legacycentral bbs

The STI pistons are made so that the area that the top of the rod fits into gets narrow, so the tops of the rods must be angled to fit.

douglas vincent wrote:The STI pistons are made so that the area that the top of the rod fits into gets narrow, so the tops of the rods must be angled to fit.

I was wondering why you were milling at an angle on a rotary table....

OK, I commited.

Its going together with the HUGE deck to piston gap......

I DID pin the cylinders to the block though with brass 5/16" pins.....

And the rods are connected to the crank, I would have it done, but I forgot to by block goo, be done tomorrow morning.

im so confused as to what your doing.

first off phase2 rods are 52mm crank journal and phase 1 is 48mm so you have to have mathching crank and rod bearing sizes. also 2.5 is the shortest rod see stroker application??

so yeah im confused.

[quote="douglas vincent"]
I DID pin the cylinders to the block though with brass 5/16" pins.....
[quote]


Do you have any pictures of this? Im wondering how its done.

Its my God Given Duty to confuse asian people.

Pretty sure that 2.5 rods are the longest ones. The piston pin location is raised closer to the crown to compensate.

A 2.5 piston has the pin almost in the oil control ring if I'm not mistaken.

I will have some pics tommorrow.

douglas vincent wrote:Its my God Given Duty to confuse asian people.

quote worthy

well that didnt help.

and stroker = shorter.

cylinder pinning is sweet!
did you pre drill or is it a really tight press fit? only worry with really tight it that its possibly doing something to the bore roundness or something. i think I can see some pre drilling but not sure.
how about adding a couple more, overkill?

Im curious as to how those are installed - Do you mill out a hair under 5/16 bang the pins in and mill them flush? What about thermal expansion? Is pinning the cylinders common?

I used a hand drill and a 5/16th REAMER. A reamer gives a much better round hole and is "easier" to drill with.

Then I used my little lathe and turned 3/8" rods of brass down to individually fit each pin. Then I tapped them down.

The block may or may not be out of round now, but I dont really care because this is a test build just to see if it works. If I have to do another one, then I will take the block to a machine shop and have it bored.

What about thermal expansion?

I'd have to look and see what the differences between brass & aluminum are, but if they are reasonably different, then all the work could not do squat, or it could hurt you.

Ideally, you'd want to use a material that has the same thermal coefficient as the block material.

Legacy777 wrote:What about thermal expansion?

I'd have to look and see what the differences between brass & aluminum are, but if they are reasonably different, then all the work could not do squat, or it could hurt you.

Ideally, you'd want to use a material that has the same thermal coefficient as the block material.

+1

If I recall correctly, brass has a much lower thermal coefficient than aluminum...

I snub my nose at physics.

I dont think it will be an issue with such a small surface area. but why not some aluminum rod doug? it's quite cheap.
also there's maybe a possibility of some kind of galvanic corrosion but perhaps not.

Surface area really doesn't matter, the thickness of the material does.

I looked in one of my books and here's what they have for the average coefficients of linear thermal expansion:

Aluminum Alloy = 12.8 x 10^-6 (1/(deg F))
Brass = 10.0 x 10^-6 (1/(deg F))

If you work out the thermal deformation equation for area, you get the following change in area for each material:

Aluminum Alloy = 2.55 x 10^-4 in^2
Brass = 1.99 x 10^-4 in^2

Those are pretty small numbers, and the difference between them is even smaller. However if it were me, I'd still probably do some looking into things....but you'll probably be fine.

With the way Doug goes through motors electrolytic corrosion won't be an issue.

^^^haha thats so true!

updates?

311 hp 354 torque at 23 psi

multiple 12.7 @ 109 mph 1/4 miles!

Runs awesome!

You need to update your sig now

Geeze .