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machinehead
01-05-2002, 10:58 AM
I am currently building a pair of 540s for a friend of mine.They have rec port heads with 2.250 int. 1.88 ex.the motors will have 10 to 1 comp.Howards hyd roller cams.612/.629 with 236/242 dur.We are planning for Team G manifolds with single 1050 on each motor.The boat is a 1991 35 Cigarette it is very heavy .My question is have i over cammed these motors or too much carb? the boat is run at altitude on Lake Tahoe so i think the compresion can only help .Would appreciate any input from anyone from experience with a similar combination.

Tinkerboater
01-05-2002, 11:40 AM
The cam looks small and I would run the Holley HP 950. Also think about 2.30 intake valves. What heads are you using.

machinehead
01-05-2002, 11:56 AM
The heads are factory rec ports engines were originaly 502s they are un ported with 2.250 int although i have not finished machining them and still can make changes to lay out of motor [QUOTE]Originally posted by machinehead
[This message has been edited by machinehead (edited January 05, 2002).]

Racing Ray
01-05-2002, 06:40 PM
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[This message has been edited by Racing Ray (edited March 12, 2002).]

machinehead
01-05-2002, 07:20 PM
Thanks for the input .Do you think the compression ratio is a problem . I was thinking that at altitude it would probably help. Although I am still in the process of machining the parts .I can still make changes if I need to .

Racing Ray
01-05-2002, 09:56 PM
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[This message has been edited by Racing Ray (edited March 12, 2002).]

Tinkerboater
01-06-2002, 11:34 AM
You need headwork to get those heads to flow. Stock they won't do what you want. And as far as bottom end I am running a bigger cam with extensive headwork on the stock rec. port iron GM heads with 2.3 intake valves. On a 34 SCARAB that is heavier than and 1 ft. longer than the 35 FOUNTAIN and I can pull skiers up. The boat is a rocket. E-MAIL Jim Valakeo at valakoraceheads@aol.com
[This message has been edited by Tinkerboater (edited January 06, 2002).]

Racing Ray
01-06-2002, 02:27 PM
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[This message has been edited by Racing Ray (edited March 12, 2002).]

machinehead
01-06-2002, 04:13 PM
I am currently trying to talk the owner into some aluminum heads. If he declines then I will reexamine the stockers although with two engines everytime I suggest something his wallet gets twice as thin

Tinkerboater
01-07-2002, 03:04 PM
Just remember that you want to do the job right or it will come back to bite you. If you use the stock heads make sure you have a reputable head shop that works on boats do the work. And make sure you bronse wall the guides even if the heads are new. If you don,t do anything to the stock heads make sure the boat owner knows that you will not be responsible for him not having the extra 100 HP per engine. YES that is about what JIM VALAKEO will get you. All Jim does is boat engines. He can set you up with a package or just the heads then you can put it all togeather and look like a hero to your buddy. LEAVE THE DISIGN WORK TO THE EXPERTS untill you know what your doing.
[This message has been edited by Tinkerboater (edited January 07, 2002).]

machinehead
01-07-2002, 05:10 PM
I am a machinist with 20 years exp. I have built some very special engines but all my performance exp. is with cars so I have been picking everyones brain to put together the best package I can.I have limited exp. with marine but have consulted some of the big names and some small ones .You guys have been very helpful also.I really wanted input from boaters and you guys came through thanks.

Tinkerboater
01-07-2002, 06:40 PM
Bottom line is boat motors need much more bottom end airflow than a car engine. You need a lot more cam for a boat. I usually design my cam,intake and all other parts for about 1000 rpm more than you want your top rpm to be. Just remember that 75% of your hp gain is in the heads. A poor job on the heads can kill any chance of a good torque range and proper flow at the proper rpm. You will also need GOOD header type exhaust unless you are supercharging the engine. Bottom line when I build a motor for someone I know I build it stronger than it needs to be so that it doesn,t come back to me in pieces.

NordicHeat
01-10-2002, 11:42 AM
Boating at 6200 feet is another world and yes it does effect cam selection. You want to maintain all of the cylinder pressure you can at high altitudes which will require less cam than you would use at sea level. I personally run a 540 with aluminum heads and 9.3:1 CR between 3700-6000 feet. The cam choice is an Ultradyne 232/240 114 .600/.600. This was chosen by Ultradyne (the sea level version would have been 236/244 114 .600/.600).
This cam idles at 750 rpm and revs easily to 5500 rpm and so far has been an excellent choice. If I had to make a move however, it would be slightly bigger so your probably fine with the extra compression. It just idles so well that it sounds like it needs more ;o)
If you do go with aluminum you may want to look at large oval ports such as the Edelbrock Victor marine series. Although you'll get a bunch of different responses, the bottom line is the motor pulls very hard up to 5500 rpm with these heads and 540 c.i., even at sea level.

machinehead
01-11-2002, 07:50 PM
We have decided to go with aluminum heads.Compression will not be quite as high as we thought probably 9.8:1 .

BOOSTDADDY
01-25-2002, 06:10 PM
MACHINEHEAD-THE COMPRESSION WILL BE A GOOD THING AT 6,000 FT. MOST OF MY CUSTOMERS AVERAGE 4LBS MORE BOOST AT 6,000 FT ELEVATION VS SEA LEVEL. I KNOW YOUR APPLICATION IS NOT BLOWN, BUT IF YOU CAN RUN MORE BOOST YOU CAN RUN MORE STATIC COMPRESSION! GOOD LUCK!

machinehead
01-25-2002, 06:41 PM
That was my thinking but im realy glad to here real world experience thanks for your help!

NordicHeat
02-01-2002, 08:22 AM
Hey MachineHead,
here is a useful calculation for us high altitude guys.
CR-((altitude/1000)x .2)= corrected CR
Your case
10 -((6200/1000)x .2)= 8.76
Pretty mild I'd say not to mention the aluminum is worth another .8.
Just make sure you take some boost if you ever head down to the Delta.

machinehead
02-01-2002, 10:11 PM
thanks for your help! comp ratio has worked out to 10.2:1