Alternative header attachment on 525EFI's ?
 

Every spring before the season, I remove and pressure test my headers (all 6 of them) for leaks and every year, I wrestle with getting the two inboard headers on the two rear engines back on. Getting those header bolts started and ensuring they don't cross thread while trying to maneuver the socket wrench and not drop the bolts into the bilge is always a challenge and due to the angle of the inboard port engine header, there are two bolts that take forever to get started and I usually end up with bloody knuckles. I use two headless bolts on the end holes to hold the header while I get one or two bolts in and that gave me the following idea.

I was thinking of screwing 3/8" stainless steel fully-threaded studs into the head, dropping the header in, and then securing with serrated flange nuts torqued to the same value as the header bolts normally are (ie: 35 ft/lbs).

Is there a reason(s) that this wouldn't work or is a bad idea?

Yep, Id do it on all three engines, that's why the header gasket is notched, slide the header on start the outside nuts and drop in the gasket from the top and it rest's on the studs

F2- Speedy is all over the answer. Also switch out the bolts to STAGE 8 LOCKING BOLTS. Then they won't loosen up throughout the season. They stay tight. Just my 2 cents

Just to be clear, are you saying that you agree that I can do what I'm proposing?

Great suggestion, although loosening bolts has never been a problem for me. I'm also trying to get away from using bolts; that's the whole point of using studs and nuts.

yes, install the studs in the outer two holes in the heads

OK, I should have been clearer in my initial post. What I'm proposing is using studs in ALL 8 (per side) of the holes in the head, not just the outer two.

The complications I can think of are whether there is enough clearance between the bolt holes on the header flange to accommodate the increased width of the flange nuts and is their enough room to get a 9/16" socket in there versus a 3/8" socket.

I see, if you have the clearance on the tubes, those CMI sweeper headers tube angle get tight on the left bank

Wouldn't it be easier to just leave them on and pressure test with air?

I see no problem with the idea. But clearance for the nut (and a wrench/socket) will generally be the problem with this idea. You may look at ARP for a solution. I think some tubes will be ok, but others are going to require a bolt with small head.

Yes, it definitely is and I've done it that way but when there is a small pinhole leak somewhere, the bleed-down is so slow and gradual that it is hard to discern whether the leak is from a hole or if it's from what I'm using to seal off the header. I've found the most effective way to detect leaks is to pressurize the header with air and submerge in a big tub of water and look for the bubbles. But you are right, I could test the way you're suggesting and then if there is a leak, I still have to remove it and test in the tub to find the leaks. I'm just trying to make my life a little easier when re-installing them.

Yeah, that is my suspicion as well. I have an old header at home, so I can at least test the nut clearance and I can probably stand the header up to simulate it being on the engine and see if I can get the socket in there and whether the angle on the socket extension is feasible when it's between two headers.

Back when I was hot rodding, I've heated many a header tube to dimple it and gain access for a socket. ...can't really do that with boats.

OK, so I took an old header and test fitted the studs and the flange nuts and there is definitely enough room between the bolt holes to allow both flange nuts to seat properly. But this header is for my center engine and has fully upright tubes, so what I can't tell from this is whether I will be able to get a 9/16" socket in between the tubes on the swept back headers.

use a 12 pt jet nut. they are 3/8 thread but use a 7/16 socket. that is what I used on all the race boats with all of then studded.

Thanks for the suggestion. those things are expensive... :poopoo:

ARP makes exactly what you looking for. SS studs with SS locking nuts in 6 or 12 point. I used them on my Pantera.

I've found the nuts, any idea on the part number for the studs?

Never mind, I've found it.

post up what you're using, I may switch

I'm not 100% sure these will work yet, but I've found what seems to be the only kit that might work, it's ARP #400-1403.

I was able to pick up the ARP #400-1403 kit this afternoon from my local speed shop. These studs have a 3/8-16 threaded side for insertion into the head and a 3/8-24 for the 12-pt nut side and a raised "stop" in the middle of the two threads. The length of the 3/8-16 portion is 0.550" and the overall length of the stud is 1.670". The depth of the threaded hole in the head is 0.830", so these studs do not bottom out in the head, but I don't think the standard header bolts do either. The standard header bolts are 1.000" UHL and when you factor in the thickness of the header flange plus the gasket, I would imagine the length of thread that is left is very close to that of the thread on the stud. I also happen to have a spare 525 (without headers) sitting around so I test fitted the studs in the head and they seem to fit fine. The key is going to be whether I can get the 7/16" socket in between the tubes and I won't know that until I try it.

For me, the two bolts between #2 and #4 are the ones that give me the most grief. They are just about impossible to get the thread started. And the end one forward of #1 because of the oil filter lines.

My current header bolts are 1.25 in with a 3/8 12 point cap and found that a long extension and a swivel socket works the best and #2 & 4 I use a 3/8 ratchet wrench

Glad you got it figured out. By the way, I never did attack those trim tab cables on my boat. I just took it somewhere to pay someone else to do it. (lazy ass evidently)

Thanks. FYI, I measured the protrusion of the standard 1" header bolt below the header flange and gasket and it's 0.575", so the header stud is pretty much the same. Can't do anything more on this until end of next month when I remove the shrink wrap. Thanks to all for input.

their proud of those things, do they have the allen head in the end ?

I just bought stainless 3/8 header bolts with a 5/16 head. Should be no trouble getting a socket on. Maybe you could use those on the inner holes?

They should be; they are definitely quality parts and they're priced accordingly. They do not have an allen head in the top, that would be ideal. Now should they be installed hand tight until they hit the stop in the center or do I have to torque them in as well? Because they don't bottom out, it would seem that if I torque them in, I run the risk of damaging the top thread by jamming the stop into the crown of the hole.

not sure on the install

I had iron heads so I used red loctite and snugged them tight at maybe 10# of torque.

The 525 has aluminum heads.

I think blue LT would be okay, I think Mercury uses red LT on the lower valve cover studs, I had to heat one up with a torch to get it out

I installed the ARP stainless studs on my Brodix heads to install lightning headers. I ended up having to remove one on each side (forgot which ones) and install short bolt due to clearance issues. I did snug them down with the old 2 bolt method and have no thread issues. I checked them every time before we went for a while and they stayed tight.

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