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jetboataholic
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Discussion Starter #1
I'm thinking about putting a cam in my good ol' Chevy 427T, but I don't know what I'm doing when it comes to this. A little info about my boat. The enigine is a 427 truck block that has been bored out .060", I have Bassett OT headers that I run wet, an Edelbrock dual-plane intake manifold, Mallory Marine Point style dizzy, GM Hi-Perf oval port heads, Holley mechanical fuel pump, and a Holly 750 cfm HP series carb that was custom built for my engine. The pump is a Berkeley 12JC with an AB cut impeller and a Place Diverter.

I found this CompCams Xtreme Marine camshaft that says excellent for jet boats.

Hydraulic Flat Tappet
Grind 288, 244*/254* Duration, 570*/.575" Lift

Is this a good cam?:)Unsure I still want to be able to idle, not be too choppy (loppy?), and run water in my headers.

What would be the benefits of putting a new cam in my engine, like I said I'm clueless when it comes to this stuff, so school me please.

Thanks, you guys are the best!:D

:)hand
 

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HJ,
what heads are you running? Size valves? Compression Ratio?

Might help you decide on a cam.

Also it is good to talk to one of the Jet boat "gurus", they are more familiar with what works well in a jet than the cam manufacturer.

I talked to a jet "guru" and then plugged the info into the Desk Top Dyno program, trying all the different cams. I found the one recomended by the "guru" made better power than the ones the cam company called a jet boat cam.

Also I would suggest you upgrade your distributor to electronic ignition. Points are a pain in the butt and you can install a Pertronics set up for about the cost of two sets of points. More reliable, better spark control and you never have to replace them or set dwell. Of course an MSD would be a plus, but on a budget the Pertronix is an excellent option.

Doug
 

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jetboataholic
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2,798 Posts
Discussion Starter #3
HJ,
what heads are you running? Size valves? Compression Ratio?

Might help you decide on a cam.

Also it is good to talk to one of the Jet boat "gurus", they are more familiar with what works well in a jet than the cam manufacturer.

I talked to a jet "guru" and then plugged the info into the Desk Top Dyno program, trying all the different cams. I found the one recomended by the "guru" made better power than the ones the cam company called a jet boat cam.

Also I would suggest you upgrade your distributor to electronic ignition. Points are a pain in the butt and you can install a Pertronics set up for about the cost of two sets of points. More reliable, better spark control and you never have to replace them or set dwell. Of course an MSD would be a plus, but on a budget the Pertronix is an excellent option.

Doug
Unfortunately, I don't know a lot about the specifics of the engine because I bought it already assembled.

The heads are GM oval port iron heads that came with the long block I bought, along with the current cam that is in it, which I don't know anything about either. I assume that their both basically factory stock, but it is a marine block, so I don't know. I do know that it has flat top pistons in it, so that will bump the compression up a little bit, right? But that's all I know about them too.

Don't know if this will help, but the casting number on the heads is 14092359. When I ran the numbers, all it said was 86-90.....oval.....OPEN.....366T, 427T, Marked "HiPerf". The block number is 473478. When I ran it, all it said was 427T.....77-90.....4-bolt.

Don't know if this helps either, but here's a picture of the heads when I first got the engine, I have not changed anything about them.



Sorry I don't know much more about my setup. Maybe you guys can figure out more about them than I was able to.

Thanks.:D

:)hand
 

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Premium Member
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1,681 Posts
HJ,
I would hold off at this point in the season and run the boat as is. From the picture the springs have the stock shield around the springs so more then likely you have stock springs on this engine. Also you have the welded ball pushrods which are not condusive to hot rodding as the balls like to come off.

I would budget now and pull the heads off over the winter. Get them checked out and if the casting are in good shape put some bigger valves in them, bowl bend, and then re-cam along with some rockers and pushrods to build a better top end. At this point putting a cam in it without know details about the heads could lead to a "shortened '08" boating season.

Just my thoughts...
 

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jetboataholic
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2,798 Posts
Discussion Starter #5
HJ,
I would hold off at this point in the season and run the boat as is. From the picture the springs have the stock shield around the springs so more then likely you have stock springs on this engine. Also you have the welded ball pushrods which are not condusive to hot rodding as the balls like to come off.

I would budget now and pull the heads off over the winter. Get them checked out and if the casting are in good shape put some bigger valves in them, bowl bend, and then re-cam along with some rockers and pushrods to build a better top end. At this point putting a cam in it without know details about the heads could lead to a "shortened '08" boating season.

Just my thoughts...
Thanks. I think that that's probably what I'll do.

But, are these good heads to run with a hotter cam and stuff? Or would I need to get some better aftermarket heads down the road?

Thanks again.
 

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jetboataholic
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2,798 Posts
Discussion Starter #7
How much power do you want?
500-600 hp would be nice. 650 hp would be even better, but I think it's a little out of reach for right now.

Someday I'd like to step up to a 502, but that's years down the road, unless I hit the lottery or something.:D

Are Dart heads any good?

Thanks.
 

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500-600 hp would be nice. 650 hp would be even better, but I think it's a little out of reach for right now.

Someday I'd like to step up to a 502, but that's years down the road, unless I hit the lottery or something.:D

Are Dart heads any good?

Thanks.
HJ,
For that type of power you want CID. I would build a 496 out of your TD. With this type of CID and your heads the 600 mark is doable but would take a healthy cam and some compression to do so. The better route for longevity would be an aftermarket head on top of 496 CID.

You could over the winter put the cubes under those heads and have a good solid 500HP engine. Run it for a couple of years then add heads and camshaft.
 

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jetboataholic
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2,798 Posts
Discussion Starter #9
HJ,
For that type of power you want CID. I would build a 496 out of your TD. With this type of CID and your heads the 600 mark is doable but would take a healthy cam and some compression to do so. The better route for longevity would be an aftermarket head on top of 496 CID.

You could over the winter put the cubes under those heads and have a good solid 500HP engine. Run it for a couple of years then add heads and camshaft.
How reliable would the 496 be? I'd like to have more power, but still be very reliable and not have to worry about popping it, if I get on it a little too hard. I'm basically looking for "get in and go" horsepower, if this is possible.

While searching around on the JE website, I went looking for a 496 combo for a 10.180" deck block. But, I could not find one. The smallest cid that I was able to find was PN#131670 a 525 cid combo that uses: 4.310" bore, 4.500" stroke, 6.535" rod length, and 1.395" compression distance. Would this be an even better alternative to a 496? And again, what kind of reliability and longevity would I be looking at? Here's a link to that page.
JE PISTONS

And now on to heads, I found this Dart top end kit. Would this be a good set of heads and intake manifold for my engine? Here's the link.
DART IRON EAGLE TOP END KIT

Or would it be better to step up to the aluminum version? Here's that link.
DART PRO 1 ALUMINUM TOP END KIT

Or if I decide to go the aluminum route, spend the little extra money on the Brodix heads? Here's that link.
BRODIX BB-2 PLUS TOP END KIT

Thanks for all your help.:D

:)hand
 

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HJ,
By using the CID to make the power it is less stress on the engine combination as the large CID will make power at lower rpms. If your looking at no maintenance at all just jump in and go I would build a 500HP engine. Your looking at getting 200 to 300 hours out of the engine before any major check ups. If you looking for more power then a little maintenance is going to be neccessary so that you don't have any major catastrophys. 600 to 650 is doable but your looking at a good check up between 100 and 150 hours.

With a tall deck you have more options on rod lengths. What your looking at is the compression height of the piston. A 4.500" stroke in your block will require major clearancing and a stroker oil pan. A 496 with 4.250" is fine for what you want.

Going Dart or Merlin heads in iron for what you want will work. If you want aluminum heads you can go that route but for what your wanting to do not neccessary.
 

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Using a 4.250" stroke crank and a 6.535" rod you can use a piston with a CH of 1.520"
 

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jetboataholic
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2,798 Posts
Discussion Starter #12 (Edited)
HJ,
By using the CID to make the power it is less stress on the engine combination as the large CID will make power at lower rpms. If your looking at no maintenance at all just jump in and go I would build a 500HP engine. Your looking at getting 200 to 300 hours out of the engine before any major check ups. If you looking for more power then a little maintenance is going to be neccessary so that you don't have any major catastrophys. 600 to 650 is doable but your looking at a good check up between 100 and 150 hours.

With a tall deck you have more options on rod lengths. What your looking at is the compression height of the piston. A 4.500" stroke in your block will require major clearancing and a stroker oil pan. A 496 with 4.250" is fine for what you want.

Going Dart or Merlin heads in iron for what you want will work. If you want aluminum heads you can go that route but for what your wanting to do not neccessary.
A little maintenance is ok and going through it would be alright too, I just don't want it to come apart on me. Basically, I want longevity. A check up once a year would be just fine with me, it only costs a gasket kit and oil, as long as nothing serious has happened.:D

So, for a 496 cid, I could use a 4.250" stroke crank, 6.385" rods, and pistons with a compression distance of 1.670", correct?

Thanks again.:D

:)hand

Using a 4.250" stroke crank and a 6.535" rod you can use a piston with a CH of 1.520"
Sorry I wrote my other post before you typed this one, I am experiencing internet problems so I was just now able to submit it.


Which is better, longer rod or taller Compression Height?

Thanks.:D

:)hand
 

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E-7 Sheepdog (ret)
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6,834 Posts
Straub is working good advice and info for ya HJ. Good luck with the upgrades.
 

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jetboataholic
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Discussion Starter #14
Straub is working good advice and info for ya HJ. Good luck with the upgrades.
Yeah, he's the best!:)devil

Not in any hurry right now, I just got bored and started planning my winter upgrades, in the middle of summer.:D
 

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jetboataholic
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2,798 Posts
Discussion Starter #16
So how does your 427 run.
If I knew that, I wouldn't be bored.;) I would have been out on the water today because I had the day off, along with tomorrow. Unfortunately, everything about this boat likes to fight me. Apparently, it likes being in pieces.:mad: But, it's close if I can get the wiring buttoned up, it should be on the water next week, assuming it even floats.:)sphss

I just know that I will get bored with it quick cause I have a very heavy lead foot, so I'm trying to plan ahead so that I know how much money I need to set aside to go faster.:D

Thanks guys.:D

:)hand
 

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For your first forray into performance upgrades I'd also wait till after the season, however, I'd take small bites into the performance world before you take one big bite. Especially if your budget is how you say it is.

You should pull the heads so you can give to a performance machine shop to install the springs and such you'll need for the cam swap.

Before you buy stuff and giive heads to them, we need to take a look at the pistons. Look up a part# if they are stamped or measure dome or dish volume if they don't have part#. Also, need to measure how far under the deck they may be. Then, we can figure out your compression ratio and then help pick a cam for you.

There's a good chance your motor presently has a lame cam since your springs have oil shields on them. A change to a modern performance cam will put a grin on your face and get you down and dirty enough to learn something all performance enthusiasts should learn how to do - change the cam and see/understand what else needs to be done for this swap.

Large ovals with stock valves will still make a bunch of power. Not the hp you state above you want (don't we all want that same #) but a bunch more none of the less and will give you more fun and more knowledge before you save and learn to build your 600hp goal.

My 02. I don't know you and don't really know exactly what you can afford and what your real expectations are. I know / see what you stated, but tons of people state the same thing 'just because.' Thus why I mentioned what I did - just in case you said those hp figures 'just because.'

===========================
BTW: if your on a super tight budget, why not just follow Smokin Lowriders's lead ?
 

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jetboataholic
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2,798 Posts
Discussion Starter #18
For your first forray into performance upgrades I'd also wait till after the season, however, I'd take small bites into the performance world before you take one big bite. Especially if your budget is how you say it is.

You should pull the heads so you can give to a performance machine shop to install the springs and such you'll need for the cam swap.

Before you buy stuff and giive heads to them, we need to take a look at the pistons. Look up a part# if they are stamped or measure dome or dish volume if they don't have part#. Also, need to measure how far under the deck they may be. Then, we can figure out your compression ratio and then help pick a cam for you.

There's a good chance your motor presently has a lame cam since your springs have oil shields on them. A change to a modern performance cam will put a grin on your face and get you down and dirty enough to learn something all performance enthusiasts should learn how to do - change the cam and see/understand what else needs to be done for this swap.

Large ovals with stock valves will still make a bunch of power. Not the hp you state above you want (don't we all want that same #) but a bunch more none of the less and will give you more fun and more knowledge before you save and learn to build your 600hp goal.

My 02. I don't know you and don't really know exactly what you can afford and what your real expectations are. I know / see what you stated, but tons of people state the same thing 'just because.' Thus why I mentioned what I did - just in case you said those hp figures 'just because.'

===========================
BTW: if your on a super tight budget, why not just follow Smokin Lowriders's lead ?
Good information in there! Thanks cfm!:D

Those hp numbers are my ultimate goal. I want to slowly build the motor up over several winters, and be able to run it during the spring/summer boating season. I know a really good engine builder here in town, so when I go to make major modifications, it will be going to a professional.;) Trust, I'm not going to try to attempt this on my own.

Thanks again to everyone who has responded.:D

:)hand
 

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Sorry I wrote my other post before you typed this one, I am experiencing internet problems so I was just now able to submit it.


Which is better, longer rod or taller Compression Height?

Thanks.:D

:)hand
I'm looking at "shelf parts" which will be easier on the budget. The 4.250" and the 6.535" rod will allow you to run a shelf stock piston.

You mention a local machine shop, if you are speaking of Steve Estes he is real good. Also Smith Automotive out around Frankfort/Lawerenceburg is also very good.
 

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jetboataholic
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2,798 Posts
Discussion Starter #20 (Edited)
I'm looking at "shelf parts" which will be easier on the budget. The 4.250" and the 6.535" rod will allow you to run a shelf stock piston.

You mention a local machine shop, if you are speaking of Steve Estes he is real good. Also Smith Automotive out around Frankfort/Lawerenceburg is also very good.
Ok, thanks.:)

The guys I know are at Robert's Precision Machine (RPM).:D It's a small operation, 2 guys. I know both of them really well, I worked with Roberts only employee when he worked at the machine shop that I worked at, for awhile. Robert is a Chevy guy and Keith is a hardcore Ford guy. But they can build anything, for awhile they were building 1500 and 1700 horsepower twin turbo Nissan VQ engines. Those were bad ass engines.:)devil

Chris, do you have any family in Lexington? I went to school with a Straub, can't remember his first name right off, but I remember he was a real big kid with red hair and freckles, but he was a big football lineman.

:)hand
 
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