Shimming Hydraulic Flat Tappet Lifters
 

What gains in dyno HP, MPH, RPM peak gains have you seen from shimming hyd flat tappet lifters on a stocker cam?

Re: Shimming Hydraulic Flat Tappet Lifters
 

When working on my sons LS1 street car we struggled with the short travel lifters and valve lash. In the end with adjustable rockers we found around 90 hp, this was on a roller lifter. Tom

Re: Shimming Hydraulic Flat Tappet Lifters
 

I think the original reasoning behind shimming the hyd lifters was to stop the lifter from collapsing and thus breaking the stock rockers or blowing the pushrods through the seat. It also (if properly adjusted only gave the lifter about .0075 to "float".) The HP gains came later when we discovered that stiffer valve springs, very light motor oil and much higher RPM thresholds yielded big gains in performance. One of the few "win-win" deals in drag racing. Solids are legal now so most won't use this method anymore.

Re: Shimming Hydraulic Flat Tappet Lifters
 

When did NHRA alllow solid lifters on a stocker hyd ?

Re: Shimming Hydraulic Flat Tappet Lifters
 

Allowed this year. Lifter style must remain the same (can't replace a flat tappet lifter with a roller lifter).

Re: Shimming Hydraulic Flat Tappet Lifters
 

Shimming the hyd lifter to .010 on my Buick 315/455 was worth 12 HP and carried the power out past the peak much better and the engine was happier. Spring pressure was 170/350. I opted to stay with the hyd lifter only because it was living nicely with my cam, if that wasn't the case I would be running a solid lifter.

Re: Shimming Hydraulic Flat Tappet Lifters
 

I run GM Rollers Lifters in my LT1

What advantage do Short Travel Roller Lifters they have over the GM Roller Lifters?

d

Re: Shimming Hydraulic Flat Tappet Lifters
 

What advantage do Short Travel Roller Lifters they have over the GM Roller Lifters?

About 30HP, Maybe more depending on your tenacity.

Re: Shimming Hydraulic Flat Tappet Lifters
 

What they're saying, no loss of lift or duration with shimming. Now, just use a solid lifter
Mike

Re: Shimming Hydraulic Flat Tappet Lifters
 

Converting from a hydraulic lifter to a solid sounds good , but how does that work ? Wouldn't you have to develop a new camshaft ? Wouldn't you lose some lift due to whatever valve lash you use ? Are there some stocker profiles out there that are solid but are designed for very tight lash , say under .012" . Just asking , I am interested !