Shimming Hydraulic Flat Tappet Lifters

HP HUNTER · 05-14-2017, 12:35 AM

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

Tom Meyer · 05-14-2017, 02:10 PM

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

Tom Turner · 05-14-2017, 03:13 PM

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.

rich freitag · 05-16-2017, 08:58 AM

When did NHRA alllow solid lifters on a stocker hyd ?

Alan Nyhus · 05-16-2017, 09:28 AM

Quote:

Originally Posted by rich freitag

When did NHRA alllow solid lifters on a stocker hyd ?

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

HP HUNTER · 05-16-2017, 09:32 AM

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.

Dan Fahey · 05-16-2017, 10:35 AM

I run GM Rollers Lifters in my LT1

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

d

Tom Turner · 05-17-2017, 02:07 PM

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

About 30HP, Maybe more depending on your tenacity.

Coleydog · 05-19-2017, 05:16 PM

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

ss3011 · 05-19-2017, 06:44 PM

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 !

05-14-2017, 12:35 AM	#1
HP HUNTER Senior Member Join Date: Feb 2012 Location: Colorado Springs Colorado/Thousand Oaks Ca Posts: 656 Likes: 82 Liked 371 Times in 129 Posts	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?

05-14-2017, 02:10 PM	#2
Tom Meyer Senior Member Join Date: Aug 2003 Location: Pierce NE Posts: 934 Likes: 75 Liked 351 Times in 120 Posts	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 __________________ Tom Meyer 5240 SS Stock ???

05-14-2017, 03:13 PM	#3
Tom Turner Member Join Date: Jan 2005 Location: Lake Tapps, Washington Posts: 137 Likes: 0 Liked 0 Times in 0 Posts	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.

05-16-2017, 08:58 AM	#4
rich freitag Junior Member Join Date: Mar 2008 Location: cicero n.y. Posts: 29 Likes: 7 Liked 0 Times in 0 Posts	Re: Shimming Hydraulic Flat Tappet Lifters When did NHRA alllow solid lifters on a stocker hyd ? __________________ Rich Freitag 1440 SS

05-16-2017, 09:32 AM	#6
HP HUNTER Senior Member Join Date: Feb 2012 Location: Colorado Springs Colorado/Thousand Oaks Ca Posts: 656 Likes: 82 Liked 371 Times in 129 Posts	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. Last edited by HP HUNTER; 05-16-2017 at 09:35 AM.

05-16-2017, 10:35 AM	#7
Dan Fahey VIP Member Join Date: Oct 2008 Posts: 2,127 Likes: 1,084 Liked 184 Times in 113 Posts	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

05-17-2017, 02:07 PM	#8
Tom Turner Member Join Date: Jan 2005 Location: Lake Tapps, Washington Posts: 137 Likes: 0 Liked 0 Times in 0 Posts	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.

05-19-2017, 05:16 PM	#9
Coleydog Senior Member Join Date: Jul 2014 Posts: 569 Likes: 36 Liked 53 Times in 38 Posts	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

05-19-2017, 06:44 PM	#10
ss3011 Senior Member Join Date: Feb 2002 Location: Southeast Michigan Posts: 908 Likes: 70 Liked 238 Times in 113 Posts	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 !