Depends how short. How long are the rods? Having a button to support the oil ring is fine. The CH will only be 0.025" less than with a "normal" deck. Not very much really.

Rich Krause

 

The shop that ruined your block should refund your money at the very least, and if they are at all responsible for their own work, they should supply you a new block. It's rediculous that they can't deck a block with a reasonable degree of accuracy.

Sounds like they didn't use a BHJ type fixture and/or their machines are not level. A decent shop would have verified the reading of the level with a dial indicator also. Regardless, you need a new block, not a custom set of pistons. Don't throw good money after bad!

My first phone call would be to the hack that ruined your block.

 

ok, i went to the machine shop to see what he was talking about today. To get it all true by decking the block using a "block true plate" that was placed inthe cam journals, he had to deck it to a deck height of 8.965, the deck *was* 8.995 before he stated in on it. So it seems it was way out of whack. I called the place that did the machining to my block before and he said that all he did was square up on the factory surface, and resurface the deck, he didnt actually deck it to a certain height...i believe this to be true because he only charged me for a resurfacing of the deck after i read my old receipt...but this brings up a couple questions aobut this. first, i believe the stock deck height is 9.025 on the lt1 block so this means that just to resurface the block they would have had to shave .030" off of it, and that seems like way to much to me for a resurface OR the block has had some crappy mahcine work done to it back before i had it back when it was still in the vette...i have no idea, but my prior machine shop swears they didnt take off near that much to resurface it. so anyway, im still left witht he problem that i have now regardless...so heres a couple ideas and id like to have your info on them. the pistons i have now are lunati 20cc dish....the machinist said that he could cut the lip around the piston dish down .030, so it will be flush with the new deck height. option 2: get a new dome piston ( I have to get new pistons anyway because my old .030 are out of spec) and shave down the area that sticks out of the hole and the areas that may hit the head (dotn think this will work and will be costly mistake if it doesnt) or 3: get a custom piston, i called JE and tehy said that it would be around 150-200 more for custom pistons over off teh shelf pistons...but theres a 4 week wait, and if i ever burn one id have to buy them in sets of 4. any suggestions? what do you think about shaving the "lip" aroundt eh piston edge down .030? that area doesnt make contact with the cyllinder walls anyway, but would it affect anything, especially with spraying nitrous?
I have 6" rods and the pin height on these pistons i have now is 1.095"...if i decided to go with custom pistons, should i just get teh pin moved up to a height of 1.065"?
It is sounding more and more like im pretty much screwed either way, i guess its just figuring outwhats the best way to get screwed Id rather not get a new block if possible even though it may be best int he long run, its just a lot of machine work that would have to be done, and this block is perfect besides this problem. thanks guys

Chad

 

If going custom [je or who ever] just tell'm where the deck hight is at and how far in the hole you want the piston to sit hung on a XXX lenght rod with XXX stroke and let them set the pin height in the pistons.
Let them do the math thats what your paying for.

As for chucking up and shave'n what's the verdict guys?


ps.. you might want to check the port to port fitment on the intake to head once your back together. Just to be sure the intake won't need shaved to line up after you drop those heads some more.

 

I'll call JE tomorrow and see what they say about this mess and get some definite prices. I think i'll definately have to do some lining up ports and bolt holes with the intake and probably th hole in the alt bracket will have to be elongated also. As far as cutting the lunati dish pistons down....i measured the dish from teh top of the lip to the bottom of the dish and it was .100", so shaving it .030 would leave me with .070" of a dish. Seems like there would be plenty of strength still in the piston.

Chad

 

To me the comp height of your current pistons seems really low, my 16cc SRPs for 6" rods 3.75" stroke are 1.125, and are pretty standard I think. Did your previous machine shop order the pistons after they **** your block up?

Are you positive that is the right height?

Thats not very important, just kinda stuck out to me. IMO, Id be scared to run that block again, even if he does "FIX" it, just seems all really fishy to me. Might be better off starting from scratch, would be expensive now, but might save you money in the long run.

 

Chad,

If your needed a 1.095 piston before and you need a flat top piston with a lower compression height look at the SRP PN 144995, that will work for you and it's a off the shelf piston.

At least it will work with a 4.030 bore 3.750" stroke and a 6.00" rod on the deck height you are talking about.

Bret
Bret

 

Have you considered all the other compromises you'll have to make in order to use that block? Your compression height is now 1.065? Sounds like a pretty small area in which to make a dish piston to me. How you're going to need a $$ set of pistons, custom pushrods, and your intake will most certainly need milled. I'm sure it's still cheaper than a new block, but given what you know about their work, I'd be really nervous using that block.

I still can't get past the fact that they owe you another block. They made a huge sophomore error, and it should be their responsibility to make it right. You paid good money to this shop and they screwed up. It happens, but a decent shop will make it right.

Best of luck to you.

 

I agree with NOS, dish pistons on that compression height are not a good idea but you migh be able to get a small dish piston.

Believe me a new block is most likely a better way to go.

Bret

 

ok guys, first i want to thank you all for the advice you have given me, i really appreciate it. I guess one good thing out of all this is that i have learned alot about all these ,measurements adn what they do. The more i look into it, the more questions pop up about this setup. heres what happened today: I called lunati, gave them the part number of my piston, they said it wsa a 20 cc dish, with a CH of 1.120, and a pin thickness of .927". the thing is that i have measured several times and so has the machinist im working with now and the CH of the pistons comes up to be 1.095-1.100" thats .020" difference between what we're getting and what lunati says it is! whats up with that? all we're doing is taking the distance from the top of the piston to the top of the pin bore, then adding the pin diameter (.927)divided by 2, gives us 1.095..i am so confused on all this because one person is saying one thing and i am seeing another! the only variable difference isthat i bought the stroker kit used from a guy i knew a few years back, it only had afew hundred miles ont eh rotating assy., and he went with a different setup, so i guess he may have turned down the pistons .020 for some odd reason...that seems to be the only explanation, am i right?

I am going to run some numbers past you guys as somethings have changed and i found out some different things. please let me know if i am figuring correctly because i have to order some new pistons if i am going to keep this block (even though now im leaning towards a new block) but this is just for my curiousity/knowlege and to prove that my CH is what i have measured.

the machinist measured the deck height to be 8.965" right now after all the decking to square it up.
The piston right now at TDC sticks out of the hole .005"
so i take the stroke (3.75) div by 2 and get 1.875 +6 in. rod + 1.095 (my measured CH, not lunati's) and get 8.970" so that seems correct being that the piston is out .005", right? what the hell is going on here?
where is the best place to get a CNC lt1 block that you guys are talking about? I looked in jegs and summit and only saw SBC blocks. I am thinking of just starting all over with a new block if JE doesnt have any shelf pistons with a 1.095" CH, it would be better in the long run. sorry to be a pain, but i jsut want to see if i am figuring correctly because it all jsut seems really odd.
Thanks
Chad

 

If you're only .005 out of the hole, you are home free. Fel Pro makes gaskets that are .041 which is perfect. Ran that exact setup this year on our race motor.

Edit: it sounds like your machinist overestimated the amount he'd have to remove or he didn't square it?

 

nosfed: the piston i currently have (lunati 20cc dish) is only .005" out of the hole because of the difference in the CH...theres a .020" difference unaccounted for between my measurement and lunati's....so yes these pistons would probably work at .005 out of the hole, but i need new pistons because 1)the skirt is close to out of spec at 4.022" in a 4.030 bore, and im looking for a flat top piston this time around for higher compression. Thats where my problem comes into play with custom pistons or a new block.
I guess the machinist did over estimate a little, but all in all he took about .030" off the deck total. (8.995 originally to 8.965 now.)I think he actually noticed the block being that far off when he started to deck it in teh machine and it started to take off a good size chunk with the pass that wasnt near level. then he started looking further into it, put back in the crang and piston in all 4 corners, and noticed how bad it was. from what i can put together, what caused all of the confusion was the pistons i currently have, they are just.....odd to say the least. so even though the deck height was originally 8.995" the pistons were sitting down in the hole .020" because of the CH. I'm still trying to figure out whats going on, and what couldve happened.