PDA

View Full Version : '89 PS 190, 351 blown headgasket, new GT40 heads, happy ending!


Kevin 89MC
08-02-2011, 01:06 PM
Well I overheated my 351, blew a headgasket and cracked a head. I had rebuilt my carb this spring, and then just chased down a high speed stall (turned out to be fuel filters) and it was finally running great, then I hear the dreaded alarm, notice the temp gauge is pegged, so I shut it down. Open the engine cover and see the pump cover sitting in the bilge. Somehow I must have forgotten to tighten the raw water pump screws. Scrounge around, find 3 of the 4 screws, put it back on, let it cool down, and boat home. Put in a new impeller, luckily I had an old brass screw at home (never did find the other one, somewhere in the bilge I assume), new gasket on the impeller cover, and it seems to run just fine. I took it out a few times, and slowly it gets louder, sounds like an exhaust leak, but I canít isolate it. Then I ran it without the engine cover, so I could try to isolate where the noise is coming from. Exhaust appears fine, so then I ran it without the spark arrester (fire extinguisher close at hand), and up at speed I can hear what sounds like an exhaust leak coming up back through the carb. Then it occurs to me, I better check compression. I get a compression tester, and #1 and #2 were showing 30 psi, everything else over 100. I bet I was hearing the combustion of what turned out to be #2 out through #1. Should have done that first, lesson learned.
I clear out the garage so I can get the boat in, and tell the wife her truck will be spending some time in the driveway. Start tearing into it, get the starboard head off and sure enough gasket is blown between #1 & #2. Here are a few pictures:

Kevin 89MC
08-02-2011, 01:09 PM
I order up all the gaskets from Skidim and ARP headbolts from Summit. That intake was heavy! Thought about upgrading that, but a little short on cash right now. Got the old head gasket off, and notice the block deck had swelled between #1 & #2, probably due to me driving it to chase what I thought was an exhaust leak, but was really a blown head gasket. Being cheap and trying to avoid pulling the engine, I decide to take a metal file and with some cutting oil, and file down the raised edge. I kept checking my progress with a straightedge, and it actually worked out quite well. Spent a lot of time with razor blades and gasket remover getting the deck clean. A few more pics:

Kevin 89MC
08-02-2011, 01:13 PM
Then I went to clean up the head and reinstall it, and noticed that it is cracked between the intake & exhaust valve. I had done some research on here (I love this site!) and notice that I can get GT40 or GT40p heads from a 90ís Explorer with the 302. I found one in the local junkyard where you pull your own parts that has the 302. It had the GT40 heads (couldnít find one with the GT40p heads) so I figure they will be much better than my stock heads anyways. Plus they are only $38 each! It took a lot longer to get the heads off the Explorer than the MC, spent more time getting all the accessories & exhaust out of the way, than actually pulling the heads. But for that price I canít complain. Wow, those valves are way bigger than the stock heads! Getting excited. Took the heads to the local machine shop, and he said they checkout OK, no cracks. He cleans them up, does a valve job, puts new valve stem seals, changes out the plugs to brass, and drills out the head bold holes to ĹĒ. The bill was a lot ($450), but the heads turn out really nice, he did a great job so it was worth it. Check out the pics:

Kevin 89MC
08-02-2011, 01:15 PM
I went to the auto parts store to get the RTV for the intake corners, and figure I better paint the heads so they donít rust. I could have gone with black to match the block, but I thought that sounded boring, the engine needs some color! My first thought was red, but the can says ďChevy RedĒ and I thought that would be bad karma, so I found ďFord BlueĒ and thought that should look nice! Here they are in my high tech paint booth:

Kevin 89MC
08-02-2011, 01:18 PM
So then I go to pull the port head, and that thing would not budge at all. The starboard head just lifted right off, so now Iím getting concerned. I triple check to make sure nothing is holding it on, and I anchor a come-along strap to the beam in the garage ceiling, and crank on it until I think it is going to break. No dice, someone must have welded the head on! Seeing as I knew I was not going to reuse the head, I figured Iíd whack on it with a brass drift and 5 lb sledge hammer. It took 2 solid blows for it to pop. I thought Iíd find some issues, but the head & deck look just fine. Took a bit to get all the gasket off, but the deck cleaned up OK.
Got the heads on, and the one thing I donít like about the Skidim kit is the wimpy cork gaskets for the intake. Too bad they donít have the original rubber ones. Somehow I was able to get the intake on (with the distributor still on) without moving the gaskets around. They donít appear to leak, but I will keep a close eye on them. I checked compression cold before putting the exhaust manifolds back on, just because it is easy. #1, 3, 5, 6 and 7 are all at 140, #4 and 8 are at 150, but #2 was at 112, then 122 with a bit of oil added in. I know cold numbers donít mean much, but it appears that #2 may have some lingering problems, time will tell. Getting the exhaust manifolds back on was a real pain, I had left the risers on the manifolds and the hoses attached, and that was a lot of weight to deal with while trying to get the holes lined up, but I eventually got it. I was just about to finally fire it up, and then realized the old plugs wouldnít fit the new heads (they were only a year old). It was late Sunday night, so I had to wait until Monday, but the anticipation was killing me! More pics:

Kevin 89MC
08-02-2011, 01:20 PM
Finally got the plugs in, wish I could have found the p heads, the GT40 heads are actually worse than the old heads for getting at the plugs! I was VERY nervous firing it up, but it started up easily and idled nicely in the driveway. Took it out for a water test, and it seemed to run great! Re-checked compression with it warmed up, and I feel much better, #1 was 129, #2 was 125, #6 was 130 and #8 was #125. That was all I felt like checking, I was having a real hard time getting the compression tester into the holes. Changed the oil & filter too. When I winterize I plan to pull all the plugs and inspect them, and check compression on all cylinders then.
Now for the really good news: I took it out over the weekend and skied behind it. It now skies MUCH better than it used to. Before the pull always felt a bit “hard”, and I think it was due to me being able to slow the boat down enough that it would “recover” when I released at the ball, and it would be running a bit fast when I hooked up. Having a 1:1 trans doesn’t help either, but now having more power has made a noticeable improvement. In the past I was barely able to run 15 off at 34 on mine, but on other boats I can run 22 and get into 28. I was able to run 22 off behind mine for the first time ever on Friday, so that felt great! The pull is definitely “softer”, and times were right on. Power is up across the board, and by quite a bit I think. I re-calibrated perfect pass from 30-36, and had to pull between 35 and 135 rpm’s off all speeds. The biggest difference, though, is my top speed increased from about 42 to over 46! It should be better for footing, as we could really slow it down sometimes. It is apparent that heads make a noticeable difference in performance, as I know it takes a lot of HP to gain a few mph at top speed. I know an upgraded cam and intake would help more, but in light of Kyle’s experience, I don’t have the time or money to pull the engine now. Time will tell if I made a foolish decision by not freshening up the bottom end.
It was a ton of wrench time, but so far it appears to have paid off. I’ll be on it tomorrow night, then taking it on vacation for a week next week, so that will be a good test. This site is the best, I got the courage to dig this deep only by reading of other’s experiences on here. This site, Skidim and the Indmar owner’s manual are essential tools for wrenching on boats. Long live the old MasterCrafts!
Kevin:steering:

gr82bgreen
08-02-2011, 01:44 PM
Very cool. job well done. nice to not only fix the engine, but improve it as well.

woodrowskis
08-02-2011, 02:03 PM
I had an 86. Around 2000, I upgraded to the GT 40 heads but also changed to an Edelbrock manifold, and roller rockers. It was definitely a power upgrade. With the lighter weight of that boat it was very quick. I had already put a more modern Mallory marine distributor on. That did not give more power but it had a lot more precision in the response. But that could have been to my original alternator being worn

thatsmrmastercraft
08-02-2011, 02:32 PM
Great job - nice write up. Next time you get the itch it won't take much effort to upgrade the intake.:cool:

MasterKraftS&S
08-02-2011, 02:36 PM
NICE! Both intimidating AND Inspiring! BTW Got the following TIP from a guy at SKIDIM - Buy GT40p heads from www.tristatecylinderhead.com. Just ask them to drill the head bolt holes for a 351, $598.00 for a pair. - That's about the same price Kevin paid(after machining) minus the trip to the junk yard. Much better than skidim's $2200+/pair(as if . . ). I'm gettin' HEADs for Christmas! (Careful there I said HEADS!!):smile:

Kevin 89MC
08-02-2011, 02:54 PM
Yeah, I had looked at tristate cylinder head also, almost went that route. But I figured shipping would be $$$ (the heads are heavy!) and did not think my machining bill would be so much. Knowing what I know now I would have looked harder for GT40p heads locally, or got them from tri, if only to make checking spark plugs easier. Great upgrade either way, good luck with yours!
Kevin

LYNRDSKYNRD
08-02-2011, 06:49 PM
Great write up!

j.mccreight@hotmail.com
08-02-2011, 11:28 PM
Did your use the original rockers, lifters and pushrods, was there any issue there?

Kevin 89MC
08-03-2011, 04:49 PM
Did your use the original rockers, lifters and pushrods, was there any issue there?

Yes I did reuse it all. The 302 rockers were identical, but they were pretty dirty. Mine looked much cleaner, just a quick wipe and they looked good as new. The pushrods all checked out to be straight, ends looked good, so I cleaned them up, blew compressed air through the centers, and reinstalled them. I did not touch the lifters. No issues so far, but it's only been on the water twice.

mmpol30
10-16-2011, 03:01 PM
So then I go to pull the port head, and that thing would not budge at all. The starboard head just lifted right off, so now Iím getting concerned. I triple check to make sure nothing is holding it on, and I anchor a come-along strap to the beam in the garage ceiling, and crank on it until I think it is going to break. No dice, someone must have welded the head on! Seeing as I knew I was not going to reuse the head, I figured Iíd whack on it with a brass drift and 5 lb sledge hammer. It took 2 solid blows for it to pop. I thought Iíd find some issues, but the head & deck look just fine. Took a bit to get all the gasket off, but the deck cleaned up OK.
Got the heads on, and the one thing I donít like about the Skidim kit is the wimpy cork gaskets for the intake. Too bad they donít have the original rubber ones. Somehow I was able to get the intake on (with the distributor still on) without moving the gaskets around. They donít appear to leak, but I will keep a close eye on them. I checked compression cold before putting the exhaust manifolds back on, just because it is easy. #1, 3, 5, 6 and 7 are all at 140, #4 and 8 are at 150, but #2 was at 112, then 122 with a bit of oil added in. I know cold numbers donít mean much, but it appears that #2 may have some lingering problems, time will tell. Getting the exhaust manifolds back on was a real pain, I had left the risers on the manifolds and the hoses attached, and that was a lot of weight to deal with while trying to get the holes lined up, but I eventually got it. I was just about to finally fire it up, and then realized the old plugs wouldnít fit the new heads (they were only a year old). It was late Sunday night, so I had to wait until Monday, but the anticipation was killing me! More pics:
Why did you need new spark plugs, and what kind are the new ones you needed? My spark plugs have less then 10 hours on them.

Kevin 89MC
10-17-2011, 12:49 PM
The GT40 heads need the longer plugs. Not sure about the GT40p heads. The old plug threads would not even catch the plug holes. I think the new plugs are Autolite 764, the old ones were Autolite 24 I believe. Yeah, 6 of my 8 plugs looked very clean, haven't thrown them away yet, anybody want them?
Kevin

joniron1
10-17-2011, 06:50 PM
odessa cylinder head (can be found on ebay)reman gt40p w /brass plugs installed and bolt holes bored are $200 per head w shipping included. I couldnt be happier with the workmanship or performance ugrade.