formula31

Dennis, Ive never done it but doesnt the Mark 4 blocks lifter bores have to be bored perpendicular to the cam centerline to use rollers? Thats what I was told a few years ago. maybe they have better roller lifters now.

blown formula

I would be happy to have more than 450 hp per engine, but I also want maximum reliability without having to replace valve springs every season. That is a real hassle!! and broken engines in the middle of the season is not good either...

formula31

I hear that, been there, done that. I think the problems that people were having with the hp500 were the valve springs causing failure of the roller lifters. Crane and/or Merc screwed up and used a valve spring that was way to strong or had the wrong spring rate causing failure of the roller lifter. I would still find out about the mark 4 block and how well it accepts roller lifters before I considered that avenue. If you go the flat tappet route, break them in religiously (no idle time at all) and they will be fine for a long time.

blown formula

When you are saying flat tappet, are you referring in fact to "hydraulic" flat tappets or solid ? I would think with solid lifters, the valves would continually have to be adjusted (bad in a marine setup), and higher spring pressures would be required??
Yes/No???? I do not really have an objection to hydraulics as I know they are reliable but rpms are limited also, are they not? What is the limiting rpm of hydraulics? flat tappet versus roller??

formula31

Oh yea, hydraulic flat tappets, you dont want to go solid unless you are after every last pony and they are a pain. Hydraulics are totally ok to 5500 rpm, maybe more I think. I dont really know, Ive run them to 5500. It mosly depends on spring pressures I think. You wouldnt really want to push your bravo over that anyway.

blown formula

So, is it possible to reliably get 500 hp out of these engines and not be tearing them down all the time? That would be nice to have a cool 1000 hp in the Sonic!!

excaleagle42

it's easy to get 500hp out of those engines and be trouble free. i had 400 hp MARKIV's. now they are right about 500's. i used a comp cams extreme 4x4 cam to keep the low end torque and still make good hp. redline is 5800 R's. 223int /234exh .544lift intake/ .564 exhaust with 111* LSA. clean the casting flashing up on the runners and the heads are good since they flow well already. i changed to EMI thunder from stock and have no reversion problems. my boat weighs 13,600 lbs and still has plenty out of the hole( not that i use it like that). don't believe rectangular ports can't make good torque down low. they can.
and if you use torquer 2 springs, no machine work is needed to the head.

KAAMA

I agree with Dennis about the hydraulic roller---they're a good and reliable way to go and will give you more HP/TQ. You also might want to take the heads and have the bowl/pockets cleaned up, have the short turns radiused, and unshroud the valves. This would usually be termed as a "street port" and might cost only about $250 per set or so. Also, something that many people don't do on a 454 is to have the cylinders "bore notched". The person doing it has to know what the heck he is doing for it to be done correctly otherwise the block could be ruined or have the cylinders sleeved. Thing about it is that it's a VERY INEXPENSIVE way to get more HP from a naturally aspirated 454. The cost of a "bore notch" is only about $50-$75 per block and takes only about an hour or so to do. A guy could even do it himself---it just has to be done correctly. When dealing with the 454" block, speed shops may know what "bore notching" is, but they may not always know the extent of what bore notching can really do and therefore they don't really think it's that big of a deal, and thus don't offer it to the customer----when actually the bennefit is worth roughly 25hp/tq or so on the dyno. It may not sound like much, but it all adds up----not a bad value for the money spent! If you decide to have it done, take it to a machine shop/speed shop that BELIEVES in bore notching and actively does so and offers it to their customers. That way the chances of having the job done correctly are much better. This is NOT a process that is needed on every engine, but makes a nice increase in power on a 454" engine that I think is worth the time and money spent.

"Tinkerboater" had done this for guys around the area on their 454's and "JimV' offers it in his shop.

Dennis, you know, you are right about the synthetic oils being used in many of the everyday cars/trucks "grocery getters" with roller cams/lifters without problems. I didn't really think about that and have over looked that point. I always thought marine engines run under a harder load and more sustained RPM's---and they do, BUT I guess it (the engine) still doesn't know whether it is in a boat or a car---right? I think I have embarassed myself and get the dunce cap DANG!---what was I thinking??? And here I am giving guys advice. Take it ALL with a grain of salt gang!!! I think I'm going to go BURRY myself in my room for a while! Oh well, at least I have decided to use a synthetic in my roller cam equipt boat engines next spring. Therefore, I get to save a little face----not much, but a little anyway.

Dennis Moore

KAAMA,
You're a little hard on your self aren't you?
Read a couple of FAMILY AND PERFORMANCE BOATING MAGAZINES and fergetaboutit!
Dennis

KAAMA

Well, that's just it Dennis! I already DO buy FAPB Magazines! I even have your book----the book you authored! I had to beat myself up a little!