Suggestions stripped bolts oil pan

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66corsaguy
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Suggestions stripped bolts oil pan

Post by 66corsaguy »

Hello again. I’ve had my oil pan weeping so i looked at torque spec 100lbs. Set my torque wrench for 100 lbs. almost all my bolts are stripped. They won’t tighten and than of course i broke a bolt so now i have a lot more work to do

Is this unheard of or common? Do i need new bolts, larger bolts or do i need to re cut the threads for slightly larger bolts? I’m going to have to pull the broken one out and who knows if the hole will get tore up but it has to be done. Not sure what went wrong here. Maybe my harbor freight torque wrench is not stopping at 100lbs? I dunno.

What do you all suggest and have you experienced this?



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Jim in Wis.
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Re: Suggestions stripped bolts oil pan

Post by Jim in Wis. »

Those are 1/4 -20 bolts in aluminum. I don't know what the book would call for, but 100 foot pounds is extremely tight - no little bolt in aluminum could possibly be tightened that much. Maybe it said 100 inch pounds?
The holes could all be heli-coiled to fix them.
Usually when something like an oil pan is leaking, making the bolts tighter doesn't stop the leaks. It would be more likely to make it leak worse. Straightening the flange and getting a new gasket is a better way.
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Re: Suggestions stripped bolts oil pan

Post by Jerry Whitt »

The torque readings are stated as 85-100 INCH pounds of torque
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Re: Suggestions stripped bolts oil pan

Post by 66corsaguy »

So i am new to the torque wrench. I didn’t see any setting of inch only lbs.


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66corsaguy
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Re: Suggestions stripped bolts oil pan

Post by 66corsaguy »

I’m thinking about this mathematically and logically. My wrench is only feet. Does that mean i have to convert from ft to inches? If it is 100 inches i need to divide by 12 and get 8.3 ft lbs torque?


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Re: Suggestions stripped bolts oil pan

Post by skipvair »

You need an inch pound torque wrench. What about drilling them out, tapping, and using 5/16 bolts?


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Re: Suggestions stripped bolts oil pan

Post by Jerry Whitt »

An "INCH POUND" torque wrench is needed for accuracy. Trying to do a conversion will really get things fouled up, and you already have a problem.

Invest in the correct tool. It will come in handy over the years.

One approach is to tap it to the 5/16 size. The 5/16 tap will usually have the proper drill size noted on the tap. Special note, the 1/4 bolts have 20 threads per inch. 5/16 usually have 18 threads per inch. As this is aluminum, the more threads in a soft metal can make a difference.

There is an alternate approach. Most auto parts stores have kits to repair damaged threads. Various names are used, but usually involve drilling the hole a little larger, then installing an insert that has the proper size threads. One name is "HELI-COIL" but there are lots of others. If you can keep the bolts all the same size, over the years, you will be much happier, because at some future time, the oil pan will have to be removed again.

Good luck
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Re: Suggestions stripped bolts oil pan

Post by terribleted »

I would go buy a 1/4"X20 Heli-coil set and start drilling and rethreading all the holes. There are like 19 holes so you will need the 1/4x 20 set with the bit, tap, inserts and insert tool . and also an extra box of 10 inserts (at least). Do the inserts and then install standard oil pan bolts and torque to 90 or so INCH POUNDS using an INCH POUND torque wrench. If you were using a cork gasket when you did this, replace it, it will not be any good after this over torque. By the way tapping the holes out to 5/16 x18 may require slightly enlarging the oil pan holes. I much prefer the heli-coil routine on these holes it is stronger and better in the long haul IMO. If somehow someone screws up a heli-coil down the road the 5/16x18 option is still available at that time either directly or via a 5/16x18 heli-coil install.
Last edited by terribleted on Sun Feb 04, 2018 9:29 pm, edited 1 time in total.
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Re: Suggestions stripped bolts oil pan

Post by 66corsaguy »

I have 3 torque wrenches!!! It’s crazy that NONE of them are inches. They are basically useless

I am thinking of just using next largest largest bolt and do the helicoil as a last resort. And i will look for the 20’s

Thanks everyone for the schooling. As much as i am good at following instructions and i have been able to do a lot of work on this car it’s still kind of humbling to be learning what seems like really basic stuff. But i dont have a teacher and just looked for 100 on my wrench.

Not sure why the oil pan is leaking. I did think it was undertightened but something else must be going on. I think the bolts have been stripped previous cos it did not take much for me to strip them.
Thanks. Will update you when i have everything fixed.


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Re: Suggestions stripped bolts oil pan

Post by 66vairguy »

Yes - 12 inch pounds equals ONE foot pound!! 100 inch pounds = 8.3 ft pounds. In reality even that is TOO much torque for the oil pan gasket unless you run the original thin paper gasket. With the thicker gasket 100inch pounds will squeeze the gasket out and bend the oil pan holes (VERY COMMON).

All kinds of opinions on how to properly seal an oil pan - some even work well.

Sorry about your problem, but now you get to learn about thread repair of aluminum. I rarely find an old engine now that doesn't have at least one stripped out hole.

BTW - 100 ft lbs is typical for a 5/8" bolt into aluminum. Also note any adjustable torque wrench except the "beam" type must be set back to ZERO after use or it will go out of calibration and be useless until re-calibrated.

That reminds me - I need to teach another class at the club meeting on how to use a torque wrench and approximate torque for different bolt sizes and materials.
Last edited by 66vairguy on Sun Feb 04, 2018 9:42 pm, edited 1 time in total.
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Re: Suggestions stripped bolts oil pan

Post by terribleted »

66corsaguy wrote: Sun Feb 04, 2018 9:27 pm I have 3 torque wrenches!!! It’s crazy that NONE of them are inches. They are basically useless

I am thinking of just using next largest largest bolt and do the helicoil as a last resort. And i will look for the 20’s

Thanks everyone for the schooling. As much as i am good at following instructions and i have been able to do a lot of work on this car it’s still kind of humbling to be learning what seems like really basic stuff. But i dont have a teacher and just looked for 100 on my wrench.

Not sure why the oil pan is leaking. I did think it was undertightened but something else must be going on. I think the bolts have been stripped previous cos it did not take much for me to strip them.
Thanks. Will update you when i have everything fixed.


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What type of oil pan? Stock? Aluminum replacement ...and if so which one? If it is a stock pan you should be using a cork/rubber composite gasket or I have heard the silicone gasket Clark's sells is good. You need to make sure the bolt holes in the pan are not mushroomed (after trying to put 100 ftlbs on them I bet they are). You very well may need to hammer the oil pan holes flat again. I do this by putting a 1/2"x1/2" piece of steel bar stock in my large bench vice using it as an anvil to place the oil pan on hole by hole. I use a nice flat hammer to hammer each hole flat again. A little mushroomed toward the outside is ok too:) If you have an aluminum pan you should be using a hard paper gasket in most cases and block and pan surfaces must be perfectly clean and flat. If it is an aluminum pan and it is not a Clark's Ultimate oil pan or an Otto parts unit, I would not use it preferring a stock parts over the cheap aftermarket pans I have seen.
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Re: Suggestions stripped bolts oil pan

Post by bbodie52 »

The 1/4-20 bolts used on the oil pan have a torque specification of 85-105 inch pounds. That specification is from the 1965 Corvair Chassis Shop Manual. It is interesting to note that the 1961 Corvair Shop Manual oil pan torque specification was only 40-60 inch pounds. The bolt size in both shop manuals was the same. Apparently Chevrolet engineers decided that the increased torque specification in 1965 was acceptable with that bolt size and the aluminum threads, and was apparently desirable to help reduce oil pan seepage. The Corvair oil pan is unique in that it must contain all of the oil that is stored above the gasket line. Most conventional engines use an oil pan that serves as a trough, or sump, and stores the oil that it contains below the gasket, so that the gasket must only seal against splashing oil. But the Corvair engine, with its unique flat oil pan makes much greater demands on the gasket. It is not a good idea to over tighten the oil pan bolts in an attempt to provide a better seal. This not only risks stripping the aluminum threads, but it often causes damage to the sheet metal oil pan by crushing and deforming the oil pan mating surface directly beneath the bolt head. Over tightening can push the deformed oil pan surface into the thick gasket material, which then presses against the aluminum cases while leaving inadequate pressure on the oil pan mating surface between adjacent bolts. In effect, this damages the sealing surface of the sheet metal oil pan and provides a very uneven seal pressure against the gasket material. It is important to check the mating surface of the sheet metal oil pan, paying particular attention to the area around each bolt hole. If the sheet-metal is deformed (mushroomed) a hammer and dolly technique can be used to flatten the mating surface. A fresh gasket and an inch-pound torque wrench can then be used to correctly tighten the oil pan. (I've found that inch-pound torque wrenches often use a smaller 3/8 inch drive head, which is a good fit in the tight space when torquing connecting rod nuts). The inch-pound torque wrench also provides a more accurate torque than a foot-pound torque wrench when attempting to use the heavier wrench at his lowest calibrated range.
ImageImage

A cast aluminum oil pan has the advantage of using thick cast aluminum machined sealing surface that will not crush under each bolt head. This helps to apply a more-even pressure along the entire gasket surface, which can help to provide a better seal. The aluminum oil pan also does a better job of helping to transfer oil heat to the outside air, which can reduce oil temperatures.

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Re: Suggestions stripped bolts oil pan

Post by 66corsaguy »

66vairguy wrote:Yes - 12 inch pounds equals ONE foot pound!! 100 inch pounds = 8.3 ft pounds. In reality even that is TOO much torque for the oil pan gasket unless you run the original thin paper gasket. With the thicker gasket 100inch pounds will squeeze the gasket out and bend the oil pan holes (VERY COMMON).

All kinds of opinions on how to properly seal an oil pan - some even work well.

Sorry about your problem, but now you get to learn about thread repair of aluminum. I rarely find an old engine now that doesn't have at least one stripped out hole.

BTW - 100 ft lbs is typical for a 5/8" bolt into aluminum. Also note any adjustable torque wrench except the "beam" type must be set back to ZERO after use or it will go out of calibration and be useless until re-calibrated.

That reminds me - I need to teach another class at the club meeting on how to use a torque wrench and approximate torque for different bolt sizes and materials.

Yes!!! Please teach the class. As basic as it seems if youve never used a torque wrench properly than you will continue to use it incorrectly. This is not the first time I’ve used a torque wrench but in the past i have tossed it aside because it did not click and my gut told me it was too tight. The two new ones i have are from Harbor Freight so i doubted their accuracy.
I have click style and beam style but they are all in foot lbs. i will purchase inches.

I will keep in mind 8.3 is still too tight. I’ve had an issue with my oil pan weaping. I had not used a torque wrench previously and only tightened until cork just slightly squeezed. I read that was a way some guys to it. Wondering if even that was over tight? Or particulates or pan is bent. This season is my first time touching the pan so i think it may have been bent previous and i made things worse. So i may purchase a new pan also. Not sure.

ted- thanks again for the great advice. After thinking about it overnight I’m going to do the helicoils. Like you mention they are stronger and leaves other options. I’ve never used them before although i have used inserts in wood (I’m a woodworker) and it’s the same principle. I will buy the appropriate tools and extra inserts.




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Re: Suggestions stripped bolts oil pan

Post by 66corsaguy »

terribleted wrote:
66corsaguy wrote: Sun Feb 04, 2018 9:27 pm I have 3 torque wrenches!!! It’s crazy that NONE of them are inches. They are basically useless

I am thinking of just using next largest largest bolt and do the helicoil as a last resort. And i will look for the 20’s

Thanks everyone for the schooling. As much as i am good at following instructions and i have been able to do a lot of work on this car it’s still kind of humbling to be learning what seems like really basic stuff. But i dont have a teacher and just looked for 100 on my wrench.

Not sure why the oil pan is leaking. I did think it was undertightened but something else must be going on. I think the bolts have been stripped previous cos it did not take much for me to strip them.
Thanks. Will update you when i have everything fixed.


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What type of oil pan? Stock? Aluminum replacement ...and if so which one? If it is a stock pan you should be using a cork/rubber composite gasket or I have heard the silicone gasket Clark's sells is good. You need to make sure the bolt holes in the pan are not mushroomed (after trying to put 100 ftlbs on them I bet they are). You very well may need to hammer the oil pan holes flat again. I do this by putting a 1/2"x1/2" piece of steel bar stock in my large bench vice using it as an anvil to place the oil pan on hole by hole. I use a nice flat hammer to hammer each hole flat again. A little mushroomed toward the outside is ok too:) If you have an aluminum pan you should be using a hard paper gasket in most cases and block and pan surfaces must be perfectly clean and flat. If it is an aluminum pan and it is not a Clark's Ultimate oil pan or an Otto parts unit, I would not use it preferring a stock parts over the cheap aftermarket pans I have seen.
I have the stock pan. I will hammer out like you say but am considering buying Clark’s pan. There’s the econo pan and the Clarks. I don’t want the Otto cos than i am under the impression i would need a new oil pick up also. The econo i am assuming you say stay away from? So i will go with ultimate if i buy.
I will buy a new gasket depending on which i use
Thanks for the advice i will take it.


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Re: Suggestions stripped bolts oil pan

Post by 66vairguy »

I usually tighten the pan bolts by hand feel and use lock washers, but I use the thick gasket so a torque wrench isn't of any help because the torque is so minor. I just watch the gasket squeeze.

I DO USE an inch pound wrench when I re-build steering boxes to set the bearing pre-load.

Go online and search for a bicycle inch pound beam wrench. Typically only used on expensive bicycles now.
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Re: Suggestions stripped bolts oil pan

Post by terribleted »

66vairguy wrote: Mon Feb 05, 2018 6:07 pm I usually tighten the pan bolts by hand feel and use lock washers, but I use the thick gasket so a torque wrench isn't of any help because the torque is so minor. I just watch the gasket squeeze.
Indeed with a cork gasket I simply tighten until it just starts to move (squish out) at the edge of the pan by each bolt.
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