[Shift'n Gears]

Hi - Just picked up a 78 S/E with a W72 pontiac 400. I'm not sure how long the car has been off the road, but the carb and intake are in the trunk, so there is no telling what was going on before I got the car. To be on the safe side, the engine will need a full rebuild to stock specifications. I'm mechanically inclined and considering doing the rebuild myself. Are there any good guides out there for rebuilding a W72 and are there any pitfalls I need to be aware of?

[PontiacJim1959]

First thing you want to do before anything, is take the engine/parts to a machine shop and have them hot tank and magnaflux the parts looking for cracks. Then the shop will evaluate what you have - ie what bore size to clean up the engine.

Do that first, then you go from there on your build. No need to plan anything else and start choosing parts if the engine turns out to be bad.

[Grand73Am]

"How to Rebuild Pontiac V-8's" by Rocky Rotella.

And the 1978 Pontiac Service Manual.

Those should be all the guides you need.

[78w72]

w72 is the same as any other pontiac engine of that era as far as rebuilding, if thats what youre asking. follow standard engine rebuild procedures.

consider forged pistons over stock cast but for a stock rebuild cast are ok too. send the carb to cliff ruggles or SMI for a rebuild or do it yourself with a kit from cliff.

[Shift'n Gears]

PontiacJim1959 - Thanks for the advice. Will definitely take the parts to a machine shop to have them checked out.

Grand73Am - Thanks! Got the 78 shop manual already and will have to get the book by Rocky (didn't know he wrote it). I know he has a lot of insight on the 400's and I am sure it will be a big help pointing me in the right direction.


78w72 - I was looking for some resources like Grand am mentioned so I could do some research to see if it is something that I wanted to attempt. This will be strictly a stock build for my Y84 as it's primary duty will be a show car. I'm actually hoping all I have to do is put in new rings/bearings/ etc... to freshen it up since I am looking for originality and not modifications. Still pondering the forged pistons as I know they are better, but not sure they will be needed in this case. By the way where is SMI? Never heard of them. Cliff is pretty much the Q-jet guy, I've but I head he has a VERY long back log. Do you have any experience with SMI?

[78w72]

Originally Posted by Shift'n Gears

PontiacJim1959 - Thanks for the advice. Will definitely take the parts to a machine shop to have them checked out.

Grand73Am - Thanks! Got the 78 shop manual already and will have to get the book by Rocky (didn't know he wrote it). I know he has a lot of insight on the 400's and I am sure it will be a big help pointing me in the right direction.


78w72 - I was looking for some resources like Grand am mentioned so I could do some research to see if it is something that I wanted to attempt. This will be strictly a stock build for my Y84 as it's primary duty will be a show car. I'm actually hoping all I have to do is put in new rings/bearings/ etc... to freshen it up since I am looking for originality and not modifications. Still pondering the forged pistons as I know they are better, but not sure they will be needed in this case. By the way where is SMI? Never heard of them. Cliff is pretty much the Q-jet guy, I've but I head he has a VERY long back log. Do you have any experience with SMI?

i agree cliff is the man for q-jets, he's done 2 for me but back log can be an issue & if you dont need custom performance mods then other alternatives can rebuild it.

does it run ok now? if it runs & has good oil psi & passes a compression test, maybe it just needs a valve job & cleaned & regasketed? & a carb rebuild.

SMI is sean murphy inductions, he/they do great work for rebuilds & full restorations, been around awhile & some here have used them. i had them do a 1978 q-jet for a friends mild 467 stroker, it was a stage 2 rebuild & it looked & ran great. had about a 3 week turnaround.

https://www.smicarburetor.com/

[Shift'n Gears]

Between the ones that cliff has done for you and the one from SMI, which did you like better for functionality and aesthetics? Since this is for a show car, I do want to make sure it is replated correctly as well.

As far as the engine, When I purchased the car, the Carb and the intake manifold were taken off, so it wasn't in running condition and I don't know why. In theory I could do a compression check, and if OK, put the carb and intake on. But not knowing the history of the car, it seems like a safer plan to just pull it apart and go through it to make sure it is right. I'd hate to restore the rest of the car and have an issue and then have to pull the engine again.

[78w72]

the 2 cliff did were rebuilds with mods for performance, one was for a 78 W72 4speed t/a with a mild cam & headers i rebuilt with speed pro forged pistons, runs great right out of the box, havent even tuned idle screws on that one. the most recent is another 78 q-jet i used on a 500+hp alum head stroker engine in a 72 firebird, converted to elect choke & again runs great in all ways, street, strip to low 11's & hot or cold weather. both those carbs were in good condition & didnt need any restoration.

my friends SMI carb was also in good shape but needed some resto work, had most parts replated & when cleaned up it looked great too. was a decent price for what was done too. that carb ran very good & did 430hp on a couple dyno pulls during break in.

if this is mostly stock & only does shows or cruises i think youd be very happy with SMI, send a message to them & ask for a quote for what you want done. or check around your local area or a google search, there are quite a few places that do rebuilds.

[68ragtop]

Are you going to turn this into a build thread?

Did you check all the numbers & dates on the block, heads, intake, carb etc? Is this a Auto trans W72 or a 4 speed? Guessing a 4 speed based on production numbers, but just curious.

There is a great thread with many pictures that Bentwheel bob has of his 78 S/E where originality was covered on endless detail items, especially & primarily underhood stuff.

Post some pics if you don't mind, & congrats on the project!

[Shift'n Gears]

68ragtop - Yes. Before I purchased the car I verified that the VIN on the engine block and BW T-10 matched the VIN. The carb is the correct part number (VINs are not stamped on carbs) and it has the correct 78 intake. It is a Numbers matching 1978 Y84 W72 WS6 4sp with PHS documentation. I looked for a car like this for over 20 years and was real happy I could bring it home.

The real point of this thread was to help get some direction on the engine rebuild and to see if I wanted to attempt it myself. However I like your idea of a thread documenting the rebuild of the car.

Here are a couple of Pics the day I brought it home. There will definitely be more to follow.

[ponyakr]

Originally Posted by Shift'n Gears

Between the ones that cliff has done for you and the one from SMI, which did you like better for functionality and aesthetics? Since this is for a show car, I do want to make sure it is replated correctly as well.

As far as the engine, When I purchased the car, the Carb and the intake manifold were taken off, so it wasn't in running condition and I don't know why. In theory I could do a compression check, and if OK, put the carb and intake on. But not knowing the history of the car, it seems like a safer plan to just pull it apart and go through it to make sure it is right. I'd hate to restore the rest of the car and have an issue and then have to pull the engine again.

Cliff posted that he quit plating & is not taking on any more rebuilds now.

http://forums.maxperformanceinc.com/...3&postcount=21

Here's another builder, in Texas, that's said to be good.

https://quadrajetpower.com/contact-us/

Here's one on the East coast.

http://www.everyday-performance.com/...arburetors.htm

[ponyakr]

If you go with new pistons, DON'T buy cast pistons.

The cheapest forged pistons are the Speed Pro brand. I've read that they quit making the SP 455 pistons. May have also quit making the 400 pistons. But, they are still listed on some sites. Vendors may just be selling what's on the shelf. Anybody know if SP is still making the 400 forged pistons ?

https://www.ebay.com/itm/Speed-Pro-T...YAAOSw-xVaFdO8

If no SP forged pistons are available when you get ready to buy, I recommend Auto Tec brand. They cost more than SP. But they are lighter & can use floating pins & bushed forged rods, which I also recommend. Good forged rods & pistons are a good idea, even for near stock rebuilds. Don't have to use a big lumpy cam or have the heads ported, just because it has forged rods & pistons.

https://shanonsengineering.com/produ...at-top-pistons

"...This will be strictly a stock build for my Y84 as it's primary duty will be a show car. I'm actually hoping all I have to do is put in new rings/bearings/ etc... to freshen it up since I am looking for originality and not modifications..."

Gotta be careful on this site. Many of these guys will have you building a hot rod engine. Their famous saying is that you don't wanna leave any power "on the table". For what you seem to want, all that extra power would be best LEFT on the table. No reason to build for 400hp, if all you wanna do is putter around & go to some shows. You just need a low lift, low duration cam that will idle smooth, & have decent torque, under 3000 rpm, where you'll be operating, MOST of the time.

Now, if you wanna burn lots of rubber & wind it past 5000 rpm, on a regular basis, that's a different thing all together.

[78w72]

Originally Posted by Shift'n Gears

68ragtop - Yes. Before I purchased the car I verified that the VIN on the engine block and BW T-10 matched the VIN. The carb is the correct part number (VINs are not stamped on carbs) and it has the correct 78 intake. It is a Numbers matching 1978 Y84 W72 WS6 4sp with PHS documentation. I looked for a car like this for over 20 years and was real happy I could bring it home.

The real point of this thread was to help get some direction on the engine rebuild and to see if I wanted to attempt it myself. However I like your idea of a thread documenting the rebuild of the car.

Here are a couple of Pics the day I brought it home. There will definitely be more to follow.

nice looking car. if you werent aware, at some point that was repainted & someone added huge wheel well flares that are not stock. do you plan to keep that look or go back to stock looking fenders & quarters? if originality is the goal they should be changed.

as for the comment about "being careful on this site" i dont think anyone will tell you to build a hot rod engine for your goals or stock rebuild & being a show car, but just the same, you do not need forged rods & technically dont "need" forged pistons. forged pistons are stronger & a benefit for higher horse power but not needed for a basic stock rebuild. when i mentioned them i wasnt sure what your plans/needs were for the engine rebuild.

FWIW, i rebuilt a 455 with 6x-4 heads off a W72 in my 78 t/a on a budget back in the 90's with a cast piston kit from summit, put a decent size cam in it & headers & holly carb etc, as a teenager & into my mid 20's i beat the livin crap out of that car & raced it on the street almost daily & nightly... not the crazy street racing you see today, just stop light to stop light while "cruisin the ave" or for serious races we has a 1/4 mile marked off on a divided 4 lane highway where there were no other cars. point being, cast pistons & rods lived just fine for almost 10 years of abuse & countless 6000rpm runs. back in the day we didnt have forged rods for pontiacs & the majority of them lived fine under lots of racing & abuse, your stock engine will be fine with cast parts for your purpose.

best of luck on the resto!

[68ragtop]

As long as you guys are talking pistons, Do any of the piston mfg's today have anything closer to zero deck?
I have found many of the aftermarkets slugs are often .030" in the holes. I am guessing this is so they will fit all
blocks even if they have been surfaced or decked from previous rebuilds. I rebuilt a 72 455ho a number of years ago & those pistons
were identical to the originals. sunk in the holes maybe .005 - .008" as I recall from memory. Others I ended up
having to deck the blocks to get them nice & tight. Not going to make a big difference on a 6X head,
but I was just curious if anything has changed.

[Poncho Dave]

Building a w72 motor for my 78y82. Using the speed pro forged pistons and had to deck the block to bump the compression up. Cylinder head castings were very sloppy. Spent quite a bit of time cleaning them up. Sending the exhaust through some repo RA manifolds rather than those pathetic logs and a true dual exhaust.

Looks like some wild old flares on that car! Hopefully the metal is still good. If you need to change quarters, I’ve installed a few and have been pretty satisfied with the repos.

[Shift'n Gears]

ponyakr - Yes I contacted Cliff and he wouldn't accept my carb. Said he had too much of a backlog. He hadn't mentioned anything about not plating though, So it looks like I will be shopping around to get the carb rebuilt.

78w72 - yes very much aware that the flares were added (to my horror). The next step is to see if the fenders and quarters need to be replaced, I'm not so much worried about the fenders, but i am nervous about the quarters as I have not patched metal before and I am fairly confident that they will need to be replaced.

Poncho Dave - What brand quarters do you recommend? I'm hoping there are repos that will match fairly well without much adjustment.

[abefromen]

Originally Posted by ponyakr

Here's one on the East coast.

http://www.everyday-performance.com/...arburetors.htm

Avoid Avoid Avoid

Had one done by him a few years back and it was so poorly done and so effed up I sent it to Cliff to have redone. It was a mess.

I believe Cliff is recommending the people in Texas.

[68ragtop]

ITs amazing to me how well these quadrajets can run if tuned by someone who really understands them. Had mine done by a local carb wizard, but its his part time work / hobby & it took over 6 months with pestering to get mine done for my GTO. He took all the info from my engine. cam, compression exhaust / intake & then went to work. Also has a flow setup he build to simulate vacuum. I am simply amazed at how well the car runs & starts cold. I never had a carbed car run as good as this one. One of the biggest problem quadrajets have imo is they are tightly designed around engine vacuum, so when you have a bigger cam with lower vacuum, a stock tuned quadrajet starts to become a problem. biggest is the idle circuit. there is a sweet spot for the primary blades & with less vacuum you have to open them up to get a decent idle speed & this messes with the circuit design. This is why you see holes in the blades of the older ram air carbs. allows more air flow to the engine while keeping the blades in the right area. They are truly amazing carbs that don't get enough credit. I always knew they didn't work well on modified engines & it was very cool to learn why and start understanding them a little better in recent years.

However, on a stock engine, with stock W72 parts & the correct carb, I would think just a good rebuild by someone who knows what they are doing should be all you need?

I have a 79 W72 4 speed, all stock & it runs great. Well, at least the last time I drove it, it did.

I don't recall what bentwheelbob did with his 78. he camouflaged a 455 & put his number matching engine under the workbench, but made it look completely stock down to the factory zip ties. No doubt his quadrajet was modified, but I am not sure who did his. maybe he will chime in at some point.

[ponyakr]

"...Do any of the piston mfg's today have anything closer to zero deck?..."


YES ! As I've posted many times, it has been said that Auto Tec will move the pin hole, at no extra cost. That way, you can get whatever pin height you need, in order to get near zero deck height, WITHOUT having to cut EXTRA material off the block.

https://shanonsengineering.com/produ...at-top-pistons

Paul Knippen here, can order Auto Tec pistons for you. Probably some others , also.

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

As has also been mentioned here many times, the machine shop should do the square-up deck cut, or whatever you wanna call it. BUT, after the decks are square with the crank CL, if you get the correct piston pin height, no more material will have to be removed from the decks, in order to achieve zero deck height.

The biggest pin height I'm aware of for a shelf 400 piston is 1.720, for the Icon brand pistons.

https://www.cnc-motorsports.com/ic89...4150-bore.html

May also be some others, including the KB "hypercast" pistons.

https://www.summitracing.com/parts/u...0/make/pontiac

The SP L2262F is 1.714.

https://www.ebay.com/itm/Speed-Pro-T...AAOSw-xVaFdO8I

I think the SP cast pistons are now 1.700.

Obviously, if you have the money for high dollar full custom pistons, you can get the pins where you want 'em. I think the Ross pistons are somewhere around $800, probably more.

https://butlerperformance.com/i-2445...tegory:1234850

[Poncho Dave]

Have installed nothing but AMD as I believe they are the only ones stamping them. The only area needing messaging are the marker indentations. All I’ve had to do was slot out the holes to center the bezel.