[Atomic Ed]

Just thought I would start a discussion on the pro and cons of using a lash cap to boost fuel delivery. I’ve walked through both the Corvette and HP tuners forums and found several interesting threads. BTW, for those of you who haven’t heard of this, the lash cap trick is just adding a valve lash cap to the end of the pump plunger to increase stroke. Seems the LS7 lash cap is the current choice. Comp Cams also manufactures a lash cap to specifically fit our HPFPs.

It seems to be divide into two camps on the use of a lash cap. Those with an LT4 pump tend to have problems, particularly with the slightly larger camshaft pump lobe on the LT4 camshaft. There were several reports of binding of the pump due to the use of the lash cap.

On the other hand, those that have used a lash cap on the LT1 pump don’t seem to have a problem, with the exception of improper installation, which seems easy to do wrong. The argument here is that adding a lash cap functions the same as adding a bigger cam lobe. The lash cap users are seeing around a 20% gain in fuel flow. Lingenfelter even discusses the use of lash cap to compensate for the smaller camshaft base circle on their aftermarket high volume HPFP.

And just to add to the discussion, I found this statement in an HP tuner thread:

“The LT1's pump FACTORY flows 2176 PSI, but in the tune has a HP PUMP MAX of 3118 PSI

The LT4's pump FACTORY flow 2901 PSI, but in the tune has a HP PUMP MAX of 3989 PSI”

No real hard opinion on my part. Just want to throw this out for discussion/information building. Anyone with real world, rubber on the road, experience?

[steelheadrob]

Good topic. I done some research on this as well. Looking forward to see if anyone has done this and the results.

[Atomic Ed]

Originally Posted by steelheadrob

Good topic. I done some research on this as well. Looking forward to see if anyone has done this and the results.

So how does your research compare to mine? Any different thoughts?

[steelheadrob]

I am seeing similar to your original post, guys claiming a 20% increase. I haven't seen any proof. I have been looking for a before and after dyno for someone that was hitting the fuel wall. I just wonder if the lash cap alone does much with out switching to the LT4 injectors.

[EDFHOBBIES]

Fuel system upgrades seem to be very secretive MTI in Houston had an open house a few months back I think they told me they do the Lash cap, LT4 Injectors, and the pick up pump with good results for those of us that cant afford to have the 5k wrapped up in a cam swap.

[toohighpsi]

Originally Posted by steelheadrob

I am seeing similar to your original post, guys claiming a 20% increase. I haven't seen any proof. I have been looking for a before and after dyno for someone that was hitting the fuel wall. I just wonder if the lash cap alone does much with out switching to the LT4 injectors.

I can't see what a lash cap does on a stock system unless there is some amount of lost motion within the cam follower. With a smaller base circle cam it's completely understandable.

With a completely stock LT1 fuel system the most I was able to make was ~620 RWHP. It's important to note that I'm running at standard conditions on most days. I'm at 100 ft above sea level with a temp normally right about 65F, so there isn't really much of any dyno correction - the car is making the power that the dyno displays. When testing at higher altitudes you could get a higher RWHP number on stock parts but that would be because of the correction factor that is applied by the dyno to the data.

I'm now running the stock LT1 injectors in the Camaro with the Lingenfelter Big Bore HPDI fuel pump to the tune of 690 RWHP which is the point where the low pressure system was down to under 30PSI (didn't run out of fuel, but wasn't comfortable to go further). We are switching to the ZL1 in-tank pump right now and I'll get back on the dyno to see if the stock LT1 injectors will go 700 RWHP with the help of the ZL1 in tank and Lingenfelter big bore pump.

Now in my mind, I have a tough time recommending the LT4 pump, on my Z06 with TVS 2300 the LT4 fuel pump lost capacity at just over 650 RWHP (I thought that 700 would be in reach). With the cost of the LT4 pump at about $800 it seems like the best choice is to go right for the Lingenfelter Big Bore pump along with LT4 injectors as the injectors still had capacity left when the LT4 HPDI pump gave up the ghost. I'm thinking there is 750 RWHP capability with Big Bore pump and LT4 injectors on an otherwise stock engine (good fuel of course).

Lingenfelter has a really big set of injectors that they recently released, capable of over 1K HP if I remember correctly.

I am working on additional fueling for the Camaro beyond that point and will be happy to share as soon as I have some performance data on it.

[sub_ETCS_ret]

Originally Posted by toohighpsi

I can't see what a lash cap does on a stock system unless there is some amount of lost motion within the cam follower. With a smaller base circle cam it's completely understandable.

With a completely stock LT1 fuel system the most I was able to make was ~620 RWHP. It's important to note that I'm running at standard conditions on most days. I'm at 100 ft above sea level with a temp normally right about 65F, so there isn't really much of any dyno correction - the car is making the power that the dyno displays. When testing at higher altitudes you could get a higher RWHP number on stock parts but that would be because of the correction factor that is applied by the dyno to the data.

I'm now running the stock LT1 injectors in the Camaro with the Lingenfelter Big Bore HPDI fuel pump to the tune of 690 RWHP which is the point where the low pressure system was down to under 30PSI (didn't run out of fuel, but wasn't comfortable to go further). We are switching to the ZL1 in-tank pump right now and I'll get back on the dyno to see if the stock LT1 injectors will go 700 RWHP with the help of the ZL1 in tank and Lingenfelter big bore pump.

Now in my mind, I have a tough time recommending the LT4 pump, on my Z06 with TVS 2300 the LT4 fuel pump lost capacity at just over 650 RWHP (I thought that 700 would be in reach). With the cost of the LT4 pump at about $800 it seems like the best choice is to go right for the Lingenfelter Big Bore pump along with LT4 injectors as the injectors still had capacity left when the LT4 HPDI pump gave up the ghost. I'm thinking there is 750 RWHP capability with Big Bore pump and LT4 injectors on an otherwise stock engine (good fuel of course).

Lingenfelter has a really big set of injectors that they recently released, capable of over 1K HP if I remember correctly.

I am working on additional fueling for the Camaro beyond that point and will be happy to share as soon as I have some performance data on it.

Just curious as to why you went the route of the ZL1 in tank pump first before changing out the injectors? The path of least resistance would say that you would go for the injectors first. Are you thinking that the ZL1 pump is going to give you the most bang for your buck?

[Perdieu]

Originally Posted by toohighpsi

I can't see what a lash cap does on a stock system unless there is some amount of lost motion within the cam follower. With a smaller base circle cam it's completely understandable.

With a completely stock LT1 fuel system the most I was able to make was ~620 RWHP. It's important to note that I'm running at standard conditions on most days. I'm at 100 ft above sea level with a temp normally right about 65F, so there isn't really much of any dyno correction - the car is making the power that the dyno displays. When testing at higher altitudes you could get a higher RWHP number on stock parts but that would be because of the correction factor that is applied by the dyno to the data.

I'm now running the stock LT1 injectors in the Camaro with the Lingenfelter Big Bore HPDI fuel pump to the tune of 690 RWHP which is the point where the low pressure system was down to under 30PSI (didn't run out of fuel, but wasn't comfortable to go further). We are switching to the ZL1 in-tank pump right now and I'll get back on the dyno to see if the stock LT1 injectors will go 700 RWHP with the help of the ZL1 in tank and Lingenfelter big bore pump.

Now in my mind, I have a tough time recommending the LT4 pump, on my Z06 with TVS 2300 the LT4 fuel pump lost capacity at just over 650 RWHP (I thought that 700 would be in reach). With the cost of the LT4 pump at about $800 it seems like the best choice is to go right for the Lingenfelter Big Bore pump along with LT4 injectors as the injectors still had capacity left when the LT4 HPDI pump gave up the ghost. I'm thinking there is 750 RWHP capability with Big Bore pump and LT4 injectors on an otherwise stock engine (good fuel of course).

Lingenfelter has a really big set of injectors that they recently released, capable of over 1K HP if I remember correctly.

I am working on additional fueling for the Camaro beyond that point and will be happy to share as soon as I have some performance data on it.

Looking forward to your thoughts and results on the ZL1 pump. I just put mine in.. not fun if you have big hands LOL..

[wnta1ss]

Mr Jannetty said that the lash cap he used on the gray car was only to make up for the reduced base circle of the +32 fuel lobe on the aftermarket camshaft.

[toohighpsi]

Originally Posted by sub_ETCS_ret

Just curious as to why you went the route of the ZL1 in tank pump first before changing out the injectors? The path of least resistance would say that you would go for the injectors first. Are you thinking that the ZL1 pump is going to give you the most bang for your buck?

No, it's just because I hadn't yet hit the injector pulse width that would drive me outside the injection window, once I hit that I'll install the LT4 injectors that I have for it.

[sub_ETCS_ret]

Originally Posted by toohighpsi

No, it's just because I hadn't yet hit the injector pulse width that would drive me outside the injection window, once I hit that I'll install the LT4 injectors that I have for it.

When you get it installed and tuned could you post your findings in your ready for the track thread?

[ProCharger]

After watching plenty of people for the past couple years knock their HPFP's right off the engine block...
My best advice is talk to your cam provider to see what they want you to do with the HPFP.
Since not all lobes are the same...

Otherwise you could end up with the "rattle rattle, thunder clatter, boom boom boom" ....
The sounds of the HPFP bottoming out, and eating itself alive.
(Personally have never used a "lash cap" nor had a reason to.)


For "normal" street cars making less then 800 rwhp with boost.
The simple combo is just a nice cam (with extra lobe)
And voltage booster for the LPFP. (plus a touch of meth)
That combo will allow you to make MORE power then a stock LT can handle.

A local shop here in KC (House of Boost) has been cranking out 750+ rwhp combos week in and week out like that, using the following combo.

HOB 2016 Camaro F/I Cam (no cap, stock HPFP)
ProCharger P1SC System
Snow Meth System

Simple, Proven, "Bang for the Buck" Combo that = Fast Camaros. (and vettes)


Otherwise you are talking spending MAJOR money on the fuel system, for the same results.
Fuel Pump Swap for LP side. (or booster, or aux pump)
LT4 Pump Swap for HP side
LT4 Injectors

Not saying thats "bad"...but thats a LOT of coin to get the same results.
Since at the end of the day you are trying to get a LOAD of fuel into the cly in a small injection window.
(Plus D/I really isn't that fantastic at WOT anyways, hence why you see Ford swapping to a blend of D/I and Port Injection in 2018)

[SGDM]

I thought the LC's were heavy and added weight to the valve. May be needed to change geometry if I remember. With a custom cam and tune you should not need em. Good discussion

[JANNETTYRACING]

Originally Posted by Atomic Ed

Just thought I would start a discussion on the pro and cons of using a lash cap to boost fuel delivery. I’ve walked through both the Corvette and HP tuners forums and found several interesting threads. BTW, for those of you who haven’t heard of this, the lash cap trick is just adding a valve lash cap to the end of the pump plunger to increase stroke. Seems the LS7 lash cap is the current choice. Comp Cams also manufactures a lash cap to specifically fit our HPFPs.

It seems to be divide into two camps on the use of a lash cap. Those with an LT4 pump tend to have problems, particularly with the slightly larger camshaft pump lobe on the LT4 camshaft. There were several reports of binding of the pump due to the use of the lash cap.

On the other hand, those that have used a lash cap on the LT1 pump don’t seem to have a problem, with the exception of improper installation, which seems easy to do wrong. The argument here is that adding a lash cap functions the same as adding a bigger cam lobe. The lash cap users are seeing around a 20% gain in fuel flow. Lingenfelter even discusses the use of lash cap to compensate for the smaller camshaft base circle on their aftermarket high volume HPFP.

And just to add to the discussion, I found this statement in an HP tuner thread:

“The LT1's pump FACTORY flows 2176 PSI, but in the tune has a HP PUMP MAX of 3118 PSI

The LT4's pump FACTORY flow 2901 PSI, but in the tune has a HP PUMP MAX of 3989 PSI”

No real hard opinion on my part. Just want to throw this out for discussion/information building. Anyone with real world, rubber on the road, experience?

It appears there is a misunderstanding of what a lash cap purpose is.

When grinding a 32% lobe they cut the base circle down on the cam which then creates a space between the cam follower and the cam lobe, this space must be compensated for by adding a lash cap.

The result is longer stroke there for more fuel per stroke.

To say that a lash cap increases fuel flow is the same as putting longer pushrods and expecting more valve lift.

Maybe I am missing something here but that is my take on it.