poltergeist 02

iTrader: (65)

I have a set of ported 799 heads that I installed some 2.00/1.55 Manley Race Flow/Pro Flow valve in. After the install I noticed that all of the intake valve stems are about .025 lower than the exhaust valve stems. I know I will need to measure for pushrod length again. Should I just make make up the difference in pushrod length to retain correct lifter preload?

poltergeist 02

iTrader: (65)

Also, if I did make up the difference with pushrod length do you think it will throw off the geometry of the valvetrain?

96capricemgr

iTrader: (1)

Did you blindly throw bigger valves at already ported heads without a valvejob?

poltergeist 02

iTrader: (65)

the heads are new GM 799 castings that were hand ported. the valves I put in are manley 2.00 intake and 1.55 exhaust cut on a 45*

96capricemgr

iTrader: (1)

So I looked it up and that is stock size but that doesn't mean the valve seat angles are the same. Did you have a valvejob done?

poltergeist 02

iTrader: (65)

no, it's a factory valve job. I think I figured out what is going on though. the 45* cut on the stock valve is much closer to the bottom of the valve head than the manley valve. I may have to take pics to better explain.

KCS

iTrader: (20)

Do you mean there's a larger margin on the Manley valves?

Just use different pushrods, it won't hurt anything. The pushrods do not change rocker geometry like it would in a stud mount rocker system. I did the same thing with my engine.

poltergeist 02

iTrader: (65)

Are you running two different size pushrods between the exhaust and intake valves?

KCS

iTrader: (20)

Yes, it is intentional too.

poltergeist 02

iTrader: (65)

Did you run into the same problem with the valves sitting at different hights?

KCS

iTrader: (20)

Yep. After the valvejob for the larger valves they were at two different heights.

poltergeist 02

iTrader: (65)

Thanks KCS for the responses. I just didn't want to bolt the heads on only to find out I have to pull them back off and buy new bolts and gaskets. How far off were your valves from intake to exhaust?

KCS

iTrader: (20)

Not 100% sure, but I used pushrods .025" different to get the preload right.

poltergeist 02

iTrader: (65)

maybe geometry was the wrong word to use but did you still have a nice centered wipe pattern?

KCS

iTrader: (20)

The pushrods won't change that, moving the rocker's fulcrum is what would though. The LSx stuff has a shaft mount rocker system that's bolted down, so the only way to move the rocker's fulcrum is shims or milling the stands.

Burken01

iTrader: (88)

Just curious but if you run into a problem like this couldnt you just grind the valve tip down a bit to make them all level? I just had some heads done at a shop and was curious to know what you usually do when you encounter this...

this topic nearly ever comes up so I think its interesting..

RockinWs6

No you can't grind the tips of the valves, they are hardened.

KCS

iTrader: (20)

Actually you can grind them. It's done pretty regularly.

You can have the tips ground or use different length pushrods, I don't think it really matter much on most street cars.

poltergeist 02

iTrader: (65)

Yes I have heard of thiss but it can be limited by the hight of the retainer to the tip of the valve stem.

KCS

iTrader: (20)

Well, you probably grind through the hardened tip before that happened, but yeah I'd say that would be the limiting factor lol.