Freshing up a pair of 420's gen4
 

The engines are stock 420 gen4 big blocks ,Both engines need cams, is there a better updated cam Then using the stock ultradyne 288/296 -h12 cam.
231/239
550/575
112
I was thinking since that's a 25 year old setup there could be something better ,I talked to someone at Bullet he couldn't answer that question but he could grind that same cam in about 2-3 weeks out

I want to stay w/ the hyd flat tappet cam


Thanks

Upgrade to roller cams, it's a tad pricey but worth it.

If you can swing it. Look into getting a set of AFR 265 heads and talk to Bob Madera about cam selection. First off the head will pull 150lbs out of the back of you boat which is a good thing. They flow much better than anything you could do to your current heads which may have cracked exhaust seats. Talk to Bob he is a wealth of knowledge.

http://marinekineticsonline.com/

I just want to change cams some people say that UD cam was to big for the 420 it hurt performance , I can get the same cam built at Bullet just don't want wait 3 weeks if there is something better out there

I thought they had a crane #132561 cam originally, and that cam is still available off the shelf. There may be better flat tappets out there, but I don't know what they would be.

Your right they did but Mercury changed to the ultradyne 288 -296 cam toward the end of production of the gen 4 block

That cam you posted, was what came in the 454 440HP and 460HP "cyclone" series engines, in the early 80's. Merc #41436 . The 400HP, 420HP, and 425HP Gen IV engines, had merc part # 451-7892, which was the crane 132561 cam . The 440/460HP cyclone engines, had pretty agressive sounding idles, and ran dry pipes, with the 110 LSA of that cam they had. The 400, 420, 425's, were a bit more tame .

http://crane.carshopinc.com/product_...d/16042/132561

I believe lunati is carrying that original 440HP cyclone cam, and possibly "elgin" cams. Calling them would be a good idea.

http://www.summitracing.com/parts/lu...make/chevrolet

wisconsin, so no salt, but those heads rot thru at the exhaust guides with fresh water too. blocks are pretty tough, but those heads are at the end of their lives.