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Discussion Starter #1 (Edited)
I have a std bore 454 short block from gm, I got it second hand from another boat. 30 cc dome pistons (gm 3963550), mismatched but both rectangle port closed chamber heads. Machine shop says the cylinder walls will clean up with only a hone and cross hatch. Over transom headers currently, could move to through transom headers someday. I believe this to basically be a ls6 "clone"?


I am running a jacuzzi wj with a B impeller, which is as I understand similar to berk A impy.




I have a set of retrofit hydr. roller lifters (crane), but no cam to match. The current cam is a solid flat tappet that came in the motor from gm I believe. I am very interested in putting a roller cam in this motor, not looking to go 100 mph or anything, just a good match to the motor and pump combo. Need 3100 to 3800 for sure inside the power band, that is about what we ski at. Boat is a 18 ft, medium to heavy layup.
 

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I have a std bore 454 short block from gm, I got it second hand from another boat. 30 cc dome pistons (gm 3963550), mismatched but both rectangle port closed chamber heads. Machine shop says the cylinder walls will clean up with only a bore and cross hatch. Over transom headers currently, could move to through transom headers someday. I believe this to basically be a ls6 "clone"?


I am running a jacuzzi wj with a B impeller, which is as I understand similar to berk A impy.




I have a set of retrofit hydr. roller lifters (crane), but no cam to match. The current cam is a solid flat tappet that came in the motor from gm I believe. I am very interested in putting a roller cam in this motor, not looking to go 100 mph or anything, just a good match to the motor and pump combo. Need 3100 to 3800 for sure inside the power band, that is about what we ski at. Boat is a 18 ft, medium to heavy layup.
I think you meant clean up with a hone? Anything will clean up with a bore. With the exception of maybe a crack... :)eh:)

I am probably going to pounded into the mud face first here, but I am a fan of the Comp Cams Xtreme Marine XM270HR for applications such as yours. 11-445-8 - Xtreme Marineâ„¢ Retro-Fit Hydraulic Roller Camshafts


As for the 3100-3800, not really, you should build a jet boat motor to achieve the desired WOT RPM within a given pump set up, the load on a jet pump is linear, so it takes less power the slower it spins..

Hope this helps...

Good luck
 

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I have a std bore 454 short block from gm, I got it second hand from another boat. 30 cc dome pistons (gm 3963550), mismatched but both rectangle port closed chamber heads. Machine shop says the cylinder walls will clean up with only a bore and cross hatch. Over transom headers currently, could move to through transom headers someday. I believe this to basically be a ls6 "clone"?


I am running a jacuzzi wj with a B impeller, which is as I understand similar to berk A impy.




I have a set of retrofit hydr. roller lifters (crane), but no cam to match. The current cam is a solid flat tappet that came in the motor from gm I believe. I am very interested in putting a roller cam in this motor, not looking to go 100 mph or anything, just a good match to the motor and pump combo. Need 3100 to 3800 for sure inside the power band, that is about what we ski at. Boat is a 18 ft, medium to heavy layup.
30cc dome with closed chamber heads isn't a pump gas engine in a jet boat, in case that is what you are thinking? Depending on chamber volume, you could even be 13-1
 

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30cc dome with closed chamber heads isn't a pump gas engine in a jet boat, in case that is what you are thinking? Depending on chamber volume, you could even be 13-1

Never thought that high, was thinking 11.25 at the highest, he is in New Mexico, altitude?

Just random thoughts.. :indifferent0001:
 

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Never thought that high, was thinking 11.25 at the highest, he is in New Mexico, altitude?

Just random thoughts.. :indifferent0001:
I did some quick calculations, bunch of different closed chamber sizes, 98cc with zero deck is about 13.34-1. With 118cc open chamber, around 10.5.

Earlier this year I rebuild an engine that a shop had built for a guy, stated on invoice 9.6-1. I looked at the heads, did some calculation, it was around 12-1 or so, and melted some pistons after very few hours.
 

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I did some quick calculations, bunch of different closed chamber sizes, 98cc with zero deck is about 13.34-1. With 118cc open chamber, around 10.5.

Earlier this year I rebuild an engine that a shop had built for a guy, stated on invoice 9.6-1. I looked at the heads, did some calculation, it was around 12-1 or so, and melted some pistons after very few hours.


So this thing outta get it for a little while....:bananadance:
 

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Pistons are oem ls6 with closed chamber heads. 11-11.25-1...Don't know how well they will work in a jet but in a v-drive they are fine.I run a .020 head gasket on 91 octane without any problems. CC the heads might be a good idea, mine are 107cc and 109cc.
 

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Pistons are oem ls6 with closed chamber heads. 11-11.25-1...Don't know how well they will work in a jet but in a v-drive they are fine.I run a .020 head gasket on 91 octane without any problems. CC the heads might be a good idea, mine are 107cc and 109cc.
You may want to recalculate the compression again. It the chamber is any smaller than 109, and the piston is anything higher in the hole that .020, the compression is little closer to 12 to 1.



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Discussion Starter #9
I think you meant clean up with a hone? Anything will clean up with a bore. With the exception of maybe a crack... :)eh:)

I am probably going to pounded into the mud face first here, but I am a fan of the Comp Cams Xtreme Marine XM270HR for applications such as yours. 11-445-8 - Xtreme Marineâ„¢ Retro-Fit Hydraulic Roller Camshafts


As for the 3100-3800, not really, you should build a jet boat motor to achieve the desired WOT RPM within a given pump set up, the load on a jet pump is linear, so it takes less power the slower it spins..

Hope this helps...

Good luck
yes, I meant hone, sorry. Corrected in orig post.

So, the cam selection won't matter as far as lower rpm "cruising"? What about coming off idle and slowly climbing rpm for inexperienced skiers? I personally like being pulled out pretty hard, but others need to be pulled out slower. Will cam selection effect the ability to do this?
 

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yes, I meant hone, sorry. Corrected in orig post.

So, the cam selection won't matter as far as lower rpm "cruising"? What about coming off idle and slowly climbing rpm for inexperienced skiers? I personally like being pulled out pretty hard, but others need to be pulled out slower. Will cam selection effect the ability to do this?

That is probably the one unique feature of a jet, at low engine speeds you can really ease into them from a dead start, the torque required to increase pump speed is LINEAR, you don't have to "pull the stump" so to speak.

I can assure you that it wont be an issue unless you go turbo LMAO, the lag will come into play and you may have issues.

You will be able to drive it down to the point where it simply falls off plane.

I learned to ski as a little kid behind my Dads Glencoe with an Olds and my sister learned to ski behind his 18' Renegade with a crazy Bassett headered 427 Chevy.
 

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Discussion Starter #11
That is probably the one unique feature of a jet, at low engine speeds you can really ease into them from a dead start, the torque required to increase pump speed is LINEAR, you don't have to "pull the stump" so to speak.

I can assure you that it wont be an issue unless you go turbo LMAO, the lag will come into play and you may have issues.

You will be able to drive it down to the point where it simply falls off plane.

I learned to ski as a little kid behind my Dads Glencoe with an Olds and my sister learned to ski behind his 18' Renegade with a crazy Bassett headered 427 Chevy.
Cool, makes sense, loads itself with more water the higher the rpm.
 

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Discussion Starter #12
Never thought that high, was thinking 11.25 at the highest, he is in New Mexico, altitude?

Just random thoughts.. :indifferent0001:
Altitude is around 4200 ft
 

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really should get the heads cc'd after there done . if you've got 396 or 427 heads or if they've been cut for comp. you could have close to 12:1 like has been said . in which case you would be in trouble with pump gas with a cam as small as the the xm 270hr . if you've got LS6 heads that haven't had more than a 010 or .015" resurface the valves seats have prolly been sunk enuff that your under 11:1 . should make a nice ski-boat engine :))THumbsUp
 
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