food nd cars

Talked to my engine builder today and he is recommending forged probe dish pistons. He says that with California gas running flat tops will put me in danger of detonation. I am still not convinced but I NEED to let him know tomorrow exactly what pistons I want.. I did a CR calculator and these pistons put me at 10.2:1 CR with .026 gaskets and .020 deck clearance.. which I'm not even sure is correct.
Here are the pistons
http://www.summitracing.com/parts/PBP-12342-030/
All this being said, this car is NOT a race car and will be commuting more than anything.. However, that does not mean I don't want all the power i can squeeze out of it. So what do yall think? Are these pistons a big NO NO? or are they okay? It's killing me to think that they might be a big mistake, I can easily call him tomorrow and let him know that i would rather have some forged flat tops with 5cc reliefs.. Will this put make my CR too high for crappy CA 91 octane?
I haven't seen any threads about anyone even running these pistons.
FYI this is a N/A build with plans of light nitrous use in the future.

3.8redbird

iTrader: (3)

What is the combustion chamber size? What head gasket?

Id be ok with 11.0 on 91 but that is just my preference

food nd cars

I want to call him up and tell him to use these pistons instead.
http://www.summitracing.com/parts/PBP-12336-030/
CR should be 11.5:1 with the .026 head gasket with these.. Will that be pushing it with 91 octane in CA?

henry172

iTrader: (2)

BS I am running these with 4.030" bore and 54cc heads with no problem at all. And I am running victor reinz 5898 .026" head gasket
http://www.probeindustries.com/Chevy...ns_p/12334.htm with CA 91. I ordered mine from ebay they came directly from probe in the LA area and I got them in two days for 419.99. They are nice and light; something like 28 grams lighter than the stock piston. I would go with the piston I am using as they are slightly lower compression.

gregrob

iTrader: (8)

You need a new engine builder! I wouldn't let that ****** touch another thing.

henry172

iTrader: (2)

Yes the builder must not be a pro when it comes to building lt1's. I had many old sbc guys tell me I could not build my motor the way I did.

food nd cars

whoa whoa. He's just the builder and he was initially going with flat tops but the OWNER of the shop tried to be a smart *** and he butted in with his "opinions" and thus caused my builder to sway in favor of what the BOSS said.. Anyways how are these pistons?
http://www.summitracing.com/parts/PBP-12336-030/
they save me 20 bucks in the long run and I can always blame you guys for screwing me over instead of my engine builder

Wicked94Z

iTrader: (26)

I'd run about 11.5:1 for a driver on that oxygenated crap gas

idformula

Duh-ummmmm, stock comp ratio is 10.4:1, so. Tell the boss that this isn't a sbc! Also tell him what the stock compression is and see what he says. 11.5:1 should be ok even with premium cali paint thinner.

RamAir95TA

iTrader: (2)

Just because they recommend a lower compression ratio doesn't mean they are an idiot. From a SBC perspective he is far more accurate in his suggestions, but obviously is not as well versed about the LT1. Most SBC builders are not aware of the benefits of the LT1 so sometimes it takes a bit of educating on your part.

My suggestion is to emulate what others have done and what has been shown to work. Don't worry about the builder too much assuming all things aside his workmanship is top notch.

food nd cars

I'm not worried at all about their quality and their ability when it comes to machining and assembling motors, but I understand that they are some SBC guys and they were just trying to do what they thought was "best" for my setup. I'm def. going to call them up today and change the order to the flat tops mentioned above.

BTW these guys just built a Chevy, big block, magna charged, AFR headed, 950+ HP motor. Its sitting right by the parts counter, so I'm sure that they can manage my little LT1.

RamAir95TA

iTrader: (2)

I guarantee they know more about supercharged BBCs than they know about N/A LT1s. That doesn't automatically qualify them as LT1-competent.

The builder that assembled my short block also had the same mentality with my motor when I told them about the 12.5:1 compression. After a few discussions with them and showing them comparable cars they delivered.

joelster

I would go with the flat-tops. Plenty of guys in here running well over 11-1 on pump gas. My new motor will be over 11.5-1 and it will be on pump, but I can get 93 everywhere around here. I know some of you guys are stuck running 91.

ElkySS

iTrader: (6)

im sittin at 11.5 and daily driving. of course thats on 93

gregrob

iTrader: (8)

A boosted 950hp big block is a tad weak. Maybe its a low boost street motor though