Cam guru's please read
 

My winter project is upgrading power in my 97 252 Islander. I bought a Gen VI based 509 that has worked over 088 heads,stock crank and rods,JE Flat top pistons,ARP bolts throughout etc. It came with build sheet and dyno results. When originally built it was EFI with a Whipple with 5 psi and made 622 HP@5200 and 756 TQ @ 3300. When I bought the motor a couple months ago it had approx 250-300 hours so naturally I tore it down sent heads,block,crank,rods and pistons to machine shop to be inspected cleaned so I can put it back together fresh with new bearings,rings and what not. Anyway long story short it will now be a carbed motor with Vic Jr intake and Pro Systems 970 cfm carb with a DUI dist. Here is what I'm not sure of... I need someone with cam expertise to steer me on this. The cam that I have for the motor is what was in it when it was EFI boosted. Specs are 224/230 @ 50 duration and 569/578 lift on 114 LSA. Would this be a good cam for a N/A carbed application? If not what would be a better option. I will be running at least Stainless or EMI exhaust and risers (no silent choice),possibly Lightning headers if the right deal comes along.

Thanks in advance for advice

How much power are you looking to make? Are the heads stock? Ported? Deck milled to reduce chamber volume? What boat? Intended use of the boat?

I would contact the OSO cam guru himself. Bob Madera. He is the most knowledgeable on this subject.

http://www.marinekineticsonline.com/

As has already been said, call bob.

x2!

Bob is the guy...period

I call bob on a regular basis and it is my suggestion also that he be contacted before buying anything. But it would be nice if we give some insight here so that there is some available reference to educate people and have a better understanding of what they will be getting and why.
The cam is very mild but looks to have a decent I/e split for the lacking exhaust port of the stock heads. If your ok with around 475hp (rough guess) that cam will work. But to get the most and best for your specific application give bob a call and he can go over everything. Get a pen and paper ready, even with the decent amount of knowledge and experience I have, every time he picks up the phone school is in session.

what pistons are in the engine? if they are dish blower pistons then changing cams is not going to be your answer..compression = hp,,

Pistons are Flat Top JE

I would like to be in the 500 range,heads are 088's with some port work and a 225 intake valve I believe the build sheet states 116 chambers, Boat is a 97 Baja 252 Boss (not an Islander,dont know what I was thinking when I put that not that it matters for this conversation anyway lol). We cruise around and occasionally like to haul ass. I want the boat to cruise 50-55 with ease and be able to pull low to mid 70's if the mood strikes. With base 310/330 HP carbed GenVI 454 boat cruises nice at 40-45 and light load good water might hit 60 all out

I think you are going to find you are too low on compression. The std merc/gm long blocks are 8.75 to 1 with a DOMED piston and 118 cc chambers. An option might be to find some heads with smaller chambers. Lower compression in n/a engines really hurts performance. If you go with what you have, that cam is plenty big.

i agree with wetbar. some 113 cc alum heads would be the way to go. not chineseium though...

113cc heads aren't going to help much if the pistons are .025 in the hole. Discuss options with your shop to get the compression up to at least 9:1 if not there already.

You mentioned 509cid.

Are these the pistons ?


#257984
cid 509
Bore 4.500
Stroke 4.000
Rod 6.135
Deck Height 9.780
Compression Height 1.645
110cc 9.5
118cc 9.0
124cc 8.6
Dome Volume -3.0cc
Grams 690

http://www.jepistons.com/Catalogs/Au.../flat_top.aspx

with that piston&114 cc chamber you are slightly over 9 to 1 and with your existing cam i would expect 500 hp.i 100% agree that you should call bob m before proceding with this build.i have been selecting camshafts for my engine building needs for years but since i started working with bob i realize that i will make more power with his knoledge behind me.bob is a great guy and very easy to talk to.

Thats them

My build sheet says 116 cc chambers so still at least 9.0/1 .I did send Bob an email to get his opinion

With that small of a motor I would want a 112 lsa but as stated b4 you just can't beat a custom billet cam and distributor from Bob for $350. There is a big shot out there with a carb shop that builds overpriced carbs with bad fuel curves and has magical cam grinds that are ground when the stars are perfectly aligned. He charges $500 for his cams that can be bought from Erson with the identical specs for $250. Bobs cams might not be ground when the stars are in perfect alignment but you would think they were after you drop the motor in the boat and take it for a sea trial...

741

as mentioned,thats if your deck height match's the piston's spec's of (Deck Height 9.780 )...

BTW call bob,,his knowledge will smoke your mind,,

What he said ^^^^^. If your deck height is 9.79 and your using a .039 thick head gasket you don't have 9:1 compression.