Chevy Trailblazer SS Forum banner

1 - 20 of 26 Posts

·
Registered
TrailblazerSS
Joined
·
658 Posts
Discussion Starter #1
My motor is currently at the machine shop and found the knock was the #1 piston skirt destroying itself. All of the coating is gone and beat up but the bore is good.

My question is, Do I have them throw a set of forged pistons in and hone to fit or just toss some stockers back in?

Since the crank and rods are clean, i'll be re-using them with ARP main studs and ARP rod bolts. (Yes they will be checking the rods with the new bolts before installation)
 

·
Registered
TrailblazerSS
Joined
·
121 Posts
I am going threw this now. I can tell you what I have found.
The block needs to be honed and checked to see if the cast pistons will still work with the clearance after honing.
Most likely thy will not.
I went with JE .005 over forged pistons as this was the best priced piston with a small over size. This way you are only paying for a hone job not a boar and hone.
Thy are lighter than the cast stock pistons so the assembly needs to be balanced.
I was told do not boar the block if you do not have to. The steel sleeves are thin in the stock alum block.
Cast pistons are .020 over at the smallest over size.
I was advised not to go there if at all possible.
I am also using the stock rods and new stock crank.
Thy have a pile of stock rods in the scrap heap. some times thy have to go threw a dozen to get a good round core.
Also the rod bearings are tricky with the stock rods. thy have to measure the crank and the rod for each journal to get them right. Takes lots of different size bearings on hand to do this. Then thy have to go on the journal thy match with.
Also the block will need to be line honed or board to set the main journal clearance with the soft bearings. The hard bearings come in more sizes but the cost is more than the soft ones and the hone job.
Not saying all shops do this....But well you know........
This is what I have bin told by the machinist doing my block work.
 

·
Premium Member
07 TrailblazerSS Imp
Joined
·
9,386 Posts
I went all forged with Mahle pistons and Eagle H Beams after the block was cleaned up .050 just made sense to do it all now and not some now and some later.
 

·
TT AWD TBSS Jeep
TT AWD SS Pwrd Jeep
Joined
·
5,825 Posts
Go forged pistons and rods, then your set up for big HP later.
 
  • Like
Reactions: dfwwiz

·
Registered
TrailblazerSS
Joined
·
658 Posts
Discussion Starter #5
Thanks for the input so far. I have a 10 sec drag car already so don't need to go all out on this one but the forged rods do sound like an option if the labor to reuse stockers is high.

I'll have to see how everything measured up when I swing by the shop on Friday.
 

·
Registered
TrailblazerSS
Joined
·
658 Posts
Discussion Starter #7
I generally stick with Wiseco or Diamond
I have my eye on the 4.005 Wiseco pistons but would need to special order them a little less than 11.6:1 unless thicker head gaskets are an option. This is my first LS build so still learning.
 

·
Registered
TrailblazerSS
Joined
·
658 Posts
Discussion Starter #10 (Edited)
Give me the rest of the engine specs.
Currently stock bore, don't want to go more than 4.005". Won't know till tomorrow if it's too loose to use stock slugs or 4.000 honed to fit a forged set.

Stock head gaskets with 243 heads. Should be 64cc and .051 compressed gasket IIRC. I'm not seeing thinner gaskets to use with off the shelf -3cc Wisecos that BTR has in stock.

Stock LS2 crank, doesn't need turned or polished. Stroke 3.622".

I'll be using the PCM Rob grind with capable springs/pushrods and LS7 lifters plus new trunion upgraded LS2 rockers since I had three chewed up pushrods.

^^unless you can work with me on a cam/piston/spring/lifter/etc. combo since I see your name get thrown around a lot :)
 

·
Premium Member
2007 TBSS AWD
Joined
·
31,502 Posts
Currently stock bore, don't want to go more than 4.005". Won't know till tomorrow if it's too loose to use stock slugs or 4.000 honed to fit a forged set.

Stock head gaskets with 243 heads. Should be 64cc and .051 compressed gasket IIRC. I'm not seeing thinner gaskets to use with off the shelf -3cc Wisecos that BTR has in stock.

Stock LS2 crank, doesn't need turned or polished. Stroke 3.622".

I'll be using the PCM Rob grind with capable springs/pushrods and LS7 lifters plus new trunion upgraded LS2 rockers since I had three chewed up pushrods.

^^unless you can work with me on a cam/piston/spring/lifter/etc. combo since I see your name get thrown around a lot :)

Well a -3.2cc Wiseco with a GM gasket and 64cc 243s and stock 3.62 stroke will be closer to 10.6:1 then 11.6:1.

If you wanted to get back to the stock 10.9:1 I'd mill the heads to 62cc and use a GM gasket. You will still have plenty of intake valve clearance with the small cam.

I sell all those parts too if you wanted a package with everything put together.
 

·
Registered
TrailblazerSS
Joined
·
121 Posts

·
Moderator
Trailblazer SS
Joined
·
15,616 Posts
Hone the block to 4.005 and get diamond 4.005 Pistons.
 

·
Premium Member
2007 TBSS AWD
Joined
·
31,502 Posts
Cometic Head Gaskets Domestic items in c5477 store on eBay!

Thin gaskets for the head with a 4" bore. Not a over size boar gasket like the stock ones are.

Use the thin ones and it is the same or more than cutting the head .016

You have to run the calculations. Also the exact boar of the gasket will gain some.

It may also change depending on the piston to deck measurements after the assembly.

run the number around in this. http://www.wallaceracing.com/cr_test2.php

Its bore man. Bore
 

·
Registered
TrailblazerSS
Joined
·
658 Posts
Discussion Starter #16
I wish I had the coin to go e85 since its available here, then I could worry less. I'm not afraid to take it a little over 11:1 but unsure of the pros/cons

I'll update tomorrow when I get to see the bare block and probably call Matt. Thanks for the gaskets links.
 

·
Registered
TrailblazerSS
Joined
·
658 Posts
Discussion Starter #17
Well a -3.2cc Wiseco with a GM gasket and 64cc 243s and stock 3.62 stroke will be closer to 10.6:1 then 11.6:1.

If you wanted to get back to the stock 10.9:1 I'd mill the heads to 62cc and use a GM gasket. You will still have plenty of intake valve clearance with the small cam.

I sell all those parts too if you wanted a package with everything put together.
Thanks for the #s, the original Wiseco I saw was a dome and I just typed the specs off the sheet.
 

·
Registered
TrailblazerSS
Joined
·
121 Posts
Remember the cylinder pressure is what maters not the CR.
The valve timing will change the cyl pressure with the same CR.
With a bigger cam you will need more CR to maintain the same cyl pressure.
Unless some one has the same cam and knows the CR it is hard to calculate cylinder pressure.
Don't think many even check there cranking pressure to tune a eng setup.
On out board eng making 300+ prop shaft HP it is every thing.......145psi is the max on 93 pump gas.
Thy don't have knock sensors to control detonation..........
Then if you are on the sensor you are leaving power on the table.......
So what are the cranking pressures on some different setups ???????
YES bore.............never said I could spell........LOL
 

·
Premium Member
2007 TBSS AWD
Joined
·
31,502 Posts
With the cam the OP was talking about using you would want to stick to the 10.9-11.0 range on pump gas.

With that said I have TBSS running 11.5:1 on 91 octane and higher on lighter cars. Much bigger cams though
 
1 - 20 of 26 Posts
Top