Pistons

[jhanson1750]

Help!!! I'm ready to take the GN block to the machine shop but I'm looking for realworld info on pistons. Please post what pistons you are using and what your thoughts on then are. I would like to go JE's but with the levels I'm looking for I think I may not need a $700 set of pistons. I'm looking for @ 11.50-11.80 E.T.s I have to get the block bored due to a scratch in one of the bores or else I would have done a light hone and new rings. My plan is home ported heads, 60 lb injectors, 3" DP, new TT chip, home ported intake and matched stock exhaust. I am leary of pushing real hard on my 86' as it's a "T" top car. Thanks Jon Hanson

 

[87we410877]

JE and other after market rods such as Diamond, require a full floating wrist pin which in turn requres a different connecting rod. TRW makes a stock replacement piston with a pressed pin and should work for your application and times. Im sure they make .020, .030, and .040 over pistons. They are forged.

If your changing the rods as well i would go with Diamonds. I have them in my motor and if your machine shop actually gets you the correct piston to wall clearence like mine did, they are quite as anything. ALot of people complain about JE or Weisco being loud but i dont hear anything with the Diamonds. HTH.

 

[Boost231]

Zimmermans and Nick Micale are doing my motor and im pretty sure there using CP pistons in my motor. also im looking to go low 11's.

 

[KWIKR 1]

FM Hypers are very good , quite , less cyl scuffing and very inexpensive . I have them and running 11's with no worries . I would have no problem pushing them into the 10's with a good tune (my car should be in the high 10's with a good 60ft) . There are a few people on this board who run them . they are alot stronger than some people think . for a car that is mostly street driven and goes to the track a few times a year , IMO they are ideal .

 

[MSDGN]

JE and other after market rods such as Diamond, require a full floating wrist pin which in turn requres a different connecting rod.

Where did you get this information...it's absolutely not true...I have JE's in my motor with stock rods and pressed in pins...no problems at all...

 

[Hot Air]

FWIW,
Don't take your block to the machine shop UNTIL you have your pistons! If the shop tells you otherwise, find another shop.
Conrad

 

[87we410877]

Where did you get this information...it's absolutely not true...I have JE's in my motor with stock rods and pressed in pins...no problems at all...

Really? Thats what i was told. I know the diamonds require a full floating pin. I thought the JE and weisco did as well. Thats what i remember when i was building my motor. I guess i was miss informed. sorry.

 

[jhanson1750]

Thanks guys, The reason I'm wanting to have the machine shop check the block is to determine how bad the scratch in the bore is. That way I know how much of a cut it's going to take to clean up. Then I will order pistons. I'm also looking at a girdle. Anything to the price differintal between the two girdles that are out there??????? They both look like good pieces. I like the idea of the girdle IF later on I want to turn things "up a little".

 

[bodycount]

I am using Probe piston on stock rods, cheaper and lighter than the TRW's.

 

[jhanson1750]

Oh, by the way. Where are you guys finding these pistons? I've looked on Full Throttle, Summits and Jegs and am not finding much. I like spending my Buick bucks with "our" people if I can find what I'm looking for. Well, I also have not called or e-mailed anybody yet just looking on the web. If you folks could post where you got your brand of pistons that would help me out a lot. Thanks Jon Hanson

 

[gnxtc2]

FWIW,
Don't take your block to the machine shop UNTIL you have your pistons! If the shop tells you otherwise, find another shop.
Conrad

Why

You should bore the cylinders first then order your pistons.

Billy T.
gnxtc2@aol.com

 

[jhanson1750]

WHAT????^ the proper chain of events is check the block to see the minum you have to go diameter wise and then you get your pistons. Then you deliver the block and pistons to the machine shop along with the spec for the piston to wall clearence that is needed. This I am positive of!!!!!!! Hope you havent been led wrong elsewhere. Thanks Jon Hanson

 

[KWIKR 1]

as far as I know all piston manufactures "build" the clearances into the pistons . so... no real need to have pistons on hand for boreing block . but, all clearances must be checked on final assembly . your machine shop may want "pistons in hand" just to check them .

 

[gnxtc2]

I like to bore the block first then order the pistons.

Examples:

-There is a gouge/scratch in the cylinder wall, "looks" like it'll clean up to
.020" over. Order the pistons. Get the pistons and bring the block and pistons to the machine shop. Machinist starts to bore the block and the scratch doesn't clean up, need to go .030" over to totally clean up.....now you have to return the pistons and hopefully they were not custom.

next

Ordered the oversize pistons and have them on hand. Put the block in the boring standing and the cylinders are not totallly round and they are not true to the crankshaft line. Have to go to a overbore to everything in line. (seen this presonally)

Moral: Sometimes the eye can't see things that a machine could.

If you want to order pistons first, go right ahead, it's your money and time.

All of the above was my opinion.

Billy T.
gnxtc2@aol.com

 

[Nick Micale]

I like to bore the block first then order the pistons.

Examples:

-There is a gouge/scratch in the cylinder wall, "looks" like it'll clean up to
.020" over. Order the pistons. Get the pistons and bring the block and pistons to the machine shop. Machinist starts to bore the block and the scratch doesn't clean up, need to go .030" over to totally clean up.....now you have to return the pistons ................Billy T.
gnxtc2@aol.com

Billy's opinion is the best way to go.

The final fit for the pistons in the bore is by final hone, which is a day long process. We have seen blocks trashed because all the machine work was "done" when the customer brings his block for final assembly and the bore is too big for final hone. OK, not trashed, but lots of $$$ wasted.

Basically there are 2 kinds of engine build shops, production and custom.

Production shops say "what are your specs or tolerances?", and you get what they normally do anyway.:biggrin:

Custom or race shops ask "how are you going to use this engine, track, street or both". They then lay out a build and parts plan to suit your specific needs. They then proceed to build it to EXACT tolerances, not just OK, but pull the crank or pistons or whatever needed to get it RIGHT if necessary.

Needless to say, the custom build cost more, but you get what you pay for - hopefully!:wink:

 

[FastGN007]

i have a t-top car as well with goals of running high 11's. I went with JE pistons and stock rods. I had the rods polished and shotpeened with ARP bolts. I had the rods bushed so that i could have floating wrist pins. Here are some pictures.

Scott

 

[m233roller]

J & E's noisey ?? B. S. Iv'e been running a set of them for 7 years, freshened the motor once and they don't make noise. DONE RIGHT DONE ONCE !!!

 

[gnxtc2]

If the piston is noisy upon start up, then the engine builder did not machine the bores to proper clearances. When the piston heats up and expands, the noise usually goes away.

Should bore the cylinder within .005" of final bore then hone the rest.

I've used JEs and Diamonds and no noise with either.

Billy T.
gnxtc2@aol.com

 

[Hot Air]

Forged pistons are the most robust piston currently available and can operate in a range of temperatures & loads that cast and hypereutectic pistons can only dream of.

If one is installing forged pistons, it is generally assumed that they will be running elevated boost and exhaust gas temperature, hence the piston and ring clearances are set up on the loose side to allow for the inevitable expansion from the increased heat in the combustion chamber. You certainly don't want the end of the rings to butt together and you don't want the pistons to expand to the point where O.D. is greater than the cylinder wall I.D. Neither of which would be a good thing! Tends to turn engine blocks into scrap metal.

The loose clearances will frequently cause more piston noise (piston rock) upon cold start-up. Typically, that is the nature of the beast. Once everything gets warmed up, the noise should go away. However, if the machinist sets the clearances too loose (even for forged pistons)....then you could have a problem.

I, for one, would never let anyone but a shop that deals exclusively with Buick turbo motors mess with my engine. Support our TB vendors!

Conrad

 

[jhanson1750]

Thanks a lot guys! I have never had to deal with a scored hole before. I have done motors like I posted before, but new to this issue. I spoke with the machine shop and he told me that he would prefer to get the scar out and then order parts. So looks like I learned something new today as well!!! I really like having this website, you guys have loads of info that helps others learn. Thanks Jon Hanson