RIPVTEC

Hello ls1tech,

I have been doing some reading and looking around.

Members are suggesting I run a 11/32 push rod. This apears to be in the $200 price range.

I do in fact have the 243 heads off the car as I have an extra set that were at the machine shop getting a valve job, milled, and springs put on.

Some say 3/8 pushrod clear some say they rub.
It sounds like it would be easy enough to enlarge the hole a tad to be able to clear a 3/8 with ease.

A 3/8 is much more price friendly at $100.

So my question is, is it okay/safe to just enlarge the push rod holes with a 1/2" drill bit.?

Is 1/2 in fact the correct size ?

Thanks again

Boyes50

Hi RIPVTEC. I would recommend getting in contact with Al @ Manton Pushrods. Al recently explained to me the pushrod selection decisions and guided me towards the 11/32" Series 5 Pushrods for my specific application. You can get a set of Series 3 11/32" Pushrods just below $200.00, and with the heavier walled 11/32" they will provide similar rigidity and better valvetrain harmonics then a cheaper, thinner walled 3/8" pushrod.

You would likely enjoy a reading of this thread from Corvette Forums. An excellent break down and explanation of pushrod size and requirements.

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

I considered drilling or opening my heads for larger pushrods but ultimately decided against it as I already had the heads mounted and torqued to the motor

reaper68

iTrader: (3)

You can also run tapered 3/8's from trend as an option they work fine in my 799 castings

dailydriver

Jegs also told me that Comp cams has a custom pushrod built program (albeit with a 2 week lead time) that will do 11/32nds for ~$150.00.

Now, whether or not they are nearly as strong/rigid as the Manton/Trend 11/32nds mentioned above, who knows.

BlackDuk98

iTrader: (34)

Go for the 11/32 Manton series 5, that is what I am also running. Max lift on my setup is .629. They clear fine with stock 799/243 pushrod holes. When I was changing my rocker bolt holds to m10s', I also drilled out the pushrod holes out with a tapered reamer and they are now 9/16, tons of clearance.

The 5/16 pushrods are .080 wall and the series 5 mantons are .120.

DietCoke

iTrader: (18)

You don't want tons of clearance, you want .005 or so, because the head is going to expand a little bit. The head supports the pushrod in the same manner as a guideplate. 1/2" drill is the correct size.

vettenuts

iTrader: (4)

Trend makes the pushrods for Comp, they don't make their own including the 5/16".

RIPVTEC

1/2" it is, thanks!

BlackDuk98

iTrader: (34)

I have heard multiple ideas on this subject. I have heard of having the clearance like I have, I've heard that you can have them actually slightly rub and work like a guideplate - but they need to be checked with a sharpie marker and barely rub the marker off. I have seen 1/2"-9/16" used for clearancing.

On stock 243 heads with 5/16 pushrods, you have way more than .005 clearance

dailydriver

Will they also clear the stock, un-drilled 241 head (and even earlier 2000 M.Y. f body heads') pushrod holes??

Boyes50

Al @ Manton advised me that 11/32" Pushrods will clear all factory LSx Cylinder Heads. Call them and have a chat with Al, he was beyond helpful with my build

RIPVTEC

Again I'd like to save the extra $100.

4 mins with a drill to fit 3/8 is no biggy

DavidBoren

That $100 is not worth saving... Don't skimp on your valvetrain...

blk00ss

iTrader: (66)

Be careful not to go through the intake ports lol.

RIPVTEC

It's not skimping.
It's going to bigger od push rod.

always faster

iTrader: (6)

Go read the VETTENUTS thread.The ID of the pushrod will make little difference in stiffness, the OD is the major controller.

Since my head was on the car i chose to run some Manton 5 series double tapered 3/8 .120'' wall pushrods.

If you got the head out of the car, just drill them and be happy to run better/bigger pushrods