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Some guys never learn.
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Discussion Starter #1
So I'm kicking around the idea of doing some motor work this winter. Either a valve job with a cam upgrade or a full rebuild.

Here's what I have. 1981 Eliminator V-drive cruiser. Engine is a Harman Marine 405hp 454 that has never had the heads off to my knowledge. It has rectangle port heads, RPM air gap manifold, MSD dist with 6-AL box. I believe but am not sure that it is a 4 bolt block with a forged crank and rods. Also I believe the cam is an Isky marine cam.

I currently run 60mph at 5000 rpm and thats all she goes. At 5000 rpm I start to hear noises that make me feel nervous about my valve train. I have broke rockers and pushrods when I first bought the boat but I believe the valves were not adjusted correctly. It has now seen 3 summers of abuse with no real problems. But I've got to think the valve springs are tired and it's ready for at least a valve job after 27 years.

Important fact: I am on a budget.

What I hope to accompish is a little more HP maybe 450 and around 5500 rpm wide open.

I do want to go with a hydraulic roller cam and my first question is looking for cam recomendations. I was looking at the Comp Cams Extreme Marine kit with springs, lifters, timing chain etc. There is just so many cams to choose from.

Also I was looking around on Ebay and I noticed few choices in roller rockers and lifters at good prices. Are steel roller rockers OK for my application. Should never see 6000 rpm.

Last time I checked my compression I was 145 to 155 in all cylinders. Squirting oil in the cylinders did not raise the compression at all. I am going to check it again before digging in but if it's the same I'm considering pulling the heads and seeing what the cylinders look like and how much ridge there is. If it looks good can I get away with just a valve job? Or am I asking for trouble not doing the whole motor.

Interested in all opinions.

Thanks

Gary
 

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steelcomp was here
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26,512 Posts
What are you running for exhaust?
If you're thinking of a valve job, then you might as well go through the bottom end. New top end, especially with a cam upgrade will put "new" cyl pressure on tired rings, and they'll let you know it. The old "can of worms".
Hyd roller cams aren't cheap, either, by the time you buy the cam, lifters, and springs. My guess is if you freshened up the engine, qualaity valve job, flat hyd. cam, adn maybe an intake/carb/exhaust upgrade, you'd have more than your 50hp you're looking for. If cyl/piston wear is at a min., you're only talking rings and bearings...no hard parts. Valve job, springs, cam and lifters. A set of inexpensive aluminum roller rockers would do wonders.

Edited to add: Will 50 more hp give you 500 more rpm?
 

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Cantard
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5,017 Posts
You didnt mention your carb. I am with Steel on the dont just do the top thing. Probably skim a little of the heads. In my experiance hyd rollers are not that great in the 6000 + rpm range but if you stay under 6000 should be fine. Maybe sell your intake and pick up something like a victor and a hyd flat cam?
 

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Some guys never learn.
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658 Posts
Discussion Starter #4
What are you running for exhaust?
If you're thinking of a valve job, then you might as well go through the bottom end. New top end, especially with a cam upgrade will put "new" cyl pressure on tired rings, and they'll let you know it. The old "can of worms".
Hyd roller cams aren't cheap, either, by the time you buy the cam, lifters, and springs. My guess is if you freshened up the engine, qualaity valve job, flat hyd. cam, adn maybe an intake/carb/exhaust upgrade, you'd have more than your 50hp you're looking for. If cyl/piston wear is at a min., you're only talking rings and bearings...no hard parts. Valve job, springs, cam and lifters. A set of inexpensive aluminum roller rockers would do wonders.

Edited to add: Will 50 more hp give you 500 more rpm?
The exhaust is aluminum logs. I'm stuck with those because they fit in my motor box. The intake is an RPM Airgap which I think is agood manifold for the rpm range I'm in. I currently am running a Holley 750 vacuum secondary that works great. If I end up needing bigger I have an 850 in a box that I can rebuild.

Not sure if 50 HP will give me 500 rpm more. Tha's just my wish list here.

Gonna be asking a lot of questions because the last time I got this deep into a motor was 32 years ago.

I know the roller cams are pricey but I hear to many stories about new cams going flat. After 27 years I'm pretty sure I need new valve springs anyway. I think the boat may have sat several years in a storage yard at one point.

Thanks for the input.
 

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It's what we do
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723 Posts
Just a little info. The Eliminator 21 cruiser has a radiused keel (the 1970's did and I believe the early 80's did too) and is harder to pick up speed above 60 mph than a true vee bottom. It will take a lot more than 50 HP to pick up 500 rpm's. Not saying it's not worth doing, just be realistic of the gains you expect.
It may not be in the budget, but I agree if you can, do the bottom end too.
 

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Registered
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2,426 Posts
Just a little info. The Eliminator 21 cruiser has a radiused keel (the 1970's did and I believe the early 80's did too) and is harder to pick up speed above 60 mph than a true vee bottom. It will take a lot more than 50 HP to pick up 500 rpm's. Not saying it's not worth doing, just be realistic of the gains you expect.
It may not be in the budget, but I agree if you can, do the bottom end too.
Reed Cams in Peachtree Georgia, give them the application and they will custom grind a cam, They are very reasonable and everything I have bought from them always worked better than an off the shelf........... You can do a home eng warm up, chances are your block won't have much of a ridge, I would recommend new cam bearings if you have it down, send your crank out have it checked and polished, if it is under have it turned, main and rod clearence critical.................. You can probably hone the thing yourself.............. usually about 50 bucks around here to have it stress honed................ Buy the whole hydraulic flat tappet cam kit with valve springs and have your machine shop guy set the spring height as recommended so they don't coil bind, Also, I personally would pop for all new stainless valves, it only hurts fo a little while and they are worth it.................... DON't buy a cheap set of roller rockers, buy the cranes or harland sharps............ I have seen some offbrand cheap rollers fall apart.............. Then you are wrenching instead of boating......... May The Force Be With You!!!!!
 

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Distinguished Member
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5,771 Posts
So I'm kicking around the idea of doing some motor work this winter. Either a valve job with a cam upgrade or a full rebuild.

Here's what I have. 1981 Eliminator V-drive cruiser. Engine is a Harman Marine 405hp 454 that has never had the heads off to my knowledge. It has rectangle port heads, RPM air gap manifold, MSD dist with 6-AL box. I believe but am not sure that it is a 4 bolt block with a forged crank and rods. Also I believe the cam is an Isky marine cam.

I currently run 60mph at 5000 rpm and thats all she goes. At 5000 rpm I start to hear noises that make me feel nervous about my valve train. I have broke rockers and pushrods when I first bought the boat but I believe the valves were not adjusted correctly. It has now seen 3 summers of abuse with no real problems. But I've got to think the valve springs are tired and it's ready for at least a valve job after 27 years.

Important fact: I am on a budget.

What I hope to accompish is a little more HP maybe 450 and around 5500 rpm wide open.

I do want to go with a hydraulic roller cam and my first question is looking for cam recomendations. I was looking at the Comp Cams Extreme Marine kit with springs, lifters, timing chain etc. There is just so many cams to choose from.

Also I was looking around on Ebay and I noticed few choices in roller rockers and lifters at good prices. Are steel roller rockers OK for my application. Should never see 6000 rpm.

Last time I checked my compression I was 145 to 155 in all cylinders. Squirting oil in the cylinders did not raise the compression at all. I am going to check it again before digging in but if it's the same I'm considering pulling the heads and seeing what the cylinders look like and how much ridge there is. If it looks good can I get away with just a valve job? Or am I asking for trouble not doing the whole motor.

Interested in all opinions.

Thanks

Gary
Gary,
Since you are on a budget, the first thing I'd suggest is a quality rebuild. Check everything and see what you need. Wouldn't be surprised after 27 years if it needed bored, pistons and such. After you figure costs for a nice rebuild, then consider how much budget is left over for upgrade. Once you've got that figured out, then you can start looking at upgrades. Focus on making sure your valve train is upgraded enough for the RPM you want to run. IMHO roller rockers are mandatory for any performance marine applications. You don't necessarily need the heavy duty race stuff we run, but you should include them as part of the build.
I'm in Pleasanton and would be happy to help any way I can. PM me if you want to discuss.
 

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Some guys never learn.
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658 Posts
Discussion Starter #8
Just a little info. The Eliminator 21 cruiser has a radiused keel (the 1970's did and I believe the early 80's did too) and is harder to pick up speed above 60 mph than a true vee bottom. It will take a lot more than 50 HP to pick up 500 rpm's. Not saying it's not worth doing, just be realistic of the gains you expect.
It may not be in the budget, but I agree if you can, do the bottom end too.
I'm very familiar with the issues wit the bottom of this boat. There is a long thread in the V-drive section about right now. It was also discussed on Hotboat about a year ago.
 

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Some guys never learn.
Joined
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658 Posts
Discussion Starter #9
Just a little info. The Eliminator 21 cruiser has a radiused keel (the 1970's did and I believe the early 80's did too) and is harder to pick up speed above 60 mph than a true vee bottom. It will take a lot more than 50 HP to pick up 500 rpm's. Not saying it's not worth doing, just be realistic of the gains you expect.
It may not be in the budget, but I agree if you can, do the bottom end too.
This also part of the reason for the budget rebuild. I know that there are limitations to this hull. But I've got it now and basically like the boat. At least until I can afford to go shopping for a Hallett 210.
 

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Premium Member
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So I'm kicking around the idea of doing some motor work this winter. Either a valve job with a cam upgrade or a full rebuild.

Here's what I have. 1981 Eliminator V-drive cruiser. Engine is a Harman Marine 405hp 454 that has never had the heads off to my knowledge. It has rectangle port heads, RPM air gap manifold, MSD dist with 6-AL box. I believe but am not sure that it is a 4 bolt block with a forged crank and rods. Also I believe the cam is an Isky marine cam.

I currently run 60mph at 5000 rpm and thats all she goes. At 5000 rpm I start to hear noises that make me feel nervous about my valve train. I have broke rockers and pushrods when I first bought the boat but I believe the valves were not adjusted correctly. It has now seen 3 summers of abuse with no real problems. But I've got to think the valve springs are tired and it's ready for at least a valve job after 27 years.

Important fact: I am on a budget.

What I hope to accompish is a little more HP maybe 450 and around 5500 rpm wide open.

I do want to go with a hydraulic roller cam and my first question is looking for cam recomendations. I was looking at the Comp Cams Extreme Marine kit with springs, lifters, timing chain etc. There is just so many cams to choose from.

Also I was looking around on Ebay and I noticed few choices in roller rockers and lifters at good prices. Are steel roller rockers OK for my application. Should never see 6000 rpm.

Last time I checked my compression I was 145 to 155 in all cylinders. Squirting oil in the cylinders did not raise the compression at all. I am going to check it again before digging in but if it's the same I'm considering pulling the heads and seeing what the cylinders look like and how much ridge there is. If it looks good can I get away with just a valve job? Or am I asking for trouble not doing the whole motor.

Interested in all opinions.

Thanks

Gary
What is the budget? You've got a great platform for a budget build 489 CID with the heads you have and block. More bang for the buck maybe would be to go hyd flat tappet with good lifters and put crank and pistons in the bottom end and reuse your rods out of th engine. Give you close to 500 CID and some more "umph" to push the boat.
 

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Some guys never learn.
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Discussion Starter #12
What is the budget? You've got a great platform for a budget build 489 CID with the heads you have and block. More bang for the buck maybe would be to go hyd flat tappet with good lifters and put crank and pistons in the bottom end and reuse your rods out of th engine. Give you close to 500 CID and some more "umph" to push the boat.
I would like to keep the project under $2K if I can. I hope to have a pretty good Idea what I'm going to be spending before I break out the tools.

I kind of like the idea of more cubic inches but dismissed the idea because of the cost of a new crank. What crank do you recomend? The forged ones look pricey. Will I be OK with a cast one?
 

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Some guys never learn.
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Discussion Starter #13
Gary,
Since you are on a budget, the first thing I'd suggest is a quality rebuild. Check everything and see what you need. Wouldn't be surprised after 27 years if it needed bored, pistons and such. After you figure costs for a nice rebuild, then consider how much budget is left over for upgrade. Once you've got that figured out, then you can start looking at upgrades. Focus on making sure your valve train is upgraded enough for the RPM you want to run. IMHO roller rockers are mandatory for any performance marine applications. You don't necessarily need the heavy duty race stuff we run, but you should include them as part of the build.
I'm in Pleasanton and would be happy to help any way I can. PM me if you want to discuss.
Thanks for the offer David. Will be PMing you soon.
 

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Some guys never learn.
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658 Posts
Discussion Starter #14
So I'm getting the impression that most people here think that money could be better spent than on roller lifters and cam.

On the other hand roller rockers are a must.
 

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Distinguished Member
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So I'm getting the impression that most people here think that money could be better spent than on roller lifters and cam.

On the other hand roller rockers are a must.
+1 :) :)devil
 

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The exhaust is aluminum logs. I'm stuck with those because they fit in my motor box.
Are you one million % sure you are stuck with these ? I'd spend more time investigating this since this is probably your biggest bottleneck to not only more power, but power your motor should be making now but isn't.

A rainstorm upriver of a dam already over full capacity doesn't usually end with a good story.
 

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jetboataholic
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Are you one million % sure you are stuck with these ? I'd spend more time investigating this since this is probably your biggest bottleneck to not only more power, but power your motor should be making now but isn't.

A rainstorm upriver of a dam already over full capacity doesn't usually end with a good story.
With the budget he's on, he's stuck with them. Have you looked at the prices on water jacketed TT headers lately? Just that one item will blow his entire budget, plus some.;)

:)hand
 

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Some guys never learn.
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658 Posts
Discussion Starter #18
Are you one million % sure you are stuck with these ? I'd spend more time investigating this since this is probably your biggest bottleneck to not only more power, but power your motor should be making now but isn't.

A rainstorm upriver of a dam already over full capacity doesn't usually end with a good story.
I fully agree. But as HawaiianJet pointed out marine exhaust upgrades are pricey. And I would have to build a new motor box and get it upholstered. Also it's an easy bolt on for next year if I got really stoked about the boat after the rebuild.
 

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On that budget I would recommend refreshing the engine and upgrading to a roller cam. I have logs n snails right now and an RPM air gap manifold and still have quite a bit of power (this is in a jet)
 

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With the budget he's on, he's stuck with them. Have you looked at the prices on water jacketed TT headers lately? Just that one item will blow his entire budget, plus some.;)

:)hand
I did.
And i still feel investigating it is a good avenue. Investigating does not mean 'go buy a new $2000 set'. It means, take a look at used prices, new prices, all different styles, what it would take to install, and how meaningful others engine mods will be with keeping the snails.

Basically, think it out. That's all.

Investigate = explore all your options.

BTW: I'm from the Offshore world where we deal with these big $$$ exhausts all the time. Sometimes you can get low hr good systems for halfway cheap money. 1st set I bought I paid $1800. Another set I bought was $600. One new, one was used 1 season.

Other suggestions where:
Roller cam upgrade will be $1k +
Stroker kit will be $1500 for cheap azz kit / $2k for decent kit / $2500+ for much better kit.

If it's a really cheap budget, then rebuild with a slightly better cam and a better intake if there is one.
 
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