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302 Rebuild Cam Questions |
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81nautique 
Grand Poobah 
Joined: September-03-2005 Location: Big Rock, Il Status: Offline Points: 5781 |
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 Topic: 302 Rebuild Cam QuestionsPosted: December-09-2023 at 5:34pm |
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So I am at the point where I'm getting ready to send the motor for my 1956 Collegian project out to the machine shop.
Here's what I've got and what I'm planning to do to it, I haven't ordered any parts yet so I'm not opposed to changes if you guys have recommendations. I have a mid 90's PCm 302, The boat has a Port side helm so the motor will be a standard rotation. After pulling the motor apart I was pleased to see it is a roller block. I'm going to go with a SCat 332 stroker kit, Forged Crank and Pistons. Final Compression ratio goal is between 9.5:1 and 10:1. Heads I'm looking at are Flowtek Aluminum Thumper 185 CC with 60CC chambers. This combo should get me 9.91:1 with the pistons I've chosen. Heads are set up for .550 lift Intake will be a Low Profile Aluminum, (I don't have the clearance for anything else) My big question is what to spec the cam at, I will be going roller but I'm not finding anything Marine spec other than flat tappet cams. Looks like I'll have to have a custom grind done so I'm really looking for some advice from anyone that's hot rodded a 302. I will probably not spin this any higher than 5200 and most of it's time will be spent cruising but I want throttle response and a great sounding idle. Slightly lumpy would be awesome. TIA Alan |
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Jonny Quest
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Joined: August-20-2013 Location: Utah--via Texas Status: Offline Points: 2983 |
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Posted: December-09-2023 at 7:39pm |
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I would reach out to Cam Research in Englewood, CO. They are Ford camshaft experts and can do a custom grind for your specific application. They will also have input on your roller block...should you decide to go roller vs. flat tappet. Sounds like your 302 will be a very nice engine when completed.
Cam Research Corporation 3881 S. Jason St. Englewood, CO 80110 Telephone: 303-762-0022 JQ
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Current
2003 Ski Nautique 206 Limited Previous 2001 Ski Nautique Open Bow 1994 Ski Nautique Open Bow Aqua skiing, ergo sum |
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81nautique
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Joined: September-03-2005 Location: Big Rock, Il Status: Offline Points: 5781 |
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Posted: December-09-2023 at 8:46pm |
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Thanks JQ, are they still in business? They don’t answer phone or email. I used a cam from Scott years ago for a 351.
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Jonny Quest
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Joined: August-20-2013 Location: Utah--via Texas Status: Offline Points: 2983 |
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Posted: December-09-2023 at 9:25pm |
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I last communicated with them back in 2017 or 2018...so I don't know of their current status, sorry. I just assumed that their business is a going concern.
JQ
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Current
2003 Ski Nautique 206 Limited Previous 2001 Ski Nautique Open Bow 1994 Ski Nautique Open Bow Aqua skiing, ergo sum |
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MrMcD
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Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3750 |
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Posted: December-09-2023 at 10:05pm |
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One of the biggest errors in engine building is to get too much camshaft. This becomes more true in boats. In a boat a strong idle is very important. Power is great but a lumpity lump cam will not allow you to idle in the 5 mph zones. A strong vacuum at idle gives good idle performance. I would try to keep the vacuum above 15”, a stock cam in a new engine would be close to 20”. A robust cam might be as low as 8” at idle.
Larger cams all need more idle RPM. Some not so radical cams need at least 900 RPM to idle and loaded in a boat may stall. They come on like gang busters above 4,000 RPM but you pay a price for that top end performance. This information does not get you closer to a part number to order but I hope it helps you order what meets your needs the best. A knowledgeable cam guy can get you dialed in if you are very clear with what you need in this build. What RPM do you want for idle speed? 650 RPM is pretty Normal in boats. What fuel do you plan to run? On the water Premium gasoline is not always available so you may wish to think on that a little. I know guys that have very strong cams in boats and they only care about Top Speed and how fast it will get to top speed. Not normally what owners of a Ski Nautique are after. A 302 does not offer a lot of toque in stock form so for me I might be looking at a RV type camshaft for a little extra grunt. Order what you desire and I hope it runs exactly how you wish on the water. Be prepared, on my recent engine build I was not able to get the exact cam I wanted due to backlogs. I had to take a cam that was close to what I chose. Maybe this is getting better as we are mostly past the Covid issues but getting desired parts has been pretty hard recently.
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GottaSki
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Joined: April-21-2005 Location: NE CT Status: Offline Points: 3363 |
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Posted: December-11-2023 at 8:29am |
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seems to me the trick will be finding a modest(intake duration under 220) roller cam that takes advantage of available lift over 0.500.
if your ok staying 0.500 and then you got some off the shelf options. depends if your intake flow continues to climb big after .50, or not If your ok at 0.500 ish, a TFS-51403001 or Lunati 20350120LUN have my eye its still going to rip and pull hard everywhere |
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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."
River Rat to Mole |
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GottaSki
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Joined: April-21-2005 Location: NE CT Status: Offline Points: 3363 |
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Posted: December-13-2023 at 8:39am |
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this is intriguing, lift > .500, 215/224 and big 114 LSA, COMP Cams Blower and Turbo Camshafts 35-304-8 |
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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."
River Rat to Mole |
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81nautique
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Joined: September-03-2005 Location: Big Rock, Il Status: Offline Points: 5781 |
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Posted: December-13-2023 at 11:01am |
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Thanks Gottaski for the research. I did end getting to talk to Scott at Cam Research, his recommendation was a bit milder than those with lift just shy of .5 and 112 LSA. Haven’t made a decision yet
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75 Tique
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Joined: August-12-2004 Location: Seven Lakes, NC Status: Offline Points: 6130 |
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Posted: December-13-2023 at 3:24pm |
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So refreshing to see knowledgeable questions and responses as compared to the nonsense on the FB boat pages. I had my fill and have pretty much given up scrolling those pages anymore. The answers made my hair hurt. I hope people (still) appreciate the knowledgebase over here. Even though some of that knowledge trickles in over there, it is so diluted by the nonsense, there is no way of distinguishing the nonsense from the knowledge by those asking the questions.
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“So, how was your weekend?” “Well, let me see…sun burn, stiff neck, screwed up back, assorted aches and pains….yup, my weekend was great, thanks for asking.” |
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Faceplant
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Joined: July-27-2013 Location: Otter Lake , Mi Status: Offline Points: 418 |
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Posted: December-13-2023 at 6:25pm |
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Just from the responses about Facebook, I've never opened a boat page on that site. Get my accurate info here !!
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Feels like I am hanging 10 but in reality - probably hanging 6.
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DenDen
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Joined: July-20-2023 Location: USA Status: Offline Points: 204 |
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Posted: December-21-2023 at 6:34am |
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I am building a 350 and have had the same discussion with quite a few knowledgeable people. Of course, all of them have told me you can’t have everything so pick what is most important and build on that.
Idle seems to be very important in a boat such as the ones we all love and discuss every day on this forum. I can build a high horsepower kick ass motor. Just don’t put it in a boat. |
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MrMcD
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Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3750 |
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Posted: December-21-2023 at 12:47pm |
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An option when building a 350 is to change the stroke and make it a 383, if doing this for a boat choose an internal balanced crankshaft so you can run all the factory parts for the flywheel and harmonic balancer. While only 33 cubic inches added the long stroke gives it much more torque which can motivate a boat much better than a 350. If your engine is older switching to modern heads can add as much as 40 HP. The newer 350’s with Vortec heads offer much more power and are very close to the aftermarket heads for power up to 5,000 RPM which is perfect for a boat engine.
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MourningWood
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Joined: June-13-2014 Location: NorCal Status: Offline Points: 917 |
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Posted: December-21-2023 at 1:58pm |
Sounds like a good combo. Built a 331 (nominal) from a 5.0 for a LeMons car. The engine 'math' (rod ratio, etc) is just about ideal. Went with iron GT40 heads (cuz they were sitting around) and a Edelbrock Performer (not 'Plus') manifold, small Holley 4bbl. Have to look up cam specs, but mild. Big, flat torque curve, 400 h.p on 91 pump gas. Would make a great boat engine.
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1964 Dunphy X-55 "One 'N Dun"
'I measured twice, cut three times, and it's still too short!" |
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DenDen
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Posted: December-21-2023 at 10:49pm |
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I thought about putting a stroker in it or possibly a big block. I had to change the exhaust anyway. But the reverse rotation kept screwing things up. Have a good transmission with only about 1000 hours on it. Decided to go with the 350 Doing all the normal things to make it run good. Vortex heads a little bigger cam. Protecting that precious idle of course.
I will post all the details on my other thread as I go. |
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81nautique wrote: