cp5899

iTrader: (1)

I ported, gasket matched the heads and intake, high rise intake, 850 Holley and a mild cam. The boat is a bit over propped with a 25p mirage plus and I'm only getting 4600-4700 rpms. But did gain 500-550 rpms and about 4-5 mph.

I also put 2.19 intake and 1.88 exhaust valves with avoid bit of bowl work.

dereknkathy

if you hafta buy heads and pay for the work, it would be a better idea to go square port or alum heads. the OP had access to free heads and port work, or at least favors from a bud. once you find a $350-400 set of ebay heads and the same for port work, you are approaching the used price of good heads.

cp5899

iTrader: (1)

Derek is right. I had the heads and machines to do the work. If I would have had to pay for all the work it would have been a good bit of money and would not have been worth it at all. If you were to follow the same style head build you could get a set of used alum heads for what it would have cost and gain a lot more power with a good cam over what I gained using them. But in my case I had everything and the machines to do it so it was only time.

I just recently (this last Monday) bought a 280 velocity with a 502 may. It has the 088 square ports. I'm going to start a new engine build like before, but have a 600 hp goal since I'm starting with good internals. I think I'm going the aluminum head route this time if I can find a deal on a set.

monster693

Do you know the cam specs? I would like to get a set of 088 heads but the 781's supposedly are capable of making more hp then I am after. Plus the 781's are cheaper and more readily available around here. I am hoping to make 450hp. Right now I and spinning a 23 mirage plus at 4800 WOT and reading 60 on the GPS. I have a labbed 25 mirage plus sitting my garage that I ran once. It dropped me down to 4400 at WOT. So basically my goal is to run the 25. Right now my plan is to get either set of heads, performer rpm air gap intake, and have a custom cam ground. What are your opinions? I want to stick with iron heads due to not having fresh water cooling and being in the salt water.

cp5899

iTrader: (1)

I don't remember the cam specs exactly but it was around 500-510 lift with a 224ish duration on a 115.5 grind. The cam was very mild because I have stock exhaust on that boat and from what I understand they have bad reversion issues with much cam. If you had better exhaust the power gaining potential goes up a good bit (as I understand it) because of much more cam possibilities.


I did all the work myself and was happy with overall low investment, but it i had to pay to have it all done I may have a different view on the gains I got.

monster693

I will be doing most of the work myself. I will only have to have any machine work done that I decide to do. After doing more research it seems like the biggest problem is the low compression of the motor. It seems to really limit the selection of cams. I am going to go talk to a machine shop/builder tonight that I have used before. Hopefully I can get some good info about pricing for the heads and cam selection.

cp5899

iTrader: (1)

I'm not sure what motor you are starting with but if its cast internals that's a limiting factor as well because you can only spin them up to 5000 RPMs so I've been told.

dereknkathy

ok, you have a set of 088's, are buying alum, and have a very nice set of 781's that are done up the way monster wants and you don't have a ton of money in. sounds like mebbe you should discuss selling the 781's to monster...

cp5899

iTrader: (1)

The 781's are on my 235 Baja that I'm selling. That boat is complete and ready to run. I don't have any heads sitting around. The 280 velocity I just bought has a 502 with 088's that I'm either going to work over or get a set of alum heads. Probably use the 088's as I'm starting to realize that they will get me to my hp goal.

dereknkathy

it was a thought. anyway, monster, you are talking custom cam grind. two words-Bob Madera. you don't need to know anybody's cam specs-lift profile-none of that. all you hafta know is those two words and you will get the cam that you and your motor like best...hi is gonna lean on you to convert to roller lifters though-but then all cam guys will...