502 crate

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.

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 850CFM..is 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 hurt..as 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 yet..in the boat u have with the jet and impeller..it should fly
if that motor is a tall deck..u need a manif that will match...good luck..keep us posted
Ron

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.

Ditto!.. :cool:

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.

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. :D 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.

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

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

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.

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.

love my 502. you might try and find a used set of the gm performance parts aluminum heads that come on the zz502. they work really well too.

mike.. i love your 502 aswell... :D that thing ran awsome. i never got to get too much info on what you got into it, though i do remember you saying your cam is pretty big. probably a little too much for me and what i want to do with the boat. i know it is not just the motor though. your set up works very well. i may be looking for a differant hull as i am leary about putting the 502 in the tahiti. even if i get half the HP from my 502 than what yours has i dont know that the tahiti will hold up. my building partner has a 78 rogers bonneville he bought new and has maybe 40 hours on it total. ive been trying to get him to part with it but he keeps giving me the runnaround. it would allmost be a shame to swap motors on that thing too though since its all original. 405HP 454. he even has pics of it as it was being built at rogers. took a few every time he stopped by to check on the progress. now thats cool to have. anyhow. as for the ZZ 502 heads you mentioned, that would be nice to find, but i have a feeling i will be running the edelbrocks. still havnt got in touch with my buddy that has the hook up. (wife had cancer but operated on 2 weeks ago and seems to be doing great). so i didnt want to push the issue. what chamber size did you use? the oval ports have 110 cc and would bring me to about 9.5 to 1 i think, but the rectangular heads have 118 cc chambers. keeps me at about 8.8 comp. as i remember figuring. its a tough call.

The heads used on the 502/502 are the same as the Edelbrock heads (Edelbrock makes them for GM with the GM logo). The camshaft is what makes that engine run, it is good for a marine engine and is a fairly mild grind.
Sincerely
Dennis Moore

thanks dennis. i did know that edelbrock made the heads for GM but not sure which ones they used. oval or rect. and i dont think the 502/502 heads are the marine version. but what do i know, i just swing a hammer. :p
the cam from a 502/502 would most likely satisfy me as im not looking to be the fastest, just want some good HP and a long lasting motor.
hey mike (cyclone) what did you do with your stock cam? wanna sell it? :D

Deffinately change the cam and oil pan. Other than that jam. Pistons and rings? No. Bearings? No. Heads? No. I like the Victors on these motors. Moreover I really like the 1200cfm tunnel ram fuel injected manifolds for these motors. Unless you have money to burn I wouldn`t buy new heads. If you just have to unbolt them,,,,well send them out for port work, mild chamber work and you`ll have the 502hp motor. :D

hey hoss.....
do you mean to run the stock heads on this motor, or the 502/502HP motor. mine is the truck retrofit 502. it has smaller valved heads. the bottom end is the same except for cam specs, but still roller. that will definatly be changed but would like to stay roller style. and yes i would have to agree with the porting. its amazing how much potential comes from a good port job. thats a givin on whichever heads ill run.

victor-dennis is correct about the heads being the same. I figured you might be able to save a few bucks since the gm heads dont say "edelbrock" on them. lol

yea, to be honest with yaz, i wouldnt give a rats butt which heads i ran. either one would be fine. heck i wouldnt care if they said "amc pacer" on em. the unfortunate thing is that i have the cast iron smaller valved heads. its not the 502/502 nor the 502 HO, its the 502 retro truck motor that is a legal swap for 90-92 454 tbi motors. the bottom end is the same as the 502's with higher HP except for the cam size. id even run these heads if i had to, just do some porting to em. but then the cam decision would be a total guess. if anyone out there has some GM 502 aluminium heads they want to get rid of, im all over it. but to buy em from GM would be alot more $$$ than what i can get the edelbrocks for.

victorfb:
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.
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?
I am waitin for a answer. What is the diffrence between "marine" motor and a "truck" or "car" motor.

Victorfb, I used the exact same motor. I went with the edelbrock heads 6045,and comp cams xr308hr 575 lift . I did switch the pan and head gaskets to a marine set up.
The motor needs alot of fuel. I ran a hp 950 on a tunnel ram and would suck the carb dry faster than the pump could fill it( hooley black pump). I left the stock fittings in the tank and a dual tank switch(gm came with the boat) and -6 lines big mistake. I switched to a cp performance mechanical switch a huge fuel filter and -8 lines. Problem solved.
The only other problems I had were the stock oil pump has 40 psi bypass so press. wouldnt make much over that even at wide open throttle. We shimmed up the spring for more press.
I have a gen 6 block The lifter bores are somewhat taller and the aftermarket lifters dont fit very well. The bar that attaches them deppending on the block has about .001/.002 clearance. The stock lifter set up is good until 5800 RPM.
If interested I am selling my Complete cam kit it has about 4 hours on everything . I want to switch to a solid lifter set up.Trying to get 700 HP out of it
You can determan the gen of block by looking at the timing cover. Gen 6 has only 6 bolts. Looks completly diff from a gen 4.Gen 5 is different also but I dont remember what exactly it looked like. Again its the cover.

Hey jstwkd, thanks for the info. i too am planning on the edelbrocks but im going with the marine version. (oval port) and the victor intake, with an 850 holley DP. i did allready acquire a cam "comp cam XR288HR-10" it doesnt have the lift as yours does. mines is 521/540. but its allready in my garage. just curious though, how much do you want for your cam kit?
about the oil presure, i know that you can get a higher bypass valve for the block. they are just little push in valves under the filter. im not sure if removing it entirely is an option or not. ill be researching that soon. were you saying there are more bypass valves in the oil pump aswell? will changing to a melling HV pump help this?
and if you remember, which head gaskets did you use?
hope you reach that 700HP man. thats gunna be awsome. sure would like to see that thing run. ever come down our way? colorado river?

Victor,
I'm looking for $800.00 For Cam,lifters,pushrods,springs,locks,and reatiners
I'm not sure the engine biulder upped the oil press. I think he just shimmed the pump. I wanted a new pump but he told me they have a good pump allready. Just to change the press.

You gotta love that 502, at least I do. I run the truck version in my 94' Dually. I run Edlebrock's street heads and stock cam with Edlebrock's MPI conversion and headers.
In my boat I chose the 502/502 shortblock with Edlebrock's Marine heads. Oval ports, Crane rockers and girdle. I changed out the stock 502HP cam with a slightly larger one from Crane. I use the RPM air gap intake with the 750 marine carb.
A word of caution, be sure to have a good machine shop check valve guide clearance on those heads!!! Quite a few problems with tight guide clearance have been not only posted here but we just experienced it on the new Rectangular port heads we installed on my son's jet boat.

thanks for the tip. are you talking about the edelbrock marine heads having the tight clearances?

Yes I am talking about the Marine heads. Also some people including Pace GM Performance say you should put a higher spring pressure bypass in the block due to using a remote oil filter set-up.
I bought one and was about to pull the engine back out to install it. First I checked my stock 454 Mercrusier block and found that they used the stock bypass springs so I decided to leave it alone. I just change filters more often.