View Full Version : Can someone tell me the valve drop on a stock L92 head?


hirdlej
04-22-2010, 01:36 PM
I'm just hashing through some calculations and wanting to know what the stock free valve drop is on an untouched L92 head. I'd also be interested to know for those of you running the L92 heads on a LQ4 shortblock, what's your PTV clearance like? (please state cam specs as well)

Richard@WCCH
04-24-2010, 12:34 PM
Just checked on a new "out of the box" casting:
Intake -
Solid stem (L92) .133"
Hollow stem (LS3) .133"

Exhaust -
Solid stem (L92) .160"
Sodium valve (LS3) .160"
Production tolerances will move them up or down a couple of thou.

Richard :)

Jimbo1367
04-24-2010, 12:46 PM
Just checked on a new "out of the box" casting:
Intake -
Solid stem (L92) .133"
Hollow stem (LS3) .133"

Exhaust -
Solid stem (L92) .160"
Sodium valve (LS3) .160"
Production tolerances will move them up or down a couple of thou.

Richard :)

Richard,
Do you have a theory on why the L92s have dropped a valve? Do you see the valve or bad lock as the culprit? Have you seen these happening on LY6 engines too?
thanks,
Jim

Jimbo1367
04-25-2010, 06:23 PM
zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz zz

cam
04-26-2010, 10:48 AM
I've seen a few threads pop up with the dropped valve problem and there was no smoking gun that I saw. Im chalking it up to crappy workmanship or insufficient valve springs for those particular failures until someone proves otherwise. Lots of guys running these heads on stock valves without issue

Richard@WCCH
04-26-2010, 11:43 AM
Richard,
Do you have a theory on why the L92s have dropped a valve? Do you see the valve or bad lock as the culprit? Have you seen these happening on LY6 engines too?
thanks,
Jim

The "valve drop" the OP was refering to is the dimension from the shallow edge of the valves to the deck of the head. It's a vertical measurment that is used to calculate valve to piston clearance.
We've not seen many L92 heads with broken valves. Both the solid stem and hollow LS3 valves seem to be holding up nicely.

Richard :)

Patrick G
04-26-2010, 01:07 PM
Richard,

What is the valve drop on one of your CNC ported L92/LS3 heads? With many people interested in running them with larger cams and no valve reliefs, it would be good to know how much room we're dealing with. Thanks!

Jimbo1367
04-26-2010, 02:12 PM
The "valve drop" the OP was refering to is the dimension from the shallow edge of the valves to the deck of the head. It's a vertical measurment that is used to calculate valve to piston clearance.
We've not seen many L92 heads with broken valves. Both the solid stem and hollow LS3 valves seem to be holding up nicely.

Richard :)

Richard,
I figured that out. I didn't mean to hijack the tread, but I figured you might return to comment again and you to enlighten me/us.
thanks,
Jim

Richard@WCCH
04-29-2010, 10:32 PM
Richard,

What is the valve drop on one of your CNC ported L92/LS3 heads? With many people interested in running them with larger cams and no valve reliefs, it would be good to know how much room we're dealing with. Thanks!

Excellent question Patrick. Our Stage 2 L92 heads with machine finished chambers have the following valve drop specs (with minimum surface milling):
Intake - .135"
Exhaust - .205"

I'll post up specs for our Stage 3 heads over the weekend.


Richard :)

Patrick G
05-02-2010, 09:38 PM
Excellent question Patrick. Our Stage 2 L92 heads with machine finished chambers have the following valve drop specs (with minimum surface milling):
Intake - .135"
Exhaust - .205"

I'll post up specs for our Stage 3 heads over the weekend.


Richard :)Wow, better than stock valve drop. That helps for guys not wanting to fly-cut. One of your competitors is selling a ported LS3 head that only had .089" free valve drop on the intake side (making it impossible to run anything larger than a cam in the 210s at .050").

hirdlej
05-02-2010, 10:27 PM
A stock 243 head is around .160" valve drop so the L92's are a tighter fit........

LS6
05-04-2010, 02:49 PM
informative thread