Pushrod Selection - Competition Engine Build

Reply Subscribe

Thread Tools

Search this Thread

Mar 3, 2016 | 10:33 AM

Boyes50

Thread Starter

Staging Lane

Joined: May 2013

Posts: 67

Likes: 2

Pushrod Selection - Competition Engine Build

Hi Everyone,

In the midst of putting together a mild build but relatively high RPM LQ9 engine for my pulling truck. Engine Spec's are:

- LQ9 Stock Short Block
- 799 Heads, Milled .020", Hand Ported by Poltergeist
- Tick SNS Stage 2 V2
- LS7 Lifters
- BTR Trunion Upgrade
- Manley Race Valves
- BTR Titanium Spring Kit (Dual)

Please don't riddle me with "Read and Search", but rather provide some tips. I am new to the game and have spent hours and hours researching, and including this topic, and know that everyone says to "Put the biggest pushrod in that will fit."

Unfortunately, since I live in Canada, I don't have anywhere I can grab some pushrods and if they bind, return them and change them up. Measuring seems foolish because I am unsure of the clearances of the pushrods on the wall of the heads. So my question for everyone is.

With an LQ9 Block and 799 Heads, in your opinions, what is the largest diameter pushrod I can install (I am most interested in whether 3/8" will fit without clearancing requirements)

AND

Will .080" wall thickness suffice or should I spend the extra money on .105" wall.

This engine will be redlined at 7,000RPM and since it is for truck pulling, it will hang at these RPMs for 8-12 seconds at a time going down the track. Any information you can provide me with is greatly appreciated.

Mar 3, 2016 | 11:27 AM

BOLO

10 Second Club

iTrader: (40)

Joined: Nov 2006

Posts: 3,180

Likes: 2

From: Mundelein,Illinois

I suggest calling Manton and ask for Al. He'll help you with the right pushrods.

Mar 3, 2016 | 12:05 PM

JayTS

Teching In

iTrader: (1)

Joined: Aug 2012

Posts: 23

Likes: 0

From: Some where between Orlando and Miami, FL

I second the phone call to Al@Manton Pushrods.

Mar 3, 2016 | 01:42 PM

tadams72

TECH Regular

Joined: Dec 2011

Posts: 448

Likes: 2

From: SoCal

3rd motion for contacting Manton. Biggest that will fit is generally sage advice though. Valve control gets increasingly difficult as the RPMs go up and flexing pushrods create harmonics and lead to valve float as the RPMs increase. Thicker walls help some but larger diameter tends to increase stiffness more. Keep in mind the valvetrain is a system best developed as a whole. A good read on effects of diameter vs wall thickness:

http://www.corvetteforum.com/forums/...stiffness.html

Mar 3, 2016 | 03:15 PM

Boyes50

Thread Starter

Staging Lane

Joined: May 2013

Posts: 67

Likes: 2

Thanks for the replies everyone. I always avoid calling and bugging the manufacturer before I have done my reading, but in this case calling Al was extremely worth while. I am going to be buying 3/8" Series 5 Pushrods with .095" Walls and .040" Oil Restrictors to keep top end oil flow under control! Al is an amazing resource and wealth of knowledge for anyone wondering!