Drilling 243 head pushrod holes
Thread Starter
Teching In
Joined: Mar 2014
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Drilling 243 head pushrod holes 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
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
Staging Lane
Joined: May 2013
Posts: 67
Likes: 2
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
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
12 Second Club
Joined: Sep 2005
Posts: 4,273
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From: Bucks County, Pa.
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.
Now, whether or not they are nearly as strong/rigid as the Manton/Trend 11/32nds mentioned above, who knows.
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.
The 5/16 pushrods are .080 wall and the series 5 mantons are .120.
Last edited by BlackDuk98; Apr 3, 2016 at 11:12 AM.
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.
Trend makes the pushrods for Comp, they don't make their own including the 5/16".
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Verdad Gallardo On stock 243 heads with 5/16 pushrods, you have way more than .005 clearance
Last edited by BlackDuk98; Apr 3, 2016 at 11:12 AM.
12 Second Club
Joined: Sep 2005
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From: Bucks County, Pa.
Will they also clear the stock, un-drilled 241 head (and even earlier 2000 M.Y. f body heads') pushrod holes??
Last edited by dailydriver; Apr 3, 2016 at 03:35 PM.
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
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