LSX Camaro

Here are a few pictures of 3 broken pistons from a 2017 C7 Grand Sport.

Mods Include:
Edelbrock E-Force Supercharger
Boost ~8psi
Kooks Long tube headers, catted X-pipe
Akrapovic exhaust

I DO NOT want this thread to get into a debate on what or why the pistons broke. The story behind this car is pretty unbelievable and I will share later. I am looking to hear from some Very experienced guys on what they did to upgrade their fuel system. Just the facts and no BS. The ultimate goal of the customer is ~700 RWHP on 91 pump gas.

New Plan
427 ERL All new short block.
10.5:1 comp ratio
All forged internals, built for 900 HP
Custom Weisco pistons for boost
Stock LT1 heads
Custom spec BTR Camshaft, springs, pushrods etc.
Johnson lifters
Cam-phaser
Trunion upgrade
Keep VVT
Delete DOD/AFM

My main questions are on changing the cam lobe with the LT1 pump and injectors, or upgrading to a LT4 injection pump, LT4 injectors only, a lash cap etc... I have read countless posts on different combinations between all the components. Some work and other are breaking the fuel pump bolts right off of the valley plate. Others have broken the HPDI pumps. Like I said in the beginning, I am only looking for ~700 RWHP on California 91 octane gas. For you Experienced guys who have done this, I look forward to hearing from you for real world LT DI fuel pressure recommendations.

NO Meth
NO E85

Higgs Boson

For 700rwhp just do a cam lobe and lt4 pump

FYREANT

^^this. If they plan to go higher HP in the future, throw in the Z06 injectors now.. they're fairly cheap..

Oh.. and throw the lash cap away. Nothing but problems and risks. Higgs and I both had bad experiences with it..

LSX Camaro

I have read through many threads on the lash cap. Just so I am perfectly clear neither the LT1 or the LT4 Do Not come with a lash cap on the fuel pump from the factory. Is this correct?

FYREANT

That is correct.

robert miller

From all my reading on this motor this should be all that you need to do for that rwhp.

New set up should be nice for sure. But would think with all of those parts would have some head work done on porting the heads to no more than to get them cleaned up.. Robert

JHEBERT

Without the lash cap, how are you going to take advantage of the larger fuel lobe the BTR cam provides? The lobe creates more lift by having a smaller base circle, not larger dia. lobe.

John

FYREANT

Cams with a larger fuel lobe have exactly that. A larger lobe. In some cases its a lobe thats a different shape then the standard egg shape. With the typical 32% lobe that most C7 cams have, its a larger base circle. Where did you get info that the base circle was smaller?! Thats not accurate..

7LitreC5

Do you know why it broke? Just curious.

BlueDevilZ51

Curious if he was running the Edelbrock E force tune or a custom tune.

JHEBERT

The fuel pump lobe on the LT engine cannot be made larger, the base circle is smaller to provide more lift....as for my info, it accurate.

John
"The Cam Motion Callaway"

7LitreC5

Same here.

Higgs Boson

The LT1 HPFP can handle the lash cap but the issues have been with the LT4 pump. At least 3 failures on here that I have seen.

Me, FyreAnt, LT1Z too https://www.corvetteforum.com/forums...post1591689647

The LT4 pump is basically a bored and stroked LT1 pump. The longer travel doesn't seem to leave enough room for a lash cap.

JHEBERT

Well that's going to suck, if the lt4 pump can't handle the extra .055" stroke then the larger lobe is pointless. More meth or Lingingfelter pump, that's going to be my question.

John

FYREANT

Meth has been the general consensus across the boards when needing more fuel then what the Z06 pump can dish out.

JHEBERT

Don't worry, I'm a longtime meth user, you should see how old I look

I'm already dual nozzle, I guess it's going to be what it is. At 10% more fuel, I don't think the LPE is going to be worth doing if already spraying meth. Does not help the PO though.

John

LSX Camaro

Tune was a custom tune.

New cam will have a +38% increased fuel pump lobe, also running the LT4 fuel pump.

BTR custom cam spec, Cam Motion core.

LSX Camaro

Say what?

C7&7

YUP like Higgs suggested just do the cam lobe and lt4 pump. I broke two lt4 pumps with 32% cam lobes AND lashcap. Stay far away from a lashcap if you are overdriving the pump with a cam.

erl427 seems like some extreme overkill for 700 wheel.

JHEBERT

The base circle (not an actual "round thing" lol) is about .050-.055 SMALLER, and this is how they increase the stroke of the pump. There is effectively more lift on the lobe, but NOT because it is physically larger. The lash cap is used (.050) to make up the difference when the lifter is on the smaller base. Now when the lifter hits the peak of the lobe, you get the extra stroke. Without the lash cap, there is no extra stroke of the pump. It's not rocket science here

John