ADDING STROKE / STROKING SBC

General engine tech -- Drag Racing to Circle Track

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joespanova
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ADDING STROKE / STROKING SBC

Post by joespanova » Mon Nov 13, 2017 5:32 pm

Will going from a 3.48 stroke to a 3.75 really make much difference in performance? There isn't a std port 23 degree head that I know of that'll make a REAL difference in power over my current heads.........so stroking is another option. BTW , my heads are fully ported by 2 reputable head porters.
All things being equal , going from a 377 to a 406 in a full drag race engine.
It would have to be worth .15 to .2 in E.T.
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Re: ADDING STROKE / STROKING SBC

Post by Ericnova » Mon Nov 13, 2017 5:35 pm

If the cam spec is changed to match, it is easily worth it,

29 cubic inches @ 1.5 HP/Cubic inch is 45HP

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Re: ADDING STROKE / STROKING SBC

Post by swampbuggy » Mon Nov 13, 2017 6:17 pm

You (MAY) also need a change in the induction system to achieve MAX. gain ??? Mark H.

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Re: ADDING STROKE / STROKING SBC

Post by panic » Mon Nov 13, 2017 6:31 pm

More plenum volume
Larger, longer primaries
More duration
Shorter LSA
Later IVC

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Re: ADDING STROKE / STROKING SBC

Post by joespanova » Mon Nov 13, 2017 6:52 pm

I've got plenty of cams to play with , anything from a 107-112 , same basic lobes.
Induction is "fixed" and won't be changed , Victor Ram , can't really do much with it. so it gets left alone.
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Re: ADDING STROKE / STROKING SBC

Post by Newold1 » Mon Nov 13, 2017 7:25 pm

All sing out my MANTRA again! In most all N/A performance and racing engines "THERE AIN'T NO REPLACEMENT FOR DISPLACEMENT!" gET IT ANYWAY YOU CAN WITH STROKE OR BORE!

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Re: ADDING STROKE / STROKING SBC

Post by geraldtson » Mon Nov 13, 2017 7:46 pm

Yes will make you happy. Lot of hard work grinding block for rod clearance,ground a lot out of many and never hit water but had to be close. Check cam to rod clearance closely also i don't like the older eagle cranks and H beam rods usually require more clearancing.Would go with Scat. If your going all out with forged Crank would be money better spent down the road to go with the 3.875 stroke but you will for sure have cam to rod issues with std base circle cam. Most all the cam company's now will steer you away from small base circle cam (.900) or tell you they don't exist there trying to push what cores they have in stock. I even have a .850 base circle. If you go 3.875 go with small base cam or just simply grind the rods and don't worry about it they'll be just fine.

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Re: ADDING STROKE / STROKING SBC

Post by bigjoe1 » Mon Nov 13, 2017 7:54 pm

The cams I run are so big, they all have a 900 base circle without even asking-- I have NEVER had any problems using the 900 base circle cams in big stroker engines




JOE SHERMAN RACING

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Re: ADDING STROKE / STROKING SBC

Post by geraldtson » Mon Nov 13, 2017 8:26 pm

Big Joe confirmed my point use a .900 or smaller base circle cam but you can also just grind the rods!
Last edited by geraldtson on Mon Nov 13, 2017 8:43 pm, edited 1 time in total.

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Re: ADDING STROKE / STROKING SBC

Post by pdq67 » Mon Nov 13, 2017 8:31 pm

IMHO, "Poking and stroking", are nice as is, "GAS", but as for myself, I'd rather be, "blown"!

He, He!!

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Re: ADDING STROKE / STROKING SBC

Post by joespanova » Mon Nov 13, 2017 9:26 pm

OK , funny stuff right there............
I FORGOT to mention , I use GRP "aluminum " rods.............I believe they can "cam cut" the rods also.
The cranks are Lunati.
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Re: ADDING STROKE / STROKING SBC

Post by geraldtson » Tue Nov 14, 2017 5:02 am

That really changes things! Hope some one else with more experience with aluminum rod big stroke engines can help with that one. Might get by with 3.750 stroke and a lot of grinding. Think in your case just add a tad of compression. Gain ain't worth the pain and money. Forgot to mention if you go with to small a base circle cam for rod to cam clearance it'll drop lifter to far down in the hole and cause to much lifter side loading.

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Re: ADDING STROKE / STROKING SBC

Post by joespanova » Tue Nov 14, 2017 6:45 am

geraldtson wrote:
Tue Nov 14, 2017 5:02 am
That really changes things! Hope some one else with more experience with aluminum rod big stroke engines can help with that one. Might get by with 3.750 stroke and a lot of grinding. Think in your case just add a tad of compression. Gain ain't worth the pain and money. Forgot to mention if you go with to small a base circle cam for rod to cam clearance it'll drop lifter to far down in the hole and cause to much lifter side loading.
I'll use the same .900 base stuff I already have......just add stroke and cut domes down some. I don't know if 15-1 compression might be a tad high.
Anyone care to suggest the safe limit on compression? I was thinking more like 14ish.
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Re: ADDING STROKE / STROKING SBC

Post by Frankshaft » Tue Nov 14, 2017 8:04 am

Leave it 15:1 and run Q-16. I bet it would be a solid .1- .15. Instead of say 13.5:1- 14:1 and c-12 or something like that.

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Re: ADDING STROKE / STROKING SBC

Post by panic » Tue Nov 14, 2017 10:02 am

can't really do much with it

2" open spacer

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