509 or 540
 

I want to repower 1990 27 datona but dont know witch to go with i have merlin 320 heads & intakes gil exhust anyone tryed ohio crank short blocks & witch cams to use - twin engines

What short blocks are in your boat now?

30 over 454s

If you are going to go blown go with the 509 if you want to go na go with the 540.......Each are real easy to get 650 -700 hoarse power

If they are 4 bolt engines you can buy high quality rotating assemblies for around 1800 each and punch them to .060 over. THat will make you a 496. Buy the pistons for 8-1 static. Use everything else that you all ready have. Maybe upgrade the fuel pumps if you havn't all ready. Add small blowers with 5-7lbs of boost and you will easily get 6-650hp for a lot less money.

Rotating assemblies 1800 each
Weiand 177 blowers - 2000 each

That will cost you less than ordering short blocks for the same outcome and they will make gobs of torque.

Just my .02 if you are on a budget.

If you want short blocks, call Scott at Dyno Flow and he'll sell you 572-598 short blocks for the same price as most guys sell a 540.

want to stay na and short deck 9.8 blocks

You can do 572" NA with a really small cam and get in the high 6's low 700hp's with the heads and intakes you have all ready.

I have done somw very similar all ready.

GL with your project. What kind of boat did you say they were going into?

i built a pair of 496's na not the merc 496 but a 60 over bore with a 4.25 crank in a 454 block and made 640 and 6000 a 496 will make more power then a 509 eather way

What is your definition of small cam? HP500cam or Crane -731 or bigger?

Crank is longer

ANything around a .590 lift 240up to 248 duration @.50 witha 112 center.

then what, a stock 454 and 502 is 4.00 inch i used a 4.25 inch with a 250 long rod and a 60 overbore

I was agreeing with ya. Have a happy new year. :cool-smiley-026:

ok thanks i was not sure what you ment i know the merc. crank for the 496 is a 4 3/8 stroke with a smaller bore, i thank .

Are you kidding me on that.

John

I always thought it was the regular 4.25x4.310 but I have never taken 1 apart either. I know you can't take the genV and VI 502 blocks to a 4.375 crank, so I wonder why you would be able to do this with the 454 block.

Who knows. My 496's are built like yours. I havn't run them yet because I don't have anything to put them in right now they are collecting dust.

Happy new year. I am on my way out in a bit.

Probably a pretty big cam, but it is not impossible

When all else is equal there is no replacement for displacement;)

The right combonation goes along way.

Agreed. That is why I use 582" engines at every oportunity.

i think 540 s is the way to go ohio crank & dyna flow short blocks both about 4100.00

Last time I shopped these guys, they were using different components. Tell them to send you a breakdown before you get them.

Have RMbuilder spec out your cams for you after you get them and give hime your info on the top end. You will not be sorry. He gets a great price and the stick will be right.

Good luck. PM me and let me know what you are going to do with your old SB's.

Jeff

i will be selling old sb 5403712570 tommy

540. PM me for pricing. I can help you with your needs before you by the wrong parts. or call (216) 398-8500