Goign to redo my freakin' 383. Suggestions?
 

OK, I'm about tired of this particular setup that my builder cannot get right. I have an engine that is perfectly suited for drag racing, but completely useless for the marine environment. My biggest problem is that it has too mcuh cylinder pressure. I'm pushing 200 PSI after four revolutions of the engine during a compression test. I spoke with Dennis Moore and he suggested retarding the cam timing to a 110* intake centerline to reduce the cylinder pressure some, though I've found that I'd have to really retard (in other words, get a completely different cam) in order to make any real difference (I could probably get it as low as 190 PSI by retarding). So what I have now is a high compression small block that I cannot run hard at all due to detonation. I explained this to the builder, but he built it this way regardless of what I said. Unless there is some really good advice on how to get this to live in the boat, then I'll be tearing it apart over the winter and doing it right (which I should have dome originally anyway).

How should I do this thing up? I still going to run the Vortec heads, but what about cam and compression? I might even go roller to get the power up. I want to do this right and I'll be doig it all myself.

This thing has been beyond frustrating. Any suggestions would be great.

Thanks!

drop a stock 500 hp in and call it good:rolleyes: :D

you never said what boat hull it's in... or what other componets are in the boat??

Booat specs:

'83 4 Winns 225 sport boat, low drive height, etc. 20-something degree deadrise.

3498 pounds unloaded. Hold 70 gallons of fuel, etc. Estimated weight is roughly 4800 pounds with the wife and I with fuel, etc.

This all started because I could not get the boat to run well with the props that I had. Speed was just about the same with as with my old crappy motor. I could not turn the right RPM with a 17 or a 21 (though all the calculators said that a 21 or 23 would do it right) and then the engine melted an intake valve (which I was told was because the valve was defective... BS I think). So I took it all apart, put in new Ferrea valves, and ran a new compression test. Pressure was at 200 PSI on all holes. I can't use the engine this way.

So now I'm here.... frustrated.

put it back to stock and have fun....sounds like you have and will continue to open can after can of worms...what about the drive...alpha, yes? or omc...not the king cobra...external steering?? x dem. you said was low...

There are some nice stock crate engines out there or rebuilds. Save yourself the headache. Try 1-800-runs-new, and others.

I'm not one to give up on these things and I don't think that I'm going to open up another can of worms with it. I'm not asking to be flying down the river at 80 MPH, I just want it to run better. I don't want it to be a go-fast boat. My goal was to make it perform better. It will perform better, the problem is that the engine is not usable in its current form because of the compression.

I have an Alpha on the boat. It will work just fine if I baby it out of the hole (the boat goes absolutely berserk out of the hole if I gag it hard anyway... I don't like that) and just be nice to it.

I was just talking with the builder (I don't know why I even bothered) and he said that I could easily knock off about 15 PSI by retarding the cam by 8*. Maybe I'll try that first.

Tom,
good luck brother...A LOT of people out, some here on this board, have made the mistake too...the marine environment is VERY unforgiving unlike passenger vehicles. the engine is one of LAST areas where you should look for performance gains and the most unreliable...HELL, even my friends do it after i drill it in 'em...take a damn good running boat with an engine that will go over 400 hours in stock form...mess with it, go slower, blow drives, puke engine in under 50 hours...miss a ton of great weekends,,,,on and on and on,,,for what 2 mph???...DON'T look at a boat as seperate systems,,,,look at it as one and address them in a logical order....my opinions are based on; i like to boat EVERY weekend, i like to win races and you can't do it if you don't start or finish.

tom, don't take this the wrong way....i love the water,,,no matter if it's in our low budget bayliner, racing the APBA pro series, on our poker run boat, or racing sail boats....cobra marty and i both are just look'n out for ya....we see a lot of sob stories here
:(

ps...one you may not thought of...take a 10 year old drive that has run within X parameters....now increase loads and rpms.....good luck! it's not a good thing to ask ANYTHING to do something it hasn't in 10 years.:eek:

I am running the vortec heads, RPM air gap intake, 750 holley, EMI exhaust, crane roller cam, 222-230 dur, .509/.528 (.543/.563 lift with 1.6 rockers on mine) with SRP dished piston to match the combustion chamber w/ comp ratio of 9.9 to 1. ( compression test .. all cylinders were around 185 PSI). total timing at 32. spins my 25" at 5300. perfect. i guess around 400-410 hp.. I have put 78 hrs on it with only one wierd piston failure.. But 58 hrs since that. and it is not babied. I run here 4000 rpm plus all the time, she has held to gether and the alpha drive is just fine too. 18.5 ft.. 2650 dry wieght. stock 270 hp mag did 58 mph, now with the 383 i saw 73.1 on gps..

This winter bigger heads and maybe a little bigger cam, and EMI's stainless tube riser's . Chatted with dennis Moore and he said if i didn't want to increase my RPM past 5300 to just put a set of the GM "fast brun alumnuim heads with there 200cc intake ports and big valves. I think i am headed towards a bigger head and increase my rpm to about 5500, and a little bigger cam to go with it.. Gotta do my homework for a few months before i find the perfect combo..

If you just want a nice motor to make boating a little more fun, don't go wild, just make a little power and get relaibility. Myself I have nothing to lose, so i go wild, if it scatters I have a spare motor for a backup..


Good luck

Travis

TomZ might try bending this guys ear , he has built quite a few Marine 383's mine being one of them Doug 419-389-9990 prob have to leave a message but he'll call back good luck

TomZ, sorry to hear of your problem. Which piston are you using. My guess is a flat top, ie the high comp.. The 400s long stoke necessitates using a dished piston to keep the comp. down to reasonable levels. I helped a friend get a 400 built last winter and ran into the same problem with the builder. He insisted on flat top pistons, would not listen to us. So, we paid the bill and left with the parts! No point in building something you can't use. Found a builder down in Syracuse and had him finish the work. Used KB Hyperetics with a 30cc D dish for about a 9.1 comp. ratio. Turned out to be one sweet motor, very torquey. Runs on 89 oct. all day long. The SRPs would be stronger of course, but more money. The 400 went into a Formula sport cruiser, so we figured the KBs would suffice. My suggestion, if you got flat tops, start over with the correct parts. Trying to make do with them will only lead to a broken motor. Also refer to Dennis Moores book for a good cam. Way too many engine builders have no idea what constitutes a good marine cam. Chuck

Traviss,

What part number did you use for the pistons? I'm shooting for about 9:1, but I want to look at your pistons in the catalog to see what the specs are for comparison.

Chuck,

That is exactly what I've run into, though with mine the whole job was basically a freebie. They use a totally different (or same depending on how you look at it) way of thinking over there.

I'm going to replace the pistons, rings, and bearings over the winter months. I'll probably have Comp custom grind a cam for me that will match the application. They already recommended that I go this route, but I already had the cam installed, etc. so anyway, I'll be fixing that as well.

There are some pitfalls when lowering the horsepower potential of these stroker motors. As the horsepower comes down the torque seems to skyrocket. I don't think that the Alpha will like that, but hey... it's insured (and fairly new... it was evidently replaced about four years ago) and so far it has been fine.

Crane H-272-2
 

The Crane H-272-2 works very well in a high (static) compression (9.0:1 to 10.5:1) 383 small-block stroker marine engine. This cam bleeds off lots of cylinder pressure. Here is the cam card. Also, be sure to use the matching valve springs as well. One more thing that you should look at is to make sure that your quench clearance is 0.035" to 0.040". Everything else you have there should work fine.

Tom.. the part number for the SRP pistons are #183103, they are forged and have a dish of 16cc's ( i can't really remember) this part number is for .030" over. The part number will be diffrent for the oversize you have..

Traviss,

Thanks for the part number. If I decide to make the change, then I'll check them out. I've already been to the website.

ForrestC,

So that cam will really help me out? I looked at the cam card and the numbers look comparable to the Comp XM-262 that I ran in the motor that got trashed. Crane lists the cam as being usable over 10:1... I believe that Comp says not to go over something like 9.5:1 or so with their cam (I guess because of the incredible cylinder pressures).

Have you or anyone that you know used that cam in a marine small block?

Thanks!

Tom- in my 383, I used the same cam as Travis (119831).

I went from a stock Volvo 280 (350) to this 457HP 383 (460+ft/lbs). I truely believe that the hydraulic roller (with the steeper ramps) makes the difference. I went with the Edelbrock Performer RPM heads, with some porting & blending.

I am using TRW 10-1 forged pistons, 18/36 timing.

In my old, heavy (slug) boat, I went from spinning a 21" prop @ 4,400 RPMs, to a 23" prop @ 5,000 RPMs...

Tom,
What is the timing set at?
Have you checked the plugs? Does the engine run too lean?
What oct. fuel do you run?
GEOO

Timing right now is set at 31* with 7* initial. The engine sounds really pissed off at idle :D but performance is quite sluggish the way it is. A milder cam might solve some of this. The plugs were all OK except for one which was ever-so-slightly damaged at the tip of the ground strap. I had a problem with that particular cylinder where an intake valve tuliped. All of the plugs were a nice tan in color, even the damaged one. I run 93 octane from Mobil or Amoco (gas station fuel since I trailer it).

TomZ, I run the H-272-2 cam in all three 383 marine engine that I built and currently run (18 Donzi and 27 Magnum). Compression that these engines run is in the 9.3 to 9.5 to 1 range. I can run 89-octane in any of them and the total advance is 32- to 34-degrees BTC (10 to 12-degrees BTC initial and total in by 3500 rpm). Don't cam your marine engine like a drag car. You want to make sure that there is enough duration to reduce dynamic or running compression, and that the ramps are smooth enough so as to close the valves gently.

BTW TomZ, what is your current compression ratio? I think that must be verified before any "fix" recommdations can be made. If you know your combustion chamber volume, your piston manufacturer can provide you with the correct compression ratio.

The piston manufacturer claims that with this piston compression should be 10:1 with a 64cc head. The problem though is that Vortec heads actually 61cc when measured though GM claims them to be 64cc. My builder says that the calculated compression ratio with a .038 compressed gasket is 10.3:1. He claims that it should run OK on premium fuel. Obviously, that's wrong. Maybe it works OK in the auto world as the engine doesn't see continous load. I've heard it ping, though it was at a time when the gas was being recycled to freshen it up.

I never made it out of the past weekend to check it out like I wanted to. Maybe it's OK and live-able. The cylinder pressure is what bothers me the most and I'm afraid of really ruining something. Will that cam drop the cylinder pressure to somewhere a little more usable?

Thanks!

I checked the cc's on my vortecs and they came to 64cc.. right on the money..

Hey Tom,

Sorry to hear it's not working out. My .02:

You're close so stick with the 383. It should be a nice engine for the boat you've got, and the alpha will hold up fine if you take care of it.

It looks like all your design choices are oriented towards max performance. Start thinking reliability first performance second.

1. Change the pistons to get your compression down.
2. Change your cam to one of the Comp XM cams (or similar). I know you've worked over the heads so you might want to go roller cam to maximize hp.
3. Make sure your exhaust will support your choices above.

Now the only question is how much $$$$$$.

Open up the chambers?
 

Tom,
Just a thought here. Maybe you could take the heads to someone really sharp on airflow and convince them to grind out some of the combustion chamber and bring the volume up to 70 cc's or so. Who knows, it may even increase the flow of the heads by unshrouding the intake and exhaust valves. By now there must be some circle (automotive) track guys that know quite a bit about the Vortech combustion chambers. The first place I would check would be Brzezinski Racing @ wwwcastheads.com You could also check with Joe Mondello, he was interested in the Vortech heads and possibly a magazine article on them the last time I talked to him.
Sincerely
Dennis Moore
FAMILY AND PERFORMANCE BOATING MAGAZINE

Welcome Dennis. Tom and I built similar engines, except his is a 383 and mine are 409's, based on alot of the info that you give in your books. Thanks for the help.

Jeff