Tomei Poncams Valve lash specs

[gezed]

Is there a different set of specs for Tomei Poncams or do they just follow the oem specs

Also, the first head i put together had too much valve clearance and it ticked when it was warm, but this time, I may have set the clearances more or less on the tight side, is there anything wrong with that?

for example, feeler gauges show intake valve clearance of .402mm whereas the FSM states that it should be .45+/- .03mm

Any insight would be much appreciated

[allwheeldrifter]

i also bough poncams for my gtr, im also interested in knowing......but i would assume that we gotta use the oem specs..... ps... i hate valve noises...lol

[gezed]

^ me too, I've got another set of shims and going to make the valve clearance a bit tighter than OEM spec, hopefully it turns out well.

Since poncams are direct drop in cams im gonna assume they follow oem valve lash specs too

[GT-RJules]

.45 in / .38 ex +/-.03 its same as factory, im assuming you found this already it easily accessible.

[Terrh]

whatever the paper that came with your cams says. For mine (procams) it says .45mm in and .38mm exhaust.

which is ~18 thou intake and ~15 thou exhaust.

[feyd182]

Just remember everything expands as it gets hot, adjusting too tight can prematurely wear things out, run hotter due to increased friction, and possibly bend valves. Factory specs are the rule, not a suggestion. I've seen too many damaged heads due to not following OEM guidelines.


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[Terrh]

Just remember everything expands as it gets hot, adjusting too tight can prematurely wear things out, run hotter due to increased friction, and possibly bend valves. Factory specs are the rule, not a suggestion. I've seen too many damaged heads due to not following OEM guidelines.


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Having the tolerances exact is key, but following OEM specs is a recipe for disaster with non OEM parts.

Your cam paper will tell you what specs exactly to use.

For all tomei RB26 poncams/procams (they're all the same according to the sheet)

Intake is 0.45mm ± 0.01 mm (Roughly 0.017 inches)
Exhaust is 0.38mm ± 0.01mm (almost exactly 0.015 inches)

Assuming that you're using stock valves in stock guides.

Good luck getting them to within 0.01mm, or even finding feeler gauges in increments that small.

Factory says ± 0.03mm which works out to just over 0.001" .

For new motors I've tried to get them exact as possible and said anything within 2 thou is close enough after I've had the cams out a dozen times. They've gotta get adjusted after break-in anyways.

For new cams, the clearance is going to change anyways as everything breaks in (even more so with new valves/valve job) so get it within a thou or two (MAX) and then check it again at 10,000KM and make it all right.

Checking clearances on GTR's that ran fine I found some valves as tight as 0.005" and some as loose as .025".
Setting the valves back to factory however made the car run noticeably quieter.

[gezed]

if valve lash is as tight as you mentioned, any abnormal wear to the lifters or cam lobes? and i don't think running tighter specs would cause valve tick or any noises right?

[mitch32]

You can burn the cam out and cause excess wear on the cam if the clearances are too tight.

I've done 4 valve adjustment jobs on the rb26 and its not bad. I was able to get them within 0.001". For the rb26 its better to go a little looser, so if you have one at 0.014" and it should be 0.015" try to get it to 0.016" rather then 0.015".

[Terrh]

if valve lash is as tight as you mentioned, any abnormal wear to the lifters or cam lobes? and i don't think running tighter specs would cause valve tick or any noises right?

Too lose = noisy engine, less power from less cam lift, extremes = lobe damage and bucket wear from the cam slamming into the bucket instead of working properly.
too tight = hot start problems, burned valves (valve can't cool), way too tight = less compression because the valve won't shut fully.