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big block swap

jazzy

jazzy

Well-known member
Hey guys, i corked my motor last fall and am getting ready to rip it out this weekend. Ive got a few quotes from machine shops for rebuild/performance options and then i went online to look at prices for motors. Surprisingly you can buy a better motor aka a 502 for cheaper or the same price as it would cost to take a 330 454 up to similar horsepower. What changes need to be made to accept a different block. i have a bravo 1. I also would assume that i would have to find different exhaust manifolds due to different ported heads but im curious what else i would need thanks :popcorn:
 
how much you looking to spend and what HP range you looking to obtain?
look for a take out 502 if nothing else. you would need heads, intake, carb, valve covers (maybe).....many other little things, but all the access on the front will/should bolt up.
Id sell my 502 500ish HP for the right price i guess. long way away though!
 
i found a 502 right about 500 hp fresh rebuild if you really want to make a deal pm me im trying to figure out what else i have buy on top of the motor i know carb cause mine isnt big enough and either headers or manifolds cause the heads are different but what else, does the different block just bolt up or do i need different motor mounts
 
Your manifolds will bolt up to any bbc except 496 or some really expensive heads, 502 is a much better choice, the upgrades on motor size is much better and if you buy a gen 6 it is already a roller motor zz 502 requires a cam swap or it will suck water back into the engine. 500 hp in that boat will do 75 allday long
 
yep, mine was running 73-74 pretty well. mine started as a zz502, it needs a cam swap, just the wrong one in there. otherwise, you would do what i did and bolt on the access on the front and run it! i have carb to pan, nice build too. i will pm
 
oh yeah, give up some details of what you found, we can all give some input! your carb and intake wont cut it. motor mounts, flywheel, bell housing etc will all work, you will want to change up the ignition system too. yours should have a rev limiter on it at 4600ish..... you can still run the thunderbolt 4 ignition with an hp20 or hpv8 module and itll run well.
convincor242 had his flyin!
 
502 longblock with carb approx 500 hp just emailed for full details wasnt gonna bother till i knew it would work easily
 
I always get a kick out of these terms.

similar horsepower.
approx 500 hp
about 500 hp fresh rebuild
up to similar horsepower.
500ish HP
 
convincor242 said:
Your manifolds will bolt up to any bbc except 496 or some really expensive heads, 502 is a much better choice, the upgrades on motor size is much better and if you buy a gen 6 it is already a roller motor zz 502 requires a cam swap or it will suck water back into the engine. 500 hp in that boat will do 75 allday long
Click to expand...

I disagree 100% with you on this the. I ran the zz 502 cam and never had reversion problems at all. I also know a guy that has a Checkmate that is also running the zz572 620hp gm engine and has no reversion on that cam either. He also has another mate with a different build and is using the zz572 cam in that one to with no reversion.

Both engines are running wet exhaust not dry
 
so why would you have to change a cam out of a mercruiser motor or are you guys talking about buying a crate motor from chevy
 
jazzy said:
so why would you have to change a cam out of a mercruiser motor or are you guys talking about buying a crate motor from chevy
Click to expand...

The zz engine is a gm crate engine not a merc, and a cam change is not necessary in those two engines. The cam in those engines are good cams and build a lot of torque.
 
I know I'm a bit off topic, sorry but I'm trying to learn.
If you buy a GM crate engine even if it's a zzHipo or heavy duty service unit, don't you still need to do a few things to prepare it for marine service? Head gaskets, frost plugs, other? Just asking cause I will need to replace my small block one day and if GM crate engines are an option that's helpful as I am a long ways from the marine engine builders.
 
karzrus said:
I know I'm a bit off topic, sorry but I'm trying to learn.
If you buy a GM crate engine even if it's a zzHipo or heavy duty service unit, don't you still need to do a few things to prepare it for marine service? Head gaskets, frost plugs, other? Just asking cause I will need to replace my small block one day and if GM crate engines are an option that's helpful as I am a long ways from the marine engine builders.
Click to expand...

You are right
I would recommend to buy a GM Marine crate engine, They are different" and you will not have to change anything, The marine 350 vortec is rated 310 hp as a carb application with stock exhaust and intake. With headers, good intake and ignition 350 hp. you get a 1- year warranty with the marine engine.
The Marine crate engine will cost a little more but it is for a reason they are not assembled the same. If you try to convert a automotive engine the time and money to change things would not be worth it and you would void your warranty on the automotive engine.

Due to budget reasons people still try to use a auto engine anyway. for the long run they are shooting them selves in the foot.
http://www.mkhammer.com/index.php?main_page=page&id=3
 
karzrus said:
I know I'm a bit off topic, sorry but I'm trying to learn.
If you buy a GM crate engine even if it's a zzHipo or heavy duty service unit, don't you still need to do a few things to prepare it for marine service? Head gaskets, frost plugs, other? Just asking cause I will need to replace my small block one day and if GM crate engines are an option that's helpful as I am a long ways from the marine engine builders.
Click to expand...

The only thing that needs to be done to the zz502 is head gaskets and freeze plugs. You just buy it disassembled and put it together yourself. Better exhaust valves might be needed if boost is going to be added.

I can only vouch for the GM zz502 and the GM zz572 620hp. These 2 engine's have been used with full success.
 
k i thought you were talking about gm's crate motor lineup i found a rebuilt merc motor so what parts in the motor compartment are different for a 502 than a 454
 
ZZ 502

I started with a zz 502 block I had water reversion with full water lightning headers with low water headers they were ok, the reason is the lobe separation is 110 it needs to be 112 or greater this is just my findings, now it is a 555 inch with 700 hp, used to be 950 with 1071 at any rate great motor to start with.
 
Big Red said:
I always get a kick out of these terms.

similar horsepower.
approx 500 hp
about 500 hp fresh rebuild
up to similar horsepower.
500ish HP
Click to expand...


sometimes i agree with you RED, but sometimes things are better off abreviated "500ish HP"
I will clarify, mine made 558HP on the dyno, but that was with dyno headers and not all the access. on the front of the motor. you do the calculations on how much loss there is from access and drivetrain and let me know how much i have less. I guess thats the best I could do!!

convincor242, thats always what i heard too until a couple guys say theyve been running them with exhaust like Revolution Marine etc, good info though!!
 
ok so yeah i bought a mercruiser hp 500 which does have 500 ish hp i know they make more than they rate them for and havent dynoed this particular one so im not quite sure what to say about that either im not quite sure if the shot was taken at me or boatn70
 
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