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Siezed GT40

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TimSpangler View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TimSpangler Quote  Post ReplyReply Direct Link To This Post Posted: May-18-2012 at 12:40pm
Originally posted by TRBenj TRBenj wrote:

Originally posted by TimSpangler TimSpangler wrote:

I believe that biggest difference in the GT-40 (at least I know from an automotive perspective) was the airflow. The GT-40 eliminated a lot of the airflow restrictions and generally allowed the engine to "breathe" better.

I believe the GT40 and the other PCM HO 351w's (carb/TBI) shared the same longblock (block/heads/cam/pistons). The only difference was the intake (and of course the fuel system). They all performed similarly well, and had similar hp ratings (285-310hp).


I think that it was the short block that was the same. The heads I know where different between the std and the the GT-40. (at least from an auto perspective), but yeah they all were close in performance.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TRBenj Quote  Post ReplyReply Direct Link To This Post Posted: May-18-2012 at 12:42pm
Note that I said "HO" PCM's above. They made both a 240-255hp "standard" version, as well as HO (aka Pro Boss) versions (starting in 1992). First carb, then TBI ('94-95) and then multiport (1995-2002). All HO PCM's used GT40 heads, the GT40 MPEFI included.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bri892001 Quote  Post ReplyReply Direct Link To This Post Posted: May-18-2012 at 12:46pm
Originally posted by TRBenj TRBenj wrote:

Note that I said "HO" PCM's above. They made both a 240-255hp "standard" version, as well as HO (aka Pro Boss) versions (starting in 1992). First carb, then TBI ('94-95) and then multiport (1995-2002). All HO PCM's used GT40 heads, the GT40 MPEFI included.


Any idea where they get the 15hp difference in the 240-255hp Standard versions? I've seen both ratings listed, but it sounds like basically the same motor.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TimSpangler Quote  Post ReplyReply Direct Link To This Post Posted: May-18-2012 at 12:47pm
Sorry Tim. I'm not as much up on the marine stuff as I am on the auto. The "HO" on the auto side only really got you a roller cam. So you say the "HO" came std with GT-40 Heads?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TimSpangler Quote  Post ReplyReply Direct Link To This Post Posted: May-18-2012 at 12:50pm
Originally posted by Bri892001 Bri892001 wrote:

Originally posted by TRBenj TRBenj wrote:

Note that I said "HO" PCM's above. They made both a 240-255hp "standard" version, as well as HO (aka Pro Boss) versions (starting in 1992). First carb, then TBI ('94-95) and then multiport (1995-2002). All HO PCM's used GT40 heads, the GT40 MPEFI included.


Any idea where they get the 15hp difference in the 240-255hp Standard versions? I've seen both ratings listed, but it sounds like basically the same motor.


I know that the GT-40 heads had larger valves.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TRBenj Quote  Post ReplyReply Direct Link To This Post Posted: May-18-2012 at 12:53pm
Im not sure if PCM ever called them "HO", but rather used the term "Pro Boss" to denote the higher hp version. But yes, all Pro Boss motors came with GT40 heads.

Brian, I think the 15hp difference is purely marketing. The 2 ratings seemed to be used interchangeably throughout the standard 351w's life (early 70's through late 90's), both in CC's and Waukesha/PCM's literature.

Tim, I think Brian's question was what the differences were between the 240 and 255hp "standard" 351w's. I think the answer is "nothing". Obviously the longblocks were slightly different between the standard and Pro Boss engines, most notably the GT40 heads (which youre correct had slightly larger valves than the standard E7's).

The same goes for the 285hp carb'd ProBoss vs. the "300+hp" TBI and the 310hp GT40. Other than the fuel and intake systems, the engines were the same (same longblock).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TimSpangler Quote  Post ReplyReply Direct Link To This Post Posted: May-18-2012 at 1:04pm
Originally posted by TRBenj TRBenj wrote:


Tim, I think Brian's question was what the differences were between the 240 and 255hp "standard" 351w's.


Gotcha. That's what I get for tring to work and surf the net at the same time.

So has anyone used the GT-40P castings? With the different plug angle they look as though they may be a better head for a marine application. I know they were rumored to be a better head than the GT-40.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TRBenj Quote  Post ReplyReply Direct Link To This Post Posted: May-18-2012 at 1:15pm
Originally posted by TimSpangler TimSpangler wrote:


So has anyone used the GT-40P castings?

Oh yes, very common upgrade around here- Im surprised you havent heard of them. Ive been running them for 6 years on my '90.

Youre correct that the plug angles are a bit better for our upswept manifolds. The smaller chambers and slightly better flow make them a very good, economical head choice when upgrading a Ford.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TimSpangler Quote  Post ReplyReply Direct Link To This Post Posted: May-18-2012 at 1:21pm
Originally posted by TRBenj TRBenj wrote:

Originally posted by TimSpangler TimSpangler wrote:


So has anyone used the GT-40P castings?

Oh yes, very common upgrade around here- Im surprised you havent heard of them. Ive been running them for 6 years on my '90.

Youre correct that the plug angles are a bit better for our upswept manifolds. The smaller chambers and slightly better flow make them a very good, economical head choice when upgrading a Ford.


I've heard of them, used to run them on my Mustang back in the day. Very economical replacement for the E7. Wasn't sure if it was the same here. on the auto side, the plug angle was a bit of PITA. I suppose most of the upgrade from the auto side can be used here as well.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TRBenj Quote  Post ReplyReply Direct Link To This Post Posted: May-18-2012 at 1:26pm
I meant heard of them being used on this site, in our Correct Crafts. Very common, and discussed often.

Yes, the plug angle that makes them less desireable in Mustangs (often requiring special headers) makes them better for us... better performing, better plug angle, and less desireable for the car guys = cheaper!

Yes, nothing inherently different about marine vs. auto heads. Though, brass casting plugs are usually recommended for marine. There are people here who run AFR, Trick Flow and RHS heads in their CC's.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TimSpangler Quote  Post ReplyReply Direct Link To This Post Posted: May-18-2012 at 1:29pm
Makes sense.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Silver15 Quote  Post ReplyReply Direct Link To This Post Posted: May-20-2012 at 1:58am
One notable difference between the GT40 and older engines, is that it turns the opposite direction. The transmission contains a reducer, and an inverter which changes the direction of the rotation.
Anyway, I spent most of today cruising around the lake on the Ski Nautique. Seems to run great! GT40 has LOTS of power compared to the '86. It's really unbelievable how effortlessly it plains. Pics coming soon! Can't believe how this boat was literally brought back to life!
-Jake
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TRBenj Quote  Post ReplyReply Direct Link To This Post Posted: May-21-2012 at 11:24am
Originally posted by Silver15 Silver15 wrote:

One notable difference between the GT40 and older engines, is that it turns the opposite direction.

^^That is not quite correct.

The vast majority of PCM engines used in CC's have been LH (standard) rotation since 1989. This includes all of the HO versions that were introduced in '92 (carb), '94 (TBI) and '95 (MPEFI GT40), as well as the standard (non-HO) versions.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote slmskrs Quote  Post ReplyReply Direct Link To This Post Posted: May-21-2012 at 2:27pm
Sorry for my ignorance, but I want to re-confirm that rotational direction is based on looking at the engine from the rear. A LH rotation engine turns the crankshaft pulley clockwise when viewed from the front (which is where I am usually looking at it from). :)
Gordon '97 Ski Nautique, GT40
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bri892001 Quote  Post ReplyReply Direct Link To This Post Posted: May-21-2012 at 2:29pm
Originally posted by slmskrs slmskrs wrote:

I want to re-confirm that rotational direction is based on looking at the engine from the rear. A LH rotation engine turns the crankshaft pulley clockwise when viewed from the front (which is where I am usually looking at it from). :)


This is correct.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TRBenj Quote  Post ReplyReply Direct Link To This Post Posted: May-21-2012 at 2:41pm
Originally posted by Bri892001 Bri892001 wrote:

Originally posted by slmskrs slmskrs wrote:

I want to re-confirm that rotational direction is based on looking at the engine from the rear. A LH rotation engine turns the crankshaft pulley clockwise when viewed from the front (which is where I am usually looking at it from). :)


This is correct.

Yup, you have it right... assuming we're talking about marine engines. I believe the automotive world views things opposite (from the front) which can be very confusing if you start mixing worlds.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Silver15 Quote  Post ReplyReply Direct Link To This Post Posted: May-22-2012 at 10:40am
Oh, okay. I wasn't sure which ones were which. I know the older ones such as the one in or older Nautique spin the opposite direction. This posed a confusing discussion when we were buying a starter.... The technician said that it was evident that it was spinning one direction while we suggested that HAD to be impossible. Can I get some people's opinions on the best oil for the Gt40? Synthetic?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TRBenj Quote  Post ReplyReply Direct Link To This Post Posted: May-22-2012 at 11:07am
RH rotation Ford Windsors require CCW starters. LH rotation requires a CW starter.

Oil for flat tappet cam motors (including the GT40) has been discussed at length... search if you want the back story. 2 good choices that have been identified are:

Valvoline Racing VR1 20w50 (conventional oil)
Mobil1 15w50 (synthetic)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Silver15 Quote  Post ReplyReply Direct Link To This Post Posted: June-01-2012 at 4:51pm
Okay, Thanks, TRB. I'll search up a thread on that. Unfortunately, it seems that we've run into a more immediate problem, though. After the boat ran great for several days with the new alternator etc, we finally cleaned up the interior and put it all back together to use it for the summer. As soon as we put the boat in, I noticed it was running a little rough. Trying to plain out I could feel it hesitating. Drove for 15 minutes or so back to the house and it never fixed itself. I could feel when it would surge into full power and then pull back again almost as if a cylinder was getting bad spark or something. Our good friend, Art, came over to take a look at it. (Very experienced Correct Craft mechanic of many years)Based upon what cylinder was not firing (confirmed with heat gun) and the engine's horrid mantainance history, he diagnosed it as a burned out valve. Great. I guess this means we'll be pulling the heads. Again, this hasn't been 100% confirmed. Could still be a fuel or spark issue. So, now we're back at square one. A little frustrating, but can't complain. Hopefully sourcing rebuild parts for these heads won't be too much of a hassle.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TRBenj Quote  Post ReplyReply Direct Link To This Post Posted: June-01-2012 at 4:53pm
Originally posted by Silver15 Silver15 wrote:

Based upon what cylinder was not firing (confirmed with heat gun) and the engine's horrid mantainance history, he diagnosed it as a burned out valve.

Thats an interesting way to draw that conclusion. Better do a compression test, followed by a leakdown test (if necessary) before jumping to conclusions and tearing the engine down.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bri892001 Quote  Post ReplyReply Direct Link To This Post Posted: June-01-2012 at 4:57pm
Originally posted by Silver15 Silver15 wrote:

..I noticed it was running a little rough. Trying to plain out I could feel it hesitating... I could feel when it would surge into full power and then pull back again almost as if a cylinder was getting bad spark or something...Based upon what cylinder was not firing (confirmed with heat gun) and the engine's horrid mantainance history, he diagnosed it as a burned out valve...


But it sometimes gives full power? Wouldn't a burned valve miss consistently. I would imagine that as a perfectly timed miss coming with every engine rotation.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Silver15 Quote  Post ReplyReply Direct Link To This Post Posted: June-02-2012 at 1:58am
TRB, right. We won't be making any definite conclusions until we have time to stick the compression gauge on that cylinder and see how it reads out. Brian, you have a good point about it surging. For the first little while, it would surge and try to go full steam, but now it's a fairly constant missing on at least one cylinder. The strange thing is, this issue is in direct conjunction with us reconnecting the built in tank. We figured it was getting bad fuel. The fuel it's pumping is clear and clean, though. We changed the FFC filter and added an additional inline filter for good measure. No difference. So, from that, I suppose it is reasonable to conclude that it was just a coincidence. The main reason we suspect the valve at this point, is mostly based upon Art's experience with these engines. Could definitely be wrong though. We'll find out soon enough. Not at all looking forward to the tear down of this complicated monster. One other point would be that it was previously running on 93 octane, and now, on 87, it's having this problem. Does this sound like a connection, or does it really matter the octane on this engine?
Jake
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bri892001 Quote  Post ReplyReply Direct Link To This Post Posted: June-02-2012 at 10:28am
I know my, older more simple, engine is supposed to get 89. I'd imagine the GT-40 would have the same or greater requirement. 87 is not high enough, whether or not that's what's causing the problem is another question.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Silver15 Quote  Post ReplyReply Direct Link To This Post Posted: June-03-2012 at 12:20am
Strangely enough, the problem turned out to be a spark plug, or perhaps multiple. Weird; they're all new plugs..... Anyway, it runs good for now. First evening of skiing behind it. This boat's got some great pull and an awesome ski wake in comparison with the older nautique. Do you think running 87 would damage it? Thanks for all and any words of wisdom. Tried to upload a video, won't work :(.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Donald80SN Quote  Post ReplyReply Direct Link To This Post Posted: June-03-2012 at 1:20am
Mine will not run on regular. I run premium, but could probably run mid grade.

FYI,

Donald
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bri892001 Quote  Post ReplyReply Direct Link To This Post Posted: June-03-2012 at 1:04pm
I'd stay away from the 87 if possible. Most likely, you don't need 91 or 93 but you should at least be running 89.

Congrats on a simple fix and getting on the water
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Post Options Post Options   Thanks (0) Thanks(0)   Quote slmskrs Quote  Post ReplyReply Direct Link To This Post Posted: June-03-2012 at 2:03pm
Originally posted by Silver15 Silver15 wrote:

Strangely enough, the problem turned out to be a spark plug,


How'd you determine it was a plug?

Also, my GT40 manual says use 89, which is what I've always used with no problems.
Gordon '97 Ski Nautique, GT40
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Silver15 Quote  Post ReplyReply Direct Link To This Post Posted: June-18-2012 at 6:52pm
We figured we'd try the "process of elimination" tactic, and new spark plugs ended up solving it. Yeah, it's run pretty well on 87... I guess from a longevity standpoint it would be beneficial to run better quality....
Jake.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Silver15 Quote  Post ReplyReply Direct Link To This Post Posted: August-02-2012 at 1:09am
Hey, all, I'm back with a problem. Boat has been running excellent and faithfully pulling me skiing with no issues until today when the tranny started slipping on hard turns and takeoffs halfway through my run. Come to find out, the fluid was low as I had figured. It's definitely leaking from somewhere because the bildge is a nasty oily mess now. Could it be one of the main seals, cooler, or hoses to cooler? Filled it back up and ran it watching closely for leaks. Can't see any. Anyone had a similar problem? I'm stumped. Thanks in advanced!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote slmskrs Quote  Post ReplyReply Direct Link To This Post Posted: August-02-2012 at 1:29am
Did you run it under load? If you are not seeing it, I'd clean out the bilge as much as possible, fill it, then run it hard (maybe even with the engine cover off so you or someone can watch). Maybe put some paper towels or something else under the tranny to catch anything leaking (hopefully seeing where it is leaking).
Gordon '97 Ski Nautique, GT40
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