RPM Kit

dereklola

IndyLights
Jan 25, 2003
98
2
8
80
near Detroit
At what RPM does an RPM Kit become necessary?

Just bought new valves and valve springs from Ferrea and they say with their valve springs RPM Kit not necessary - keeping to 7000 max.

Anyone agree? Disagree?
 

rag231

Well-Known Member
Apr 30, 2005
1,432
133
63
Charlotte, NC
I have a stage 2 headed motor spinning to 8200 now. I know that it can go higher than that, learning the limits of a 275 tire. It has a rev kit and ISKY roller lifters. I know of a few motors that spin higher using the Manley Sever duty valves and some of the titaniums without a rev kit. I am sure a short stroke INDY Lights motor can hit 7000 in a blink of an eye. I dont recall seeing any pics in the stage 2 picture threads that were using a rev kit, I 'll look again. I had a guy who sold me a rev kit thinking it was a bar that the JESEL rockers mounted to. Hopefully some builders will chime in. It would be interesting to find out how the spring pressure on the lifter factors into your spring pressures used to open and close your valves or if they are completely independent and used just to control the lifter.
 

dereklola

IndyLights
Jan 25, 2003
98
2
8
80
near Detroit
Sorry - Rev Kit - not RPM Kit - just shows I'm not really an engine guy.

My engine was originally built by Brayton Engineering before George Montgomery got the business. It came with a Rev Kit - see pic below taken earlier this year. It's possible but I doubt it that a previous owner added it. I know that similar engines built for IMSA generally (always?) used a rev kit but then they frequently used 8500rpm not being limited to 7000 as the Indy Lights are.

Bottom line is valve springs have improved enormously in the intervening 30 years - Ferrea did mention that they thought it would not be needed at "only" 7000 - and I'm now about to start the rebuild. Obviously I'll be talking to Ferrea again but thought recommendations from Buick experts would be useful too.

Also pertinent is that I use a mild cam grind to get better/easier driveabilty (we race 100 miles, not 1/4 mile !!) which reduces the valve train acceleration values.

valley Feb2017.jpg
 

bison

Moderator
Staff member
Dec 19, 2005
16,804
1,512
113
42
CT
Use softer lobes and look into getting the correct valve springs and make sure you’re operating in a range where harmonics are minimal. What’s on the valve side of the fulcrum matters 90%. Id use at minimum 3/8 pushrods in that engine also.


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dereklola

IndyLights
Jan 25, 2003
98
2
8
80
near Detroit
1 - valve springs were Ferrea's recommendedation - I hope they were good.
2 - How do I identify minimal harmonics? Typical race RPM is 5800-6500, with occasional 6800-7100. Engine does have harmonic balancer, came with engine, do not know specs. Engine is SII, on center, even fire.
3 - by "valve side of the fulcrum" do you mean minimizing weight of the valve etc? Or something else?
4 - I do have 3/8" diam pushrods.

Appreciate your help so far.
 
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