HOW TO: Installing a Fuel Pump Lash Cap in an LT1 and Checking for Proper Clearances
05-17-2018, 06:39 PM
#41
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I just wanted to say thanks for this great writeup. I installed an LT4 fuel pump on my stock cam and stock valley cover LT1. I measured for preload and max lift clearance using this guide and found it very helpful. FYI the pump was perfectly fine and did not require a lash cap.
Oh, and since I didn't have the tool for checking lobe location, I used a large socket with an outer diameter just smaller than the hole size, then I put a short extension into the socket from the wrong end (insert the extension from the size that typically goes onto the bolt/nut). I then used this as my height tool. i put the extension side down because it was small enough to sit on the lifter plunger, and then the socket was low enough to touch the opening walls and stay in place. I wrote on it with a marker for measurements. I had to use the extension because when I tried just dropping the socket in there alone, the plunger went through the 1/2" opening for the wrench and wouldn't ride the lifter.
Oh, and since I didn't have the tool for checking lobe location, I used a large socket with an outer diameter just smaller than the hole size, then I put a short extension into the socket from the wrong end (insert the extension from the size that typically goes onto the bolt/nut). I then used this as my height tool. i put the extension side down because it was small enough to sit on the lifter plunger, and then the socket was low enough to touch the opening walls and stay in place. I wrote on it with a marker for measurements. I had to use the extension because when I tried just dropping the socket in there alone, the plunger went through the 1/2" opening for the wrench and wouldn't ride the lifter.
07-13-2018, 07:17 PM
#42
Instructor
Has anyone here done the lash cap on a stock cam with stock LT1 HPFP and had a before and after test done to confirm the 25% fuel delivery increase? I've been told it's more like only 10%.
03-09-2019, 11:40 AM
#45
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So, please infer from my educated observation and please assess your own approximation of fuel difference.
Ant
03-17-2019, 01:50 AM
#46
Melting Slicks
Does the factory setup actually have lash or zero preload on the pump?
I'm confused otherwise, you aren't changing stroke or stroke frequency, so how does fuel rate change?
I'm confused otherwise, you aren't changing stroke or stroke frequency, so how does fuel rate change?
03-17-2019, 10:48 AM
#47
The fuel rate changes because we are stroking the pump an additional .055. We need the lash cap because the lobe has a smaller base circle, so we are changing the stroke...
Last edited by JHEBERT; 03-17-2019 at 10:48 AM.
03-17-2019, 12:26 PM
#48
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I’m planning to take an LT1 pump apart to show the guts at some point. I “believe” that it is not that the stroke itself changes, but that shaft thw stroke goes in has a relief that is better optimized by changing rhe stroke depth slightly resulting in the increase.
03-17-2019, 09:28 PM
#49
Melting Slicks
On an aftermarket cam with smaller base circle the lash cap makes sense. I just dont understand increased flow by adding the cap on a stock cam. You add .055 of upward stroke, but you loose .055 of downward stroke. Thats like saying you get more lift on a cam by adding lifter preload. The lift doesnt change.
03-17-2019, 09:29 PM
#50
Melting Slicks
That at least is a theory that could make sense to me! I look forward to your dissection if it ever occurs
03-18-2019, 07:24 PM
#51
Burning Brakes
On an aftermarket cam with smaller base circle the lash cap makes sense. I just dont understand increased flow by adding the cap on a stock cam. You add .055 of upward stroke, but you loose .055 of downward stroke. Thats like saying you get more lift on a cam by adding lifter preload. The lift doesnt change.
Like someone already said maybe that.055 is just eating up some factory preload
03-18-2019, 07:34 PM
#52
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I already started disassembling my LT1 pump and taking pics. I’m at a point where I can’t figure out how to open the side where the spring and shaft go in so I’m working on that. Once I get that open I can post pictures with a detailed explanation of how these things actually work mechanicaly. Gimme a few days..
03-18-2019, 09:12 PM
#53
Burning Brakes
Thanks Fyreant! On my Z06 I have the fic injectors and the LPE big bore pump which I believe begins it's life from a stock LT1 pump. Without a cam to over drive it, I'm still out of fuel. I'd love to add a lash cap and avoid a cam, but i don't want to derail this thread with my individual setup. I'm genuinely curious what the inside of one of these pumps look like
Adding that small lash cap to my last Stingray with a cam and LT4 pump was a big help. It was definitely bottoming out on the down stroke without the cap
Adding that small lash cap to my last Stingray with a cam and LT4 pump was a big help. It was definitely bottoming out on the down stroke without the cap
Last edited by 555ctsv; 03-18-2019 at 09:13 PM.
08-05-2019, 07:05 PM
#55
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I would personally remove the whole pump lifter out and then you can work on it a little easier. It sounds like it was too tight to begin with. I would carefully try to wiggle it off continuously even if it takes a while to get it off. I would not try prying or anything like that.
08-07-2019, 03:54 PM
#56
I recently installed a TSP 218/226 .635/.635 with a 32% fuel lob with a lash cap into my L86 6.2 myself. This was my first cam install I've ever and it went pretty smooth. I had alot of help over on the Performancetrucks.net forum. I had a pretty big thread about it where I listed out the video's I watched to show me what to do.
Fast forward to at least 2500 miles later. I started getting a tapping sound coming from the back center of the engine. At first it was ever now and then and very faint but just the other day it got much louder. I parked the the truck and ordered a new fuel guide because when I installed the cam. My stock cam had a scoring mark on the fuel lob. Rockauto.com sent me two fuel guides that where all rusted and I sent them back. So by the 3rd fuel guide it wasn't perfect but was much better than the others and I need to have my truck up and running so I cleaned it up and went with it.
I haven't pulled the intake off yet. I'm waiting until I get my new fuel guide and I also order a new lash cap from TSP.
That was before I came across this thread. Is it safe to say with my stock L86 pump with should be the same as the LT1 pump and my 32% over fuel lob. I would need the .060 lash cap instead of the .080 TSP sells. I only say this because that's what your car measured with a 32% over fuel lob and a stock LT1 pump. It shouldn't be any different for another engine?
Fast forward to at least 2500 miles later. I started getting a tapping sound coming from the back center of the engine. At first it was ever now and then and very faint but just the other day it got much louder. I parked the the truck and ordered a new fuel guide because when I installed the cam. My stock cam had a scoring mark on the fuel lob. Rockauto.com sent me two fuel guides that where all rusted and I sent them back. So by the 3rd fuel guide it wasn't perfect but was much better than the others and I need to have my truck up and running so I cleaned it up and went with it.
I haven't pulled the intake off yet. I'm waiting until I get my new fuel guide and I also order a new lash cap from TSP.
That was before I came across this thread. Is it safe to say with my stock L86 pump with should be the same as the LT1 pump and my 32% over fuel lob. I would need the .060 lash cap instead of the .080 TSP sells. I only say this because that's what your car measured with a 32% over fuel lob and a stock LT1 pump. It shouldn't be any different for another engine?
08-07-2019, 04:55 PM
#57
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That was before I came across this thread. Is it safe to say with my stock L86 pump with should be the same as the LT1 pump and my 32% over fuel lob. I would need the .060 lash cap instead of the .080 TSP sells. I only say this because that's what your car measured with a 32% over fuel lob and a stock LT1 pump. It shouldn't be any different for another engine?
08-08-2019, 10:34 PM
#60
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Part number is: 12642273 but it may have changed to a new number at this point. Call your dealer to check pricing and availability. Hope it helps!
Ant