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95_190_PS_PS 03-20-2012 05:19 PM

Working on LT1 engine swap
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I'm working on swapping my LT1 engine with a cracked cylinder wall. I have the engine stripped down to the block and the replacement engine sitting in my back yard right now. I'm not sure if I want to build a platform to raise my engine hoist up of if I should borrow my neighbors pickup truck and lift from the bed (I'm sure I'll get hell for even having that idea).

I have a few questions at this point...does anybody know if there is any gasket or seal between the engine and transmission that will need to be replaced when connecting the powerslot trans to the new engine? Aside from cleaning the bilge out while the engine is out, is there anything else that is recommended? I've read about repacking the shaft stuffing, I'm not sure if it is necessary or not, since I haven't ever had the boat in the water and don't know the drip rate.

On the Northstar distributor, I have a pretty badly rusted spark plug wire connector (I don't know what it's called, so I'll attach pictures). The best solution seems to be to replace the individual coil, the question is will there be any issues with having one new coil and 3 originals from 1995? The replacement coil looks to be part number "DEM GN10123" which I can order from Napa or Autozone...I just want to make sure I get this boat running the best it can.

It also seems like the aluminum honeycomb panel aft of the engine needs to be replaced as well, it is pretty spongy, or at least not firm anymore. Is replacing it with marine grade plywood coated with fiberglass resin the way to go, or should I attempt to find more aluminum honeycomb?

Thanks for any advice.


mikeg205 03-20-2012 06:01 PM

Great thread...keep the pictures coming...I'm sure you'll get and answer from someone.

pram 03-20-2012 06:30 PM

Can you clean up the post?

and if so, will the plug wire still firmly snap on?

95_190_PS_PS 03-20-2012 07:05 PM


Originally Posted by pram (Post 823970)
Can you clean up the post?

and if so, will the plug wire still firmly snap on?

After a few minutes with some fine sandpaper, most of the rust is off, I'm sure that the wire will still snap on firmly, this seems like it would work fine as a temporary fix. What concerns me is that the rust will come back quickly...after something starts rusting, it seems like it will just keep coming back. I can't imagine how cylinder #7 was firing with all the rust on the post, I can only assume that the added resistance would hurt the spark.

When I ran my compression test, cylinder #7 had the highest at 215psi, 10psi higher than the next highest. I wonder if a lack of spark could have possibly minimized wear in that portion of the engine.

mikeg205 03-20-2012 07:16 PM

Put some dielectric gel on it for a good connection. 10psi difference...I would say that's in spec... the engine pro's will confirm or correct....

pram 03-20-2012 07:17 PM

The rust is an easy issue re-occurrence

Vaseline , the lube that keeps on giving, will keep that rust away

pram 03-20-2012 07:18 PM

I would think that lack of spark would have had a negative effect on compression. Excess fuel not being burnt causing piston wash???

now ten percent higher than the next? what were all the cylinders?

95_190_PS_PS 03-20-2012 07:26 PM


Originally Posted by mgorczak1 (Post 823979)
Put some dielectric gel on it for a good connection. 10psi difference...I would say that's in spec... the engine pro's will confirm or correct....

10psi is definitely in spec, that however was between the highest pressure and the next highest. here are my results averaged over 5 tests.
#1 205 #2 165
#3 190 #4 205
#5 205 #6 195
#7 215 #8 180

The manual says that the compression pressure should be between 200 and 225 psi, and calls for a variation of 25% max between highest and lowest and if my math is correct the minimum allowance would be 161psi for the lowest pressure. However a 50psi variation seems like it should be out of specs. The numbers on the left side of the engine seem respectable, but the issue is definitely on the right side. I saw the crack in #2, but #4 fills up with water when the engine runs, so I don't know exactly what the engine issue is. Fortunately, I have a replacement ready to go in.

95_190_PS_PS 03-20-2012 07:51 PM

8 Attachment(s)
Buying the boat with 1700 hours and water in the oil, I knew that it had some issues, I hoped that swapping the exhaust manifolds and risers would have fixed it, and thought that I could get a year or two out of it before the rebuild. There was rust all around on both the manifolds and risers on the left and right manifolds and risers. When I pulled the risers and manifolds, the water jackets were in poor shape, almost looking clogged with crap. After replacing the manifolds and risers and still finding water in the oil, I pulled the heads to find that they were in even worse condition. The previous owner said that he had the heads pulled and checked at a machine shop, I imagine now that he was full of it since he said he had put less than 1 hour on the boat since having them checked and they seem to be clogged, both the left and right side. If they were checked, I imagine the crap would have been cleaned out of the water jacket. I got a good deal and knew that there were engine problems when I bought it. I also knew that the previous owner wasn't all there when he wouldn't return my calls requesting him to sign the trailer registration over to me which was missed in the original sale (Florida DMV helped me out with that one).

mayo93prostar 03-21-2012 01:28 PM

Regarding the floor panel, I had same problem with my 93 and I replaced it with plywood and epoxied over the plywood and then glued new carpet over that. It works well. the aluminum honeycomb is expensive at over $300 per 4x8ft sheet.

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