Building 505ci bbc for 74 sleekcraft

[Irrational_decisions]

Top of the afternoon

Going with a 505ci bbc, what kind of compression are people rec. California native, 91pump "good gas ". Thinking about 10.5.1 with a nice cam to bleed compression with aluminum heads. Do you think that is to high?

Any response would be appreciated

 

[farmo83]

Personally I would run it around 9.5 if sticking to 91 but that's just me. I'm sure people with more knowledge and expierance will chime in.

 

[obnoxious001]

Tell me more about the boat, size and type of usage?

One problem you have to consider is will you always get a decent quality fuel from the pump? For the amount of horsepower gained, it may make sense to stay a little more conservative with compression.

 

[Irrational_decisions]

Tell me more about the boat, size and type of usage?

One problem you have to consider is will you always get a decent quality fuel from the pump? For the amount of horsepower gained, it may make sense to stay a little more conservative with compression.

Boat is a summer toy, 21ft Berkeley pump. Toy for havasu, el sinore and pudding stone....do you think 10.5.1 is to high.

 

[obnoxious001]

Boat is a summer toy, 21ft Berkeley pump. Toy for havasu, el sinore and pudding stone....do you think 10.5.1 is to high.

I believe the boat is too heavy, and also a jet boat, so personally would not go 10.5-1, even with aluminum heads.

Jet boats get run with your foot to the floor often, and for extended periods of time. How much horsepower do you figure you will sacrifice with one point of compression? I built a 468 for a jet boat some years ago when Puddingstone was practically in my backyard. 9.6-1, iron heads, roller cam, 617 hp.

The other thing to take into consideration with a jet is where you want/need the power, and the jet pump needs to be built accordingly.

 

[84miller]

I just had a 505 build (only 2 hours run time still), wanted/requested build to run on pump gas. Compression 9.8.1. Boat, 20 foot v-drive, two speed power glide,

 

[Irrational_decisions]

I believe the boat is too heavy, and also a jet boat, so personally would not go 10.5-1, even with aluminum heads.

Jet boats get run with your foot to the floor often, and for extended periods of time. How much horsepower do you figure you will sacrifice with one point of compression? I built a 468 for a jet boat some years ago when Puddingstone was practically in my backyard. 9.6-1, iron heads, roller cam, 617 hp.

The other thing to take into consideration with a jet is where you want/need the power, and the jet pump needs to be built accordingly.

Question do you have cam specs?

 

[obnoxious001]

Question do you have cam specs?

That cam would likely not be perfect or suitable for your 21' boat, depending on what RPM range you plan to run. A lot of factors come into play, number of cubic inches, induction and exhaust, and what sort of head work has been done.

I have worked with the same custom cam grinder for many years, and his dad before him. I can get a cam ground for you if you like, I occasionally do that for people whose engines I am not building. Cheaper than many shelf cams, and certainly cheaper than some of the other "custom" grinders.

 

[StraubTech]

Top of the afternoon

Going with a 505ci bbc, what kind of compression are people rec. California native, 91pump "good gas ". Thinking about 10.5.1 with a nice cam to bleed compression with aluminum heads. Do you think that is to high?

Any response would be appreciated

I would build for what gas you can buy at the marina where you boat. That way you don't have any worries if its been a good day on the lake and you need fuel.

 

[Lavey 29]

And do not forget at times marina gas does not turn over as fast as land gas pumps. A lot of marina places gas use Valvetech fuel additive but I have seen that really does nothing. Kind of like people - you can not stop the aging process and at times marina gas can sit for periods at a time. I am not a fan of marina gas.