15 replies to this topic

[TerrA LX]

Can anybody give me info on the 253 or 308 strokers which offset grind the standard crank and run chev rods and pistons.
Looking for anything i can get basically i.e. specific rods, and bearing mods needed, specific type of pistons needed, who does them etc etc.
Thanx in advance.

[Struggler]

I am doing one of these right now for a circuit racer.

The parts I am using are, offset ground 308 crank, narrowed SJ SBC conrods and ACL Race Series 9353 pistons. This is not the only way to do it. This has been discussed here in depth before on another thread.

If doing a 253 you offset grind the 253 crank, use the same rods and get the block overbored about 0.125" and use 305 Chev pistons.

I didn't use the 253 crank this time as the ACL pistons are too heavy to allow easy (read cheap)balancing. If using a quality lightweight piston you can opt for the 253 crank for a lighter rotator.

Hope this helps.

Edited by Struggler, 05 May 2007 - 12:39 PM.

[TerrA LX]

^ thats the one Struggler i was thinking with the chev rods but the big end bearings need narrowing as well i assume.

Do you have a like for the thread in particular as i have seen it meantioned a few time but could not find nothing specific.
Cheers.

[TerrA LX]

Thanx Chopper,
If i can use the above pistons that Struggler suggests then i am really chasing the rod and bearing mods required.
I think once the chev rods are narrowed on the correct side to fit the crank you take two caps bolted together, with the bearing inside and fitted to a lathe to turn them down as i am not aware of off the shelf bearings to suite.

[Struggler]

The rods get narrowed on both sides, about 0.010" on the side that faces the other rod, about 0.055" off the counterweight side. Prostroke charges $10 a rod to do this. The machine shop I use charges $8ea.

The bearings I do myself. I put a length of 2.00" (SJ SBC big end journal size) aluminium bar stock in the lathe, hold a pair of bearings on it with a hose clamp (with the amount requiring removal hanging over the edge) and turn off the excess. Turn 'em over and clean up the other side. The bearings don't have to be exact width ways, as long as they are narrower than the rod and don't foul the crank fillet radius (narrower bearings have less friction!!!). Alternatively you could buy bearings from Prostroke as well. Obviously you start off with Small Journal SBC rod bearings.

That 9353 piston is a champ. It is advertised as an unfinished 350 piston. It is almost perfect in pin height for a 326 stroker and has a flat top with no valve reliefs. For use with HQ heads comp will be high (almost 11.0:1).

Hope this helps.

[TerrA LX]

Cheers Struggler, exactly the info i needed

Oh one other thing, does anybody know of any surface treatment needed due to the big end being ground so far?

Edited by ALX76, 06 May 2007 - 01:15 PM.

[Struggler]

The big end has only been ground to SJ SBC size.
back in the day the SJ SBC was the engine to have.
Don't be in any way concerned about grinding the b/e down to this size. Its been done a million times before with no problems.

[TerrA LX]

Thanx guys i was more concerned that the journel would need treatment as grinding that far would take away the surface hardening from fatcory.

Now does anyone know of anyone in Sydney or close by that i can talk to about a crank i have in mind or is there someone doing an exchange crank rod and piston set?

[Struggler]

99% of cast cranks don't have a factory heat treatment or surface hardening.

Sorry, I'm not familiar with any Sydney machine shops.

Prostroke can do yours, but due to weight you will need to truck it there.

If you can get your junk to Canberra I can get it done for you, I travel to WSID fairly regularly so we may be able to work something out there.

Hope this helps.

[TerrA LX]

Thanx again Struggler sounds good. I have a crank i would like assesed and cleaned up can you give me a rough estiment and i will work it out with you from there.

[Struggler]

Offset grind is $400 locally, conrod narrowing $64, close and hone big ends and fit new rod bolts $176. Hot tanking the crank might cost an extra $25, depends how smelly it is.

You might consider this... http://www.gmh-toran...=ST&f=3&t=17231

[TerrA LX]

The parts I am using are, offset ground 308 crank, narrowed SJ SBC conrods and ACL Race Series 9353 pistons.

How far up/down the bore do you find these sit before finishing.

What is a good compression height to aim for (thats pin height right?)?

[Struggler]

The parts I am using are, offset ground 308 crank, narrowed SJ SBC conrods and ACL Race Series 9353 pistons.

How far up/down the bore do you find these sit before finishing.

What is a good compression height to aim for (thats pin height right?)?

All depends on how much offset you get ground into the crank. This can vary the stroke up to 0.050", and therefore your final deck height by up to 0.025"

350SBC piston pin height is 1.560"
308 1.690"
ACL9353 1.618"

Before you had to either deck the block to suit the 350 piston (up to 0.080"), or machine down the 308 piston (0.060-0.080"). The ACL should put you right in the ballpark. The correct answer will be found when you dummy assemble the short.

Sorry I can't be more specific.

[TerrA LX]

All good. Thanx for the info

Edited by ALX76, 09 May 2007 - 08:08 PM.