+0.02" Rod w/ 0.01" Head Gasket Question

[SquidBonez]

I plan on doing a +0.02" billet rod and a thinner than stock 0.01" head gasket on a Predator 212 hemi. I want to get some stock length chromoly pushrods as well (since I'm pretty sure the thinner head gasket doesn't make enough of a difference to need different length pushrods) but will I have any valve clearance issues with a longer rod paired with a thinner head gasket? Don't want to put it all together and have the piston hit a valve. Will be using stock valves/head for reference.

 

[madprofessor]

You must be a little fuzzy on the numbers, but it's clear what you mean. My hemi got the stock rod replaced with a billet rod that's .020" over stock length, which brings a flat top piston to .005" from top of cylinder without any machine work being done. Since the most important thing you can do to save your engine is replacing that stock rod, then it makes perfect sense to do it, and wouldn't make any sense not to get the billet rod longer for the same price as a stock length rod.
There are various thicknesses of head gaskets out there, but my performance guy up in N.C. puts a .012" stainless steel head gasket in his hemi high performance gasket set. Here it wouldn't make much sense to stay with a stock thickness (.050" ?) since you need to buy a sump sidecover gasket anyway because of the rod change, and if you get the whole hi-perf gasket set instead ( $14 ) it's only 4 bolts on the head to change that head gasket after the 4 bolts on the valve cover, which also gets a new gasket in the set, and not a cheap paper one at that.
With my piston and head brought .058" closer together with the overlength rod and thinner head gasket my compression's greatly increased and makes a lot more horsepower. This setup is what the best small engine performance expert I know recommends and sells for the 212 hemi, and nothing hits anything. At least not with my stock pushrods, valves, retainers, and lash caps. Speaking of which.........
My guy says the stock valve retainers are the weakest link in the valve train when running new 22# valve springs like on mine, and are only good and safe to about 7200 rpm.
Want to know how close the piston gets to the head? Unbeknownst to me, my sloppy welding on a temporary header for testing before the changes caused a piece of steel welding slag to fall down through the exhaust valve into the cylinder. It was a little round ball not even near as big as the size of a standard .177 BB you were shooting as a kid. It was discovered when trying to rotate the engine for access to the rod bolts, and the motor would have to have a little firm head start to twist it past top dead center, or it would hang up there when turning slowly, only go backwards. That was with the stock rod and head gasket.
BIG NOTE: Please follow the instructions that come with your billet rod to the letter. The new bearings get mated to the rod in that process, and it's all really necessary. Torqueing by 20's to 100 and back down, then by 20's to 170 and then taken apart, then by 20's to 170 in the engine. All that will be wrong if you don't first dip the rod bolts in oil, they're special "yield-to-fit" bolts. Remember, rod bolts to inch-lbs., NOT foot-lbs.
Best of luck to you.

 

[SquidBonez]

You must be a little fuzzy on the numbers, but it's clear what you mean. My hemi got the stock rod replaced with a billet rod that's .020" over stock length, which brings a flat top piston to .005" from top of cylinder without any machine work being done. Since the most important thing you can do to save your engine is replacing that stock rod, then it makes perfect sense to do it, and wouldn't make any sense not to get the billet rod longer for the same price as a stock length rod.
There are various thicknesses of head gaskets out there, but my performance guy up in N.C. puts a .012" stainless steel head gasket in his hemi high performance gasket set. Here it wouldn't make much sense to stay with a stock thickness (.050" ?) since you need to buy a sump sidecover gasket anyway because of the rod change, and if you get the whole hi-perf gasket set instead ( $14 ) it's only 4 bolts on the head to change that head gasket after the 4 bolts on the valve cover, which also gets a new gasket in the set, and not a cheap paper one at that.
With my piston and head brought .058" closer together with the overlength rod and thinner head gasket my compression's greatly increased and makes a lot more horsepower. This setup is what the best small engine performance expert I know recommends and sells for the 212 hemi, and nothing hits anything. At least not with my stock pushrods, valves, retainers, and lash caps. Speaking of which.........
My guy says the stock valve retainers are the weakest link in the valve train when running new 22# valve springs like on mine, and are only good and safe to about 7200 rpm.
Want to know how close the piston gets to the head? Unbeknownst to me, my sloppy welding on a temporary header for testing before the changes caused a piece of steel welding slag to fall down through the exhaust valve into the cylinder. It was a little round ball not even near as big as the size of a standard .177 BB you were shooting as a kid. It was discovered when trying to rotate the engine for access to the rod bolts, and the motor would have to have a little firm head start to twist it past top dead center, or it would hang up there when turning slowly, only go backwards. That was with the stock rod and head gasket.
BIG NOTE: Please follow the instructions that come with your billet rod to the letter. The new bearings get mated to the rod in that process, and it's all really necessary. Torqueing by 20's to 100 and back down, then by 20's to 170 and then taken apart, then by 20's to 170 in the engine. All that will be wrong if you don't first dip the rod bolts in oil, they're special "yield-to-fit" bolts. Remember, rod bolts to inch-lbs., NOT foot-lbs.
Best of luck to you.

Thanks for the helpful reply!

 

[65ShelbyClone]

will I have any valve clearance issues with a longer rod paired with a thinner head gasket?

I know the answer, but you really should clay the piston as a matter of routine to find out. It's good practice.

they're special "yield-to-fit" bolts.

They're not special nor are they "yield-to-fit(?)". They're 170kpsi fasteners common to the automotive aftermarket.

 

[madprofessor]

Shows I wasn't an auto mechanic by trade. Question: Is that kpsi kilopascals per square inch? Not really big on metrics myself. I do know for sure that the ARC billet connecting rods' instruction sheets require 170 inch/pounds of torque for their rod bolts when dipped in regular motor oil, and 150 inch/pounds when moly lube is used instead. You can look on youtube at "ARC Racing Connecting rod installation" from 12/22/2015 for a proper explanation by their instructor. Don't remember where I heard the term "yield-to-fit", but he explains clearly how it's the "stretch of the bolt" that acts "like a spring" to tension it and keep it in place. Good call on using the squash media technique to see just exactly where your parts are moving internally. Never did it myself, but saw a real good video of it on youtube, think it was the "Cars and Cameras) guys using Play-doh.

 

[65ShelbyClone]

Is that kpsi kilopascals per square inch? Not really big on metrics myself.

No, it's "kilo," meaning thousands of pounds per square inch. The actual industry abbreviation is just ksi; I though adding the "p" would help clarity. The metric rating for fasteners is MPa or mega(millions) of Pascals.

 

[madprofessor]

Thanks for the metric info, my metric conversion chart right here on the bulletin board at my desk doesn't have a pressure section, just the mundane stuff. Still confused though. If you were saying 170 kilos per square inch then I get it, that would be 374 pounds per square inch. But if 170 thousand per square inch it makes no sense to the nonmetric me. Still, the manufacturer only gives their rod instructions in inch/pounds of torque, which has nothing to do with pressures at all, so I'll quit trying to figure it out. Where'd that instruction sheet go? Gotta go find it.........

SquidBonez, one thing I should have mentioned earlier, just in case you don't know or you forgot: When you go to put that piston back in with the new longer rod, make sure the splits in the circlips holding your piston's wristpin are rotated 180 away from the little opening on the lip.
Then make sure the 3 rings that make up the oil wiping assembly ring (thick 3-piece bottom ring) have the splits in the 3 rings rotated 120 apart, or just get roughly evenly spaced. Make sure to get the wiper's (wavy middle ring of the assembly) split to overlap correctly where the 2 ends meet. You can see it from the side sitting unevenly if it's wrong, only 1 right and 1 wrong way to do it.
Then make sure the top ring of those 3 oil wiper rings, and the piston's middle ring, and the piston's top ring, are rotated 120 apart just like the wiper assembly. That's where the rings will seat with the new stretch, and give you the best compression and least blow-by.
Saturate everything with oil before putting it together, get it sloppy, can only be helpful. Just don't leave oil pooled on top of the piston.