84mm crank with 5.4 inch rods

John Massengale · Post by **John Massengale** » Mon Feb 04, 2002 12:29 am

I have an 84mm crank and I am going to buy some 5.4 inch H beams for it. I plan on making a 2332 with it, My question is- With the 1.63 rod ratio,

What would be involved in building and clearencing standard 94mm cimas? I figure the skirts would need trimmed.

What engine characteristics should I expect? Piston speed, scuffing, RPM limit, low end, high end?

Advantages to this low rod ratio?, disadvantages?

Thanks for the help, John Massengale

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Mon Feb 04, 2002 8:03 am

@ 84mm I recommend no less than a 5.5 rod,a short rod also makes assembly a pure pain, and the engine will have more blow by, since the pistons are rocking severely at BDC, especially with thick cylinder shims.

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Jake Raby
Raby's Aircooled Technology
www.aircooledtechnology.com

Searoy · Post by **Searoy** » Mon Feb 04, 2002 12:35 pm

Here's a related parts question.

Digging through my old HVW performance special issue (circa 1997 I think) I found a piston article. According to this, "A" pistons have 1.5something inch compression height, while "B" pistons have 1.3something compression height. That doesn't seem like much. KRE had 1.1something compression height pistons, with "turbo" ring lands. These sound good.

Why is there so much less difference between A pistons and B pistons than there could be. I mean, running an 84 crank with 5.5-5.7 rods would be much easier, I think, with a 1.090" compression height on the piston.

Keith Black makes cast pistons that are 94.89mm, with "turbo" ring lands and a 1.090" compression height. And, since they are regular stock they should be super cheap. They're just made for a 305 Chevy.

Thoughts?

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*** Teach a Man to Fish ***
Searoy

"I tend to lean toward a tighter gap and a
looser skirt....a little slap never hurt." -- Joe of the West

Ed Brewer · Post by **Ed Brewer** » Tue Feb 05, 2002 7:14 am

I think a 5.4" rod would be fine on an 84mm crank. I have seen as short as 5.352" (Porsche length) used on 84mm cranks. Aircooled.net sells 5.325" rods (no, I'm not dislexsic, there really are two different 5.3**" rods) that they say are good on 84mm cranks. So go for the 5.4", they should give snappy low end response. Plus they keep the engine narrower!

Post by **Tom Notch** » Tue Feb 05, 2002 9:16 am

I'm running 5.4 Pauters on my 84 crank. The under neath of the piston needed a slight clearance relief on one pin boss. Motor is a streeter and has lots of low end grunt. With the heads I run, the engine only grew about .250 in width total. Haven't noticed any undo wear on the pistons.

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Tom Notch
Tom's Old VW Home

Chuck Schneider · Post by **Chuck Schneider** » Tue Feb 05, 2002 12:18 pm

I have used 5.4 in the past on a 2333. It really beat up the pistons. They were really scuffed up. It also wouldn't keep the rod bearings in it , but that was more oil related but it may have been partially from the short rods. I am going to a 5.7 rod now on the same engine. It seems that the long rod cars run better times if you ask me.
I did notice that the engine really responded well with the short rods but it was too responsive if you ask me. I would rather that extra torque up in the powerband where I am gonna use it not wasted in low rpms where the car revs right past as soon as I pull out.

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12.70 @ 104