N/A 4.1 shortblock..for my 87 gn..ne1 done this??

[phillyvader]

Hello guys... I just want some opinions...I just got a production 4.1 complete running engine from the j yard 90k mi..it is a 291 block and it does have the turbo crank and rods..but it has the factory buick pistons...and the motor has definitly never been rebuilt all signs point to a factory engine...I want to use this short block in my 87... stock turbo stock everything..ne1 else do this??
......It will be a street motor, Iam not racing it, would like to run 18lbs of boost tho for the ocassional corvette red light meeting....I am going to have a custom chip burned and upgrade my fuel system with a denso, adj fp,injectors ect.. any input in appreciated thanks guys

 

[dr_frankenstein]

the NA pistons wont last. they will need to be replaced.

finding good pistons, is the hard part.

most are comfortable with using the hyperutectic pistons that are off the shelf. I do not and so custom pistons are in order for forged.

But for what you are wanting to do, hyperutectics should work just fine.

but here are the key things to remember.

1, needs drain back hole drilled.
2, has 14 bolt oil pan/timing cover
3, old style block, requires 4.1 cam bearings.

:biggrin:A.j.

 

[phillyvader]

the NA pistons wont last. they will need to be replaced.

finding good pistons, is the hard part.

most are comfortable with using the hyperutectic pistons that are off the shelf. I do not and so custom pistons are in order for forged.

But for what you are wanting to do, hyperutectics should work just fine.

but here are the key things to remember.

1, needs drain back hole drilled.
2, has 14 bolt oil pan/timing cover
3, old style block, requires 4.1 cam bearings.


:biggrin:A.j.

Thanks for the info.....but now u got me thinking....are the stock pistons made of the same material as the turbo 3.8 pistons?? I understand that they do not have the re -enforcement steel built in like the turbo pistons do...the reason i ask is because i have a shop near by who can coat the piston tops with ceramic..this way i dont have to rebalance the whole assembly.

 

[dr_frankenstein]

Thanks for the info.....but now u got me thinking....are the stock pistons made of the same material as the turbo 3.8 pistons?? I understand that they do not have the re -enforcement steel built in like the turbo pistons do...the reason i ask is because i have a shop near by who can coat the piston tops with ceramic..this way i dont have to rebalance the whole assembly.

well the problem, is that there of NA design, which is different than the turbo casting itself. The stock turbo piston has a much heavier crown, top, and added material to the wrist pin to give strength during boosted use. The NA is just the basic design of what the piston needed to be to run for naturally asperated use, a light weight, low expansion casting.

if you hold an NA slug and a Turbo slug next to each other you will feel the definite weight difference between the 2.

While many have successfully used an NA shortblock for a temporary fix, it takes a solid understanding of tuning to pull it off, I myself can vouch for how easy it is to make a mistake. A simple timing error on my NA block with a CARB turbo..... and the result was a huge mess.

But why take the chance? its not any fun pulling and dropping a GN motor.... why do it twice cause you cooked the slugs right out of the block? do it once and forget about it.

if you need a set of pistons I have a new set of .030 hyperutectic 4.1 pistons with rings that i could cut ya a deal on.

:biggrin:A.j.

 

[phillyvader]

well the problem, is that there of NA design, which is different than the turbo casting itself. The stock turbo piston has a much heavier crown, top, and added material to the wrist pin to give strength during boosted use. The NA is just the basic design of what the piston needed to be to run for naturally asperated use, a light weight, low expansion casting.

if you hold an NA slug and a Turbo slug next to each other you will feel the definite weight difference between the 2.

While many have successfully used an NA shortblock for a temporary fix, it takes a solid understanding of tuning to pull it off, I myself can vouch for how easy it is to make a mistake. A simple timing error on my NA block with a CARB turbo..... and the result was a huge mess.

But why take the chance? its not any fun pulling and dropping a GN motor.... why do it twice cause you cooked the slugs right out of the block? do it once and forget about it.

if you need a set of pistons I have a new set of .030 hyperutectic 4.1 pistons with rings that i could cut ya a deal on.

:biggrin:A.j.

Well considering a carb motor uses a distributor and a carb i can see how its ez to have a timing issue and a tuning issue. I think im gunna give eric a call and see what he can do as far as a chip goes. I actually have a set of pistons but i really dont want to use them yet. I think with a power logger and a turbo tweak street chip,and good fuel system I might be ok for my application. I searched this and there is a guy on here who ran this set up with a cam and ta49 and went 11's on n/a pistons.... I like a challenge...we'll see if i have the same attitude next week? if this thing holds! hahaha....Hold those pistons! hahaha

 

[phillyvader]

bump

 

[phillyvader]

Cooooommmee ooon GUYS! Spill the beans! Has anyone else attempted this with sucess???... I know its a touchy subject and goes against the laws of forgedphysics..Im not judgeing...Im sure most of u have 1k pistons in your motor now...but u were young at one time???..u know how it is........ coooooomeeee ooon... be a paaaal !!! lol

 

[yullose]

Cooooommmee ooon GUYS! Spill the beans! Has anyone else attempted this with sucess???

I think most on this board know better than to try it. :wink:

You would be far better off using a stock 86/87 turbo shortblock.

If that's not an option, just put good pistons in it.

Cutting corners and trying to save a buck will always come back and bite you on the ass...

 

[charlief1]

The pistons are the key to doing this. If you don't at least use a hypetutectic piston you will have problems.

 

[phillyvader]

Thanks for your input yullose.....I actually just spun a bearing in my 87 turbo motor, so i bought the 4.1 to play with...Im really not trying to be cheap,my 87 motor is in the machine shop now...I like to experiment and brainstorm ideas thats all....its a great street motor so im thinking with a good tune, bigger cam, bigger intercooler and focus on lowering the oil, incoming air and coolant temps, I think that might keep detonation at bay. Im using a stock turbo, most of the time boost will be at 15lbs...i have a denso fp, fpr. Horse power in the 400s?? maybe?? Some say im cutting corners by using these pistons...well i say good pistons are a band aid for a bad tune, unless your motor is making some serious hp and boost. Simply I think it CAN be done.

 

[charlief1]

TurboBuicks.com - Build a Budget 4.1 Motor!

This should help some.

 

[phillyvader]

TurboBuicks.com - Build a Budget 4.1 Motor!

This should help some.

Thanks Charlie.....I have read this...and it was very helpful...but...it conterdicts itself... its sayin somtimes there good..sometimes there bad...due to what???? bad tune? BINGO... It says they are good past 600hp..my motor is around 400. A hyper piston is aluminium with silicon content..which makes it expand less and harder to melt and it will bend before it snaps...I get it. Heat in the combustion chamber causes pre ignition. Keep the heat out no detonation..keep the egts warm lol and incoming air, oil, and coolant at a lower temp detonation stays away..IMO pistons live Can anyone argue this??

 

[phillyvader]

Im just gunna put the hypers in. Def the smarter thing to do thanks guys. All tho I do still believe that these pistons can be made to work if detonation is held back.. but it would limit power potential.. If I had the actual ratings of these pistons that would help alot, not just the hp of the n/a motor. Open ur minds up alittle guys there is more than one way of doing things. Not ev1 wants to be the fastest.

 

[yullose]

Those stock junk pistons are good for exactly what they were designed for... about 150hp. They are heavy, they are cast, they are weak and brittle. Basically everything you DON'T want in a piston.

You are making the right decision by putting the hyper's in it.

And FWIW, if you want to do a poor man's balance job... just balance match the pistons. It will still be better balanced than a stock motor from the factory.

 

[phillyvader]

Those stock junk pistons are good for exactly what they were designed for... about 150hp. They are heavy, they are cast, they are weak and brittle. Basically everything you DON'T want in a piston.

You are making the right decision by putting the hyper's in it.

And FWIW, if you want to do a poor man's balance job... just balance match the pistons. It will still be better balanced than a stock motor from the factory.

Thanks again. Stock pistons are BAD!! Bad pistons! I hate Cast aluminum!!!Anyone have a big scale??...coome on all u older guys dig in ur
80's closet...im sure u have one next to the beer bong and the high school jacket lol hahahaha

 

[charlief1]

Thanks Charlie.....I have read this...and it was very helpful...but...it conterdicts itself... its sayin somtimes there good..sometimes there bad...due to what???? bad tune? BINGO... It says they are good past 600hp..my motor is around 400. A hyper piston is aluminium with silicon content..which makes it expand less and harder to melt and it will bend before it snaps...I get it. Heat in the combustion chamber causes pre ignition. Keep the heat out no detonation..keep the egts warm lol and incoming air, oil, and coolant at a lower temp detonation stays away..IMO pistons live Can anyone argue this??

Well...you can always go the way I decided on. Get some 6.65" long rods and have a custom piston made. It will have more bottom end than you want but it will launch like a rocket after all.:biggrin: LOL

 

[phillyvader]

Thats a good idea...the longer rods will also aid in keeping detonation away by keeping the piston at tdc longer....But they will also move the piston pin up closer to the crown, putting more stress on the pin and depending how far it moves up the ring lands may also move up closer to the heat..might beat the rings up??? What motor is the rod out of??.. what times are u looking to get out of this thing?

 

[v6fever]

4.1 build

I have a good set of used forged pistons, and a few other items for a 4.1 build if you are interested.

 

[phillyvader]

sure send a pm what do u have?

 

[charlief1]

Thats a good idea...the longer rods will also aid in keeping detonation away by keeping the piston at tdc longer....But they will also move the piston pin up closer to the crown, putting more stress on the pin and depending how far it moves up the ring lands may also move up closer to the heat..might beat the rings up??? What motor is the rod out of??.. what times are u looking to get out of this thing?

The rods are Carrillo and are made for the V6 Buick. It moves the oil ring down to the pin location. PCH is 1.125 if I remember right. I'm fighting a sinus infection right now so thinking is kinda cloudy at the moment.