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Cylinder Head Guru's. Repair question I have a like new set of aftermarket heads in which need a rocker bolt time sert repair for 1 of the rocker holes. I plan on dropping the car off for upgrades along with the heads. Will the proper time sert mess with the rocker geometry? Is it a reliable fix? https://cimg7.ibsrv.net/gimg/ls1tech...2aa599e521.jpg https://cimg9.ibsrv.net/gimg/ls1tech...92df833dae.jpg |
I'm no "guru", butt... Will the proper time sert mess with the rocker geometry? Is it a reliable fix? I tend to Heli-Coil all of those on heads anymore, they tear up so often, especially used heads where they've been gorilla'ed befor I ever got em. Those teeny tiny fine threads in aluminum are kinda too close to a one-use-only thing, it seems. |
timesert is fine, a better repair than a helicoil |
Originally Posted by Scott Danforth
(Post 20645000)
timesert is fine, a better repair than a helicoil |
Originally Posted by Scott Danforth
(Post 20645000)
timesert is fine, a better repair than a helicoil |
I recall Xler service manuals from the mid 60s, when those cars were brand new... the automatic transmission section gave you the steps of rebuilding a 727 or 904... step 1 was teardown, step 2 was cleanup, step 3 was "Heli-Coil every bolt hole"... |
Originally Posted by gnx7
(Post 20645005)
Timesert always better than helicoil |
Originally Posted by grinder11
(Post 20645015)
Heli-Coils are stainless steel wire, and have no galvanic/dissimilar metal reaction in aluminum. ... look at the galvanic chart. they literally are on the opposite ends of the chart. https://cimg0.ibsrv.net/gimg/ls1tech...82cc19774d.png timeserts or other threaded inserts are usually hardened inserts, the standard material is steel, however you can also get them in 303 stainless as well as about a dozen other materials. you choose the exterior threads by the material you are going into, irrespective of the fastener thread pitch or diameter. you must tailor the insert to the application. they are for cyclical loading, and considered a permanent repair. it is also what GM and Toyota specify for head fastener hole repair in aluminum blocks.. where helicoils are a band-aid approach, governed by the thread pitch of the fastener. one wrong slip with the over-sized tap and you can ruin what you are working on. |
Originally Posted by Scott Danforth
(Post 20645028)
aluminum and stainless together are the epitome of galvanic corrosion. just add a bit of salt or a stray current to start the reaction. add a copper washer and you can power a lightbulb. look at the galvanic chart. they literally are on the opposite ends of the chart. https://cimg0.ibsrv.net/gimg/ls1tech...82cc19774d.png timeserts or other threaded inserts are usually hardened inserts, the standard material is steel, however you can also get them in 303 stainless as well as about a dozen other materials. you choose the exterior threads by the material you are going into, irrespective of the fastener thread pitch or diameter. you must tailor the insert to the application. they are for cyclical loading, and considered a permanent repair. it is also what GM and Toyota specify for head fastener hole repair in aluminum blocks.. where helicoils are a band-aid approach, governed by the thread pitch of the fastener. one wrong slip with the over-sized tap and you can ruin what you are working on. So in essence, what? 😄 Time sert good, Heli coil bad. |
Sure, a TimeSert repair is overall stronger and a more permanent solution to a problem. If I’ve got a hurt threaded hole in an aluminum head, block or whatever, and I can’t afford to go to a larger size because of space, or other constraints, I’ll use a TimeSert if and only if it’s a high torque application. A HeliCoil on the other hand is useful for low torque applications in a REPAIR situation. I’ve had my hands in a lot of high end builds over the last 30 years and I can assure all of you that the very top endurance engine builders install HeliCoils in most all threaded holes in both aluminum blocks and aluminum heads, while the unit is new, to help avoid threaded hole issues later, before they start. As a preventative defense, before there’s a problem, it’s smart. In a high torque repair situation, after the problem has occurred, it’s a bandaid at best. Rich2342, a TimeSert here is smart and will not affect geometry at all as long as the machined surface HEIGHT where your rocker arm stands sit isn’t altered. On the other side of that, if this is an 8mm rocker bolt, it won’t see over 26 ft lbs, and a properly done HeliCoil will suffice. If it’s a 10mm bolt, it will see too much torque for a HeliCoil…in my opinion…and I personally would revert back to the stronger, and more expensive TimeSert repair here, if this were in my shop. |
Originally Posted by Che70velle
(Post 20645075)
Sure, a TimeSert repair is overall stronger and a more permanent solution to a problem. If I’ve got a hurt threaded hole in an aluminum head, block or whatever, and I can’t afford to go to a larger size because of space, or other constraints, I’ll use a TimeSert if and only if it’s a high torque application. A HeliCoil on the other hand is useful for low torque applications in a REPAIR situation. I’ve had my hands in a lot of high end builds over the last 30 years and I can assure all of you that the very top endurance engine builders install HeliCoils in most all threaded holes in both aluminum blocks and aluminum heads, while the unit is new, to help avoid threaded hole issues later, before they start. As a preventative defense, before there’s a problem, it’s smart. In a high torque repair situation, after the problem has occurred, it’s a bandaid at best. Rich2342, a TimeSert here is smart and will not affect geometry at all as long as the machined surface HEIGHT where your rocker arm stands sit isn’t altered. On the other side of that, if this is an 8mm rocker bolt, it won’t see over 26 ft lbs, and a properly done HeliCoil will suffice. If it’s a 10mm bolt, it will see too much torque for a HeliCoil…in my opinion…and I personally would revert back to the stronger, and more expensive TimeSert repair here, if this were in my shop. I would hope most shops can perform a proper time sert, but that is my concern. I am not sending the heads out to a machinist who I would be fairly confident things would be precisely measured and fixed. I just assume buy a new set of heads if this is something iffy for a shop to get right. I don't want the rocker coming out or side loading the valve tip, dropping a valve. |
Sounds like your mind is made up. I wish you the best of luck. The only things I'll add are: GM used plain cast aluminum for threads, and it works for 99% of us. AFR uses heli-coils as standard equipment, and I've never heard of any issues with them, so they work. I doubt you'll experience any galvanic reactions when said thread lives in an oil bath. Again, hope it will work out no matter what route you take. |
Originally Posted by Scott Danforth
(Post 20645028)
aluminum and stainless together are the epitome of galvanic corrosion. just add a bit of salt or a stray current to start the reaction. add a copper washer and you can power a lightbulb. look at the galvanic chart. they literally are on the opposite ends of the chart. https://cimg0.ibsrv.net/gimg/ls1tech...82cc19774d.png timeserts or other threaded inserts are usually hardened inserts, the standard material is steel, however you can also get them in 303 stainless as well as about a dozen other materials. you choose the exterior threads by the material you are going into, irrespective of the fastener thread pitch or diameter. you must tailor the insert to the application. they are for cyclical loading, and considered a permanent repair. it is also what GM and Toyota specify for head fastener hole repair in aluminum blocks.. where helicoils are a band-aid approach, governed by the thread pitch of the fastener. one wrong slip with the over-sized tap and you can ruin what you are working on. |
Originally Posted by grinder11
(Post 20645113)
Sounds like your mind is made up. I wish you the best of luck. The only things I'll add are: GM used plain cast aluminum for threads, and it works for 99% of us. AFR uses heli-coils as standard equipment, and I've never heard of any issues with them, so they work. I doubt you'll experience any galvanic reactions when said thread lives in an oil bath. Again, hope it will work out no matter what route you take. Actually no.. Found a machinist and dropped them off today. They need a cleanup cut, so while I'm in there... What is the correct deck clearance on sbe ls3? Ive seen anywhere from .005 to .007, used. 11 degree 260 heads with 69cc chambers out of the box. https://cimg9.ibsrv.net/gimg/ls1tech...449571540c.jpg |
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