Why did you compound the problem by re-tapping the holes to 5/16" when you already knew they were supposed to be 8 mm? It seems you have perpetuated the work of a hack. I wonder what the next guy that gets it, or the guy after him, will say about your work?

RACE ON!!!

If the holes are already half mangled you can't reduce them back down to 8mm!

I would've done the same.

The starter threads were completely beat to shit. They were forced to 5/16. For me to try to cut them back to 8MM would have fucked them up.

5/16s is .3125 8MM is .314. There is very very little difference. We're talking .002 inches.

Why do you have an issue with it? Again we're talking .002 inches.

Why would it matter anyway? It's the bolts that hold the runners to the manifold....this application it makes no difference.

CHill out everyone, damn. You all are starting a pissing war. Dont make me pull this thread over

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CHill out everyone, damn. You all are starting a pissing war. Dont make me pull this thread over

Ahhh CFI was right, I edited my language. Sorry guys..

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CHill out everyone, damn. You all are starting a pissing war. Dont make me pull this thread over

Ahhh CFI was right, I edited my language. Sorry guys..

Dont worry bout it. We just trying to get along here. And to the ones pushing others buttons.....stop it. Gosh!

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Why do you have an issue with it? Again we're talking .002 inches.

I DON'T have an issue with it. Ir was YOU that started a thread titled, "Why I do my own work........" in which YOU stated, (asked?) "How do these hacks stay in business.". I was just wondering what people down the road will think, expecting metric threads, will think of your work.
RACE ON!!!

pewter99 and IrishMack here,

You guys cut it and play nice or your banned!!!

Metric bolts on an a/f car yep that makes sense! Wot were the genius,s thinking. I,d be PO,D to.

The bottom line is that it worked out, and for that I'm pleased for the OP. But changing the thread pitch from metric to 5/16 NC could only have done more damage than would have chasing the threads back to what they were already cut to. The two sizes are virtually identical as far as diameter goes, as has already been stated here. So making the slight change to the pitch would only remove that much more metal. This makes the bolt fit a bit looser and problems more likely in the future.

it makes me wonder... why would the mechanic go out of his way to use 5/16" bolts when 8mm should have been included??? In other words, it would not have surprised me if Accel included the wrong bolts.

I would have tapped them to the 5/16"... if for no other reason than to standardize all those bolts to standard measure.

I'm going to put some RTV on the threads and that should solve that. This application is one of torque, so it will torque down the way it is.

I always say I can F it up as good as any mechanic can

NO WAY!! Are u yanks going GAY! OOPS gone GAY that was 20 yrs ago! Say it isn,t so!! R U sure Case I,ve been play,n round in the door of my Z51 an it,s all A/F??

I'm going to put some RTV on the threads and that should solve that. This application is one of torque, so it will torque down the way it is.

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I'm going to put some RTV on the threads and that should solve that. This application is one of torque, so it will torque down the way it is.

Actually why don't you just put Loctite on them? That'll hold them better than RTV and will still seal them too, if that's a concern. I'd go with the blue, #242 I believe. The red (#271) might be a bit much in this case. It's generally for larger bolts and higher torques.

That's what I'm going to do. I have the red here, I'll use that. Use what ya got.

The red will work fine.

Since I tapped them and the holes at 8MM are.002 larger, a little locktite in the threads wouldn't hurt. I just don't want them to come loose.

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That's what I'm going to do. I have the red here, I'll use that. Use what ya got.

The red will work fine.

Since I tapped them and the holes at 8MM are.002 larger, a little locktite in the threads wouldn't hurt. I just don't want them to come loose.

The red will be okay if you don't put too much on. That stuff's pretty aggressive though. I just don't want to see you have problems when it's time to take them loose again.

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I always say I can F it up as good as any mechanic can

If that's you, what the !@#$% can I say?

Food for thought -- the difference in thread pitch (threads per inch) is the critical item that determines what strength is left in the holes. The holes are definitely weaker by being re-threaded, but the amount the holes are weakened is a function of the difference in thread pitch between the two bolts and less to do with the 0.02 inch difference in diameter.

Think of it this way -- when the holes were originally tapped for 8 mm bolts, a certain amount of metal was removed.

Now the holes are re-tapped for 5/16". More metal is removed, now from different parts of the hole wall. Not a good situation.

You now put your 5/16" bolt into the hole and torque it. The threads are not supported completely -- if the holes have been weakened enough, the hole wall will fail before you reach the torque specification. That's probably the best thing to happen, as you will now have to bring the unit to a machine shop and have them repair the holes correctly. What is likely to happen is that the hole walls will support the torque spec, but will fail when the engine is under full load.

Why? There are gaps where the original 8 mm bolt tap had already removed metal. The RTV, or threadlock or any other additive is not going to increase the ultimate strength of the bolt in the hole. All they do is to resist the bolt from turning. However, when the load is placed on the bolt, it is straight out of the hole, the additives have no affect.

This is harder to explain than I thought, and I'd be happy to try again, but the bottom line is that I wouldn't trust your "fix".

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Food for thought -- the difference in thread pitch (threads per inch) is the critical item that determines what strength is left in the holes. The holes are definitely weaker by being re-threaded, but the amount the holes are weakened is a function of the difference in thread pitch between the two bolts and less to do with the 0.02 inch difference in diameter.

Think of it this way -- when the holes were originally tapped for 8 mm bolts, a certain amount of metal was removed.

Now the holes are re-tapped for 5/16". More metal is removed, now from different parts of the hole wall. Not a good situation.

You now put your 5/16" bolt into the hole and torque it. The threads are not supported completely -- if the holes have been weakened enough, the hole wall will fail before you reach the torque specification. That's probably the best thing to happen, as you will now have to bring the unit to a machine shop and have them repair the holes correctly. What is likely to happen is that the hole walls will support the torque spec, but will fail when the engine is under full load.

Why? There are gaps where the original 8 mm bolt tap had already removed metal. The RTV, or threadlock or any other additive is not going to increase the ultimate strength of the bolt in the hole. All they do is to resist the bolt from turning. However, when the load is placed on the bolt, it is straight out of the hole, the additives have no affect.

This is harder to explain than I thought, and I'd be happy to try again, but the bottom line is that I wouldn't trust your "fix".

I don't disagree with your assessment. My repair is just that, a repair. If it goes badly, I'll take it off and Helicoil the hole. THe threads were so trashed I didn't have much of a choice.

I'll admit, it's a shot. Not too much material came out of the hole, I know what you are saying about thread pitch. Essentially, if there isn't enough meat on the threads, the bolt can pull right out.

At the point I was at, there wasn't much I can do without complete dis assembly. So I took a shot. If it has to come back off, it's not that big a deal, it's external...

We'll see what happens.

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Food for thought -- the difference in thread pitch (threads per inch) is the critical item that determines what strength is left in the holes. The holes are definitely weaker by being re-threaded, but the amount the holes are weakened is a function of the difference in thread pitch between the two bolts and less to do with the 0.02 inch difference in diameter.

Think of it this way -- when the holes were originally tapped for 8 mm bolts, a certain amount of metal was removed.

Now the holes are re-tapped for 5/16". More metal is removed, now from different parts of the hole wall. Not a good situation.

You now put your 5/16" bolt into the hole and torque it. The threads are not supported completely -- if the holes have been weakened enough, the hole wall will fail before you reach the torque specification. That's probably the best thing to happen, as you will now have to bring the unit to a machine shop and have them repair the holes correctly. What is likely to happen is that the hole walls will support the torque spec, but will fail when the engine is under full load.

Why? There are gaps where the original 8 mm bolt tap had already removed metal. The RTV, or threadlock or any other additive is not going to increase the ultimate strength of the bolt in the hole. All they do is to resist the bolt from turning. However, when the load is placed on the bolt, it is straight out of the hole, the additives have no affect.

This is harder to explain than I thought, and I'd be happy to try again, but the bottom line is that I wouldn't trust your "fix".

I don't disagree with your assessment. My repair is just that, a repair. If it goes badly, I'll take it off and Helicoil the hole. THe threads were so trashed I didn't have much of a choice.

I'll admit, it's a shot. Not too much material came out of the hole, I know what you are saying about thread pitch. Essentially, if there isn't enough meat on the threads, the bolt can pull right out.

At the point I was at, there wasn't much I can do without complete dis assembly. So I took a shot. If it has to come back off, it's not that big a deal, it's external...

We'll see what happens.

why not drill them out and grow the hole to 9mm or 10mm? Just a thought. I don't know the area and have no idea if there is enough meat left.

I am looking for the spec on these bolts buy I'm expecting no more than 40 FT LBS. All they do is keep the gasket tight between the manifold and the runners.

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I am looking for the spec on these bolts buy I'm expecting no more than 40 FT LBS. All they do is keep the gasket tight between the manifold and the runners.

40 is too high for 5/16th, even for grade 8. Here's a good table:

[url]http://www.engineershandbook.com/Tables/torque.htm[/url]

40 ft-lb? the intake base uses 25 ft lbs.

I would be it's more like 40 INCH ounces of torque on those... only so as to not tweek things.