Stroker clearance question

[Jeff Rand]

I built a stroker 109 engine with a 3.625" crank and Molar long rods with ARP bolts. So it is sitting on the engine stand and I decided to go with a larger Comp cam. Duration at .050" is: intake 218 and exhaust 212. 112 lobe separation and lift intake = .511, exhaust .504. I attemped to look into the bottom end to see if I had enough clearance betweem the crank and cam but it is difficult with an assembled engine. I was wondering if someone ran this combo and could put my mind at ease.
Thank you,
Jeff

 

[bad V6]

My combo consists of a 3.625 stroker crank, Comp Cams 218/212 camshaft' and Eagle 5.97 rods with Diamond pistons. My engine was assembled by Weber, therefore I do not know how much work had been done to clearance the internals.

 

[TurboBuRick]

Does it hit when you rotate it by hand? I remember running into that. If I remember right, we had to disassemble and put one piston in at a time. Went through the opposing bore to check clearance. Had to massage one particular rod pretty good on the radius above where the bolt screws into.

Good luck

Rick

 

[robzombie]

Does it hit when you rotate it by hand? I remember running into that. If I remember right, we had to disassemble and put one piston in at a time. Went through the opposing bore to check clearance. Had to massage one particular rod pretty good on the radius above where the bolt screws into.

Good luck

Rick

I hope that you took the same weight off all the other rods, especially if you had to massage it pretty good as you put it on the one rod in question.

That will cause a serious imbalance issue depending on the amount of weight removed.

 

[Wahoo]

So that big of a cam only a problem in strokers? Theyre ok in stock displacement 3.8s?

 

[BEATAV8]

So that big of a cam only a problem in strokers? Theyre ok in stock displacement 3.8s?

strokers are just problematic in general with respect to the cam / rod clearance. Just need to watch it.

 

[cruzn57]

Jeff , is that a small dia cam? (vs std base size) I doubt the lift will cause problems. where the problems arise
is the odd/ different overlap. or "quick ramp" / aggressive lobe ramps, \
I'm sure you thought about the clearance problems, as you normally build big cam , big HP motors,

 

[No disintegrations]

I built a stroker 109 engine with a 3.625" crank and Molar long rods with ARP bolts. So it is sitting on the engine stand and I decided to go with a larger Comp cam. Duration at .050" is: intake 218 and exhaust 212. 112 lobe separation and lift intake = .511, exhaust .504. I attemped to look into the bottom end to see if I had enough clearance betweem the crank and cam but it is difficult with an assembled engine. I was wondering if someone ran this combo and could put my mind at ease.
Thank you,
Jeff

Bigger cams are skinnier than small ones on the base circle. They make more lift by reducing the diameter of the cam. That being said,if one cam fits another similar one should fit.

 

[Jeff Rand]

The orginal cam was .516 lift for I and E
206 Intake duration, 210 Exhaust duration
110 lobe separation
I don't think there would be any issue

 

[Jeff Rand]

Does it hit when you rotate it by hand? I remember running into that. If I remember right, we had to disassemble and put one piston in at a time. Went through the opposing bore to check clearance. Had to massage one particular rod pretty good on the radius above where the bolt screws into.

Good luck

Rick

No it rotates fine. I have always used the figure of .060" min. between the rod bolt and cam lobe but in this case I would almost have to disassemble the engine to check.

 

[ek02]

Molnar rods are clearanced a small amount for stroker cranks. If you compare it to a K1, there is a difference. I took an additional .040 off my Molnars and tapered the ends of the bolts on the cylinders that are close to the cam. I use a .060 feeler gauge between the rod and the cam through the opposing cylinder. You would have to pull some pistons. You also need .060 on # 1 rod bolt at the oil passage relief. I try not to grind too deep. I round off the end of the bolt head a little until I can get a .060 drill bit between the rod bolt and the relief. Some people grind into the passage and then insert a copper tube in the oil galley. I have done 4, 4.1 blocks this way with no problems. It's hard to sonic test the curved relief to be sure how thick the block is there, but I usually end up with roughly .125 by testing the thickness next to the relief, then checking the depth of the relief.

 

[fastblackracing]

Camshaft phasing plays a roll in this as well, since disassembling the engine is not
feasible, assuming you have a 9 position crank gear put the cam at -8, 0, and +8 and check for free rotation.

If it clears in all 3 settings you a likely good.

Your other option would be to put say a bead of play-doh or clay around the cam lobes and flatten
it out, install the cam and rotate.....then look at the lobes down thru the lifter bores to see if
there are any witness marks and how deep.

 

[ek02]

Great idea fastblackracing. I have noticed that even 2-4 degrees in cam timing makes a difference in clearance.

 

[Jeff Rand]

Camshaft phasing plays a roll in this as well, since disassembling the engine is not
feasible, assuming you have a 9 position crank gear put the cam at -8, 0, and +8 and check for free rotation.

If it clears in all 3 settings you a likely good.

Your other option would be to put say a bead of play-doh or clay around the cam lobes and flatten
it out, install the cam and rotate.....then look at the lobes down thru the lifter bores to see if
there are any witness marks and how deep.

Good stuff. Thank you