My guys guy stroked my crank to 4.25 after we request it to be stroked to 4.5. He will take it back and stroke it the rest of the way if I want for the same price but he nor my engine builder will warranty it not to blow up on the dyno. If I leave it at the 4.25 stroke they will warranty it until it comes off the dyno.
What do I do?
The crank guy says in his exprience with this type of crank style or type or something about the rod journal shoulder, with weaken it dramacticly and therefore no warranty for more stroke.
Were going pretty far on the bore size already and will still get to the 260 inch with the 4.25 stroke, but if it blows up do to other failure(s) I am sure I bought it stroked or unstroked.
I explained that others had done the 4.5 stroke and his reply was that are target output is higher than those he has read about online and it would not be safe. Well just "turn up the RPMs a bit and make the same power safely".
The 4.25 stroke is bought sold and I own it. Do I for free go to the 4.5 less the warranty?
I am thinking not.
Your thoughts please. We hav'nt ordered the custom forged pistons yet.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

My guess would be that your builder does not want to reduce the overlap between the rod & mains. This would weaken the crank, though it should be fine if you keep the speed down. Personally, I'd keep the current stroke: a little faster revs, more RPM capability, tougher bottom-end, and a promised engine. It might stand up better with nitrous, too.
My humble opinion......

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225 Cubic Inches of Iron-Head American Muscle

225 bored .040 /.100 off block, Schneider Cam 224@.050~ .480 lift - Stock valves, blended bowls, Offenhauser intake with 500 Edelbrock carb

if you have 260 cubes with a 4.25 stay there and you'll be safer... also BBB has a very good point there with the overlap math...

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

You are damn lucky that any hot rod engine builder will talk about warranty at all.

My motor came from the best damn motor shop in the country with a Nebraska warranty on it. "Blow it up and all the pieces belong to you."

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Official Cookie and Mater Tormentor.

You can still get 260 inch with the 4.25 crank? That will take a bore size of 3.60! A 4.5 crank will last longer than a 3.60 bored block!
I wouldn't worry about reduced overlap on a 4.5 crank. The S6 has more to begin with than most other motors. I think the grinder is talking about not much of a rod journal fillet on the stroked side.
If the 4.25 crank will make the same power goals as a 4.5 by turning up the RPMs, why not keep the stock 4.125 and turn it just a bit more?
Were you told this before the crank work was done? Do you feel that you may be getting played a bit? So far you have bought a 4.25 crank you didn't ask for and told a torque plate, or hone plate, isn't beneficial with only 10.5 compression. If not a 4.5 crank, that you know that has been done, why not at least a 4.375? I don't know how much $ you have in the crank work, but was it worth the extra 7 cubic inches?
Warranty? I'm satisfied if the machine work is done right.
I'd cut my expenses some by using the 4.25 crank, 6.7 225 rods and cast 3.46 pistons with the skirts trimmed to clear the counterweights if needed. This will give 240", the worst thing it's a far cry from the original goal.

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Slant Cecil

Brennen: You were told this by your machine shop? I have been using torque plates on "stock" engines for years. Even "Ma" Mopar recommends using a plate on any performance engine build. Serious "Stock Eliminator" racers, not only use a plate they even run hot water thru the block, while honing. He might have thought it wasn't enough "bang for the buck" if you had to buy the plate for one engine.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

I personally have had 2 blocks done by the same guy who did not believe in plates turn up with wavy cylinder walls.

All my blocks get done with plates now.

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Official Cookie and Mater Tormentor.

I may rent the plate.
But what about the crank? Is the 4.5 stroke going to be weak? I'd really like to hear from Doug on this one. If I had to do it again I wouldn't spend the money for such a small amount of stroking, but the money is spent and I can push the crank guy to go to 4.5 with no more money.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

By all means get the plate and use it what ever it cost. I cant believe that someone would even suggest not using one. That is one of the best improvments over stock that there is . Ring seal & durability will be way down compaired to not doing it.

As far as the crank I cant say from expeirance because I have never done this on a slant. But you have already spent the money, if it has held up for others I would consider going for it. But it also depends on what kinda power you are going to throw at it. I do feel that the 4.25 is going to be stronger, and if you are going to be throwing a power adder on the engine (turbo,nos ect,ect) I would stick with what you have. Unless others have the proof of it holding under such HP levels. Which I guess is what you are looking for now. Someone with real world results that can say , Yes it will hold up. Its a hard call. I personally would not even done the 4.25 if a power adder is going to be used.


Jess

100 shot is the max planned.
I'd hate to have it blow up on the dyno from something besides the crank and have it blamed on the crank. If its crank failure, then I bought it at 4.5 stroke. If the cylinder wall gives way and it can't be proved it wasn't the crank, then I bought it again. If it blows up with the 4.25 crank on the dyno, He builds me other one. I'd likly ask for my money back and build something with 2 more cylinders.
P.S. the dyno testing won't be seeing any nitrous.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

I would keep the crank as is then. Heck if you keep the bore size to 100 over I dont see why you couldnt run more than 100 shot. You will find that with any power adder that Cubic Inches is not needed as long as you can replace it with RPM.


Back in the 1980's a bunch of us was running big NOS kits on big blocks. All my freinds where using 440 engines. I was using the 383 engine with a tunnel ram. They could not come even close to the top end MPH that I was getting ( about 13 MPH more than any of them) and this allowed me to run much faster ET wise than they did. A few of them was running 12:5 to 1 piston setups with roller cams and big bucks in there heads. I was running 9.0 to 1 with a good set of heads
(no where close to there heads though but just flowed pretty good) and a solid cam. I got by on less head flow becuase my engine was not as big. But I was able to run much more NOS than they could. It really got under there skin that I was killing them with my setup compaired to there high dollar setups but they couldnt do anything about it. I was able to pull enough RPM that I could shift at 7200 and we crossed the line higher than that. WE even stripped the syncro teeth on 4 gear at the end of the season on the tranny. I didnt have the parts to fix it so we ran the way we was and was pulling 8200 rpm at the line and never lost any ET. It was so funny because they thought that they had me but the ole gril still pulled it off. There was even two of the guys that had the engine let loose and mine held together the whole season.

But the piont of the story is you just dont need the cubes if you can turn the RPM. And the compression is not important either if you run enough power adder. And the more durability it has the better you will be because the power adder is going to rip that engine hard. But durability, good flowing head, good valve train & good ring setup will make a lot of power out of any size engine. Good luck, and lets us know the results, sounds like fun.

Jess

Its already bored to a rough bore of 3.597. When the pistons get ordered and come back the pistons will be measured and the final bore will be done. So it already got a big bore, but I am leaning towards keeping the 4.25 stroke.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

3.597!
Is that a mis-type?

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Slant Cecil

nope
3.597
Final bore with likly be 3.622.
We have sonic checked the block and found to have at least 1/8" of metal left in all areas after the final bore. If for some reason we run in to a problem he said he'd just sleave it.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

Give him another crank and have him do that one, shoot for 4 7/16" stroke. (= 4.438, tell them 4.440) Trust me, the extra .060 between 4.440 and 4.500 is not worth all the extra block prep needed to get the 4.5 to fit.
Throw him an extra $100.00 for his 4.25 "mistake" if you need to. Keep that crank around for another engine project, it would give compression increase using basic 225 SL6 parts, without block or head milling.

There is no significant difference in strenght between a welded and reground 4.250 and a welded and reground 4.440 SL6 crank
If you are concerned about crank "toughness", leave all journels .001 to .0015 oversize, have the crank stress releived and nitride hardened, then grind it to finished size.

I have 3 welded and reground SL6 cranks in use, one has been around for over 10 years, none have given me any trouble.
DD