Engine rebuild. Head surface issue.

Hi all, first post.
I just had my boat engine rebuilt by an experienced machinist that's been building race engines etc for 40 years. So I'm not doubting what he told me just wanted other opinions.

It's a mercruiser 470. So lower by merc and head is a 460 Ford. Block is aluminum, head is a regular 460 iron. So it's essentially half a big block.

There is a nick on the block where head sits on block- couldn't be tigged or shaved any more. It isn't near the cylinders. It's a thin area of metal along side where the lifter holes are. I'll attach a picture later if needed.

My machinist said just clean it really good and use a little RTV, and I'll never had a problem. He knows what's he's doing and is probably right.

But I really don't like RTV. I have even had bad luck with it sealing oil pans.

So I'm wondering would I be better off using a dab of "the right stuff" by permatex? It's a lot stickier and seems more permanent than RTV. And more flexible which would make it more permanent in my opinion anyways.

The height of the gouge is about 1/8th" deep at the most, and the metal area width wise is 1/8" to 3/16" across. I can get more accurate reading later if needed, but it's pretty small chunk.

Thanks all

We need a pic

I wonder if JB weld/devcon/moglice would be able to fill in the gouge back to deck height and withstand the high temps?

Trying to seal an oil leak with sealer is a futile task, the sealer needs a dry oil free surface to bond to. Could you drill and tap the area for a set screw?

Steve

So, why can't it be tigged?

If the divot is an "Island" that is it does not connect to either water or air and has some good surface all around then no action is needed....
If this is the case, think your guy knows it makes no difference and is suggesting RTV to fill the low spot to make you feel better...

As to sealing with RTV....You are aware that not all RTV's are oil proof....They are not all created the same...
Cheers Ross

QT:[My machinist said just clean it really good and use a little RTV,]
So are you going to install it?
With a head gasket or not?
My son is a race car and truck mechanic.. last head I put on for him he had me use a sealer with the head gasket.like some kind of glue..
I still use the old pattern method drawing all down 60% around from center then 80% then 100% never yet had a problem doing that.
The draw down even I never cared for.

I highly recommend Yamabond 4 over RTV, we used it on all engine surfaces in motorsports engines and it was recommended by every professional engine rebuilder I knew. It is only semi-drying so it stays somewhat tacky, and has enough give to move with expansion across mated surfaces. It is a direct replacement for Threebond 1215.

A 470 is bad bad news. Sorry. It is the worst engine Mercury ever released. We will not even touch one for any money and we are a Mercury dealer. The blocks warp, nothing seals properly afterwards. They're also prone to detonation which will kick the head gaskets out at the best of times. If you have any issues with the sealing surface, RTV, sealer ETC. will not hold.
By the way, do you still have the rotary flame alternator on the front of the crankshft? There is kits available to convert to a regular marine alternator.

Copper coat (Kopper Kote?) can be a lifesaver at times on head gaskets that are iffy. Follow the directions. (yeah, I know. What a thought......)

I just had my boat engine rebuilt by an experienced machinist that's been building race engines etc for 40 years. So I'm not doubting what he told me just wanted other opinions.

Click to expand...

He has 40 years of experience, guarantees his work and then you're questioning his professional recommendation? When this happens, we explain once why we're going to do what we're doing; second question and it's "come get your junk and take it somewhere else."

jack vines

Ok thanks guys lots of good info, I'll get a picture to help. Yes, it will have a head gasket. 470s are good they have to be built right. Stock they have to much compression for the valves. ( machinist told me) so that kind of makes sense with what you said Randy. I didn't know about this over compression issue until the machinist told me. Glad he knew. People either love them or hate them, pretty big following these days.

He also used the better bearings from a regular 460 instead of the merc ones. He had to hand shave them a tad. He showed me the difference between them and the mercruiser ones- there a wider and better quality. He explained why it was a problem but it was to much info at the time for me To remember as I was shelling out the cash for the work. Lol

Mine is bored over 30 and has the lower compression pistons, for the to much compression issue, and bad gas. I have an alternator set up. Stock they have over 300 ft pounds of torque. I have 2 other boats a 78 and 87 the 470s still running stock, other than alternator conversion. One boat I stole a bunch of parts for this glasply build.

I'm not sure why it can't be tigged, he explained it to me awhile back. I do remotely remember him saying something that he didn't want to remove anymore material.

he's the go to machinist for local racers in Wa state so he's def experienced on the machining end, so I'll assume this shouldn't be a big deal but...... lol

Alpha Hopefully the gouge is on an island, I'll try and get pics tonight. Maybe I'm being over paranoid, he wasn't worried about it all.

Torque, and pattern is extra important on these engines, so I've read. But it probably is on all engines.

I have a back yard mechanic to help me mount the head once I get engine back in. But I'll see what you guys have to say may need to take it to a pro. I had to put in the short block separate,
In back of boat, being aluminum wasn't to bad. The head is heavy so have to assemble in the boat.

I have read good things about the Yama bond on boating forums. But isn't that similar to permatex aviation sealer? I have some of that I really like it but " I think" it's more of a thin tac type glue to assist gaskets on slightly uneven surfaces or minor sealing? not so much for voids? But im just guessing I haven't used the Yama.

Ive used Devcon in a similar situation on a Brp 800R motor with good results. It was in the compression o ring groove between the head and jug and subject to full compression and 8000 rpm.

Here are some pictures.

It ain't junk jack and no one said it was. Maybe you should look at pictures first for one thing. I paid good money for this and I have the right To double check.

Like I said I'm assuming it's not an issue but I'm not a machinist so I really don't know what I'm looking at. Take your junk attitude and ignore my question there are plenty of others willing to help. The machinist and I have a good relationship and I did express my concern he's still not worried about it. Bit this is what forums are for. I'm not an idiot I am a steam
Fitter Forman so I have basic concepts of metal and flanges etc. and I paid him cash by the way no questions asked on my end. I was also very clear he knows what he's doing. I'll leave it at that for now "Jack" but thanks for the advice. And yes I do hope I'm paranoid and am wrong. I don't pay 2500 for junk. I dropped it off and picked it up. And he's lending me a torque wrench. Not that it's any of your business but I've paid him another 500 to machine my aluminum exhaust manifold, repair fly wheel and then some. I'm happy with his skill.

I'm trying to post pictures but not sure how, hopefully I'll get it soon.

So some fyi on the size of the divet. Approx 1/8th" x 1/16" total are. To me doesn't look to be an island area. But there is a tad of good metal left. Depth wise maybe 1/16" at most in deepest point but that's maybe in one spot most about 1/32".

If I double post it's because I'm trying to post pictures

Is devcon a brand of red RTV? So RTV can hold is what your telling me? That's good. Right now I have some red permatex RTV, and a new bottle of the right stuff. I'm trying to figure out how to post pictures, it may be because I'm using a phone. I don't see any options or ways to paste or add to an album.

I was under the impression the head was on, with the description just posted, Seiner's mention of Devcon or JB weld consumer sized version of Devcon. Clean the deck with acetone or MEK to remove oils, tape the side and fill the void. I use a razor knife blade to trim the excess on flat surfaces when dry.

Steve

Ok thanks, that wouldn't be hard to do. I'm doing the photo bucket trying to get some pics. It's a fresh complete rebuild.

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Given where this void it is can I ask why you are so worried?
Bob

l take it the void is in a good spot? I don't know, if it was near the cylinder ( bad because of pressure) or a safe island area it would be more obvious to me, but other spots on an engine I wouldn't know where a gouge would be critical. I'm guessing this spot separates oil on lifter side, and water around cylinders? So I guess my worry would be mixing. In A nut shell, I have no idea lol, just want another opinion. All the stories about failed head gaskets etc.