Intake Manifold
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=33765
Printed Date: October-08-2024 at 1:14pm
Topic: Intake Manifold
Posted By: Dan in CT
Subject: Intake Manifold
Date Posted: June-04-2014 at 11:32am
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Hey folks, two part question for the PCM guru's. After talking with Tim B. there seems to be two different stock intake manifolds for the 351w (marine). I will refer to them as the 12 bolt (mine) and the 16 bolt. Does anyone know the history? The tag on my engine block indicates a 1983 RH. The problem I encountered was an interference with the water neck stub and hose to the left exhaust manifold and my new DUI dizzy. The original dizzy was a Prestolite with a 3 inch diameter body. The DUI has a 5 inch body. Everyone I have talked with, which was confirmed by internet researches, have not had any problem with fitment on the 351w and the DUI. My guess is they have the 16 bolt manifold. Mine is the 12 bolt. My options are to return the DUI, and they will make me longer (above the the engine) dizzy so the body clears the waterneck. That is going to take time and another $75. Time is my issue right now. I am going to look at the water neck to see if I can modify it to gain some clearance. My other option would be to pull the manifold and replace it with an aftermarket. I am looking for recommendations on the manifold. http://s1296.photobucket.com/user/ctwolframs/media/1981SN%20Photos/photo2_zps6c5ba05e.jpg.html" rel="nofollow">  [/IMG]
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Replies:
Posted By: KENO
Date Posted: June-04-2014 at 12:38pm
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Hi Dan I can't help with the DUI issue, but I can help with the manifold question. The 16 bolt manifold was for earlier heads that had 16 holes for the manifold bolts, up until 74 or so. The later stuff has 12 holes in the heads so a 12 bolt manifold. Swapping manifolds won't help because no matter what kind of manifold you use, the distributor location and height of the mounting pad aren't going to change. The distributor mounts to the block. Like I said no DUI experience on a 351 w but it's not a manifold problem you have there. |
Posted By: JPASS
Date Posted: June-04-2014 at 12:42pm
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I'm curious how this plays out being that I'll be switching to a DUI in the next month or so. ------------- '92 Correctcraft Ski Nautique |
Posted By: TRBenj
Date Posted: June-04-2014 at 1:21pm
| I don't know much about stock manifolds... Other than the fact that they make great anchors! Most people installing the DUI already have aftermarket intakes in their engines. It seems possible that the thermostat housing geometry might be a little different, allowing for greater clearance. If ovaling the bolt holes doesn't buy you enough room, I'd put an Edelbrock Performer intake on it rather than have a DUI custom made. |
Posted By: backfoot100
Date Posted: June-04-2014 at 2:14pm
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This doesn't make any sense at all. Several here have had no clearance issues installing a DUI in a 351. Keno is absolutely right. The dizzy mounting location and height can't possibly change. A quick search at Edelbrock indicates that the 12 bolt intake will fit an older 16 bolt head as long as you have a 16 bolt gasket. Don't ask me how the hell this works because I have no idea. This is exactly why I'll take a Chevy any day. Ford's make absolutely no sense to me. If this is true, your 12 bolt vs. 16 bolt theory is moot. It's the same intake no matter how many bolts it has. Are you sure this isn't a 302? The 302 intake isn't nearly as wide as the 351 so the location of the water neck will be considerably closer to the dizzy. Another option might be to use this time to install a new aftermarket aluminum intake and get rid of that POS stock one. The water jacket housing might be just different enough to clear. I'm guessing that most everybody has done that when upgrading to a DUI anyway. At least that would make the most sense to me. DUI instructions specifically state that they won't fit with an Edelbrock Victor Jr. but nothing mentioned about any other intake. Sorry I'm not more help than that. ------------- When people run down to the lake to see what's making that noise, you've succeeded. Eddie |
Posted By: oldcuda
Date Posted: June-04-2014 at 2:18pm
| Have to agree put a Performer on it kill two birds with one stone. |
Posted By: backfoot100
Date Posted: June-04-2014 at 2:23pm
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Damn, Tim has beat me to the punch again. I concur with him obviously. Edelbrock Performer with stock heads. ------------- When people run down to the lake to see what's making that noise, you've succeeded. Eddie |
Posted By: KENO
Date Posted: June-04-2014 at 4:18pm
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I have an Edelbrock performer hanging around along with one of Tim's boat anchors and there is no real difference in the location of the thermostat housing mount on these 2 manifolds ( I took measurements) or in other words.... it won't solve your distributor problem by putting on a Performer. In your picture, that DUI sits quite a bit higher up than the stock smaller diameter distributor so it can clear the intake manifold right behind it. This gets the distributor housing closer to the thermostat housing also. The diameter of a Prestolite housing without the cap is 3 3/8 inches by the way. Clip down or screw down, same diameter. Add in the cap and the diameter is 3 1/2 inches. Maybe somebody who actually has done this will come along to answer your question, but a manifold change(at least to a Performer) doesn't look like the answer. I too Ken O |
Posted By: KENO
Date Posted: June-04-2014 at 4:29pm
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It seems like an easy solution would be a spacer between the thermostat housing and the manifold to move the whole housing forward enough. You'll then have clearance with any manifold you want to use. You'd need a couple of longer mounting bolts, a gasket for each side of the spacer and somebody to machine the spacer. He could use the gasket as a template. It would affect the alternator alignment due to it's bracket bracket mounting to the housing but some washers could easily remedy this. KenO |
Posted By: Dan in CT
Date Posted: June-04-2014 at 4:43pm
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Thanks for all the comments and the head scratching. I looked up the casing number of my intake manifold and it is the same one spec'd for the 351w. My initial fear was the engine, which is a replacement (1981 boat and the engine tag says '83), was actually a 302 and not a 351w as the tag indicates. I am pretty sure the cast number on the intake proves it is a 351w. As for the intake manifold not making a difference, I do not concur. If the water-in port on the front right side of the manifold was 1/2 inch longer (farther forward) then there would be enough room. Thinking back, I had an alignment problem with my alternator that required me to shim out the alternator so the pulleys would be in plane. The support for the alternator extends to the thermo housing. In looking at the thermo housing is there a spacer between the manifold and the housing. That would push the thermo out just enough. Could there be a missing part? Where can I find a replacement housing? I agree, there is something wicked about this Windsor....if that, in fact, is your name! |
Posted By: Dan in CT
Date Posted: June-04-2014 at 4:51pm
| I wonder if the Thermo housing is the wrong part. There is a casting number on it. I'll take a look. Dan |
Posted By: KENO
Date Posted: June-04-2014 at 5:06pm
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That's what I'm talking about a spacer for in my last post. It moves the housing forward. On a stock 351 with a prestolite you have about 3/4 to 7/8 inch clearance between the distributor cap and the hose to the left manifold. Slip the old one in place and measure with the cap on. The cap tapers as it goes up so measure to the cap You'll then know a little more about your stock manifold and if anything is out of whack. KenO |
Posted By: Dan in CT
Date Posted: June-04-2014 at 6:15pm
| So, I am going to take the thermo house off and see if I can get the clearance by elongating the holes. If that is a no go, I have a chunk of aluminum that I have been itching to do something with. Might machine my own spacer. I'll keep you posted. Dan |
Posted By: gun-driver
Date Posted: June-04-2014 at 10:23pm
| Why are you putting a DUI on with stock parts that's putting the cart before the horse, a big waste of money if you ask me. |
Posted By: KENO
Date Posted: June-04-2014 at 10:53pm
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Hi Dan Hope the project goes well for you. As an "oh by the way", if you had a 351 with an Indmar conversion instead of a Pleasurecraft, there is plenty of room for the DUI distributor because the thermostat housing setup is completely different. But that's mostly on them M..m..m..mastercrafts Ken O |
Posted By: 81nautique
Date Posted: June-04-2014 at 11:19pm
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I put a DUI on a 93 stock 351 carb'd nautique and although it was tight it went on fine. Looks like the same thermostat housing to me too so not sure what's going on. ------------- You can’t change the wind but you can adjust your sails |
Posted By: Dan in CT
Date Posted: June-04-2014 at 11:21pm
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Useful comment Mr. Gun Well I guess I wanted to replace the stock prestolite that was bastardized. Marine distributors are not cheap, since I was going to make the investment I figured I would get something that was highly recommended and made in the US. I also figured on taking it with me to my next boat. Besides a good strong spark can't hurt an old tired boat. Also this upgrade was supposed to be fairly painless, meaning less time lost on the water. All in all, I don't think it the purchase was a waste of money. Of course, you can disagree, I just wanted you to know that I had thought about where I was going to spend my boat money this year. Thanks for your concern. By the way, got basically the same comment from my wife. |
Posted By: Hollywood
Date Posted: June-04-2014 at 11:35pm
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Sounds like the thermostat housing is effed up but you might just want to start from the beginning and firming up what is what. ------------- |
Posted By: TRBenj
Date Posted: June-05-2014 at 12:08am
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I picked up 200rpm in both holeshot and wot when i put a DUI on my otherwise stock 90. I couldn't see spending $100+ on another junk EI kit, so I understand the rationale. Room for growth! There's definitely something oddball about the housing or that particular intake... |
Posted By: Gary S
Date Posted: June-05-2014 at 12:35am
Could do what Reid does and just put higher hp decals on  ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |
TRBenj wrote:Posted By: gun-driver
Date Posted: June-05-2014 at 12:36am
| If he went with the Mallory electronic distributor, the extra 100 bucks plus that he would have saved would put him close to half way to a better intake and get rid of the "boat anchor" intake he's trying to use. |
Posted By: TX Foilhead
Date Posted: June-05-2014 at 1:12am
| Mallory stuff isn't an upgrade anymore, it's junk. |
Posted By: gun-driver
Date Posted: June-05-2014 at 10:41pm
Junk really!! I guess I got lucky then as mine has worked flawlessly since I installed it a couple of years ago. |
Posted By: Waterdog
Date Posted: June-06-2014 at 10:09am
+1 Mallory E-spark  ------------- - waterdog - http://www.correctcraftfan.com/diaries/details.asp?ID=3896&sort=&pagenum=2&yrstart=1978&yrend=1978" rel="nofollow - 78 Ski Tique |
Posted By: Dan in CT
Date Posted: June-06-2014 at 10:44pm
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More data. Found there was not enough play in the water neck to squeeze the hose on. Going with a spacer. Found I had a piece of 1/8 brass plate. That with a couple of gaskets and I should be ok but it will still be tight. Here is a picture of my water neck. http://s1296.photobucket.com/user/ctwolframs/media/imagejpg1_zpsb0fbd72f.jpg.html" rel="nofollow">  [/IMG]
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Posted By: Dan in CT
Date Posted: June-09-2014 at 12:54am
| Just to close out this Topic, spacer was successful. Only needed 1/8 in. Thanks for everyone's help. Guess we can chalk this one up to funky one-off casting problem. Dan in CT |
Posted By: Hollywood
Date Posted: June-09-2014 at 12:27pm
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Probably too late to notice now, but was the alternator bar aligned properly before? ------------- |