stroker crank

Discussion of the Early Dodge / DeSoto HEMIs.

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Gullwing
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stroker crank

Post by Gullwing »

If I stroke my 291 I can get about 350 HP from about 350 cubic inches. However if I later decide to add a power adder such as a turbo or blower will I still have a reliable motor at 400 HP or 450 HP? or does the small overlap angle pose a problem? Would I be better off keeping the stock stroke and just raising the boost more?
TrWaters
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Post by TrWaters »

I would say it depends on how you are going to get the additional stroke. Using a 291 crank or a 330 crank.
Early hemi to late sb Mopar trans adapters. Precision billet parts for early hemis.
desotoman
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Post by desotoman »

Stock 291 cranks have been know to take 800 hp for about 30 runs at the drags on Nitro at 9000 rpm, before being replaced. You are asking a question that has alot of variables to make the right answer. If this is just a street motor you will be fine with the stock stroke crank. If this is a race motor a billet crank is the way to go, unless you want to be replacing cranks all the time. You will also need a girdle or 4 bolt main caps for racing. Desotos are not cheap to build right and have live at the race track.
DHEMI
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Post by DHEMI »

Go to Nitro Geezers,click on biographies,click on The Shrank Bros.The info won't help you one damn bit,but vrey interesting stoy of blown fuel 276 DeSoto.
desotoman
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Post by desotoman »

Funny you should mention the Shrank Brothers. I have owned 3 of their old desoto motors for about 20 some years. One is the 276 motor minus the blower. (I called years ago and tried to get the blower manifold but they would not sell it.) The other two are Injected fuel 291 motors they ran in the Jr. Fuel class. Only one has Injectors. They only had one set of injectors so they use to switch from one motor to the other. One has a girdle and one has 4 bolt mains.
Gullwing
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stroker crank

Post by Gullwing »

Are you saying that I would do better to weld up and offset grind the original 291 crank than to cut done the tall deck crank?
desotoman
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Post by desotoman »

I can only tell you what I would do. If I was going to supercharge my motor I would stay with the stock stroke crank. When you supercharge a motor one gain you automatically get is more torque. Bigger is not always better. I really don't know what you are trying to do. If you are just looking for HP numbers in the 350 range you can get that with a 300" motor set up correctly. If you are looking for torque in a normally asperated motor then stroking is the way to go. Good luck.
johnny5
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Re: stroker crank

Post by johnny5 »

Gullwing wrote:If I stroke my 291 I can get about 350 HP from about 350 cubic inches. However if I later decide to add a power adder such as a turbo or blower will I still have a reliable motor at 400 HP or 450 HP? or does the small overlap angle pose a problem? Would I be better off keeping the stock stroke and just raising the boost more?
Remember, you have to build a motor for forced induction from the start. You can't just add a blower or turbo after. The clearances, cam timing and compression ratio are much different than a naturally aspirated engine - hemi or not.
Gullwing
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Post by Gullwing »

I am building my car as a dedicated street motor. I can't fit tires larger than 235/60-15 on the car so my feeling is that anything more than 450 HP is just for bragging it is wasted HP. I totally agree with the advice that you can't build a motor to run well at boost and non-boost. I guess I was being unrealistic. My plan was to build a strong street motor with electronic fuel injection and maybe a 10.5:1 ratio then if E-85 becomes available I could run it boosted. I guess the answer is that for my needs I could probably run the cut down 330 crank at 6,000 RPMs without too much concern. I was going to run forged pistons with stock rods, 330 heads and a moderate cam.
Gullwing
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Post by Gullwing »

Realisticly, I doubt I could supercharge the motor if I wanted as I do not have hood clearance for a Rootes type blower and a belt driven Paxton ecetra would be a logistical nightmare with power steering and an A/C compressor.
TrWaters
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Post by TrWaters »

This is sort of on topic..... who are the shops that you guys have had doing your crankshaft work? And are they equipped to weld, index, and offset grind? Thanks.
If you would rather not list shop names, please PM me or email twaters@together.net

Tom
Early hemi to late sb Mopar trans adapters. Precision billet parts for early hemis.
Gullwing
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Post by Gullwing »

I have a local machine shop that has an excellent reputation for both cost and quality. While admittedly they do not see many early hemis. I was wondering what most people would pay to have a crank welded up then offset ground to 1/4" versus the cost of a high deck core crank and having it turned down and balanced?
Bailiesdad
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Post by Bailiesdad »

Do an internet search for Gene Adams. He may have a crank already done that he will sell to you.

Offset grind probably run 350-400

Weld a crank is usually 100 -125 per journal then turned to the size and stroke. 700-900 range.

Noone will guanantee a welded stroker.

Noone will weld up a cast crank either, steel cranks only.

Gee, how would I know, well tomorrow I am going to one crankshaft shops Christmas party with the owner of another crankshaft shop.....the guys are good friends... 65 years expirence, grinding crankshafts, between them. Iuse them both, depends where the crank is.
desotoman
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Post by desotoman »

If you are creative you can stroke your stock crank .200 just by offset grinding and go to ebay and buy some nascar carrillo's that have a journal size of 1.85. Just be sure to get the right width rod. Since you will be buying pistons anyway this is another way you can stroke your motor.

In the old days of Jr. Fuel it was common to offset grind the stock cranks to small dodge size jounal. By doing that you gained 1/8" of stroke. Then you just ordered Aluminum rods with the dodge journal.

If you are only looking for 1/4" of stroke, the costs involved are not worth it. A 291 .030 over is only 295.5 cubic inches. A 291 .030 over with a 1/4" stroke is only 317.5" You are going to spend all this money for only 20 inches which might get you 25HP. I think I would reconsider, but that is just me talking outloud.

Good luck whatever you end up doing. :)
johnny5
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Joined: Mon Dec 05, 2005 3:52 pm
Location: St Charles, MO

Post by johnny5 »

TrWaters wrote:This is sort of on topic..... who are the shops that you guys have had doing your crankshaft work? And are they equipped to weld, index, and offset grind? Thanks.
If you would rather not list shop names, please PM me or email twaters@together.net

Tom
I use these guys:

http://crankshaftspecialist.net/

I can post a before and after pic (if I can figure out how - help?) of my last 392 crank prepped for 354 stroker use. It looked like a boat anchor before, better than new after.
johnny5
Posts: 128
Joined: Mon Dec 05, 2005 3:52 pm
Location: St Charles, MO

Post by johnny5 »

Gullwing wrote:I am building my car as a dedicated street motor. I can't fit tires larger than 235/60-15 on the car so my feeling is that anything more than 450 HP is just for bragging it is wasted HP. I totally agree with the advice that you can't build a motor to run well at boost and non-boost. I guess I was being unrealistic. My plan was to build a strong street motor with electronic fuel injection and maybe a 10.5:1 ratio then if E-85 becomes available I could run it boosted. I guess the answer is that for my needs I could probably run the cut down 330 crank at 6,000 RPMs without too much concern. I was going to run forged pistons with stock rods, 330 heads and a moderate cam.
I think I posted this before, but my recipe was to bore the 291 to 3.75", offset grind a 330/341 crank to 3.90", turn down the counterweigths and mains to fit the 291 block, use 6.25" NASCAR H-beam rods with a SBC journal size and have custom pistons made up at whatever CR you want. I chose 9.25:1 so it could run on ANY gas you can get at the pump - personal preference.

Choose a cam in the low 220° range with a 4bbl carb, 1.94" 330 intakes and cut down or custom exhausts (1.625") to fit 276-291 heads. The 1.75" valve is too big. Stock 330-345 heads have a tendency to crack beacuase of this.

This equates to a 344.6 CID low deck Desoto with a 1.60:1 rod/stroke ratio. A great multi-purpose engine. Best guess for HP would be 375-390 if you generalize 1.1hp/cube for the average hipo hemi engine.
Gullwing
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Location: aLBANY

Post by Gullwing »

Thanks for that info. Seems to me for what I want to achieve I would save about $2,000 if I just cleaned up the stock crank, kept the stock rods and bought Ross 8:1 forged pistons. With the money I saved I could put that into a twin turbo set-up. I know my Tremac T-45 and Supercoupe IRS couldn't handle more that 450 HP. I assume this setup would handle 8-10 boost providing I got the ignition and fuel set up correctly
Gullwing
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Joined: Mon Jul 04, 2005 11:08 pm
Location: aLBANY

Post by Gullwing »

I appreciate the info on the heads. I have a set of tall deck heads. I will use the smaller exhaust valves. I saw a web site were a guy put Pontiac valves in with hardened seats. Any info on that?
johnny5
Posts: 128
Joined: Mon Dec 05, 2005 3:52 pm
Location: St Charles, MO

Post by johnny5 »

I considered the turbo setup but it was way too much money, all custom plumbing, and they don't work well without EFI. Custom manifolds, EFI, spark control and intercooling will easily double the cost of your engine build :o

The stroker setup I outlined will cost around 2K total including rings, bearings and balancing. Your 291 rotating assembly will be somewhere around $1200-$1300 with custom pistons, balancing, rebuilt rods etc.

You can't use 330 heads with smaller than original valves. They already have 1.75" exhausts. That's why I suggested opening up the holes and pockets in the low deck heads to a more reasoble size instead. As far as I know the ports are the same size so you should end up with better heads in the end.
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