Author Topic: big bore short stroke  (Read 8951 times)

Offline hemidakota

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big bore short stroke
« on: January 05, 2016, 07:58:28 PM »
Has anyone played with a big bore short stroke combo in a FED? I am going to build a 4.5" bore 3.9" stroke combo and have had a few people act like im crazy with the short stroke. I have a nice/light crank already. So I am interested in other thoughts. It is a Chrysler wedge in a KB block with a set of Brodix B1MC heads. I am sure there is a lot more to be said but I will start here...Thanks
If it jams force it, if it breaks it needed replaced anyways

Offline ricardo1967

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Re: big bore short stroke
« Reply #1 on: January 05, 2016, 08:21:55 PM »
Here's my humble $.02 worth:

Unless stroke is extreme to the point that incurs into undesirable rod/stroke ratio, too short compression height or piston skirt hanging out of the bore, the longer stroke will help you.

Summarizing, if you have all the parts on hand, go for it. Otherwise...

Now, let's hear the pros!

Offline Paul New

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Re: big bore short stroke
« Reply #2 on: January 05, 2016, 08:22:38 PM »
That's not that short of a stroke. My buddy Todd ran not positive on the bore either 4.310 or 4.375 with a 3.25" stroke .500" short deck BAE 5 heads and a std. Helix 14-71 ran 6.2 something in his AA/AM granted he spun it up!!

Offline dusterdave173

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Re: big bore short stroke
« Reply #3 on: January 06, 2016, 04:50:38 AM »
We did a pulling truck big block Mopar that had CI limit for his class--won national champ several years in row--did it with Indy heads 4.500 bore and very short stroke--that combo made much more HP than same CI with smaller bore longer stroke-- I love combos like that --They are one of the few "conventional wisdom" things that seem to be true  Go for it!
I have always had a fascination with fast cars at the expense of more normal character development

dreracecar

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Re: big bore short stroke
« Reply #4 on: January 06, 2016, 07:56:19 AM »
AGAIN - It all depends on what class you plan to run, if its a heads up and run it out the back door , then bore/stroke is critical. But if its an index class anything can be made to work because of the other options available to you

Offline Van

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Re: big bore short stroke
« Reply #5 on: January 06, 2016, 09:23:01 AM »
With the 3.9 stroke you should use the 5.00 short deck, as Paul said. As Bruce said anything can be made to work, just not as good as it could be.

Offline masracingtd1167

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Re: big bore short stroke
« Reply #6 on: January 06, 2016, 11:45:31 AM »
I would say that the big bore short stroke will give you the most HP per cubic inch . Your bore and stroke works out to 496 cubes and thats not so small ! We tried some small bore long stroke stuff with a comp eliminator motor and it never really made the same HP as the large bore short stroke stuff .

Offline hemidakota

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Re: big bore short stroke
« Reply #7 on: January 06, 2016, 12:49:36 PM »
Thanks for the info... Here is a little more about the combo. It is going to be a low deck block that is -.745 from the standard deck wedge KB block. Deck height is 9.980. I will be more than likely running a 7.60 index, would like to run 7.0 but I think that is a little further out than the HP it will make. If it makes 900+ HP I will be very happy. It will have a 3.150" kinsler stack injection set up on alky. Prob in the 15 to 1 compression range. It will prob like a lot of rpm's. My hope is to be able to slow it down to run NE1. But you know how that goes, gotta see how good it will run all out. It is a long term project that I am slowly putting together. It will have good parts in it, Light crankshaft, BME alum rods, T&D shaft rockers, titanium valves, you know the drill. This all started due to a conversation with Ken Black on building a block for me which has been done for my combo and a great cylinder head guy I have hooked up with from the EPD days. I hope it all works out and cannot wait for the day. Its a FED thing, have been helping a friend with his and out of nowhere he let me lic. In his FED and here we go...Addiction...And many great new friends...
If it jams force it, if it breaks it needed replaced anyways

Offline Van

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Re: big bore short stroke
« Reply #8 on: January 06, 2016, 07:25:22 PM »
It sounds like you have a great motor going together. OK who is the EPD guy ? 

Offline hemidakota

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Re: big bore short stroke
« Reply #9 on: January 07, 2016, 12:34:03 PM »
The EPD guy is DB Cylinder heads in Minden NV. Danny worked at EPD for many years. Engine Prototype Development built some pretty serious heads back in the day. I am sure there are a few on this site that run EPD heads still to this day...
If it jams force it, if it breaks it needed replaced anyways

Offline JWBurgess

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Re: big bore short stroke
« Reply #10 on: January 07, 2016, 06:27:03 PM »
When I bought my car 1.5 years ago it came with a tall block BBC with 4.600 bore with a 3,75 stroke, alky with a 671. It was a running car but with a LOT of small problems. I haven't run it yet because of rebuilding all the BS work. Has a PG with 3.89 gear, previous owner said he ran low 7.50s with it but when I asked a lot of detailed questions he shut up on me and wont talk any more about it (said it was part of a life he left behind?) There fore I an in search of the same answers as the original poster.

Offline Van

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Re: big bore short stroke
« Reply #11 on: January 07, 2016, 07:45:59 PM »
Reason I asked was I knew one of the original partners, Mike Mattay (sp) many years ago. Mike didn't want to make the move to Nevada from L.A. when Larry moved the shop.

Offline hemidakota

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Re: big bore short stroke
« Reply #12 on: January 08, 2016, 12:16:50 PM »
It is a small world for sure. I don't know Larry other than have met him a few times. I do know he still enjoys and works on projects quite a bit. Just wish I could download all the info he has from all the years... Danny Brewer is a great guy and has helped us out tons.
If it jams force it, if it breaks it needed replaced anyways

Offline slingshot383

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Re: big bore short stroke
« Reply #13 on: January 13, 2016, 11:05:55 AM »
Hemi or Wedge?  Mopars aren't like Chevy's and a 4.5" bore motor with either B1-TS or 572-13 heads will get you real close to that 7.0's number.
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Offline hemidakota

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Re: big bore short stroke
« Reply #14 on: January 21, 2016, 08:45:12 AM »
It's a wedge, B1MC heads. slingshot383 why are you selling your injection system? just curious? what did you change to?
« Last Edit: January 21, 2016, 09:07:29 AM by hemidakota »
If it jams force it, if it breaks it needed replaced anyways