the black on the fire ring(silver portion),,especially betw the cylinders.

getrdunn,,you are right,,gm had water running around the unprotected exhaust valve guide.plus you have to watch how you take them out,one side of the casting in the head is ever so slightly smaller.have seen a lot of heads that leaked from guide replacement.

Just caught that. I needed a little more focus.

Looks like the fire ring is split on the left cylinder of the gasket. This thing is leaking water in the chambers for sure.

Just so slightly tapered. Only one way out. If you have a good head guy he will do his best and. Cam go oversize etc. Just wonder if there is type of sealer or coating to help while installing new. Little to no clearance makes this nearly impossible but just thinking outloud.

These kind of problems eat away at me. Didn't do it before and does now type of thing. Both engines. ???
Drives a guy crazy.

You'd think especially seeing the back side of the valves but what about the cylinders. You'd surely see evidence of water there as well as Pistons. Any pics of the the Pistons and cylinders OP?

Are the guides shown OEM? Or have they been replaced

Differences

wow I did not see this that's pretty bad

look stock

looks like they've been replaced.

Jesus talk about conflicting lol. God help me.

If they were replaced it was 40 hours ago. Looks harsh for 40 hours.

For starters get inland and off the salt water. Soon! 40hrs??? You sure? Same head guy...

We run thru CT river which is fresh water to salt and then back thru fresh On way home. Yes I am sure. Original top ends were done with 300 hours. Motors now read 340. The heads were originally done by precision machine in mass.

K. I only asked cause there are a some not so honest shops and just wanted to confirm. Even on street vehicles now a days that I rarely get under the hood or underneith I've learned to use a little fingernail polish on an edge or two of some bolts/nuts. Amazing how I've busted some reputable shops who supposedly changed differential fluid, transmision repairs, (Lucas) ha, and on and on.

They think there out smarting a business man but neglect to notice the callused hands and dirty fingernails. Lol

Quick update...first motor complete and back together. Ended up replacing guides. Cleaning up the heads, valve job, dropped oil pan inspected bottom end, new gaskets, and new valves.

As for the second engine, builder is recommending to buy new heads. So the question is what set of heads to buy. He mentioned aftermarket heads requiring smaller valve stem diameters. So I would need new valves on top of new heads. Anything out there that is factory replacement that won't change this? He also mentioned heads changing height for exhaust. All of it has me nervous. Any suggestions?

Thanks

If one motor is good just pick up factory heads for the other. Likely 088 heads and there are plenty for sale all over.

Also start flushing your motors with salt away. You shouldn't have ruined a head in 300 hours. We run in the gulf and don't ruin em that fast.

They aren't completely rotted but enough that he doesn't want me doing this again in 5 years. We run in fresh water river after ocean running. So not sure what the issue is.

Where should I look for factory heads? That will fit 500efi

Probably Jegs or Summit

140970088 / 14096802 Service replacement head for the Gen V block

12562925 / 12562934 Service replacement head for Gen V / VI block with 7/16 accessory holes

12562926 / 12562934 Service replacement head for Gen V / VI block with 3/8 accessory holes

Thanks griff. Do you happen to know if they are true factory replacements. Or will I have to compete with valve guide areas being different? I don't want bastardized motors and would like to keep everything common amongst motors.

Weren't 500 efi heads just 088s? You can find them in swap shop or pbss. I sold 2 sets this year. Expect to pay around 1k for a bolt on ready set

Casting number is 12562934.

you want this one

Thanks sutphen. I just found one at summit. Problem is the 2.25 vs 2.18 valve stem area. Can this be machined? I wanna re-use valves.

934 is the same as 088.

Dont reuse your valves with new replacement heads ...... False Economy.

I see most shop install guides with an air hammer ..... If you look in the guide bore after you remove the old guide , there is usually some deep scoring in the bore . I ream oversize with a Serdi for a round straight hole . I always heat the head to around 300 in an oven , dunk the guides in some liquid nitrogen . They will damn near
fall in , I have a mandrel that I insert in them and tap in with a ballpeen. They make product called Fluid Weld , I get mine from Goodson , stuff works great , couple drops on the guide and drive it in .

Even if I replace them I will still want to keep commonality with the other engine. As I understand it replacement heads have different stem diameters. Will ask machine shop if they can be opened to be consistent with other motor. Don't want these things to be all mis matched. Same goes for push rods. Will likely have them deck it down to keep push rod lengths.

your talking valve diameter and yes,,these heads can be opened up to except a 2.25" valve.merc does it and so do any of us that needs to replace a hp500 head.

i don,t want to sound like a debby downer BUT,if one engine needs replacement heads,why not the engine next to it that runs the same amount of hours in the same water.

No idea. I left it up to the engine builders discretion. He's been doing it for 30+ years. One of the best in the area. Bill Carlquist out of Watertown. I trust his judgement.

Hindsight should have just did them both but first motor is already back together as they were being done serially.

^^^^^^ok,i get it.i won,t tell you the story about the two salt water hp 500s that went through a shop i was employed at years back.i hope everything works out for you.

Thanks.

Why did you take the motors somewhere else justin?

They are will Carlquist Competition. Fixed my post. My bad.

I hope you didn't spend good money to make new parts , like old parts , for commonality ? Especially when your old parts , were going to
need to be new parts soon? I would never do that , to , or , for , a Customer , just not logical .

Not sure why anyone these days, would want to fuk around rebuilding some old iron salt castings. Engine Quest makes a 502 Replacement head, that has 3/8' guides, the heat crossover port, etc. The head is designed to replace the GM/MERC iron head. You transfer over your valves and hardware. These castings are around 400 dollars each shipped to you.

Whats a machine shop charge to replace guides in a GM/MERC head? How about valve seats? Do they sonic check the head to find thin spots? Magnufluxing? Milling? By the time you get done with all that, you still have a 15,20,30 year old casting that cost you nearly the same money to simply just buy a new casting.

I really don't see a problem reusing old valves, as long as they check out, and there is enough margin left. If they are compromised, and new valves are needed, I would move right on to the engine quest 320 heads, that take a 11/32 valve, and is a much better performing head then the above. Or, a different performance aftermarket head if desired, dart, afr, brodix, whatever.

I've seen friends waste thousands of dollars rebuilding those old iron merc castings, dealing with rot, seat cracking, and all kinds of issues. They just aren't worth sinking money into, IMO. Now, if they are a clean freshwater set, and at rebuild time, just need a valve job, thats a different story.

Just my opinion on the topic.

Exactly.

You are coming late to the party. To save you some reading, these motors have been gone thru 2-3 times already in the last 2 years. The entire valve train is new including lifters, springs, push rods, valve seals, valve guides, valves, rockers, head bolts, gaskets, and now heads.

Trying to save myself from re-spending money on valve train components that are brand new.

In hindsight I agree. But like I mentioned it wasn't the original plan to swap heads as the ones on the first engine appear to be in good shape with the exception of the valve guides. Interestingly enough he said valve guides look to be in better shape on second engine but head looks worse. Who knows.

The fact that a mechine shop went thru these last year and didn't recommend changing them tells me they aren't bad and likely is a pre cautionary move this time around. Don't want to blow this stuff out of proportion. They aren't rotting off the motor.