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 !

Re: Shimming Hydraulic Flat Tappet Lifters
 

It depends on the lobe, of course. The acceleration ramps are theoretically different on a hydraulic vs. a solid profile. Many lobes will accept either style lifter with no issues.

Yes, you do. Since the lash isn't figured into the checking clearance (zero) a solid lifter combo is in the same boat already. On a 'hydraulic cam' that's been switched to solid lifters, .002-.003 lash (hot) is pretty normal.


Most solid lifter stocker cams that I'm around use lash figures in that neighborhood already.

Hope this helps. :) -Al

Re: Shimming Hydraulic Flat Tappet Lifters
 

So I guess the point is , is the benefit of a solid lifter worth the loss of whatever valve lift you would lose because of lash .

Re: Shimming Hydraulic Flat Tappet Lifters
 

Who makes the best solid lifter for a bigblock chev. Would you use anything different if converting from hydraulic lifters.

Bruce Cameron
1968 Nova 396 E/S

Re: Shimming Hydraulic Flat Tappet Lifters
 

Some of you guys are experimenting with things in an attempt to try things, and asking good questions. Some of the results reported in this thread rise up some other good questions as well. If some of you report large HP and MPH gains just by changing lifters to a non-hydraulic type, something must be going on here. Topping out the travel on a hydraulic lifter plus a little for lash(.002-.004), prevent the lifter from pumping up, thereby extending the theoretical RPM range of the engine, but what if the trend to stiff valve springs, low pressure oil pumps, and lightweight oil is resulting in a hydraulic lifter steadily collapsing as engine RPM increases going down the track? That would result in cam lift and duration steadily decreasing while on the back half of a run.The change to a solid lifter would prevent this, thereby maintaining valve train activity during the whole run,and resulting in ET reduction and MPH gain, in effect, more peak horsepower. That kind of lifter collapse would probably not result in audible valve noise because the lifters would quickly pump back up while slowing down and driving back on the return road. You would'nt probably hear it over the sound of uncorked headers either.If you switch from hydraulic to solid lifters,you would have to recheck your total valve lift as well, since the more accurate valve train activity might result in a change. Also, if the solid lifter was somehow shorter that the hydraulic, it would result in a change in the effective height of the valve train. Shorter or longer push rods might be necessary to restore proper lift. It would be easier to check lift because you wouldn't have hydraulic lifters trying to squash down under load at max lift anyway. One of those variables that's impossible to measure while an engine is running and the car is going down the track.