Pushrod Lengths

**ls1camino** · 08-18-2008, 08:14 PM

What is the purpose of shorter pushrods? TSP offers them with their head/cam packages and I was wondering if I should pick up some shorter-then-stock pushrods...

**Mr. Luos** · 08-19-2008, 08:47 AM

Do NOT pick up shorter pushrods unless you require them.

**Justin93** · 08-19-2008, 10:22 AM

what would be the reason for going shorter though? Im curious as well

**shady milkman** · 08-19-2008, 10:26 AM

the length of pushrods depend on the amount of lift and duration on the cam and the compression ratio. if the cam has very high lift then the push rods need to be shorter so not to damage the valvtrain..ie valve kissing

**Mr. Luos** · 08-19-2008, 10:38 AM

Originally Posted by shady milkman

the length of pushrods depend on the amount of lift and duration on the cam and the compression ratio. if the cam has very high lift then the push rods need to be shorter so not to damage the valvtrain..ie valve kissing

Actually...this isn't really the case.
Unless you are pushing the limits of the clearance...and if you are, you should get pistons rather than shorten the pushrods to clear.

My pushrods in the 402 are 7.325".
Preload on my lifters is .060-.070 less than OEM. So that is the difference.
Also had .020" milled off my heads, so that is a small amount of the shorter pushrod.

Some heads have a higher rocker arm pedistal...which will require a longer pushrod.

If you aren't sure or are wondering....measure.

**jad628** · 08-19-2008, 10:40 AM

Originally Posted by Mr. Luos

Actually...this isn't really the case.
Unless you are pushing the limits of the clearance...and if you are, you should get pistons rather than shorten the pushrods to clear.

My pushrods in the 402 are 7.325".
Preload on my lifters is .060-.070 less than OEM. So that is the difference.
Also had .020" milled off my heads, so that is a small amount of the shorter pushrod.

Some heads have a higher rocker arm pedistal...which will require a longer pushrod.

If you aren't sure or are wondering....measure.

Well, now my head hurts!

**shady milkman** · 08-19-2008, 11:01 AM

Originally Posted by Mr. Luos

Actually...this isn't really the case.
Unless you are pushing the limits of the clearance...and if you are, you should get pistons rather than shorten the pushrods to clear.

My pushrods in the 402 are 7.325".
Preload on my lifters is .060-.070 less than OEM. So that is the difference.
Also had .020" milled off my heads, so that is a small amount of the shorter pushrod.

Some heads have a higher rocker arm pedistal...which will require a longer pushrod.

If you aren't sure or are wondering....measure.

screw you C

**Mr. Luos** · 08-19-2008, 11:02 AM

Originally Posted by shady milkman

screw you C

Going with a shorter pushrod than required will just loose power and make a LOT of valvetrain noise. Also wear out the valve tips and rockers.

**shady milkman** · 08-19-2008, 11:03 AM

Originally Posted by Mr. Luos

Going with a shorter pushrod than required will just loose power and make a LOT of valvetrain noise. Also wear out the valve tips and rockers.

oh i agree with you on that..

**Frost** · 08-19-2008, 12:06 PM

They can be required when the heads have been milled as well, depending on application

**Justin93** · 08-19-2008, 12:08 PM

ya learn something new everyday here lol. thanks guys

**ls1camino** · 08-19-2008, 03:58 PM

So...5.3L heads with a MS3 cam (237/242 .603/.609") will or will not require shorter pushrods?

**Mr. Luos** · 08-19-2008, 05:09 PM

Originally Posted by ls1camino

So...5.3L heads with a MS3 cam (237/242 .603/.609") will or will not require shorter pushrods?

You want proper preload on OEM lifters. .080-.100 preload.

Most aftermarket cams actually have a slightly smaller basecircle than stock. In that case, a 7.410" would be ideal.
I honestly think this is how some of these larger cams clear...the use of a pushrod that is just a little too short.

Too determine base circle, call TSP.
Why the MS3??

**mrr23** · 08-20-2008, 01:19 PM

Originally Posted by shady milkman

the length of pushrods depend on the amount of lift and duration on the cam and the compression ratio. if the cam has very high lift then the push rods need to be shorter so not to damage the valvtrain..ie valve kissing

very incorrect. a pushrod will never correct piston to valve clearance issues.

the purpose for shorter pushrods is to have correct lifter preload and geometry. the LS1 motor rockers are non adjustable. if you mill the heads, this brings the rockers closer to the lifter. this will put more preload on the lifters. to get back to the correct preload, you shorten the pushrrod the same amount you milled the heads.

**shady milkman** · 08-20-2008, 01:41 PM

Originally Posted by mrr23

very incorrect. a pushrod will never correct piston to valve clearance issues.

the purpose for shorter pushrods is to have correct lifter preload and geometry. the LS1 motor rockers are non adjustable. if you mill the heads, this brings the rockers closer to the lifter. this will put more preload on the lifters. to get back to the correct preload, you shorten the pushrrod the same amount you milled the heads.

yea i know that now..thanks for re-opening the wound robert

**COJO_24** · 08-20-2008, 02:01 PM

the pushrod length is only to keep your valvetrain geometry correct and to cut down on excessive wear on valvetrain components

or atleast thats what i always thought...

**ls1camino** · 08-20-2008, 03:32 PM

Thanks for the responses guys, looks like I'll put it on the list of things to talk to TSP about.

Originally Posted by Mr. Luos

Why the MS3??

Changing the role of the Trans Am...I don't DD her now, and if/when I get my new job, I'll be driving her even less because I'll be provided a car I can take home. So, she's going to be a track car, with the occasional cruise. Since I won't be working 3pm-11pm Tuesday to Saturday, I'll be able to go to the track more often.

**vettenuts** · 08-22-2008, 02:18 PM

Unless you have a stud mounted rocker (such as the Crane), pushrod length only affects lifter pre-load and will not change geometry. On a stud mounted setup, pushrod length affects both geometry and lifter preload.