QUOTE]

Where are you located , I'm sure all member's here have their local Pontiac Guru.

Wow, that is a super nice '77..

77? Good choice. I owned 3, all SJ's. Great cars. You'll love it.

Welcome my Friend!
We both live near Terre Haute IN.
I help him as much as I can and told him he would get good info here.

" I'm looking to have a good solid 450 HP or so when I'm done with this rebuild. I want it to run on 89 octane..."



The "557" blocks are said (by some) to be good to 400hp. Some have lived beyond this. Some have failed below it. It's a gamble and YOUR choice. I'd save it, for possible future resale, and build using a 455 block or a non-557 400 block.

You can make 450hp with a 400 cube engine. But, it's so much easier with 455 or more cubes. Plus you can do it at a lower rpm & have more low end torque.

Your call.

"...We both live near Terre Haute IN..."

Looks like ya'll are not too far from Paul Sandoval.

http://www.sandovalperformance.com/contact

Less than 4 hours from Paul Knippen. He posts here as Paul K , I believe it is.

https://www.facebook.com/PaulKnippensMuscleMotors/

Some have mentioned this guy, in East Troy, WI.

https://www.bizapedia.com/wi/schican...mance-llc.html

It's a little over 5 hours to KRE.

http://www.krepower.com/

Just under 6 hours from Butler.

http://www.jbp-pontiac.com/

About 6 hours from DCI.

http://www.dcimotorsports.com/servic...ngine-builder/

Hey, looks like ya'll are surrounded by Pontiac engine builders. But the cheapest decent Pontiac crate engines I'm aware of are built by Len Williams. He's in OK.

http://lenwilliamsautomachine.com/Home.html

Thank you all for information,

A couple of questions............ Do I for sure have a 557 block that is suspect to failure? Is there an easy way to figure out if I have a 557? What exactly fails on a 557 block? I would think any block is susceptible to failure. :confused: I would really like to keep original block in my car if possible.

As I mentioned earlier I have no plans to race this car...... just a burnout here and there and a highway dive now and again. Are the failures of 557 series due to stress issues?

again thanks for your information,

Gregg

"...Is there an easy way to figure out if I have a 557?..."

The casting number is on a pad below the rear of the passenger side head, as seen in the 3rd pic below.

"...What exactly fails on a 557 block?..."

The thin main webs crack at one of the main cap dowel pins holes, as you can see in the first 2 pics below. I've read that Pontiac tried some hollow dowel pins(4th pic), in place of the solid pins, so that the pins would absorb some of the stress and possibly reduce the possibility of cracking the web.


Has worked for some---broke for others. Many have bragged about how much power they made with a 557 block & how long they lasted. How lucky are you ? :confused:

IMO,450 real HP with a 400 wont be a very nice driver especially trying to run 89 gas.Tom

I love Grand Prix's... but low comp. 400 + buckets of cash = 450 HP
 

[QUOTE=1977GPX;5855526]I'm looking to have a good solid 450 HP or so when I'm done with this rebuild. I want it to run on 89 octane.......

"I would really like to keep original block in my car if possible".

considering the 2 statements above are a stretch of what is possible and a definite money pit.....

I recommend pulling the 557 engine and preserving it for the future.
Buy the engine of your dreams (450 HP) , drop it in and do some burnouts.
You will also need to replace the 8.5 BOP rear end after you bust the case open with 450 HP.
Then the Turbo 400 tranny will get smoked 'cause it is in the middle of your latest upgrades.

You need a detailed plan of how to get to your end goal...and a pile of money to execute the plan!!!

This site can help you with the plan.

The 557 block is not how to get there.

Dave

Dave,

I should have mentioned this but forgot. I have already replaced rear-end with a posi-truetrack I had a reputable guy put it in for me last summer. He assured me it would take the HP that I was wanting, and would stand behind it if anything happened.

I also had the TH 400 taken out and rebuilt and reinforced to handle the 400 plus HP as well. Again this was done by a reputable local guy, that also said he would stand behind it as well. I trust both of these guys.

This 557 cast block thing is giving me concern. I really appreciate your advice. Going to talk to my builder and show him all this information. I’m still not sure if I have this block yet.,... but it’s sounding like I probably do.

If the block is the matching numbers block to the car, it will be the 500557 block

The 481988 basically were cast to the end of the year 1974, I have one that came in a 75 Transam, has a date code of Ixx4 , but stamped 75.

Their were some 481988 blocks for W72 Transam untill 1978.

Doing a search on the forum wil lget you all the info you need,

"...Their were some 481988 blocks for W72 Transam untill 1978..."


Never read that before. Everything I've read says that the '77 W72 used the 500557 block, but the '78 & '79 W72 engines all used the XX481988 block which was VERY similar to the earlier 488981 blocks, but had holes drilled & tapped only for the 3-bolt mounts.

"...You will also need to replace the 8.5 BOP rear end after you bust the case open with 450 HP..."

Actually, the 8.5 rear end can be beefed up to easily withstand that much power, and more. Just an aftermarket carrier and 30 spline axles will probably be plenty for 400hp. Or you can make a nice budget drag racing rear, with a few more mods.

http://www.superchevy.com/how-to/485...grade-install/

http://www.hotrod.com/articles/build...ip-eliminator/

https://www.google.com/search?rlz=1C....0.bJw9qPLABMg

"...Then the Turbo 400 tranny will get smoked 'cause it is in the middle of your latest upgrades..."

"...I also had the TH 400 taken out and rebuilt and reinforced to handle the 400 plus HP as well. Again this was done by a reputable local guy, that also said he would stand behind it as well. I trust both of these guys..."


If he installed a 34 or 36 element intermediate sprag, it will probably hold up. If he didn't, it probably won't, if your engine will make 500ft lbs of torque and you get good traction.

My 455 bracket engines broke 2 of the 16 element sprags, one in a TCI TH400, which was supposed to be a "full competition" model with a manual reverse pattern valve body. These engines probably didn't have much over 400hp, if that much, but they probably did have at least 500 torque at just over 3000 rpm. Replaced the broken sprags with the 34 element sprags, which, at that time I think my trans guy said was a GM part which originally came in some HD TH400's, like maybe the 500ci Caddy models. Never broke one of those in our low 12 & high 11 sec bracket cars. Hundreds of runs.

So, if it was me, I'd ask the trans guy if he used the 34 element sprag or not. If not, I'd have him go back in and do it. If it has the later model drum which had the weak roller clutch instead of the 16 element sprag, he'll have to change out the entire drum/sprag assembly. But, they are readily available. Lots of 'em on Ebay. Either the early TH400 or the later 4L80E drums will work. Ebay always has quite a few for sale, bare & complete.

https://www.ebay.com/sch/i.html?_fro...ag&_sacat=6028

Thanks ponyakr,

Appreciate all the information and advice. I'm going to take it all in. I've been researching so much information. Kinda taking the fun out of it.....LOL. Anyway will update you all when things start to take place with rebuild Hoping to start in next couple weeks. I have a lot to consider. I'm finding as much information supporting the use of 557 block as I am opposed to not using.
Guess its a crap shoot......... :confused:

The way to think of it is that by the 75 model year Pontiac knew that going forward their engines would top out at about 200 horse (net) but that the bottom end of these engine blocks had been designed for 300+ (net) horses. combine that situation with a then desperate (thanks to the 73-74 oil crisis and new government economy rules) need to lower weight and fuel consumption. The bottom end of those 557 blocks were thinned out to save a few pounds (and dollars) for use and gutless catalytic converter equipped power plants. Building up one of those blocks is fundamentally unsound, like building a house in a swamp.

Your GP is a big heavy car so why not put your original engine on a pallet and instead install an earlier 455 (or a 455 crank in an early 400 block). A set of 71-72 big valve low compression heads are cheap and will produce more power than later EGR heads. The extra cost to do this in the overall cost of setting up a 450 horse drivetrain is insignificant.

North,

Thanks for your help. I have a friend that has an early 1968 block.....YS stamp so I’m not going to take the chance with my 557 block. Going to store it and push forward with the better block. It’s just not worth the risk when I have the option now.

Gregg

That's a great one to build.

If you want to use your block, use it and run it until it blows, if it blows. Personally, I would get another shortblock, but that's just me.

Here is what I would do given the chassis, usage, and intended performance goal parameters that you have provided.

400 factory shortblock (the closer to zero deck the better)
Box stock 72cc Edelbrock d-ports
Edelbrock RPM intake
800 cfm carb
SDPerformance Stump Puller II hydraulic roller cam
RARE 68-72 GTO-style Ram Air exhaust manifolds 2.5" collector
2.5" mandrel bent exhaust front to back
TH400
3.55:1 ring and pinion at a minimum

That should get you damn close to 450 flywheel hp without giving up much low-end torque.

If you just want to do a lot of street sweeping without worrying about power much beyond 5000 rpm, look for a hydraulic flat tappet cam in the mid 220's/low 230's range, e.g. the Lunati 307A3 (which is the old Ultradyne 280/288) or the Lunati 60903.