Offshoreonly.com - Endurance Short Stroke BBC

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Offshoreonly.com (https://www.offshoreonly.com/forums/)

- General Q & A (https://www.offshoreonly.com/forums/general-q-20/)

- - Endurance Short Stroke BBC (https://www.offshoreonly.com/forums/general-q/347403-endurance-short-stroke-bbc.html)

adk61

11-02-2017 08:00 AM

Quote:

Originally Posted by mike tkach (Post 4591342)

tyler,a 509 [4.500 bore 4.000 stroke]a crane 168741 hyd roller cam and your heads will exceed 600 hp.i just finished the same combination but it has a set of the engine quest heads.it is going to the dyno next week,i will post the results but i am expecting 625 + or - 10.

the 509s (Mercury 500EFI) that Cigrocket did with my heads made 620HP thru wet exhaust in full marine trim... some left on the table if bigger injectors and fuel system were used, so I'm quite sure your 600HP target is easily attainable...

TylerBurich

11-02-2017 08:26 AM

Quote:

Originally Posted by adk61 (Post 4591475)

a note of caution... bowtie or dart/merlin block if you're planning to go 4.560 most gen IV/6 blocks will not sonic test acceptable for wall thickness in a marine application I would strongly suggest sonic check of any block used over 4.530 to verify proper wall thickness, I've seen some crazy chit in my years...

If 4.5" will do then I guess there is no need for any bigger, just didn't know if there was any power to be gained by unshrouding the valves. Definitely gonna need a bigger carb!

MILD THUNDER

11-02-2017 08:32 AM

http://rehermorrison.com/tech-talk-53-big-bore-or-long-stroke-which-is-better/

TylerBurich

11-02-2017 09:10 AM

Quote:

Originally Posted by MILD THUNDER (Post 4591484)

http://rehermorrison.com/tech-talk-53-big-bore-or-long-stroke-which-is-better/

Good Reading, Thanks Buddy!

TylerBurich

11-03-2017 07:41 AM

This piston in a World block 4.560" and a 741 looks good.. right around 9.1 cr. 6.385" rod 4" stroke.
338168 Product Detail Information - JE Pistons

What do you think?

dandercam1

11-04-2017 07:55 PM

If your going with a 4.560 World block, running 9.1 c/r, hydraulic roller cam and limiting RPM to 5500 I don't think you would be giving away anything longevity wise going to a 4.25 or even 4.50 stroke. The usable torque going to 555 or 588 inches with a 310cc head would be outstanding. You could be looking at 625+hp and 700+tq with the dock manners of a 500efi

TylerBurich

11-06-2017 09:43 AM

Quote:

Originally Posted by dandercam1 (Post 4591880)

At the beginning of this thread I wanted a nastier idle sound and higher revving engine. Things change and these builds will be based around the same reliability idle speed and quality of my current combo which is 454 with 500 efi cams. Should be a great combo for family friendly boating, it is plenty loud and does have a good tuned sound with the imco exhaust. Thanks for the input!

cigrocket

11-06-2017 09:53 AM

Quote:

Originally Posted by adk61 (Post 4591478)

628HP and 626HP ...LOL.... plus it was 100 degrees. I had bigger injectors, (50# once I replaced them. we only used 70% of them.. Plenty of fuel too. Despite my through honed polished, port matched intakes, they still starved for air after 5500. I have the arizona speed throttle bodies too. They were not 509, by the way, they were 522. I was happy with the performance of Al's heads, and I reached my goal. My ultimate goal was 625, and that is exactly where I landed.

TylerBurich

11-06-2017 09:57 AM

Quote:

Originally Posted by cigrocket (Post 4592103)

That's awesome! I followed your thread on the cylinder heads, those turned out great. What was your reason for going 522? I am thinking my build is gonna go this way, what CR did you end up at?

Thanks

hogie roll

11-06-2017 10:12 AM

Machinist on yellowbullet is claiming he takes them to 4.65 and maintains .250 thickness.

Who's gonna build a 4.65x5 with Dart 20s or SR20? :D

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