Don Terrill’s Speed-Talk

I knew someone years ago that happened to. Luckily his was water cooled and he was able to run some hot water into it and was off and running agai I designed a cam for a Daytona Prototype car, over a decade ago. The rules limited the gross valve lift and duration at .050", so I designed a cam with ...

David Redszus wrote: ↑

Thu Sep 12, 2019 12:22 pm

A ramp height of .020" over 40 deg would produce a slope of 2 deg/.001". That is to say a change in lash of .001" would result in a duration change of 2 deg.

Actually, it would change 4 degrees, because you would be changing each side 2 degrees.

Limited Lift rule cam ( duration depends on RPM range you want to run)
J842HVM Lifters: Limited Travel Hydr Lifters.
JRC15 springs: 1.250" Single Spring w/Damper, 130#@1.750", 347#@1.250", CB 1.150"

Our Sales office will be closed next week(23rd-27th), but the shop will still be open.
Production, and shipping will not be effected.

Sorry for any inconvenience.

David Redszus wrote: ↑

Tue Sep 10, 2019 1:47 pm

Do you use the same ramp slope for all cams? What slope do you use, if you feel comfortable sharing that info.

No. The ramps are matched to each cam.

235@.050" on a 107 LSA
That's your issue
Go down to a 228 on a 110, and your problem will be solved

I'm not a fan of running a hydr lifter at 6,600 rpm, for long periods of time. Any aeration in the oil, and you will have big issues.
The profile I recommended is a very mild design, and should be really easy on the valvetrain. No need for an aggressive profile, with a turbo.

I recommend staying with a mechanical roller
Cam# LS1, R70360-114
230/230 @.050"
.360"/.360" Lobe Lift
114 LSA

Mike, what lash do your cams have for the most part? We use a .012" Lash ramp on most of our roller profiles, so Hot Lash would be .012" x Rocker Ratio. We chose .012", because if you go down to a .010" ramp, with an Aluminum block and Aluminum heads, the lash growth from cold to hot, would be more...

We accomplished the same thing, by leaving the valve sizes alone, and changing the centerlines for each valve.
We opened and closed one intake valve, before the other one, and opened and closed one exhaust valve before the other one.

Doesnt the tighter lash make for more lifter life at idle? They say idle is harder on lifters part due to oiling and part i thought was from taking up that initial clearance No. When the valve is closed, and there's lash in the valvetrain, there's almost no force being applied to the roller wheel. ...

thedynoguy wrote: ↑

Mon Sep 09, 2019 6:50 am

That engine needs to go on a dyno to see what the problem is.

Agree.
Like I said, the cam is off, but not enough to be that far off on RPM.
I think it may be floating the valves, and that would be easy to check on the dyno.

1. How long have they been around ? Longer then I have 2. What was/were the reason/reasons for it's development ? Mostly for marketing, because the shorter the lash ramp, the more aggressive the cam looks, when looking at the distance between .020" and .050", even though it's no more aggressive. Th...

With a lift limit would it make sense to increase cam diameter so as to enable increasing duration in the lobes. Cam diameter does not restrict duration. In fact, the only time you need a larger cam journal on a flat tappet, is when the cam duration is so short, for a given lift, that the nose of t...

It's got a limiter at 7499RPM in the ECU but I don't know if it's ignition signal (MSD points signal) or fuel cut or some combination of both. Datalog shows an RPM dip near there but then recovering just before the end of the burnout. This would be something to look into. When the Indy Racing Leagu...