strange valve job... what the hell??

[steve g]

OK im still in process of my z24 build and time to attack the head.

I brought the z24 head to my friend who builds racing small block chevys and asked him what he thinks. After he flipped it over 2 or 3 times and saw his smirk i knew he was not really impressed with the design.

He looked a few things over...and under and he said he can rework it a bit to help with lower to midrange power (perfect for my 4x4).

He later called me and told me im paying for a 3 angle valve job but with a 30 degree valve seat grind vs the standard 45 degree.

Why? i asked... he started talking technical racing shit i couldnt understand and i gave him the ok.

Anyone familiar with this?

[ggzilla]

Some friend. Offers to help then later says he's charging you...

[Z-train]

I'd be worried.Pontiacs for instance came with a FIVE ANGLE valve cut from the factory.THere are a lot of"know-it-alls"who change it to a 3"angle" because"that's what you do".Datsun engineers weren't stupid.

[stilltwisted]

the last angle of the three or five has to do with the hight of the port ,,if its sorta flat then less degree angle will smooth the inlet charge,,but if it is a high port like bbpontiac 400/455 then less angle will cause dissturbance in flow ,,so higher degree is perfered,, also the seat and valve has too be thick enugh to dissipate heat so blueing doesnt accure,,i forget witch is hotter 3/5 angle

[ggzilla]

All the Datsuns I've worked with have a three-angle valve seat right from the factory. I seem to recall them changing the angle at some point.

[Z-train]

I was using the Pontiac thing as a example of how people shouldn't screw with some factory decisions.

[steve g]

i knew i was going to get charged... just at a good rate... this is how he makes his money so i dont expect to get anything for free.

He knows what he is doing but i am very ignorant about this one..... i cant even find info about it on the net. Its still a 3 angle valve job but with a 30 degree face "seat".

as long as it works and is reliable i am happy.

[Charlie69]

I run 3 angle on all datsun L & Z motors. Works for me. Been using 3 angle grinds since mid 70's.

[Mark_Z28]

Factory may know what they are doing but they arent grinding seats for performance, just enough to get it done while passing emissions testing and mileage. They wont take the time or expense on an engine designed for an econobox that 99% of the owners will never take to a track(at least when they were first sold). Same with most other manufacturers.

[Z-train]

You are 100% wrong.

[datzenmike]

Reducing the valve seat angle will effectively widen the valve face/seat gap for any lift setting. BUT... it also slightly narrows the port size immediately below the valve seat. Although the valve is open the same amount, the 30 degree angle will have a 'wider' opening and increased flow.

[steve g]

ok i get it now............i think.....

Along with this setup he is having me run the Mikuni cam i have been badmouthing for so many years.... I got lucky and found a new one online.