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Discussion Starter #1
I usually hang out in the v-drive boards but need some help for the family cruiser.....Here's the deal....I have a sweet 88 rcb 21' daycruiser with a 454 ho king cobra drive package. It is the cone clutch good one. The engine package was installed in 1994. My question is this....I can't seem to find in any of the manuals I have the hp specs. I need to know what compression these were out of the factory, along with cast or forged pistons. I can only get about 60 out of it and need more. It's spinning 5000 @ 60mph. I have tried a few different props anf the all seem to top out the same. I was going to put a roller cam set up new heads, intake and maybe nos if I have forged pistons.....I would really like to know the specs on the engine before I do anything.....

ANY INFO WOULD BE GREAT.....THANKS!!!!!!!!!!!!!!!!!
 

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E-7 Sheepdog (ret)
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Likely about an 8.3:1 motor, cast pistons, cast crank.

It was a factory crate motor after all.

I've been running Nitrous on cast pistons for 30 years.
The SAME cast pistons by the way. 1978 vintage. Apparently a very good year for factory cast slugs.

Just blew 150HP dose on them this past weekend @5,900RPM, 3 passes, about 10 secconds each teaching a TX a thing or 2.
 

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I usually hang out in the v-drive boards but need some help for the family cruiser.....Here's the deal....I have a sweet 88 rcb 21' daycruiser with a 454 ho king cobra drive package. It is the cone clutch good one. The engine package was installed in 1994. My question is this....I can't seem to find in any of the manuals I have the hp specs. I need to know what compression these were out of the factory, along with cast or forged pistons. I can only get about 60 out of it and need more. It's spinning 5000 @ 60mph. I have tried a few different props anf the all seem to top out the same. I was going to put a roller cam set up new heads, intake and maybe nos if I have forged pistons.....I would really like to know the specs on the engine before I do anything.....

ANY INFO WOULD BE GREAT.....THANKS!!!!!!!!!!!!!!!!!
707, Take the casting numbers off the deck of the block and go to motec.com and eliminate the geuss work you'll get around here. Motec will even tell you where to pull the numbers, AGAIN motec.com M
 

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707, Take the casting numbers off the deck of the block and go to motec.com and eliminate the geuss work you'll get around here. Motec will even tell you where to pull the numbers, AGAIN motec.com M
add an r (mortec.com) :D
 

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northern member
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no idea what omc used for these , or is it a replacement crate engine you have ? my guess.... if it came with rectangle port heads it would have a forged shortblock if it's got small oval ports it will have cast .
 

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Discussion Starter #7
I have tried all sources I could think of...I checked it on mortec weeks ago all it says is 90-91 mark 4 4bolt short deck......Thanks for the input :)
 

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I have tried all sources I could think of...I checked it on mortec weeks ago all it says is 90-91 mark 4 4bolt short deck......Thanks for the input :)
Pull the valve covers and check the head casting# this will give you an idea what you have.
 
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