470 Riser Bolt size?

nola mike

nola mike

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My 470 is once again leaking at the mani/riser joint, despite a new riser last year and having the mani refaced over the winter :facepalm:
Now of course, one of the bolts won't torque to spec without slipping. Was hoping to make it to the winter, but doesn't look like it's going to happen. Didn't want to remove the bolts before I had a chance to fix it, and it's at my remote river house, so I want to have the right helicoil set on hand before I get there.
Anyone know what size I need for these bolts?
And Terry, what was your idea about draining the system by removing the HE plug and just cranking the engine? I think that just pulling the plug drains enough AF to take off the riser, but I might give your idea a shot if not...don't think it would do any harm, right?
Yeah, and this time I'm going to double check the riser for straightness (didn't last time b/c it was new, but have read that some GLM stuff is out of line right from the start), and finally caved and bought an OEM gasket.
 
NHGuy

NHGuy

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Re: 470 Riser Bolt size?

Check out Time Serts they are really good products. I did a neighbors aluminum motorcycle oil plug with one and it went perfectly.
They lock in nicely so they can't back out, plus they can be put in limited space, I don't think they are nearly as wide as a heli coil.
 
NHGuy

NHGuy

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Re: 470 Riser Bolt size?

Mine is 3/8' 16 too. The Mercruiser counter man started to pull a .0375 bolt when I wanted some over length ones for a job I was doing. As soon as he said .0375 I realized that was 3/8s. Do the math.
Then I thought to myself, I can get them cheaper at the hardware store.
So if you are pulling the exhaust manifold for this job do that, get some longer bolts and grind off the heads. Then you can use the headless bolts as a guide to slide on the gasket and manifold. Otherwise it can be a be-otch to get everything lined up & not ruin the exhaust manifold gasket.
 
I

ihaveabrownboat

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Re: 470 Riser Bolt size?

NHGuy said:
Mine is 3/8' 16 too. The Mercruiser counter man started to pull a .0375 bolt when I wanted some over length ones for a job I was doing. As soon as he said .0375 I realized that was 3/8s. Do the math.
Then I thought to myself, I can get them cheaper at the hardware store.
So if you are pulling the exhaust manifold for this job do that, get some longer bolts and grind off the heads. Then you can use the headless bolts as a guide to slide on the gasket and manifold.
Click to expand...

Most actual hardware stores are going to have threaded studs or all-thread in their hardware section. Both would be easier than cutting heads off existing bolts. Especially since bolts of much length may or may not be threaded their full length.

However.... If cutting all-thread to length or cutting the head off bolts be a little careful. It's very easy to not have a good thread on the cut end. At the very least round down the cut ends with a bench grinder's buffing wheel and run nuts over the cut end to clean up the threads. Running a die over it would be better. Best would be just getting some threaded studs the correct length at the hardware store instead (if they have them).
 
Don S

Don S

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Re: 470 Riser Bolt size?

NHGuy said:
Mercruiser counter man started to pull a .0375 bolt when I wanted some over length ones for a job I was doing. As soon as he said .0375 I realized that was 3/8s. Do the math.
.
Click to expand...

I think you mean .375, because .0375 is just a bit over 1/32"
 
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