Oversized Pistons

[rsc]

Curiosity got me looking at engine rebuild parts today. I only found 0.5mm over pistons. Thats just 0.0156" over. Used to be you could get 0.010" through 0.040" over for most cars. What gives, is GM using a Nikasil type coating or do they not expect these vehicles to live long long enough to need other sizes?

 

[rsc]

I remember going to buy pistons for a '70's Japanese car, pistons started at about .015" over and went up to about .060" (in mm sized steps). The engines lasted so long hardly anyone bought the first oversize.

 

[High Five H2]

I thought I read about someone with a 4.0L I5, it was bored or stroked, I can't remember. I couldn't find anything about it though.

 

[atvspeed4]

I thought I remember reading somewhere that our engines were resleevable. Not sure why the heck they would do that on such a ****ty motor but that might explain why they do not offer larger pistons.

 

[rsc]

JAllen, I bet it was stroked. I don't think it can get much bigger pistons in there with the 3.7
If the cylindrs are sleeved then that would explain it.

 

[CaseyS]

The 3.7 is .100 overbore compared to a 3.5. I don't think you can get to a big enough bore to get to 4 liters. You might be able to regrind the crank and move the radius point but that would require custom rods, or pistons, or both to increase the stroke.

 

[SuperBuickGuy]

I thought I remember reading somewhere that our engines were resleevable. Not sure why the heck they would do that on such a ****ty motor but that might explain why they do not offer larger pistons.

Yeah, and those blithering idiots who spend thousands of dollars putting turbos on 455 Buicks... they really should be all lined up and shot! what a bunch of Jeep owners.

You do realize there's a guy who's setting land speed records with the 5 cyl and 6 cyl version of this motor, right?

 

[atvspeed4]

Don't get all sensitive and pull your Buick stuff into this.

My point was, if in fact the 5 cyl is resleevable I find that effort to be a waste considering that by the time that motor is in need to be resleeved it will have had to be rebuilt several times before hand for other issues.

I have done more research than most on this forum with the help of some awesome Colorado guys over on various sites. Yes, the 3.5/3.7 is capable of impressive power but it is done on a motor that is far from stock. One of the issues "that guy setting land speed records" had was oiling issues as he pushed the limits of the I6 NOT the I5. They still have not figured out a solution to the integrated oil pump not providing enough flow. If anyone is interested I can pull together all the links I have found over the years for I5 performance parts. If your willing to pay you can get almost anything. Custom pistons, rods, crank, cam etc

 

[SedonaBound]

The parts diagram for the I5 block shows cylinder sleeves and part no. They don't appear keyed, as for the sleeved aluminum blocks I've worked on, so I assume its a shrink-fit sleeve. I didn't dig any deeper, but I'd guess that the diff between the 3.5 and 3.7 bores is the iron sleeves and that the blocks are identical, and that the .100 overbore for the 3.7 is already at minimum wall thickness for finish machining. In other words, 3.7 is maxed out for bore.

 

[SuperBuickGuy]

Don't get all sensitive and pull your Buick stuff into this.

My point was, if in fact the 5 cyl is resleevable I find that effort to be a waste considering that by the time that motor is in need to be resleeved it will have had to be rebuilt several times before hand for other issues.

I have done more research than most on this forum with the help of some awesome Colorado guys over on various sites. Yes, the 3.5/3.7 is capable of impressive power but it is done on a motor that is far from stock. One of the issues "that guy setting land speed records" had was oiling issues as he pushed the limits of the I6 NOT the I5. They still have not figured out a solution to the integrated oil pump not providing enough flow. If anyone is interested I can pull together all the links I have found over the years for I5 performance parts. If your willing to pay you can get almost anything. Custom pistons, rods, crank, cam etc

actually, there was a Buick in that pickup first... a blown, straight 8 one - talk about an anchor build :gaah:.

 

[SedonaBound]

Yeah, and those blithering idiots who spend thousands of dollars putting turbos on 455 Buicks...

Yeah, but I remember a cool Buick magazine ad in 1976 that said something like "There are four production cars with turbo engines...and three of them are Buicks".
:cheers:

 

[SuperBuickGuy]

Yeah, but I remember a cool Buick magazine ad in 1976 that said something like "There are four production cars with turbo engines...and three of them are Buicks".
:cheers:

I don't mention it much because my motor is in machine shop hell (not even to bodyshop hell yet)... but I'm building a 1950 Buick Sedanette and putting a sleeved, girdled, aluminum headed 455 with twin 88mm turbos in it... it'll be in the 430 ci range. Machine shop hell - never take a motor to someone who races boats... oh well, if it ever gets done it'll be sweet... but it's starting to look like I'll be done with the FJ40 before this guy gets the machine work done. it is a lot of fine work, but the 2 years it's been with him is a bit annoying.

 

[atvspeed4]

Since these questions keep coming up over the years on what to do with the stock motor I figured it would be good to put together links of some of the information on building these motors I have found. It looks like my other links are no longer in my bookmark folder unfortunately on turbo/ supercharger info. Please add any that you think are relevant:

General Information:

http://www.sfsa.org/tutorials/eng_block/GMBlock.pdf (Only applicable to the 3.5L not 3.7L)

Forged Rods:

http://www.rrconnectingrods.com/products.html

via this thread: http://www.355nation.net/forum/forced-induction/45678-my-forged-rods.html

Custom Pistons:

http://www.jepistons.com/

Ported Throttlebody:

http://www.nec355.net/forums/showthread.php?t=396

Hi flow injectors and other bits:

http://www.lime-swap.com/products

3.5L to 3.7L swap info:

http://www.355nation.net/forum/engine-swaps/43667-3-7-engine-swap-complete.html