Hi Doc and all - have a nice healthy forged crank over here - remember the changes you guys underwent as far as casting and hydro motors never reached us so we had forgings till 78

The question is what to do - have it welded and offset ground for a 260 stroker? - For me cruising capability is important - ie WIDE torque band -

It is good crack free piece - so I would really like to put it to good use!

Opinions please

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Fanie Gerber
It's never junk, it's just a part you're not currently using

http://www.valiant50.co.za
Just say I own a few Mopars

I have read Doc's "Stroking" article and I would also be interested in an in depth discussion of building a 260 slant. I am contemplating doing this for my brother's Duster. A 260 with a low RPM cam should make a decent street engine.

And how does this affect reliability - so gents lets get talking - those who have done this please lead

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Fanie Gerber
It's never junk, it's just a part you're not currently using

http://www.valiant50.co.za
Just say I own a few Mopars

The article does a good job outlining the "stroker" SL6 engine build.
In a nutshell, adding .155 (4.440) to .187 (4.500) of stroke allows you to use the 2.2 type pistons on the 6.7 long 225 con rod and end-up around 9 to 1 compression. You get added torque from the longer stroke and increased displacement.

The key to this build is getting the crank work done. Many shops will not want to weld-up all 6 journals, then do the off-set grinding. Make some phone calls and get some price quotes, if you find a shop that will make a stroker crank at a reasonable price... get a written quote, then take them a crank and "get 'er done". (I alway get the: "I will never do this again" remark from the shops that have done stroker cranks for me)

Once you have the crank... mock it up in the block and take some mesurments, then select a piston that give you your target compression.
(there are a few different flat tops and dish types available... you will need a dish to run on pump gas)

Note #1: A 4.440 inch stroke is much easier to fit into the crank pocket of a 225. The extra grinding needed to fit another .060 (4.500) is not worth all the effort.

Note #2: Camshaft selection should be done carefully, the stroker SL6 will not want to rev-up so use a cam that is designed to make low RPM power.
DD

Exhuast sytem and induction Doc - what is your experience there ?

_________________
Regards,
Fanie Gerber
It's never junk, it's just a part you're not currently using

http://www.valiant50.co.za
Just say I own a few Mopars

Thanks Doc! It was those little extra tips I am looking for. I may well do this for my brother's 74 Duster project. He wants a "hot" street motor but won't ever drag race it.

Ran some sims

~240 BHP @4300

341 lbft at 2000 ..but it only drops below 300 at ~4100

318 killer

_________________
Regards,
Fanie Gerber
It's never junk, it's just a part you're not currently using

http://www.valiant50.co.za
Just say I own a few Mopars

Journal welding/grinding PICTURES!

Danny

Interesting article!

I'm running a welded up crank for 4.440" Stroke. It was welded back up to allow standard bearings.
Coupled with 198 rods and Toyota pistons, my deck is cut 0.125" and I'm still down the hole .070". The small end of the rod had to be bushed for the pin size. I can get you the PN of the piston if your interested.

Doug's RV15M RDP grind Erson, degreed per the card makes power to at least 4500 with my Offy 4bbl. Likely better with one of your intakes, Fanie. With the stroker, I don't think getting the power up higher would be of much utility though. This would make a spectacular pickup engine.

I've been running a 2-1/4" Feather Duster single till now. Will report in how the Dual Dutra Duals effect the power envelope.

CJ

It is coming it is coming - serious current shortage of time and moolah - YES it will work well ceej

The PN of the Piston would be nice please - I agree with the getting it back to spec sizes makes future regrinding easier PLUS adds strength?

_________________
Regards,
Fanie Gerber
It's never junk, it's just a part you're not currently using

http://www.valiant50.co.za
Just say I own a few Mopars

Where's the main stress limiting factors of this engine as far as RPM's go? I think the hemi's are easily 4.25-4.5in stroke and they can get 6200rpm. Is it really all in the aftermarket parts?

Factory SL6 con rods start failing around 350 HP but K1 has helped get us past that limiting factor.
The forged SL6 cranks start to twist and crack in the 450 HP range.
The 4 main block starts having trouble in the same 450 HP zone.

And yes, the more prep work and aftermarket parts, the higher you can push the HP, before something goes "BANG".
DD

Doc,

I would comment that your HP limits are more usually related to RPM limits. People have made well over 450 HP at lower RPM under boost and not broken cranks, rods, blocks. Usually, people try to spin higher to make more HP.

Tilley has made 630 HP at 5000 RPM w/turbo and nicely prepped stock bottom end parts with the exception of forged custom pistons. Mike J has made about 500 HP with N2O and limiting RPM to about 6500, IIRC. Coxes blew up blocks/cranks many times, but they were trying to spin 7000+.

I agree 450 HP may be on the edge, but I think it's more of an RPM thing than a HP thing...

Stock pieces can take 6000 RPM, although you may want forged pistons. Aftermarket rods/pistons and nicely prepped block/crank I would say 6400 would be my personal limit. Tilley's high HP NA motors (360+HP) made peak power at right about 6000 anyway.

My 2 cents,

Lou

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Home of Slant6-powered fun machines since 1988

hmm interesting -

_________________
Regards,
Fanie Gerber
It's never junk, it's just a part you're not currently using

http://www.valiant50.co.za
Just say I own a few Mopars