Lifter preload

[coldair]

As most of you know im building a AMC 258 i6 / 4.2l the block has been zero decked head shaved .010 and I'm installing a 4.0 head. With this combo i cant run the AMC 258 i6 / 4.2l or the 4.0 pushrods.
What way do you guys check lifter preload? With people changing the head on their AMC 258 i6 / 4.2l to the 4.0 head has got me thinking how many motors are running around with wrong pushrod length.
The best way to check you lifter preload is with a dial inducator. First bring your motor to TDC compression stroke on number one cylinder install pushrods/rocker tighten rockets down like motor is going to be run. Turn motor over so everything settles number one cylinder should be back to TDC compression stroke. Install dial indicator on valve cover gasket surface set indacator on back of rocker pushrod side, zero indicator, loosen rockers tell zero lash rocker should still be touching pushrod just enough to support it. That will tell you what your preload is on your lifters.

 

[gert]

Haven't done it in awhile but comp cams had an adjustable pushrods that you could rent from them and you adjust it til your preload is correct then pull it and measure it

 

[coldair]

I've already measured and received my pushrods just wondering If anyone is doing this.

 

[Kane]

I had to buy different length pushrods for my v8 and aftermarket heads but I also installed adjustable rocker studs so I can dailed them in exactly to what I wanted.

 

[coldair]

Kane I would love to have a set of adjustable roller rockers for my motor but at $500 think they will have to wait. Setting lifter preload would be so easy.

 

[coldair]

BTW I know my AMC 258 i6 / 4.2l doesn't need roller rocker but the added strength would be nice.

 

[jamesweed]

I used an angled straight edge(rigid) layed across the rocker cover gasket surface, TDC on cylinder, scribe mark on pushrod with rocker torqued, untorqued rocker scribe again, measured between the two marks with a vernier. I ended up going with a AMC 258 i6 / 4.2l rod spec'd to mid late 1970s(Shorter than mid 80s). The stock rod for my 85 AMC 258 i6 / 4.2l was way too long, 4.0 wasnt right either, cant remember if was too long or too short, anyway I ended up with .050 preload across all cylinders. Smooth idle and as quiet as you would expect from a AMC 258 i6 / 4.2l jeep, no complaints yet.

 

[micrablue]

I also used a straight edge and scribed the pushrod, after letting off the rocker bolt, just enough to allow me to roll around the pushrod in my fingers. This is on TDC #1. I also have a comp cams hi-tech adjustable pushrod to double check.

I'd recommend buying adjustable roller rockers, but they cost a lot as you mentioned. In the long run, if you are changing up things in your motor, plus the added strength, less friction loss, quietness, and cooler oil, not needing to buy pushrods each time, measuring preload, etc. the benefits adds up!

 

[mstar]

Don't know where you guys buy your pushrods ,but if you are interested Smith Bros pushrods in Bend, ORE. can build to spec for a reasonable price and quick turn around. Used them on my 427 FE ford and Dauntless Buick 225 V6 V6.I used adjustables on the V6 because Comp Cams specified a .030" after zero clearance and each individual valve is a little different.They worked out great.These are Very high quality race parts.
mike

 

[mstar]

Coldair, just wanted to say thanks for the tip on measuring pushrods.I will keep this in mind for next build. happy jeep'in Mike