Valvetrain Geometry
 

I have a GTP LT4 topend and Bret Bauer camshaft going into my stock bottom end motor soon. I have been doing my homework and have seen that valvetrain geometry is critical to engine life and performance.

I was wondering what I had to measure and spec to figure out if my valvetrain geometry is good. Here is what I have so far, if I need to change something I definately will.

GTP LT4 Heads, 2.02/1.60 Manley Valves (Currently has dual coil springs, but swapping for 918's) [Sizing CC's, intake ports, and flowing soon]
Comp Pro Mag 1.6 NSA 7/16"
ARP 7/16 Studs
GMPP Guideplates
Bret's recommended Camshaft, Comp 918's and related parts
Comp Hi-tech 5/16" 7.200 pushrods
Crane Lifters 10530-16
Impala or Mr Gasket Head gaskets [Depending on head CC's]

Should everything be fine? Should I have the shop that flows the heads measure or size anything else? Seat size, valve stem height, anything like that? Bret feel free to jump in with the 918 small parts if that changes anything.

Thanks

-Dustin-

Re: Valvetrain Geometry
 

Everything looks fine to me except for the fact that you will never know what pushrod length you should have until it is assembled and you check it, and thats what determines the geometry of the rocker arm over the valve stem tip which is critical. I doubt with that combo you will end up using stock length pushrods. Buy yourself an adjustable pushrod from Comp Cams. They are only like $15 and make it easy to figure which pushrod length is right for your particular combo.

My $.02 :)

Re: Valvetrain Geometry
 

So the Comp Cam's pushrod thing goes into the motor and you adjust the lenth until its perfect, then pull it and see what length it says? How can you tell what the ideal length is? I hope the stock length works, but if not Summit is only 5 minutes from my buddy's house that we are installing it all, so I guess its a quick fix. Thanks.

-Dustin-

Re: Valvetrain Geometry
 

This is what I use: http://www.powerandperformancenews.c...Category_Code=

"The unique design is easy to read and eliminates the need for expensive calipers. Each complete revolution is equal to .050”. Having the correct length pushrods in your engine is a critical factor in proper rocker arm geometry and this is the best tool to measure pushrod length. It reads like a micrometer."

on a side note, be sure to use low tension checking springs (also available from Comp) in place of the valve springs so you don't break your checking pushrod :cool:

edit: oops looks like the price has gone up since I bought mine, they are more like $20 now...

edit again: more useful info: http://www.compcams.com/Technical/Cu...ML/306-307.asp

Re: Valvetrain Geometry
 

So a pushrod length checker should be the only thing I need? I dont need to measure anything else?

Thanks for the help, hopefully one of my buddies know what to check and look for.

-Dustin-

Re: Valvetrain Geometry
 

It wouldn't hurt to check piston to valve clearance too. And you could also degree the cam.

Re: Valvetrain Geometry
 

True, and also check your pushrods to see if they are rubbing the guideplates on the part that is closest to the stud. I understand that has happened to alot of people running the GM guideplates. If they are, just take them off and clearance them a little in that area with a dremel or something like that :thumb: I clearance mine a little before I even installed them just to make sure that I wouldn't run into that problem.

Re: Valvetrain Geometry
 

Are you using stock length valves or +.050 or +.100? The beehives are
designed for a 1.80" installed height. Most of us using them go with the
10* hardware and +.050 locks to get the most installed height. But even
with this we are in the 1.75" range if you use Comp spring seats designed
for the springs. It seems like the best approach is to have a 1.80" installed
height out of the box, and then determine pushrod length with a checker
in the motor.

Since it looks like you are going all out, I would also recommend the titanium
retainers (794-16). You can get them from Bret.

Re: Valvetrain Geometry
 

The valve length is exactly why I asked about getting those measured. I heard there is a good head shop around here called Canfield Heads and I'll go there Monday to get them all checked out.

What do the Ti's have over anything else. The setup on there might already have them...

-Dustin-

Re: Valvetrain Geometry
 

Just lightens the valvetrain more. If you are aggressively opening and closing
the valves, the less weight the better. Considering what you are spending so
far, another $175 does not seem too bad. Ask Bret what he would recommend.

Re: Valvetrain Geometry
 

titanium valves are not good to run on the street and ya need to change seats.
They will be beat out in no time with street duty.

Re: Valvetrain Geometry
 

It would be a good idea to check the install height of each and every spring before putting the combo together. You can get a spring install height micrometer from Summit for around $20.

Re: Valvetrain Geometry
 

Alright so Ti isnt a good idea for a street driven car. Its a daily driver for now, but I suspect not for long.

Spring height I thought was a good idea too, thanks.

-Dustin-