Clearancing: 92mm AA Pistons, 76mm Stroker, & 5.325"

[palmettofx]

I have a set of 92x69 thickwall (94 top, 90.5/92 bottom) AA Performance P/C's that I bought for my bug before finding that the case that came with the car is junk.

I figured since I had to get a new case that I would go a little larger and get a low/middle stroker crank, 74/76mm, to go with my 92mm pistons.

ACN says I can use both a 74/76 crank with their 5.325 rods without too much clearancing fuss in their budget stroker article. When I go to look at the 5.325 rods to buy them they have the note stating piston skirt clearance will most likely be an issue with 76 cranks.

My question is, would anyone who's used AA 92mm pistons with a 74/76mm crank, & 5.325" rods have any insight on this specific combination of parts? I'd like to get a 76 but my feelings wouldn't be hurt with a 74mm crank.

To be as specific as I can, here's what I'm considering
Crank
Rods
Pistons

I understand this might be a shot in the dark but I figured I would see if anyone has this combo. I searched and didn't see any AA brand clearancing posts.

[modok]

AA's "a" pistons are are dimensionally a copy of mahle
I have used 92 "A" mahle pistons with 74 and 76 AND 78 strokes several times before, and never had to clearance the skirts.

The .070 shorter rod is like having 3mm more stroke, so.....with 74 I would not even check.
With 76-78 stroke it probably will clear, but I would take a look before balancing the pistons.

Verses a stock piston, the 92 are shorter skirt, and bigger diameter, thus less tendency to hit the crank!

[itHaKa]

this is what my brother had to do to the skirts of his AA pistons in 88 mm
76 crank and 5.4 rods, ( 1849cc) so i assume if you use 5.3 rods and a 76 crank you will have to do it even more

complete build in my signature .
_________________
76x88 , 1849cc engine build :
http://mundoescarabajo.com.ar/me/viewtopic.php?t=635

[bugguy076]

I run a 76 strokeX92A pistons with stock length H beam rods. I think the spacers are .060. The shift point is at 7200. I have run the combo for 4 years in a drag car with no problems. No clearance troubles with stock length rods.

[palmettofx]

Thank you all for your advice!

[Danwvw]

The Short rods are going to be the problem. They will likely need something like this:

_________________
1960 Beetle And 1679cc DP W-100 & Dual Zeniths!

[palmettofx]

So if I got some Hbeam 5.4" aftermarket rods this would keep them up?

The reason I was brought on to the 5.3's was I was taking with someone about it at work Friday and he mentioned they were available. I didn't really think about it but I'm not sure I really want to get a stroker crank just to negate the stroke with a shorter rod. Seems counterproductive.

[Dan Ruddock]

Hell, I am building an 84mm motor with 912 rods (5.354) with mahle 90.5 b's if there is a will there is a way. I would use a 78 crank if I were you. Better yet get some b pistons 5.400 rods and build a 82mm motor. Don't let having to do some clearancing scare you it is not that big a deal. Dan

[Dan Ruddock]

[palmettofx]

It's not necessarily the clearancing that scares me, I have a machine shop that's been pretty cool thus far just a few miles from work.

It's just that I've already bought the 92x69 AA pistons and I don't really want to go through the hassle of returning them. I sent them an email asking about an RMA since they're still in the box, untouched, so I guess I'm not against going to a larger stroker.

[modok]

I really don't see any problems, and to clearance the skirts is very easy anyway, just takes time, which I'll assume you have a little to spare.
I have 5.3 rods and mahle 92 a and 78 DMS racewight crank, maybe I mock this up real quick.

[Dan Ruddock]

82mm crank costs about the same as a 76 so why not? The bigger the crank the nicer it drives but one thing to keep in mind is the longer the stroke the weaker the crank will be and the more necessary it is for a quality piece. Dan

[palmettofx]

[modok]

it clears by over .100"

[palmettofx]

You are a gentleman and a saint.

What is the reasoning to using the 5.3" rods in your application with a 78 stroker? You're essentially ending up with a 76mm crank after the shorter rots coupled with the 78mm crank, right? Why not run factory length and 76? I'm asking in curiosity, not doubt.

[modok]

I made the 5.3 rods for the next time I build a 74 or 76 stroke, the old 92 mahle A pistons are spares.

The crank is for something else, it will have 5.5 eagle rods and B pistons

so really, I the parts are unrelated, but do fit together

[Dan Ruddock]

A 78mm crank is 78mm no matter what rods you use. The CB 82mm cranks are more because they are 4340 vs. 4140 (better steel). A dpr welded crank is about the same price 78 to 82. Dan

[palmettofx]

I didn't mean the crank was shorter with different rods, but the effective stroke would be - or am I completely off on this?

[modok]

yeah, I figure you mean "Deck height"
"Deck height" in the main engine building world means the distance from the crank center to where the head bolts on, and we like to keep this near the stock 212.5mm

In the vw world deck height can also means quench clearance, which, IMO just creates confusion.

[esde]

I am not sure what you mean by "effective stroke", my suggestion is that you read up on "rod ratio". Different length rods change the leverage that the rod has on the crankshaft.