I do fab work at a shop in Vallejo CA, handle all of the header and intake work IC fitting ect. The cars we do are all BMW and Nissans.

I personally own a 70gmc with an LT1 in it. I want to build a twin turbo setup for it and would like some input as to what turbos I should run. Its basically a stock LT1 has ARP everything in it but when I had the engine built I planned on keeping it NA. Has the GMP cam thats about it. The guys at the shop dont know anything just like pretty welds and shiny piping, ICs that are way to big so they are useless (sorry guys)

Are any of the ebay turbos worth the s@%t?

Thanks

 

some ebay turbos seem to hold together well but some are garbage its a risk that could damage your newly built engine as well.

Junkyard grand national or used mitsu 20g turbos could work well, or you could spend 1000 and get two new masterpowers and warranty

 

the lt1 wont hold much hp. Maybe 10 psi max and 500 hp if ur lucky. And who knows how long itll hold up. id say it needs forged pistons at the very least.

 

an LT1 ? the new one or old? the new LT1 are pretty good.reverse flow cooling,etc..stock they have powder metal rods and pretty good flowing heads, not the best, but pretty good for the street.. they also have almost 400 hp stock, so 500hp would be pretty easy. they will hold together for alot more than 500hp.. there are guys running nearly 1000hp with stock bottom ends on the LT1 forums. i think you will do very well with the LT1 and twins. dont let the naysayers get you down. 10 psi on a LT1 should be a hell of a lot more than 500 hp..

 

Are you sure you don't have the LT1 confused with the LS1? 10psi into an otherwise stock LT1 will typically not equal 500.

 

that guy is thinking LS1

the lt1 is 275 from the factory. I would recommend forged pistons, otherwise you can only safely run about 6 psi, and get stomped by heads/cam cars still. I would look into speedpro if you are on a budget. 400 for a set of -21.10 pistons, but they are heavy! the GMP cam should be a hotcam, or it could be a 847. either will make power, but neither is IDEAL.

run stock heads, stock intake, and you can get 550ish to the wheels without porting at about 12 PSI.

I would look at two t70 .68s. probably be a little laggy, but it'll be kille ron the topend.
If you can find some t4 turbos with around .61 A/R, those would be more ideal.

 

thank you. I agree stock pistons just wont do after 500 rwhp.

 

ya the stock 10.5:1 compression wont like boost too well.....drop some SRP 31 cc dish pistons and bore it 30 over and u could throw

 

SRP's have a high silicone content and are more prone to failure than others. Look at the new mahle 2618 -26cc's

 

im in the process of gathering parts for my LT1. I agree a forged bottom end is needed, but I believe you can make decent power on stock stuff.....for a little while. He said the motor is in a truck, Im sure boost is probably more of a cool factor than absolute power maker.

I was thinking of using 1 MP T70, with a .96a/r at first to sort my system on a stock motor. Now you recommend 2 with smaller exhaust housings. I want to be in the 600whp area. Should I consider a larger turbo, or twins?

 

Mahle's-26cc are high silicon 4032 alloy, NOT 2618.

If you want 2618 with a big dish you'll have to go with Diamond or JE.

Wiseco pro-thru, Mahle, SRP are all 4032 alloy in their dished models. Mahle has 2618 in their pro series but they are available in flat top and dome only.

 

wrong, mahle DOES have a 2618 -26cc now, you can call them and confirm if you do not believe it. I had a set on the shelf for a while.

 

got a part number?

I called them and they told me they didnt... that was just a couple of weeks ago.
My engine builder is a Mahle dealer and also told me they didnt have it... I would've got the 2618 Mahle instead of Diamond If I had known.

 

reamo04 is right. I had Mahle on the phone when these were coming out not too long ago. Some of their new pistons ARE 2618. I was looking at the -26cc and they WERE forged from 2618.

https://www.theturboforums.com/smf/index.php?topic=105985.15

 

i dont have the part number anymroe but i used them in 3 different motors for people lol

 

twin 70's is way too big for 600whp. Single may get you there, but could go 76mm to be sure and have room for more if you ever build motor up more

 

that's what im thinking. I wanna stay t4 frame for space, but I like the price of some holset/ BW T6 turbos. Im sure a 76mm with a .96a/r T4 frame should get me to 600. BTW )rr89rocz, I have been following your build on TGO, good stuff man. I am also running code 59, but I am using a LT1 with northstar coil packs and a custom made crank trigger wheel (bye-bye Opti).

 

Good deal, if you need any help with cdoe $59, feel free to ask and i'll see if i can provide some input based on my experience so far

 

well that's good to know. Had I known earlyer I probably would've gone with the Mahle... at least I got a good deal on the Diamond turbo/blower pistons

 

Re: LT1 Twin Turbo

Search back through my old posts. I have all the details in there along with a cad screen shot from the R&D guy. There in my shortblock now and are def 2618.