Verifying My Work - LT1 w/ LT4 HPFP & Lash Cap
 

last year in my winter build, I put on my s/c, LT4 HPFP, LT4 injectors, but installed the pump on the LT1 with just one factory gasket. No lash cap.

On long pulls, I can see my rail pressure will drop and injector cycle will open up some, so both me and my tuner agree I am probably out of HP Fuel Pressure. Now I do run meth on top of everything so I am still feeding it, but would like to try and feed it more E85 if I can. And FYI - my car is a 1LE so it has the larger flow low side pump, but it is just about out of flow also.

I am trying to avoid doing a cam swap, so thus far the plan this winter is a DSX aux fuel pump on the low side, and then I was planning to check my LT4 HPFP stroke. I am not trying to get a ton more flow, just maybe 10%.

That being said - has anyone run a lash cap on the LT1 cam with the LT4 HPFP? I know some have bottomed the pumps out / broken the bolts using the .080" shims, but has anyone gone thru the process to 100% utilize the LT4 pump?

I have read the article on the CorvetteForums, but it shows little on what configurations work?

How much power were you trying to make?

I would honestly hit it with a little more meth before trying a lash cap on a factory cam.. just my .02

Just going off memory but I don’t think a lash cap does anything to make a lt4 pump flow more. It just moved the piston up in the stroke and may risk bottoming out the piston if it isn’t just right. I had some posts a long time ago about it.

The lash cap is suppose to help with the smaller base circle high fuel pump lobe cams. Without it you have some wasted cam lobe where the piston isn’t moving.

This may be helpful.

https://www.youtube.com/watch?v=DL19veeM6QA

What about lingenfelter HPFP? Isn’t it good for about 10% more high side flow?

Yes the LPE big bore is worth another 10% in flow volume. I was out the other night when the temps hit the 30's, boost hit 11 psi, and I still had enough fuel system on E67 and no meth. Normally I see around 9psi above 50 degrees.

The LPE has never been a popular choice. In the end it isn't any more expensive then the LT4 + a Meth kit. I believe it's not popular because the early version was not compatible with bigger fuel lobe cams larger then 32%. So the LT4 with a 38% lobe would end up out flowing the LPE pump. Most seem to go right to a cam swap for more fuel. If you want to run a stock cam with E85, then a LPE pump will free up some headroom.

I also didn't need a Auxillary pump.


My fuel system:

LT4 injectors
LPE big bore HPFP
LT4 low side with JMS booster

This fuel setup is so far is working well. I wont push past 11-12psi tops on stock pistons, so i dont plan on touching it unless I do rod/pistons.

I would ask MTI performance in Houston I know they messed with lash caps for ages they might be nice enough to help!

I really am not doing this to pursue more power - I am content with the power level I am at for street use (700whp), I just want to get that power level on fuel delivery and not require the meth to keep it fed. I will still use the meth for temp control, but I would like to not have to worry about loosing a meth pump and detonating the engine.

I am curious if at one point in the pump stroke if the pumps flow more (IE - in the low / middle / high part of the stroke).

I do know some places machine down the valley covers by .030" to get the pumps to sit closer to the cam when running aftermarket cams. I am not apposed to running a lash cap and making a spacer too (IE - a .080" lash cap and a .050" spacer)

E-Content in Minnesota can vary from 50-85% by law, so the thing about trying to hit / maintain a certain number is that all the variations in fuel here. Even premium 91,92 or 93 can vary from 5-15%.

I can monitor by fuel sensor now, and if I am under E72ish I do not get any lean over on the rail pressure, but at about E65 my flex tune starts pulling timing, so it has a pretty narrow window that is not real easy to hit (I spent all last year trying to target E70-75).

I just want to get it where I can rely on the fuel system to keep it fed.

I have contemplated a cam swap, but am trying to avoid dropping the oil pan / pulling the engine. Im not afraid of the cost or the work, just trying to keep it a "Keep It Simple Stupid" upgrade.

You are not going to keep it fed on that fuel system without relying on meth. You will need a cam or LPE pump. Those are your 2 options. Cam makes the most sense to me and provide the most fuel headroom, but then you might as well do drop in pistons.

That would be news to me - last I knew you needed to get the cam out you need to be able to take the chain off, and in order to take the chain off you need to take the oil pump off, and in order to get the oil pump off you need to drop the oil pan. Reference - https://www.corvetteforum.com/forums...all-guide.html

We are addressing the low side with the DSX aux pump

Lethal garage has a video taking the chain off without removing the oil pump. You can use a couple small standard blade screw drivers and work the chain off the gear.

Heater & King - thanks - this changes my direction completely. The work on everything didn't intimidate me at all other than the oil pump alignment.

However this makes me wonder with Lethal's current situation ?

What's his current situation? Last I knew he tore his motor down because the chain tensioner went south, but he could of just fixed it and put it back together...instead he rebuilt the entire engine. I haven't followed him much since.