MP Solid FT cams and their lash specs

Kern Dog · Oct 5, 2019

I have a 528 solid in my 440/493. The valve lash specs are .028 intake and .032 exhaust. The Lunati I once had called for a .020 Intake and .022 exhaust. I understand that the Lunati is a modern design but I wonder why there is such a variance between the two.
Have you used a Mopar Performance cam and chosen your own valve lash specs to use? I understand that a tighter lash will make the cam appear bigger and the net lift to be higher. I'm sure the drag racers have experimented with valve lash to have some feedback.
This is a street car. I like to take trips in the car and eventually do want to take it on a road course like Willow Springs or Buttonwillow. I currently have a 727 with an 11" converter, 3.55 gears, a 28" tire and the car is 3950 lbs.

1 Wild R/T · Oct 5, 2019

I'd have no problem tightening those up .008 or more just to see how much it changes the drivability...

Kern Dog · Oct 5, 2019

Its not as if I am disappointed with the performance. I was just thinking about what effect it might have. It has a tolerable amount of clickity-clack from the solid lifters. In terms of valve lash noise, the Lunati was quieter but also a LOT wilder. I'm running 1.6 rocker arms too.

493 Mike · Oct 5, 2019

I would think the difference is in the ramp design.
Mike

yella71 · Oct 5, 2019

I ran that very cam (mopar 528) and always set the lash to .020 intake and ext. just ran it on the strip never on the street. also never tried it with the suggested lash . it seemed to work fine at .020 . also the engine had Iron heads aluminum heads may make a difference I wish I still had it id run it in my 383 but I sold it to a friend and it now sits in the engine along with the car not being used. I think if you open up the lash it will shorten the duration slightly and give you a little more lower end torque...the 440 I had that cam in never needed more lower end. If you spend the time to experiment with the lash you can tune your motor with it that way. Its a bit time consuming

BSB67 · Oct 5, 2019

Over on Moparts there is a discussion going on about cam LSA and little about lash. Some interesting comments.

Older cams seem to have looser lash spec, newer generally less. I think lash ramp design has changed but generally you can tighten any cam's lash without issue. The results just might not be as favorable as the seat timing will likely go up more on setting a tight lash on a cam with a loose spec.

Loose lash is noisier and is likely harder on parts. Looser lash on a given cam actually acts like a faster rate cam, tighter lash on the same cam acts like a slower ramp.

When the valves open and close does effect performance, and that is exactly what changing lash does. How much will be combination specific. Same with if more or less lash is better.

In my limited personal experience on dynos and track, larger lash settings made more power which is contrary to popular belief.

If you wanted too try looser lash, I would not think twice about opening it up 0.006" above the recommended setting.

Cranky · Oct 5, 2019

Generally if you tighten up the lash, it does increase lift and duration and if the car picks up ET, it's usually an indication it could probably use more cam. Need to be sure you have P/V clearance though to do it though but since yours is a street car, AND you're running 1.6 rockers, I kinda doubt you want more cam.....

BSB67 · Oct 5, 2019

Cranky said:
Generally if you tighten up the lash, it does increase lift and duration and if the car picks up ET, it's usually an indication it could probably use more cam. Need to be sure you have P/V clearance though to do it though but since yours is a street car, AND you're running 1.6 rockers, I kinda doubt you want more cam.....

This is generally true.

Tightening lash only changes seat timing a lot. A 0.004" lash change will change seat timing 8 to 12°, but only change 0.050" timing 2 or 3°. The lift difference is truly meaningless.

Kern Dog · Oct 5, 2019

There is NO problem with piston to valve clearance. I have some thick head gaskets in there and when I checked clearances several years ago, I was surprised to see the amount I had.

66Satellite47 · Oct 5, 2019

Differences in lash settings are based on ramp design. Newer cams theoretically have computer designed ramps that are "softer" on valve opening & closing, decreasing harmonics. I start with recommended & vary bit from there. Alum vs iron heads, seem to be an important consideration.

BSB67 · Oct 5, 2019

When you loosen your lash, you'll build a little more cylinder pressure, like 5 to 7 psi, depending how much you loosen it. I know you had some detonation issues before the head gasket change, or something. If you're on the edge now this might matter.

Kern Dog · Oct 5, 2019

Since the head gasket change, there has only been a few brief moments of detonation in the heat of Summer. Otherwise, it has been an effective fix.

andyf · Oct 6, 2019

Kern Dog said:
I have a 528 solid in my 440/493. The valve lash specs are .028 intake and .032 exhaust. The Lunati I once had called for a .020 Intake and .022 exhaust. I understand that the Lunati is a modern design but I wonder why there is such a variance between the two.
Have you used a Mopar Performance cam and chosen your own valve lash specs to use? I understand that a tighter lash will make the cam appear bigger and the net lift to be higher. I'm sure the drag racers have experimented with valve lash to have some feedback.
This is a street car. I like to take trips in the car and eventually do want to take it on a road course like Willow Springs or Buttonwillow. I currently have a 727 with an 11" converter, 3.55 gears, a 28" tire and the car is 3950 lbs.

View attachment 845285

The mfg recommends the lash based on the ramp design. I wouldn't recommend running a cam at anything other than what the mfg recommends. If you want a tight lash cam then buy one. The older cams typically had a lot of lash. Cam mfgs changed the ramp designs over the years and now you can buy tight lash designs if you want.

1968rt · Oct 14, 2019

Im running the .528 with .018 intake and .022 exhaust cold. runs great and sounds much better than the DC specs

33 IMP · Oct 14, 2019

I'm running the .557 at .020/.020 . I'm going to try 24/24 in a while,see if performance changes, and which way.
Running isky style iron rockers.

oldkimmer · Oct 14, 2019

My cars et never changed with valve lash adjustments. Kim

Kern Dog · Oct 14, 2019

1968rt said:
Im running the .528 with .018 intake and .022 exhaust cold. runs great and sounds much better than the DC specs

**Cold** ...Do you have aluminum heads? I set the lash .006 tighter because I always set the lash cold with mine. That makes it .022/.026 for me.
That would make your lash only .004 tighter than the spec.
I don't mind a little bit of clatter. I was just wondering if the tighter lash might make some difference in performance.

BSB67 · Oct 14, 2019

Kern Dog said:
**Cold** ...Do you have aluminum heads? I set the lash .006 tighter because I always set the lash cold with mine. That makes it .022/.026 for me.
That would make your lash only .004 tighter than the spec.
I don't mind a little bit of clatter. I was just wondering if the tighter lash might make some difference in performance.

There is only one way to find out for sure. Is there a track that you can go to to do some testing? I promise it'll be fun.

Kern Dog · Oct 14, 2019

Ha!
Yeah, we have a track south of me. I would need an external cutoff switch for the trunk mounted battery. I've never been an avid drag racer though, more of a street and curvy road type of guy.

BSB67 · Oct 14, 2019

Kern Dog said:
Ha!
Yeah, we have a track south of me. I would need an external cutoff switch for the trunk mounted battery. I've never been an avid drag racer though, more of a street and curvy road type of guy.

I like curvy. Are we still talking cars?

MP Solid FT cams and their lash specs

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