Endurance Short Stroke BBC
 

Beginning to plan out my next engine build for the ol' Formula. Currently have 454's with 500efi cams. Wanting to build a 500+ cubic inch short block to use with my current 310 Merlin aluminum heads. 600hp goal with longevity and reliability in mind. SRP has a piston for 4.560" bore that I could use with new blocks and a 6.385" rod. That makes a 523cid. Does anyone have anything similar with a 310cc cylinder head? Toying around with the idea of a Solid roller cam as well.

That would be a nice combo imo. Solid roller not really needed, being that you mentioned "longevity". That combo, a decent cam, should do 600hp without breaking a sweat using a hydraulic.

That being said, a 523ci, 10:1 solid roller 6500rpm setup, has a nice ring to it. :)

Vintage chromoly built a 516ci if i recall, made some good power.

Yeah buddy! Is it horrible that I want a solid roller for the crackly idle sound ? lol

Solid roller here. :evilb:

mine is a short stroke too. 3.920" with a 4.540 bore.

Describe crackly...it's not in my terminology. :)

Just a good crisp sound. I have the Imco powerflow manifolds and long tailpipes for the TRS.

You can't do that with a HR ? Oh, is your exhaust dry ?

Exhaust is wet but does dump pretty far back in the pipe. I know a Hydraulic Roller would do it. Wondering what effects taking weight off of the valvetrain would be with a solid lifter setup. They will probably end up with 741's or something similar but it doesn't hurt to experiment with the idea of a solid roller.

Your build has definitely been one to inspire. I bet it sounds good!

http://rs205.pbsrc.com/albums/bb293/...h=160&fit=clip]http://http://rs205.pbsrc.com/albums/bb293/...h=160&fit=clip
Thanks for the kind words.
here's a video of the engine on the dyno Tyler.
You should have no problem making the number you are after.

why 3.92? I am sure it isn't what you had laying around...

I bought an Ilmor supercat spec engine. It came with a 4000 dollar crank and Carrillo rods with CARR bolts.
At that point, I built the engine around the block, crank and rods I had.

I worked woth CP on a set of pistons with the proper compression height as the supercat pistons had a good sized dome on them. (Something like 12.5:1 CR)

ilmor or had those cranks made in the oddball 3.920" size in part so they could run a larger bore and still make the 510CI spec. That's what I was told by someone familiar with the program back in the early 2000's when they were doing supercat stuff.

Now to find out if my cylinder heads will support the overall power output that I desire. I know they flow pretty good to .600" shouldn't have to lift much more than that. Current cams lift to .598" and .610". Who would be a good choice for doing a valve job on my merlin 3's and mild porting? Thanks for all the input guys, as always it is greatly appreciated!

I got a good head guy for you if you dont mind driving up this way.

Sweet! I bought all my stuff from Teague over 5 years ago, coming up on 200 hrs of run time now with no problems whatsoever. We can just call this SecretFormula repower 2.0.

"If" I go the solid roller route looking at crane stock grinds. Part #138781 246/254 on a 114 with .615"/.636" looks good. I like that for the duration it has it doesn't lift a ton so should be easy on valve train.

Scrapped this build after pricing oiling system and exhaust for TRS capable of 6500 rpm..Gonna stick with the imco's and stock style oil system and keep the revs below 5500.

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.

Mike, would there be any reason not to use a little more bore with 4" stroke if using the world blocks? I'm a big fan of the 4" stroke in a 9.8" deck block. Thanks for your input!

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...

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...

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!

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

Good Reading, Thanks Buddy!

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?

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

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!

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.

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

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

Project kept on growing, I wanted every surface machined and cleaned up, and made perfect, and to do the best job, I had to go 522, that was the only way to make everything sweet. The problem is, that I had to have custom pistons made with a specialized displacement, which took more then a month to show up, since it was race season. Which led to my project taking longer and of course adding a chunk of change. But in the long run, everything assembled went smoothly, because all of the surfaces were machined perfectly. My Engine assembler has access to a huge machine shop and has 35+ years experience with the tools! Everything had to be balanced. In the end the price tag was large, but i know that every part was new, or machined to new specs

Were you shooting for a specific cr? Is that why you had to go custom on pistons? I'm looking at the srp line of JE pistons in 4.560" bore. Also leaning towards new scat cranks and rods. I'm not reusing any of my current short blocks.

Yes, PM sent.

After throwing around the stroke issue I'm currently going with a 550 standard deck.a hydralic roller cam 10.2 to one compression and fuel injection.

I didn't want to go with the longer stroke and tall deck for stroke and alignment of my exhaust etc.

should put out over 700hp and high 600 torque.

torque will be over 600 up to 6000.

i misquoted when i said it was a crane 168741 cam,it is a 525 efi cam. everything is the same as the 168741 except the lsa,the 741 is on a 112 and the 525 cam is on a 114 lsa. although it made good power today it did not make the 625 i was expecting,it peaked at 602 hp and 598 lbs of torque.peak hp was at 5900 rpm,the next one of these i build will get a little more lift&duration on the cam because this one ran out of gas at 5900 rpm.i will add that i was very happy with the performance from the engine quest heads.

What carb and intake Mike ?

new gen3 holley 1050 2 circut dominator and edelbrock dominator single plane intake,i don,t remember the part number.

https://www.offshoreonly.com/forums/...weekend-7.html

Photos and Videos on the last page of the thread above is how the engines are dressed out now. I know I will need more carb it currently has 800 quick fuels. Should I plan on going to a dominator style? I have room for a small spacer if needed. Thanks Mike!

tyler,i went with the dominator&manifold because everything was new,no existing parts from another build.if you already have a 4150 manifold and are on a budget imo that would work pretty well with a 1050 4150 carb.

Just caught this thread. I have a 524 similar to what you are looking to build. It's a 4.565 bore with a 4" stroke, 6.385 Eagle H-beam rods, AFR 305 Rectangular heads with CNC chambers and bowls, Brodix HV2000 intake that has been ported with the heads. Custom Holley 950 cfm 4150, custom hydraulic roller cam with .611/.623 lift 242/252 @.050, 10.1:1 compression, Crower stainless rockers with a stud girdle. MSD 6M ignition and Lightning wet headers. It sounds awesome, a little too, I had to put Gibson mufflers on it to keep from getting tickets. First time I started it after the rebuild in the marina, it sounded like thunder. I never had it dyno'd but it runs better than it sounds. I've had my boat to 90 with 4 people and a full tank of gas, I can only go half throttle getting on plane or the prop blows out. Acceleration from 45 is absolutely amazing. Big bore short stroke engines are very efficient and love to rev quickly.