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Thread: 502 crate

  1. #1
    Im looking for some input. heres the deal. the end of last year i swapped out the 454 for a 502 crate motor. (truck conversion 502, not 502/502hp)in my 91 duelly. i am now planning on buying a new truck so the 454 is going back in and the 502 will most likely go in the 74 tahiti 18' jet that still has the 390 HP 455 olds. (unless i find a nice hull that i can afford) the 502 has less than 5000 miles on it. i realize i need to replace the cam, and will most likely get a set of edelbrock marine heads, (anyone use them?) i can get a smokin deal. friend of a friend thing. a victor jr intake, and probably a 850 holley DP. and of course a 10 gt pan. id hate to disturb the factory torque on the bottom end but i know all you motor builders would kill me if i didnt freshin everything up. would i be pissin in the wind if i didnt re-ring and new bearing it?
    as for the edelbrock heads, which is more desireable, oval or rectangular? oval has 110 chambers that will bump me to about 9.5 to 1 comp. rec. has 118 chambers that keeps me at about 8.8 to 1 comp. what roller cam would you recommend? ive read on a motor building site about ordering your 502 with marine pistons and rings, what the heck does that mean? theres a differance?
    im not looking for the fastest baddest boat, OBVIOUSLY. just a nice dependable and strong motor that runs pump fuel. it will be mated to a berkeley JC-A pump with place diverter, that is still nice but will be gone through again at time of motor swap. i know this isnt the jet forum but does anyone know if the A impeller will be ok with this 502. id say it will come close to 500 HP. (or am i totally wrong)
    this is all going to be a winter project of course but i want to start researching everything now.
    any and all recommendations and input is highly appreciated.

  2. #2
    my 2 cents..dont under estimate what u already have..thats a very gd motor..alot of people are running the Edelbrock RPM manif..u might want to ck that out..Holley great..u might want to call some of the cam manufactors and talk to there tech rep's..i personally dont think u need a roller cam..a gd ign wont far as the bottom end goes..i would pull a couple main caps off and look at the bearings..then decide what u wanna do..remember the motor only has 5000 miles on it..not even broken in the boat u have with the jet and should fly
    if that motor is a tall deck..u need a manif that will match...good luck..keep us posted

  3. #3
    Heck, I'ed degrese it, put a lager pan on it and run it myself. See what it does and if you are not happy then maybe in the off season doctor it up a bit.

  4. #4

  5. #5
    Jungle Boy
    I know lots of guys that have 502's in there jetboats (the aluminum type of course), and they work great right out of the crate. The oil pan may be something that you want changed, as was mentioned, but soem do, some don't. I've never heard of any failing.

  6. #6
    thanks for all the responses so far. the RPM intakes are nice. ive run them on street machines. it will depend on what size cam i get on what intake i will run. though i just dig the way the victor jr looks. besides, its a cool name. the 502 came stock with a hyd. roller cam allready so i will want to stay with the roller style. just bigger to let this thing breath. and yes the ignition will all be upgraded aswell.
    if the baot allready was set up for the chevy i would do just that. run what i got and go from there. but i still have to get all the chevy mounts and stuff for the swap. i dont know too much about the tahiti's and somewhat concerned about doing too much and adding to much HP to it. it does not have full stringers, but there is a glassed in plywood floor. so to do full stringers i have to do alot of tearing apart and so on. are these hulls worth all the work and money? or should i look around for a better hull.

  7. #7
    Dennis Moore
    Use the specs for the 502/502 including the intake and camshaft. Don't bother with the bottom end. Neat motor that 502/502!
    Dennis Moore

  8. #8
    spectras only
    Hi Dennis, good to see you on the board again.You mentioned before that you see Bud Bailey occasionally.Would you mind asking him what prop ran best on top end of the 24 cruiser? I've got B/W 1:1 tranny ,champion V-drive with 4% underdrive, OJ 3 blade 14X14 cupped turning the LS-6 at 5300RPM. My holeshot is excellent and ready to give some of that up to a little more top end .Wonder if a 13X16 or 13X18 prop would suit my setup better. Thanks

  9. #9
    Senior Member
    Join Date
    Feb 2009
    I wouldn't put much more power to that Tahiti. The best way to describe the floor in Tahitis is the ply (not marine) set in resin, with a single layer of cloth overlapping the edge MAYBE 6 inches. Ever see UNDER the floor in a Tahiti? I would hope it's not the norm. I loved mine, and I would probably buy another, but some work definitely needs to be done to run big power.

  10. #10
    thanks roostwear. thats what im affriad of. i havnt seen the ply taken out of a tahiti yet and not sure i want to see under mine. after i bought the boat i ripped out all the carpet and found an amazing amount of red dirt in all the nooks and crannies. i cleaned it all out but obviously couldnt get whats under that ply. i do know that there are small holes from the motor well to under the ply were the water can enter and exit and it does exit so i dont think its too clogged up. but what it looks like under there is not known. i may just have to keep my eyes open for a good hull and go from there. i do like these CP hulls, but at $4000 for a used bare hull, thats a bit steap for me. looks like ill have to find a boat with a blown (damaged) motor that has all the rigging and mounting stuff. i really would like to use this 502 in a boat. but dont think the tahiti is gunna handle it.

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