Originally Posted by MILD THUNDER

Its not often, a guy has a similar cubic inch engine, with decent aftermarket heads, cam, intake , carb, etc, then basically builds another similar combo, but with different brand parts.

If you had gone from your 420hp 454 mercs, to these builds, you would probably be nominating bob m for president. Youd be happy gaining almost 10mph with your new build . Unfortunately, you arent the average guy who calls bob to upgrade his stock engines that run on 87, have stock heads, small cams, built for longevity merc engines, gains some power, and is happy as a clam. Or the guy whos building his first high performance blower build, and is amazed at the dyno sheet.

At the end of the day, its a 540ci chevy. If you cant make decent power with a aftermarket head like afr, dart, brodix, EQ, a decent induction combo, cam, etc , you really shouldnt be in the engine business. These combos been around for decades now. You can pretty much slap together a 540/650hp combo right out of the summit catalog, and have all the parts in stock and to your door in a couple days. A secret ramp profile , .040 extra valve lift, or any of that fancy talk, isnt going to do chit for your speedometer, if you way off on the cams timing events.

Originally Posted by Full Force

OK, we all know the issues I had and that's all over, well kinda I hope, I have a trans issue so I may pull BOTH engines and recam because I am still not even close to happy with my results, that being said I am thinking if trans turns out to be a valve issue (that I can fix in boat) I leave engines alone till I need to refresh or have another issue (happens a lot haha) the part that worries me is the cams I have, with HIGH lift, LOW duration, and 190/590 spring pressures....

MY cam is 241/[email protected] 680/663 on a 112

So, question, this seems to be a more recent aggressive cam choice given out to buyers last couple years... I have been informed of extremely fast ramp rates and broken lifters as a result, I think that's one reason "HE" went to Johnson because talking to the engineer I was informed they can handle MUCH more spring pressure then Morels, I had one set of heads with solid spring pressures at first and didn't hurt anything ( fixed after the "issue") I am told the valves are beating the chit out of the seats, and will surface issues at about 100 hours... I am at 65, I am looking for PROOF of good or bad info and results, lots of guys seem happy with the cam choices from "him" but then say " only logged 10 hours or so" I cannot find any info supporting LONG TERM durability...

if I hear results of guys spinning cams and springs nearly identical to mine for 300-400 hours with no issues, I may leave them until refresh time, if I see pics and proof of issues I will be replacing no matter what at 65 hours..

FYI this is not a Bob bash thread, or Poor Full Force thread, this is for FACTUAL info that's been on my mind since last winter, it sucks to spend what I did and wonder if and when my valvetrain will fail and cause me headaches...

Thx for input maybe even myself can keep on track this time lol

Originally Posted by mike tkach

tim,did bob m tell you that the valvesprings would last 400 hrs?i am asking because on some builds i did with cams from bob pretty close to yours i was told&expected way less.even mercury marine,s fabled hp500 needs springs replaced at 250 hrs and a valve job should also be done at that time.what valvesprings do your engines have.

Originally Posted by MILD THUNDER

Tim, do your engines have the pac racing springs, or the house brand afr springs ?

Originally Posted by KAAMA

Over the past winter a friend of mine took his engines to a local builder here that has a triple engine offshore boat that had Merc 500hp/549cid Buldogs with over 700hrs. He contacted Bob Madara last Fall and started lining up parts...the parts were shipped to the local racing machine shop for the builds.

I think the engines are now at least 548cid with AFR 315cc CNC ported heads, new Dominator carbs, intake manifolds, and some of Bob's .680" hydraulic roller grinds with Johnson lifters....they dyno'd all three engines and they made very close to the 700hp goal---I do not know the actuall HP numbers of all three engines, but I know one hit 704hp @5900rpm.

One engine had some cam walk issues and found that the lifter bores were not correct, so they had to machine for lifter bore bushings and this stopped the cam from walking. He's got almost 50hours on all three engines so far this season with no further issues and he is very happy.