4.1?

[chickenfried]

so i bought my 99 gtp a few months ago and i love the car, but the guy i bought it from told me that him and his uncle from minnesota bored out the motor from a 3.8 to a 4.1. he said they changed the pistons and everything but i guess my question is... is this really possible to do? i know very little about motors but i am hoping to learn something by asking these questions, so please... cut me some slack!

[OH4CompG]

For a while ZZP was selling a stroker kit that came with a new crank and rods to turn the motor into a 4.1. I suppose you could bore the motor out, and it is possible. That's a lot of displacement to get from just a bore job though.

[Bio248]

its very rare to see someone actually use the stroker kit for our cars since its usually a giant waste of money. i honestly cant think of a way that youd be able to figure that out unless you took the motor apart.

[chickenfried]

that could be what it is, anyone else please chime in opinions

[rynoman03]

Might be the stroker kit like mentioned above. I've seen the kit but have never seen anyone actually buy it and install it.

[chickenfried]

why does noone install it?

[Moips]

I work with a guy on weekends building Stage motors for Grand Nationals... the really, REALLY expensive ones are 4.1L strokers that put out 600-750 HP, depending on the customer's request. From my experience, the 4.1L mod is a very effective way to increase the torque of these motors. I don't have a lot of experience building up front wheel drive 4.1's, tho.

[Sandman]

It's expensive and not quite worth it IMO. You can already get so much out of just the stock bottom end. Isn't the stroker a 4.2?

I've seen a couple of builds over on FTV6 and I'm not sure if anyone has put down any number yet.

[chickenfried]

ok... so lets say it is bored out or has a stroker kit, what all needs to be done to the motor to do this?

[Bio248]

just about everything internal to the engine is replaced. therefore, if you ever do break the motor in some fashion then getting replacement parts is not going to be cheap.

[chickenfried]

just texted him and he says they bored out the cylinders and bigger pistons, thats it. any impressions?

[blowfishRus6]

they do have .010 over bore pistons. ask him what pistons he put in.

[blowfishRus6]

well never mind they have up to .030.

but a larger bore piston is not gonna make it up to a 4.1.

[blueguy]

Pretty sure when ZZP did up their GT it was a 4.1...but I could have sworn the stroker kit that was more widely advertised was a 4.295, or 4.3...butI could be mistaken. I do know however...it was expensive...and for the price of that you could have gone way faster with an IC/Cam/Heads/Injectors/Tiny Pulley/Tune

[Juanmiguel]

If everything else is stock and it's actually 4.1, would there be a significant difference in the dyno? or 1/4 mile E/T? That's the only way I can't think to assume it has a larger displacement with out pulling the engine appart. Perhaps also lower PSI at peak RPM?

[whiney]

I'm also assuming it would sound a lot different than a stock gp.

[chickenfried]

the only mods he put on it was this motor, and straightpiped after the resonator.

[SilvaMan61]

Im having trouble believing this

[chickenfried]

your not the only one. he said is uncle is a mechanic in minnesota and thats who helped him do it. but he does not have any reciepts or anything that gives written proof he did it. and i dont feel like taking apart the motor to check piston size. although thats what i might have to do.

if he did do this would that make it quicker than a gtp with straight exhaust, 180 t-stat, cold air intake, and 3.4 pulley? how would they match up?

[QwikGT]

he's lying and he got you to buy the car