: 1968-472 caddie motor rebuild



swivelneck
10-04-11, 03:14 PM
Hi,and i have a 472 ,1968 stock caddie motor that i recently raced in a boat the summer and did quite well with it ,my plans is to rebuild the motor a bit but due to the rules I cant go over 399 h.p.The motor has got a hei dist ,but thats about it ,Can i take the heads to a good shop and do some port work on them ,A supplier hyad told me what i need to get ,new ported heads ,new cam ,new intake and new lifters pusd rods and shaft rockers ,So my question do u think the stock crank,con rds and pistons will handle it .I plan to do a complete motor job but leaving the stock bottom end ,and rpm range is 4500 -4900 .

drmenard
10-04-11, 03:55 PM
You don't need new heads.. If you have 68 heads they are small chamber .. They are better than the later large champer heads.. Your heads just need to be redone..The crank is fine, no problem there... The pistons are 40 plus years old... Depending on your budget, you might want new ones.. The rods are OK.. But if you were going to spend money to have them reconditioned , new forged one might not be that much more...

swivelneck
10-04-11, 06:52 PM
ok, so how much hp has the stock 472 got ,we only have an alternator on the motor ,spec say 375 ,ive heard that is not right so if we put all the parts on except the new heads ,t
ake the old heads and do some porting ,what is going to be our h.p. gain,

DixieChevrillac
10-04-11, 09:55 PM
A rebuilt motor will yield the power you want it to make depending what pistons and what cam you throw back in it. If you rebuild it back to stock you should expect numbers closer to stock than the condition its in now. Depending what you're using as a drive system, expect about a 15% less difference as the output. If you PnP the heads, airflow will be smoother, but opening up the chambers will lower the CR, thus reducing a slight amount of power. If you want, just have the heads rebuilt or cleaned up and maybe polished for a few hundred bucks. If it's all running fine, I say leave it til you have money to do a complete rebuild for more power.

swivelneck
10-04-11, 10:55 PM
we need to be a close as possible to 399 h.p. but cant go over that,before we race we have to have the motor dynoed ,anything over 399h.p. is disqualifed.so thats our goal to put new rings and new bearings ,work the heads,more agressive cam,and new intake manifold ,along with shaft rockers ,I was told that if i do this the motor it should dyno close to 399.

drmenard
10-04-11, 11:38 PM
The best help you can get is MTS.. they have everything you could want, for these motors, for sale.. I bought alot of parts from them.. If you give them a call, Marty can help you get the power you need..

DixieChevrillac
10-04-11, 11:51 PM
we need to be a close as possible to 399 h.p. but cant go over that,before we race we have to have the motor dynoed ,anything over 399h.p. is disqualifed.so thats our goal to put new rings and new bearings ,work the heads,more agressive cam,and new intake manifold ,along with shaft rockers ,I was told that if i do this the motor it should dyno close to 399.

If all that matters is the hp cannot be 400 or over, then have a torquey cam spec'd and ground that'll compliment the weight and shape of the hull as well as correspond to the prop you plan on running. A taller manifold will help too. Are there restrictions on fuel or anything else? If you do the heads and rings, might as well change the pistons to bump up the compression if you do a lot is ground from the heads. Lightening up the valve train will give you a few extra horses and combined with everything else, should put you in the ballpark. If it does go over, you can always downtune it by adjusting the carb.