I'm going to start building an engine (454) for the eliminator. I bought a block and crankshaft so now I am looking at heads. Should I go with open or closed chambers. I don't think I will go over 6000 rpm's, I just want a really healthy engine. any guidence is appreciated
'049' cylinder heads seem to be a really popular head for a marine 454. As far as open or closed chamber, I don't think one is better than the other. However, to get any kind of compression, say 9:1 and up, you would have to run dome pistons with open chamber heads whereas you can run flat tops with the closed chamber heads.
Thanks jetaholic...................v-drive
If you're only going to go 6000r's "049"'s for sure, put the big valves in and clean them up and you'll make a ton of torque!.. Also since they are open chambered there are several piston configurations that will fit to give you a choice of compression!.
The standard closed chamber head will not make power with a good open chamber without "adjusting". The valves are shrouded more in the casting, and have to be upened up without hindering the chamber.
Also, high compression pistons are much more available for open chamber stuff 'off of the shelf'.
I am with GoFast on his recommendation. Run hard and don't break the bank.
JMO,
But you might consider the 781 oval ports too. They have about the same runners and a little smaller combustion chamber. I ran a ported set with 2.19/1.88 valves for years and they'll go 6500rpm easy.
Amen on the 049s. I have a set on a 454 that I built for my station wagon. Great heads for factory iron.
Careful on the compression, though. The chambers aren't very efficient and its easy to get into high octane requirements. I run mine with 36* ignition lead on 8.7:1 in the car and it can get a touch pingy in the upper ranges on 87 octane here at sea level. In a boat I would say 9.0 is about the limit on cheap gas.
The open chamber heads breathe better than the closed chamber ones because they do not have a bunch of metal in close proximity to the sides of the valves when they are open hampering the airflow (shrouding). Yes, to get a good CR (I would heavilly consider 10:1 in a boat) you have to run domed pistons, flattops only net you arround 8.3.
Large Oval ports are the best IMO for RPM below 6-grand, even the smaller rectangle ports don't flow with decent velocity on a sub-500CID engine untill arround then.
353049 castings fit both bills, but, IMO you are going to have a hard time getting much over about 450HP out of them in the vicinity of 5,000 to 5,500 RPM without porting work (I am working with the same heads on a 454), especially with a cam designed to get you a solid boat-useful lower-end midrange for a prop OR jet. I am making 400HP on a very similar setup, with a cam that pulls very hard low, yet does not sign off too early, and still has room when my heads can use it.
I would plan to have them ported, and put the larger size valves in too (2.19"/1.88"), or just shop a good set of bare aluminums. Money gets to be a wash about then.
Good luck.
are you gonna run a roller cam or a flat tappet?
Roller. Your boat is lookin good. White is a definate improvement over black. v-drive
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