hblair

Hi Guys, Here's my situation. After pretty much restoring my 79 Scarab, I did some mild engine work to wake it up some with the intentions of doing more to the engines later. Later got here sooner. These motors are stock 330 cast bottom ends. I bought Holley 750's, edelbrock air gap intakes, and had the heads machined. They are the large oval port 049's. We installed 2.15 intake valves, and 1.88 exhaust valves. Stock exhaust with thru hull. This Lunati flat tappet cam with hydraulic lifters...

The boat was running good. We were running 64mph at 4500 rpm, when the starboard motor let go. Long story short, #1 piston basically exploded. Literally. Theres pieces everywhere, even ruined the oil pan and bent other pistons up.

I want to go ahead and install a 489 stroker crank kits. Both engines are on their original bores. I want to go ahead and get roller cams as well as aftermarket exhausts.

One of my heads is ruined. I'll have to replace it. I would like to keep my 049 heads with these larger valves. Will they work acceptably with the larger displacement engine? My boat has raw water cooling and I go to the gulf a couple times a year and don't think I want aluminum heads just yet.

These motors have 2 bolt mains bearings. Will that cut the mustard?

Which stroker kit should I use? Any recommendations? I've heard good things about the scat kits.

Which cam should I use?

And of course, the big question, How much horsepower do you think I'd be running?

I'm kinda in a time crunch. I blew it up Thursday, and need to have it by the 20th. Which is prolly not realistic, we'll see. I've got this motor torn down and the bare block ready to go to my engine guy now. Gotta pull the port motor and do the same thing.

dereknkathy

cast pistons. they are ok in a cruiser that spends it's life at 3500 rpm. any full throttle use above running it to WOT to make sure everything runs according to spec before backing off to cruise requires forged pistons. 2 bolt blocks are ok to 6000 rpms or so. aftermarket roller lifters are almost as expensive as a gen 6 block which will take oem roller lifters-something to consider. replacement 049 head. i have a set you don't want. mine ran in brackish water for 20 years then sat and continued rusting away on a trailer for 15 more years. buy an ebay head from as far from salt water as you can get. if you can find a head or heads that were either pickup truck or closed cooling sportfish even better. even fresh water is hard on bbc heads. antifreeze mucho better. before buying exhaust, cams, pistons consult bob madera (marine kinetics). good luck. a friend of mine had that boat's twin brother. he loved it. swore he would never sell it. then he did...although your time crunch may force you to buy a running 330 or L29 gen 6 and throw it in as an interim motor.

MILD THUNDER

iTrader: (3)

Sounds like you had it at peak torque rpm and detonated it from a poor tune.

I certainly wouldnt expect to have TWO complete stroker engines built and installed in 3 weeks.

You may want to get those blocks sonic tested. If they have been in a boat for 36 years, there's a good chance they are rusted from the inside, eroding away at the cylinders from the back side.

A pair of crate 502's would be sounding good to me right about now, or some low hour takeout mercs. .

Griff

My opinion http://www.offshoreonly.com/classifi...-s-o62214.html

assuming they check out.

Budman II

iTrader: (1)

Hey MT, can you explain to my why running an engine at peak torque RPM would be more prone to detonation than some other RPM, such as WOT? Couldn't you get a lean spot just about anywhere in the RPM range? I'm just curious. My engine actually had two torque peaks - it was a little over 600 ft/lbs at about 3500 RPM and then again it showed 605 ft lbs at around 4700 RPM.

indysupra

iTrader: (3)

That's when cylinder pressures are highest. That's when the tune is most critical.

dereknkathy

he had it going 65 mph. sounds like he held it there. i think that was at the second torque peak. also i don't think you can make the engine produce peak torque at a lower rpm except on a dyno where you can load the engine till it is at full throttle at that rpm. the equivalent of a variable pitch prop. the engine is only making peak torque at full throttle. at 3500 if you put the sticks to the pins, the engine will not stay at 3500 and produce more torque. it'll run right up to full rpms.

hblair

We're thinking the timing was at about 38*. I had been meaning to go back and check it but it was running good so it got forgotten about.

Thanks for the information guys. I don't think I'll be buying a set of take outs at this time. Or new 502's. I'm not wanting to spend 10 grand plus on this boat at this time. Also, I didn't realize the retro roller cam kits were so expensive. I found a couple of gen6 454's in a salvage yard down the road for about 1700 for the pair, which is pretty reasoanble.
What do you all think about this kit? Help a brother out here.

dereknkathy

you want boat in water in 2 weeks. replace all rod bearings both junkyard L29 engines. then get a cam something like this http://paceperformance.com/i-6254922...oller-cam.html and put it in whichever bottom end looked better and put that one in the boat. THEN start worrying about whatcha gonna do for the 496 (492 or 3 actually) motors. but once you have 4 bolt gen 6 roller engines, that have spent their lives full of antifreeze, it will be hard to justify stroking the mk 4 blocks.

hblair

Thanks Derek. My time crunch is prolly gonna go out the window. Pretty creative plan you came up with though.

The L29 motors have 4 bolt main bearings? I didn't know that.

They don't accept manual fuel pumps correct?

I don't know I'm just thinking out loud and trying to figure out if it's worthwhile going with L29's if I have to purchase electric fuel pumps even though the retro roller cam kit is going to be expensive if I keep the mark IV engines.

Am I correct in that L29's do not have forged internals?
Sorry if I seem all over the map here. thanks for the input.