86 pickup with missing header bolts - how to fix
02-27-2016, 01:23 AM
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86 pickup with missing header bolts - how to fix
Hi All, I'm a newbie on this site and hoping for some tech help. My '86 blew out 2 of the 8 header studs (Thorley Headers) several years ago and I'm just getting around to solving the issue. This trucks been up on blocks for most of the past 7 years, and I'm rebuilding it bumper to bumper.
How it happened: Excessive load, highway speed, floored it on a small rise, big BANG, sound of exhaust leaving the manifold under the hood, slight odor of exhaust. Solution: Keep driving, open the fly window when driving or roll the window down. Give 'em the yeah-it-sounds-awesome look when accelerating from a stoplight in traffic. Actually, I do dig that throaty sound coming in stereo from the rear and the front, Flow Master in the back, wish I could replicate it with new exhaust system..but I digress.
I've got the new header gasket, studs, and block-off plates for the air intake/recirc tubes which are rusty and threating leakage. I've talked with the tech at Thorley headers and described my issues. Got the - wow, that's gonna be tough to fix response. Since the steel studs ripped out of the aluminum head I'm assuming most the threads are gone and they are stud ports not thru holes (or at least I hope they're not) using a system to tap and set a helicoil is not an option (tech's advice here). The tech suggested trying a course thread stud (replace the 10 x 1.25 metric studs with slightly larger NC stud) that way it still fits the header holes but can mash its way into the aluminum and hopefully sieze in place with enough thread bite before it rips the remaining threads out completely. It's kinda a winner take all solution, if I rip either of those holes out it's get a new aluminum head time and I have confidence in this engine (85k on it, no leaks, no oil burn).
Any and all serious thoughts will be considered, I may even consider non serious thoughts at this point.
How it happened: Excessive load, highway speed, floored it on a small rise, big BANG, sound of exhaust leaving the manifold under the hood, slight odor of exhaust. Solution: Keep driving, open the fly window when driving or roll the window down. Give 'em the yeah-it-sounds-awesome look when accelerating from a stoplight in traffic. Actually, I do dig that throaty sound coming in stereo from the rear and the front, Flow Master in the back, wish I could replicate it with new exhaust system..but I digress.
I've got the new header gasket, studs, and block-off plates for the air intake/recirc tubes which are rusty and threating leakage. I've talked with the tech at Thorley headers and described my issues. Got the - wow, that's gonna be tough to fix response. Since the steel studs ripped out of the aluminum head I'm assuming most the threads are gone and they are stud ports not thru holes (or at least I hope they're not) using a system to tap and set a helicoil is not an option (tech's advice here). The tech suggested trying a course thread stud (replace the 10 x 1.25 metric studs with slightly larger NC stud) that way it still fits the header holes but can mash its way into the aluminum and hopefully sieze in place with enough thread bite before it rips the remaining threads out completely. It's kinda a winner take all solution, if I rip either of those holes out it's get a new aluminum head time and I have confidence in this engine (85k on it, no leaks, no oil burn).
Any and all serious thoughts will be considered, I may even consider non serious thoughts at this point.
02-27-2016, 03:02 AM
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Aside from taping the hole larger you can get a bare head casting for inexpensive cost from engbldr and swap your stuff to it.
248.00
You can also get a new head with valves and springs seals for not much more.
348.00
That's the best options
248.00
You can also get a new head with valves and springs seals for not much more.
348.00
That's the best options
Last edited by 92ehatch; 02-27-2016 at 03:04 AM.
02-27-2016, 03:32 AM
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I'd go for door 2, the new head version if it came to that. But being short on time I'd rather try and attempt to solve this issue and keep running the current engine so I can continue building up the rest of the rig. Sure, I could just drop it off at the shop and pay someone else to do the entire swap out but where's the fun in that.
02-28-2016, 06:17 PM
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are header studs really any different than factory exhaust manifold studs?
i've been through the same thing, there are some great threads that cover using slightly oversized studs, threaded into the head, i'd try that first.
helicoil does not work based on thru-holes, there must have been some miscommunication there: http://www.repairengineering.com/helicoil.html
i've been through the same thing, there are some great threads that cover using slightly oversized studs, threaded into the head, i'd try that first.
helicoil does not work based on thru-holes, there must have been some miscommunication there: http://www.repairengineering.com/helicoil.html
02-28-2016, 10:20 PM
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The original idea of using a helicoil came from me to the LCE Tech. I have never used a helicoil, didn't know how they worked. Tech explained it.
The original factory exhaust manifold studs are long gone since I put headers on 15 years ago, but I've read that header studs are higher quality steel that can take higher temps. This may have been what happened, the headers were installed with the original studs. But too many years have passed so I'll never know.
It's new studs and gaskets now, both recommended for these headers by LCE and DT. And slightly oversized and NC studs for the 2 blown out ports. Sneak up on the torque loads and hope to feel my way to a suitable level. Then fingers crossed it holds at temp and pressures.
About day 9 of this project, bed is off and the entire undercarriage is stripped, blasted, coated, primed and painted. Brakes all new, Aussie leafs and shocks, bushing, new brake lines, dropped tank cleaned painted and reinstalled with new lines all around. LED tail lights on my custom bumper package, new Pro Comp rock crawler wheels with KO2s 31 10.5. Mostly cosmetic work in the engine compartment so far, but did find a vacuum leak today when fixed the rough idle and tough start issue got solved. Celebrated with a couple hours of doing victory laps in the rain. With no bed and the tires and a smooth running engine I'm drifting turns any time I give it more than an eggshell crushing pressure on the gas pedal. Still got a big old grin on my face from a fun day of playing around. Next phase into the more serious engine issues, then refit the older Flowmaster 60 series with a larger and run the 2.25" pipe all the way thru the exhaust. Fingers crossed the stud trick works for the 2 blown ports.
The original factory exhaust manifold studs are long gone since I put headers on 15 years ago, but I've read that header studs are higher quality steel that can take higher temps. This may have been what happened, the headers were installed with the original studs. But too many years have passed so I'll never know.
It's new studs and gaskets now, both recommended for these headers by LCE and DT. And slightly oversized and NC studs for the 2 blown out ports. Sneak up on the torque loads and hope to feel my way to a suitable level. Then fingers crossed it holds at temp and pressures.
About day 9 of this project, bed is off and the entire undercarriage is stripped, blasted, coated, primed and painted. Brakes all new, Aussie leafs and shocks, bushing, new brake lines, dropped tank cleaned painted and reinstalled with new lines all around. LED tail lights on my custom bumper package, new Pro Comp rock crawler wheels with KO2s 31 10.5. Mostly cosmetic work in the engine compartment so far, but did find a vacuum leak today when fixed the rough idle and tough start issue got solved. Celebrated with a couple hours of doing victory laps in the rain. With no bed and the tires and a smooth running engine I'm drifting turns any time I give it more than an eggshell crushing pressure on the gas pedal. Still got a big old grin on my face from a fun day of playing around. Next phase into the more serious engine issues, then refit the older Flowmaster 60 series with a larger and run the 2.25" pipe all the way thru the exhaust. Fingers crossed the stud trick works for the 2 blown ports.
