351w cam specs
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=5627
Printed Date: November-30-2024 at 1:55pm
Topic: 351w cam specs
Posted By: 81nautique
Subject: 351w cam specs
Date Posted: January-29-2007 at 4:45pm
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Does anyone know what the original cam specs are for an early 80's PCM 255hp 351w.
PCM oddly enough does not have that info anymore but one of you die hards has to have it written down somewhere. I'm going to upgrade but want to compare to stock specs. Thanks ------------- You can’t change the wind but you can adjust your sails |
Replies:
Posted By: AWhite70
Date Posted: January-29-2007 at 8:13pm
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I'm going on memory but I think Vince at SkiDIM faxed them to me. I can't seem to find them now. ------------- AWhite70 http://www.correctcraftfan.com/diaries/details.asp?ID=562&sort=revyear&pagenum=5&yrstart=1976&yrend=1980" rel="nofollow - '79 Ski Nautique |
Posted By: reidp
Date Posted: January-29-2007 at 10:27pm
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My best guess says it's a .418/.448 lift cam. It's what's shown in the Holman Moody manuals and the only spec I've ever seen. I have no idea as to the duration as the book shows none, but from others I've seen that are similar, I'd say it's somewhere just around 200 degrees. ------------- ReidP /diaries/details.asp?ID=231&yrstart=1971&yrend=1975 - 1973 Mustang |
Posted By: nuttyskier2002
Date Posted: January-30-2007 at 10:20am
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I've tried to find the same information on cam specs from Indmar. They told me that the cams were supplied to them by Ford with the base engine and they (Indmar) did not have the specs on hand. 200 deg sounds reasonable. Idle starts to get a little rough at anything over about 216 and lobe separation under 112 deg. For example, Comp Cams sells a cam that is 218/218 (In/Ex) @ .050 with a lobe separation of 110 deg. This cam has a noticeable idle. If you take this same cam and spread the separation to 112 or 114, idle quality will smooth out and vacuum will increase. By the way, using a cam with less than 112 deg lobe separation increases the risk of sucking water into the cylinders from the exhaust. Hope this helps in your selection. ------------- 95 Malibu Echelon w/Mercruiser 350 Magnum Skier Former boats: 88 Ski Centurion Tru Trac II 59 Chris Craft Capri (woody) |
Posted By: TRBenj
Date Posted: January-30-2007 at 12:00pm
I dont have a lot of experience on the subject, but I have to disagree. I installed a cam from Cam Research this past summer with the following specs: RPM Range: 2500-5200 Duration @.050" (I/E): 218/222 Lift w/ 1.6 Rocker (I/E): .490/.490 LSA: 110 degrees They have lots of experience selling cams to customers with ski boats, so they were very helpful. I asked about the LSA being less than 112, but they said that 110 would be plenty safe. With my 218/222 duration and 110 LSA, I honestly dont notice a difference in the way the boat idles, even at 600 RPM. ------------- |
nuttyskier2002 wrote:Posted By: 81nautique
Date Posted: January-30-2007 at 1:41pm
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Awhite, good suggestion, Karen was able to fax me the original specs and Cam research made a recommendation based on their experience with ski boats. As Tim said they seem to really have a grasp on what a ski boat needs.
Stock specs are intake 194 exhaust 200 .430 lift Their suggested cam for my application is not quite as big as Tim's but is an improvement over stock. With the new gt40p heads, 9:1 CR, Performer intake and STock exhaust here's what they say will improve hole shot, Drastically improve midrange and pull good to 5000Rpm which will allow me to leave stock rocker arms if I want to. Rpm Range idle to 5000 Duration @.050 Intake 205 Exhaust 210 lift w 1.6 Rockers .460 LSA: 112 They actually refer to this as their waterski cam and have it in quite few boats with positive results. We should make comparable or slightly more power than a 285 hp Pro Boss carbed motor as we're increasing the CR over the stock 8.4:1. I'll be thrilled with that so unless anyone has any other arguement over this set up I'm gonna get it ordered. I feel real comfortable with the guy at Cam research and also with my engine builder as he's done plenty of Marine apllication rebuilds. Think I'm good to go. Thanks all. ------------- You can’t change the wind but you can adjust your sails |
Posted By: JoeinNY
Date Posted: January-30-2007 at 3:09pm
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First post in a few months, my time in front of the computer isn't what it used to be.. glad to see things haven't changed much around here...
Juse my two cents on on the flat tappet cams, especially with aftermarket springs to be very careful on the break in, oil isn't what it used to be (they are removing the zinc-d) and its fairly easy to wipe out a lobe with too much spring pressure and standard oils. If you have double springs (like those supplied by tristate on thier gt-40p's) you should remove the inner springs for break in, as well as adding GM EOS (Engine Oil Suppliment) to some conventional (not synthetic) 30w for the break in and an oil change or two thereafter. Its a PIA but not as bad as tearing the manifold and timing cover off to replace the cam, believe me. Once I finally got one broken in and happy in my 302 (gt40p's, edelbrock peformer intake, scorpion rollers, etc) I have been pretty happy with the performance of my cam Intake 204 Exhaust 214 (at .050) Intake .448 Exhaust .472 112 degrees lobe seperation. It pulls like a bear in an 83 2001 with 900 lbs of ballast and 6 fat a$$es right off the line (you can idle it much lower than you would want to) and will get up to about 4800 rpm or 47 mph in that boat (with the people but not the ballast). I am going a little more extreme in my next project but I will start a new thread for that.. -Joe. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1477 - 1983 Ski Nautique 2001 1967 Mustang 302 "Decoy" http://www.youtube.com/watch?v=cO5MkcBXBBs - Holeshot Video |
Posted By: 79nautique
Date Posted: January-30-2007 at 3:19pm
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Mine's a little more
duration in 218 ex 224 lift in 476 ex 481 112 ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique |
Posted By: TRBenj
Date Posted: January-30-2007 at 4:04pm
This is good advice. I took advantage of Cam Research's break in service- I havent put very many hrs on the motor since then, but so far so good. Cam Research recommends a straight 30w for a certain break in period. After that, I switched to Shell Rotella-T 15w40. Good article here: http://www.hotrod.com/techarticles/engine/flat_tappet_cam_tech/ - Hot Rod As far as the cam specs, Im sure that will give you a real nice power increase. If youre so inclined, I wouldnt hesitate to go a little wilder- I noticed zero driveability issues and gained a lot of power on the holeshot through the midrange. Id trust Cam Research's recommendation, though- Ive been very happy with mine. ------------- |
Posted By: captan1
Date Posted: January-31-2007 at 11:07pm
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I posted this last summer, I replaced my stock cam/lifters/timing chain searching for a wierd ticking noise.
SpeedPro cam: Lift .444"/452", Duration 206-221 @ 050 - reverse rotation. That's the cam that comes in a 1978 351, have no idea what the lobe separation angle is. I think I ordered it from Basic Power. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=452&sort=&pagenum=1&yrstart=1978&yrend=1978 - 1978 Ski Nautique |
Posted By: reidp
Date Posted: February-03-2007 at 12:56am
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Ken, thanks for getting those modern stock cam specs. The cam your looking at is similar to the one we use often and exactly the one captan1 mentioned above. I know it works great in a 302 and should do fine in a 351 as well. Unrelated to the cam, i think you may come up with even more compression than 9:1 CR, as I believe you're going to be dropping from what is most likely a 69-70 cc head to the +/-60 cc P head, and I'll bet you should have it all over a stock ProBoss by virtue of improving at every comparible level or component. I can't remember if you said you were doing a total rebuild with pistons as well, but if you are, I'd go with the flat-tops and you'll surely see the torque increase, but you will definitely be a premium fuel only guy. ------------- ReidP /diaries/details.asp?ID=231&yrstart=1971&yrend=1975 - 1973 Mustang |
Posted By: 81nautique
Date Posted: February-03-2007 at 6:23am
Reidp, Yes, total rebuild with .030 over pistons so we have plenty of options. My rebuilder doesn't want me to go over 9:1 because of the octane issue and since we travel with the boat to many different sites there's a possibility 93 octane might not be available everywhere. I originally suggested 9.5:1, he'll do it if I want but doesn't suggest it. Any last comments on that, I drop the block off tuesday so he can get started. Thanks. I am stoked to get this thing back together and see what it can do. ------------- You can’t change the wind but you can adjust your sails |
Posted By: pornautique
Date Posted: February-03-2007 at 10:57am
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I am new here.Iam going to look at past threads,but this topic is what I am looking for help in. 1990 sport all stock.looking for cam,intake,carb recommendations.Family use
3 teenage boys,1 girl. My insurance man loves me.I am going to spend this wonderful weekend looking thru this forum.Thank you in advance for all the help.I'm sure this will be a favorite website as I am fairly new to forums. ------------- 90 sport nautique |
Posted By: reidp
Date Posted: February-04-2007 at 1:47am
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You got me there Alan. If you always fuel up at the marinas, there's a chance that 93 might not be on the menu. However, I'm finding that more and more marinas are going with it in our region, and some as their only fuel. You can always keep a few bottles of octane booster with you for those occasions, and I'm betting 20+ free HP is on the line. Many of our members run premium regardless. I wouldn't recommend the higher CR in a large cruiser, but in one of our small boats, it's a main source of torque. ------------- ReidP /diaries/details.asp?ID=231&yrstart=1971&yrend=1975 - 1973 Mustang |