LB7: Building a stock turbo puller, need help/opinions

[clrussell]

Problem is 'stock turbo' turns into 'stock appearing' for most guys, then 2.5/2.6sb later, so on & so on.... To the point you will bend a stock rod for sure if you're trying to be competitive. If you have the engine apart, better do rods. If it's not apart, yes it will do you well for a long time.

As far as which specific parts will make more power for your turbo limits, it'd be hard to find anyone that tested specific things. Compression ratio and camshaft would be two things I'd test if I was interested in that class. Pretty costly to do so, especially for that level.

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100% agree

If it was me I’d throw big fuel at a stock engine/ turbo, a solid converter and some trans mods. Then work on set up and make it work. Save some money and have fun. When it hurts something then fix it.

This is going off if your truck is not in need of a rebuild anyway.

 

[fast03]

100% agree

If it was me I’d throw big fuel at a stock engine/ turbo, a solid converter and some trans mods. Then work on set up and make it work. Save some money and have fun. When it hurts something then fix it.

This is going off if your truck is not in need of a rebuild anyway.

Right behind you guys. I ran my lb7 stock pulling and was really successful at 540hp or so to the wheels. set-up, set-up, set-up

 

[Blackmax123]

It all depends on a few things.
1. How serious do you want to get?
2. How much street time will it see?
3. How much do you want to spend?

I built my 2.5 engine at the time to move up someday. Now that I dont see that happening. I wish I'd have stayed stock appearing and raised my compression a few points.

 

[torqued2dmax]

it will be a true stock charger. this is kind of a budget build, but I have money to throw at it if I want to. I was considering wagler or lbz rods. what are you guys using to pin the crank and cam? I assume the crank gear and damper get pinned? something like a socal 3388 cam sound about right?

If rebuilding , they get keyed !

 

[boominator]

IMHO for what you are doing delipping the pistons is not worth the lose of compression. We run a full stock LB7 long block in 2.5/2.6 SB has 100% injectors a 12mm pump 2600+ Pulse and haven't had an issue. we know it is on borrowed time but it just keeps clicking them off.

 

[dirty_max]

Why would lowering the compression hurt performance? All the pistons i am seeing are for a lower compression. I suppose there would be a chance i would bump to workstock someday so i will figure rods into the build.

 

[Chevy1925]

Why would lowering the compression hurt performance? All the pistons i am seeing are for a lower compression. I suppose there would be a chance i would bump to workstock someday so i will figure rods into the build.

you will be missing the added boost pressure to increase cyl pressure back up to what the higher compression ratio would have had. There is a point where this falls off obviously. There are guys who have tried 18.5cr ratios in cases likes yours to get performance back. i wouldnt run a real loose P to H clearance either but need to keep space in there for the piston expanding. im sure it will be seeing alot of fuel.

John will make what ever CR you want. hes made high cr pistons before with his specific bowl design.

 

[Blackmax123]

^^^^ right on point.

When your air limited the higher compression makes power. I have heard there are 2.5 guys building engines 20:1. Or higher. Dont quote me on it but Dan's diesel was running one at 21:1 and was making huge numbers for a 2.5 truck.

I was forced to build my engine after 6 hooks on a Danville 2.5 vgt, 60 overs and a 12 mm stroker cp3. Before engine build truck made 670hp and 1250 on Danville dyno. Same setup after engine build made 620hp and 1300 ft.lb.

Switched to a Danville s400 true 2.5 tct charger and made 690hp and 1340.

 

[Trimox]

All this talk of compression ratio takes me back to time I spent at the circle track. Whatever motor you ran had rules on compression ratio. Builders would have a limit of say 12.5:1 on a small block. Well they would run 12.5 on the passenger side and 15.5 on the drivers side of the motor. Yes this was cheating. The lower on the passenger side because it was the easier to remove for tech inspection after a race. I do not condone this is any way.


With force induction as boost goes up you generally drop compression to a point. Like said above for a stock turbo in a performance not longevity situation more compression is the way to go, to a point. What point is up to your budget. Don't take my word for I stayed at a Holiday Inn Express last night.

 

[gmduramax]

For what it’s worth. When I had my engine built I saw no lose of power going from 17.5:1 I think is factory LMM? to 16.5:1. The motor was done .040 and a 6460 cam were the only other changes. Ran exactly the same except for slightly better spool.

 

[TheBac]

Stay at stock LB7 comp.

 

[Blackmax123]

Isnt an lmm lbz 16.8:1 stock?

I know racecar guys that did the same but only for a couple cylinders and some how those are the ones they always convinced the tech guy to pump..lol

The longevity is the ticket. The high compression motors dont last but make good power. So if you want to be one of the front runners and dont street drive the truck and have money to blow. Being air limited with a small charger I'd stay higher compression.

My new machine shop guy and I just had this same decision Monday over my lml engine that will be 16:01. But it's not gonna be a power house might see twins someday though.

 

[gmduramax]

Isnt an lmm lbz 16.8:1 stock?

I know racecar guys that did the same but only for a couple cylinders and some how those are the ones they always convinced the tech guy to pump..lol

The longevity is the ticket. The high compression motors dont last but make good power. So if you want to be one of the front runners and dont street drive the truck and have money to blow. Being air limited with a small charger I'd stay higher compression.

My new machine shop guy and I just had this same decision Monday over my lml engine that will be 16:01. But it's not gonna be a power house might see twins someday though.

Maybe that’s why I didn’t notice a difference :rofl:

 

[dirty_max]

Ok that all makes sense now. Kind of like how stock gas class chokes it and chokes it out but their compression ratios are so high they still scream anyhow. So how would reliability be affected by going up 1 or 2 points?

 

[dirty_max]

Stay at stock LB7 comp.

could you tell me why?

 

[TheBac]

For the reasons the guys said. IMO, you'll need the little bit of power the higher comp ratio can bring with the limits on boost that you'll have. If I were to do the whole stock-turbo racing thing again, Id have left my comp ratio alone instead of cutting the pistons like I did.


Now, if you decide to go stock-appearing charger, then the lower comp ratio might help you. You need to decide which turbo/fuel avenue you're going down first, and build the engine from there.

 

[dirty_max]

For the reasons the guys said. IMO, you'll need the little bit of power the higher comp ratio can bring with the limits on boost that you'll have. If I were to do the whole stock-turbo racing thing again, Id have left my comp ratio alone instead of cutting the pistons like I did.


Now, if you decide to go stock-appearing charger, then the lower comp ratio might help you. You need to decide which turbo/fuel avenue you're going down first, and build the engine from there.

Ok i got you, your saying don't delip the pistons to stay stock compression? What do you think about going up in compression? Turbo will be factory turbo. We have 2 different classes for stock turbos. Factory and stock appearing. I will run a factory charger. I was also thinking 10mm pump and 60 overs for fuel. But what i don't want to do is get this thing built and have a ton of money sank in it and look back wishing i would have done something else. That is why i am asking all you guys who have been down this road. The truck will rarely be driven on the road, maybe 1000 or 2000 miles a year. Thats about all it gets now anyways.

 

[Blackmax123]

I really dont think there is a true answer that someday you won't look back and wish you did something different. I built my lmm with that though thinking someday itd gonna be a 2.6 truck. Now with how that class has got I built the total wrong truck to start with and lowered compression so I get my ass kicked in 2.5 plus is a heavy pig...lol so there all kinds of things I wish I have done different. But what I truly should've done was built it for what my goals were at the time not for dreams in the future.

I'd stay at least with the stock 17.5:1 if you want to run lb7/lly pistons but if I was going to buy pistons I'd look into about 18.5:1. If your gonna stay true stock turbo and not stock appearing big differences there..

 

[TheBac]

Amen to that ^^

There's always something you learn later that makes you think, "Damnit, why'd I do that"...but you make your decision based on what you know at the time. I still made 580 the way I built mine.

 

[ikeG]

Your compression ratio will not be the reason you win or lose. Assuming it's within reason.

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