351 Head swap
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=49946
Printed Date: May-02-2024 at 10:20pm
Topic: 351 Head swap
Posted By: Peter Gullen
Subject: 351 Head swap
Date Posted: June-25-2021 at 4:07pm
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Hi, I have snapped 3 plugs trying to get them out of a head that has a small crack in the water jacket, which occured and was welded before my ownership (last 17 years). The crack has always weeped since I've owned it, but has been getting worse last few years. Plugs are probably 5 years old, and have rusted through. I think at this point I'm better off replacing the head, rather than trying to get the broken plugs out and deal with the crack. Does anyone know if this used 1969 C90E 351 head would be compatible with my 1993 351? https://www.ebay.co.uk/itm/224503400785 Is it as straightforward as installing with new bolts and gaskets, or is there checking/ measuring of the valves etc I would have to do? I'm in the uk, so heads are not as easy to find. Not really interested in performance upgrades, just want to get the boat operational again. Has approx 1500 hours on it, with what I believe is all original engine. ------------- 93 Ski Nautique |
Replies:
Posted By: Jonny Quest
Date Posted: June-25-2021 at 6:16pm
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A GT40P head has perpendicular plugs and will be a performance upgrade. I realize shipping to UK may be a challenge, but worth evaluating. JQ ------------- Current 2003 Ski Nautique 206 Limited Previous 2001 Ski Nautique Open Bow 1994 Ski Nautique Open Bow Aqua skiing, ergo sum |
Posted By: KENO
Date Posted: June-25-2021 at 7:28pm
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Not knowing what you have for an engine, maybe the standard carbureted 240 or so HP engine, the head in the Ebay ad will bolt up to your engine. And it's not a gt40 head like the seller says It's a 1969 head that was a very good 351w head till the gt40 and later 40P heads came along. If you bolt it on, you'll need 4 spark plugs with 18mm threads for that head, Autolite 45 would be an example to go with the14 mm threads on the other side.Autolite 24 or 25 for example. You really don't know what you're getting and how much work it may or may not need so there's that risk involved too. Click on the link below to read about a Crazy Canuck who has a boat with 2 different heads like you would have. His boat runs good with the mismatched heads. http://www.correctcraftfan.com/forum/forum_posts.asp?TID=49754&title=just-noticed-that-i-have-2-different-heads" rel="nofollow - link I figure your decision probably comes down to budget more than anything else
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Posted By: Peter Gullen
Date Posted: June-26-2021 at 12:56am
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Thanks Keno, yes it's the standard 240 HP. Regarding your comment about not knowing how much work it would need, is there any tests/ checks I should do, or is it a case of bolting it on and checking compression/ seeing how it runs? Good to know about the spark plug issue. Do you have any suggestions for a source for a new bolt on replacement if this doesn't work out? ------------- 93 Ski Nautique |
Posted By: slmskrs
Date Posted: June-26-2021 at 1:42am
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I replaced my GT40 heads with GR40P heads on my previous ('96). I don't know if your heads have the same hydraulic lifters, but if so, I wrote down the whole process step-by-step, including valve adjustements. If you go that route, happy to send info. ------------- Gordon '97 Ski Nautique, GT40 |
Posted By: GottaSki
Date Posted: June-29-2021 at 7:53am
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Totally different rocker system on those two heads. ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: KENO
Date Posted: June-29-2021 at 8:22am
This sentence should be a little longer, it should say............... Totally different rocker system on those two heads, but it doesn't matter, the rocker ratio is the same and the pushrods are the same length. It just a different way of attaching the rocker arms
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GottaSki wrote:Posted By: GottaSki
Date Posted: June-29-2021 at 8:45am
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ah I see, it comes with the rockers ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: Peter Gullen
Date Posted: July-19-2021 at 3:52pm
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Seems the valves are larger on the used head I bought (casting number C90E) , and so I would need to have it machined to accept my old valves from the cracked FOJE to avoid having one bank run leaner than the other. The valve stem is different length as well, as is the adjustment method. C90E has manual adjustment, and FOJE is hydraulic, so I'm not sure its actually possible to swap the valves. Also found a small crack in the other existing heads water jacket, so its starting to make more sense to just get a pair of Reman heads instead of trying to bodge what I have. Anyone bought from these people before, and know if these heads are compatible? https://www.ebay.com/itm/172431585501 Or suggest an alternative? Thanks ------------- 93 Ski Nautique |
Posted By: KENO
Date Posted: July-19-2021 at 4:55pm
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Like was mentioned earlier, you'd bolt the whole head on complete with it's old big valves, springs and rockers. The engine wouldn't really care, it's rich enough that a little difference in mixture wouldn't matter. Crazy Canuck has the same head mismatch above with no issues. But............since the other head is cracked too a couple of rebuilt ones would be good. I've used Odessa around 10 years ago with no complaints, but their Ebay rating "ain't too good" these days. I'd wait and see if anybody else has any recent experience
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Posted By: MrMcD
Date Posted: July-19-2021 at 5:11pm
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If you are going to spend the money on shipping all the way to England I would use a known quality rebuilder. Jasper Engines is one, or get a new set of heads. While valve size can give you a slight power increase the Chamber size is important when you swap heads. If your heads are 70cc chambers you would need to match that or be aware of the changes in compression and maybe fuel quality needed should you swap in say 60cc chambers. When chamber size is decreased compression goes up. That can certainly help power but you need to know what you have and where you want to go. ------------- |
Posted By: Hollywood
Date Posted: July-19-2021 at 6:38pm
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I just begun tearing down a running 351 last night. Had one D5TE (small plugs) head on one side and a D0OE head (large plugs) on the other. PM me if either interest you. |
Posted By: gun-driver
Date Posted: July-19-2021 at 7:05pm
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I have a set of the original heads from my '85, had about 550 hrs on them when I changed them out when I built it up for more HP. I can check the heads for numbers tomorrow.
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Posted By: Peter Gullen
Date Posted: July-20-2021 at 4:53pm
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Thanks all. I may have found a local place- will see what they come back with tomorrow. ------------- 93 Ski Nautique |