Nola Mike's 3.7/470 --> 4.3L swap thread

[nola mike]

Thanks guys, that was the diagram I was looking for (got one for the 470?). Rick Stephens , was that jig before you installed the inner transom plate? Mines not coming out, so would that work or could I just use the aft mounts somehow? And haven't looked into this too much yet, but although I know I need to glass in mounts, I'll admit that I don't know any of the specifics at all. Care to point me to the info?
I'll keep looking at the carbs.

 

[Rick Stephens]

The jig is held up, against the transom, the the top straight edge even with the top of the transom plate motor mount. The bottom edge of the jig is then the correct height for the glassed in mounts. So yeah, you use the jig with the transom plate installed and just hold it against the transom to each side of the transom plate. You can sight over the top straight edge straight across both motor mounts to get the height correct. My motor mounts ended up something like 3/4 of an inch below my deck height. Made it super easy to lay a 2 x 4 on the deck and across the bilge and make my motor mounts 3/4 inch below that. Your measurement will be different, but you get the idea.

I don't think you have any use for a 470 diagram. Moving forward it is all 4.3L for you.

Here's a pic. I have the mounts peanut buttered in and you can see I put a piece of angle across the transom plate motor mounts, then I slip the jig, which is sitting to the right, against the transom and slide it up until it touches the angle from underneath. The bottom edge of the jig is then correct height for the mounts:

 

[nola mike]

Awesome, that's super helpful!
So, for the mounts, did you just layer exterior ply to the correct height (looks like you have an interior support there as well)?

Did you do anything with the existing glass, or just sand it down and tab it in? How many layers?

Any hardware fastening the wood, or just fiberglass?

What kind of matting?

It actually doesn't look too intimidating. Looks like a 1/2 day job (according to my wife, that means it's actually a 1.5 day project)?

I don't think you have any use for a 470 diagram. Moving forward it is all 4.3L for you.

I don't want any surprises with the dimensions, particularly the engine height at the exhaust manis.

 

[Scott Danforth]

when I did the mounts for my boat, I did 3 layers of 1708 after tabbing.

I also thru-bolted the mounts to the stringers to hold them until the PB set up.

make sure you have plenty of gap between your adjustable mounts and the fiberglass. while you can add shims for height, making custom short mounts is a pain in the backside.

 

[Rick Stephens]

Layered plywood with PB and carved out a shape I thought looked good. I did not bolt into stringers. Just made darn sure I sanded down to the pink and then glassed in. The glass is where the structural strength is, not the wood. I probably way over killed how much glass I used, but better then the alternative. Structurally, tied the glass the length of the stringers and up into the transom.

 

[nola mike]

Good info guys. I've been calling around to machine shops, and have been getting very vague answers with long turn around times. Not many reviews for any, so not sure how to choose. A couple want me to strip and reassemble the block, which I don't know that I trust myself doing, nor do I think that I want to spend the time doing it. Planning on heading down today and taking the accessories off, clean, and remove the heads. BUT I was wondering if it would be worth while to pressure test the block first, and as importantly, can that be done without specialized equipment once the heads are off? And what work/price should I expect to have done, assuming it was a running engine, no huge surprises? Are we just talking polish crank, cylinder hone, rings, oil pump, bearings...?

 

[Bondo]

BUT I was wondering if it would be worth while to pressure test the block first, and as importantly, can that be done without specialized equipment once the heads are off?

Ayuh,..... Once the intake is pulled, that's off the table, without a buncha block-off plates, 'n such,......

I'd find a machine shop, 'n deliver it complete, with the heads on, a Long Block,.....

As for the amount of machine work, that's why you want a machinist to tear it down, inspect, 'n measure everything,......

You might find, just buyin' a long block crate motor a better deal,.....

 

[nola mike]

Well, I got impatient and wanted to get a rough idea of what I was dealing with, and this looks to be an almost completely unmolested sweet water engine. Everything looks original, wiring harness intact, original alternator, manifolds looked solid, etc. Even the dizzy cap looked original (though I don't know if that's good or bad). Only thing wonky was that there was orange RTV on the thermostat housing, and it looks like the tstat was missing :grumpy: . I couldn't feel it from underneath, but didn't investigate too much.

Otherwise the oil in the head looked clean, the cylinder walls looked very nice except some surface rust in #2. Wondering if a bit of rain water got in there after I pulled it, since I spun it over before. Anyway, seemed superficial and turned easy. I could feel a slight ridge at the top of a couple of bores with my fingernails, but really nothing. Probably would have been fine to throw in as is, but that isn't the point.

Only concern is still a cracked block, but I'll have the shop check that first. I didn't see any cracks in the lifter valleys, core plugs in place, no water in the drains (though I guess a cracked block is a good way to drain the block also). I forget where the 4.3's like to crack...

Found a guy with a 2 week turnaround, but man I'd like to get some references. He had like 6 good google reviews in the last 5 years.

As for the cost, a reman is >$2500, and I have $0 into this block so far. Even if everything had to be replaced...

 

[alldodge]

2 week turn around

If he's good and doesn't have much work load then all good

Not having a large work load could be due to what's happening now, and not that the place is just not that good

 

[achris]

Non-vortec engine... Hang out and see if you can find a pair of vortec heads and a manifold...

Chris.....

 

[Lou C]

blew up the pic, thought I saw some cracks on the lifter valley, left hand side as you look at it from the front...

 

[Scott06]

blew up the pic, thought I saw some cracks on the lifter valley, left hand side as you look at it from the front...

Agreed that does look like typical freeze cracks. I bought a handmans special with a cracked 4.3 and that is exactly where it was cracked on both sides of the lifter valley.

 

[Lou C]

For my next one as much as I'd like to save money, its going to be either:
a reman pre-vortec like my original engine (rated at 205 hp with the 4bbl) so all my stuff fits perfect...or....
a new Vortec 4.3 with an Edelbrock dual plane manifold, my Quadrajet, and a half closed cooling kit (can't do full on my Volvo manifolds).
I like the idea of more hp, the vortec is supposed to add about 20 hp and the manifold 'might' add another 18 according to Edelbrock, not sure that's true.
Putting reman heads on my old block was a risk too but not that much money and if it went south I could always take the route of buying a re-man short block and putting those good heads on it...

 

[nola mike]

Non-vortec engine... Hang out and see if you can find a pair of vortec heads and a manifold...

Chris.....

The plan is to grab some vortex heads from the wrecker...Manifold looks like I can buy new cast for ~$250

 

[nola mike]

blew up the pic, thought I saw some cracks on the lifter valley, left hand side as you look at it from the front...

Crap, it sure does in that pic. Now I can't get back to it until after the weekend, so I'll be thinking about it...
Worst case, I grab a long block from the wrecker. $450. If I pull it from a truck, I wonder if it's even worth doing anything to (aside from HG and core plugs), or just throw it in and go boating...
Either way, I'm still $0 in and now have everything I need for the swap except for the manifold, carb, and block.

 

[Scott Danforth]

Check the area with die penetrate. Looks like a crack, howevef could be a casting flaw

 

[Rick Stephens]

When I rebuilt mine, the machine shop had two nice cores sitting on the floor in back. He magnafluxed my block, since it had a ton of rain water in it we didn't know if it was cracked anywhere. We decided to go ahead and build mine out and it was fine. But he offered a pretty cheap deal on one of his blocks. So don't be afraid to ask your machinist if yours is cracked. He just might have something.

Rick

 

[Scott06]

Crap, it sure does in that pic. Now I can't get back to it until after the weekend, so I'll be thinking about it...
Worst case, I grab a long block from the wrecker. $450. If I pull it from a truck, I wonder if it's even worth doing anything to (aside from HG and core plugs), or just throw it in and go boating...
Either way, I'm still $0 in and now have everything I need for the swap except for the manifold, carb, and block.

If it has decent compression and oil pressure yes just change head gaskets and plugs

 

[nola mike]

Well, went in today for a closer look. No doubt after I cleaned it off a bit...This block's a goner. Missing my 470 already stonyloam ! Thanks Lou C for picking it up on a crappy low res pic. So on to plan B. I think I'll grab a long block from the pick 'n pull. I don't know if I'll know the mileage on it or not, I'll have to check in to it. They do come with a warranty. This is a setback, but not the end of the world. The accessories and brackets were always going to be the tough part, and I have all the marine stuff.
So...
1. I guess I'm now in the market for a balance shaft post '96 vortec. Will I have any problems mounting my accessories from the '89? Aside from the fuel pump? I guess the mounts are different as well. Any other gotchas? Didn't know if the RMS difference would change anything, and I wouldn't think the change to serp belt would be of concern, but IDK.
2. What do the rest of you guys think about doing anything to the block v. just marinizing it? I was thinking check compression first (wonder if I can do this before I purchase...), pull the heads and see how the bores look. Guess that would at least be the first step, and I can proceed from there.
3. What should I take from my current short block? Flywheel/coupler, Oil pan different? Dipstick...I think I've removed most of the rest. Core is only $15, so didn't know if it was worth keeping the cam, crank, etc. I've never disassembled a big engine, so I'll probably do that anyway just to see how it's put together.

Other advice always welcome...I want this on the water by the end of May. I'm not working in May as of right now, so I'll have plenty of time. Not having to rely on someone else to machine the block would be nice.

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[Rick Stephens]

None of the accessories will fit a true Vortec block. Those blocks have serpentine belts, different balancer, and different pulleys on all the accessories. I'd consider that a no go altogether. Stick with a pre-96 block and you'll save enough to get vortec heads should that be your desire.

Rick

Note: I can't post a private message.. Some bug that has the screen flashing in any browser. I mentioned to you I don't have the Mercruiser 4.3L manual. Never really needed it. A Chevy is a chevy is a chevy.