Stroker rod length computation - need sanity check

[mark belrose]

I'm currently building an L-series stroked race motor using a diesel 83mm stroke crank. This motor's configuration is much different than normal as I'm using some special JE pistons with very small pin height (1.116"). The person I got the pistons from ran them using a 240Z crank, vs. the stroker crank I'm going to use.

I have the build sheet on the rods he'd used with those pistons. Rod length was 142.24mm using a 73.7mm stroke 240Z crank. Deck height was zero.

So if I'm doing my math correctly, the difference in stroke between the two cranks is (83mm - 73.7mm) = 9.3mm. Half of that stroke is 4.65mm. I figure that when I call Carrillo up to special order, I need a center to center spec of (142.24mm - 4.65mm) = 137.6mm. Sound correct? We're going to mock everything us using a stock 240Z rod and measure how far the piston sits below the deck, as yet another check.

Should make for an interesting motor when I'm finished. I'm looking forward to seeing how well this long-rod configuration setup will work.:cheeky:

Mark

'70 restored vintage C Production 240Z

[preith]

Seems too simple, eh? Unless I'm missing something obvious, it looks good to me. You can also do:

73.7 / 2 = 36.85 + 142.24 = 179.09

83 / 2 = 41.5 + -179.09 = 137.59

With that said, yes, it sounds like you'll have a real screamer when it's all done!

[e_racer1999]

you don't want to run a little above the deck for more compression?

[preith]

you don't want to run a little above the deck for more compression?

After posting I thought of that too. I beleive my JE's protrude at least 1mm above the deck. I assume you're using an N42, the quench side of the chamber is recessed quite a bit, there's probably a fair amount of room depending on the piston dome of yours.

[mark belrose]

you don't want to run a little above the deck for more compression?

Not sure yet about that one yet. The JE's I have were designed to run at 13:0 compression at zero deck height with my N42 head and 1mm head gasket. I'm debating running more deck height to get a bit more compression; seems that most of my other motors ended up around 13.5:1 with no problem blowing head gaskets. I don't see much advantage of going higher than that. I guess if we overshoot it I can always go to a 2mm gasket.

BTW I'm looking into acquiring a set of PAR billet rods from Australia. Apparently they are somewhat cheaper than Carrillos and can be got in a few weeks vs several months.

Mark

[jmortensen]

Not sure yet about that one yet. The JE's I have were designed to run at 13:0 compression at zero deck height with my N42 head and 1mm head gasket. I'm debating running more deck height to get a bit more compression; seems that most of my other motors ended up around 13.5:1 with no problem blowing head gaskets. I don't see much advantage of going higher than that. I guess if we overshoot it I can always go to a 2mm gasket.

You really don't want to go to a 2mm headgasket. It renders the quench area of the head essentially useless. I remember when you were having trouble with the headgasket, but I don't recall the specifics. I think you were using a metal gasket that was completely dry. Did you ever try the copper spray on the gasket? I think it's pretty mandatory on that gasket to get it to seal.

[mark belrose]

I remember when you were having trouble with the headgasket, but I don't recall the specifics. I think you were using a metal gasket that was completely dry. Did you ever try the copper spray on the gasket? I think it's pretty mandatory on that gasket to get it to seal.

Hey Jon. I couldn't get the metal head gasket to seal against that o-ringed block. The o-rings had been installed pretty unevenly so that there was quite a variation in their height protruding out of the block. Apparently the metal head gasket was unable to conform over them to produce a tight seal even with copper coat. I finally filed the o-rings to a few thousands above the block and used a Victor Reinz gasket, and never had any problems after that.

Mark

[olderthanme]

You guys need an engine design tool...

Like THIS one...

[NZeder]

You could use the Kameari rods - they make a few different types 138mm and 139.5mm

see http://kameariengineworks.co.jp/catalogue-P4.pdf

and http://kameariengineworks.co.jp/catalogue-P5.pdf

Or try and find some L14 rods which are 137.6mm long (I used to have a set but you need 2 sets of 4 to get 6 rods but I sold those to a guy in Australia)