Hi everyone, could anyone give me some advice on helicoiling the inlet manifold please, I have one that has lost its thread. I’m guessing that’s why it was covered in black mastic sealer by previous owner and the reason it let coolant into cylinder bore. Going to order 5/16 unc helicoil kit, but never helicoiled before, so looking for any tips. Many thanks Steve
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Hi Steve, I used helicoils on my cylinder heads they do work but can sometime not always go in properly. In fairness that was probably my fault fortunately with some pliers easy to pull out and try a new one. First off make sure all inlet ports are plugged you don't want anything going done there! Keep drill as straight as possible and mark drill with tape for depth so you don't go to deep. I used wf40 when tapping the thread and back off half a turn after every full turn to clear swab. Ideally if you had some spare alley practice on that but not always possible. Lastly make sure the helicoil is below the surface slightly. I have seen time serts being used much better option but really expensive. Good luck1973 Tahiti Blue, TV8, ZF 4 Speed -
Hi Andy, many thanks for your advice and help. Cheers SteveComment
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I was a helicoil virgin until I did every bolthole for my inlet manifold a couple of years back. Succesfully.
AndyG has it right - but in addition, make sure you clean any swarf out of the holes after drilling and again after tapping. Blowing it out with compressed air is the best way.
If you are having to do one thread for your manifold - do them all, and while you are about it, do the threads for the thermostat cover as well, just had to do mine, with the manifold in situ, which is do-able with a right-angled drill attachment, but not the easiest way.
All are 5/16 UNC. When tapping, you can get tap-holder sockets which let you use a ratchet driver to turn the tap, as there may not be room to swing the usual tap holder.
Lastly, while you have the manifold off, replace the core plug on the underside, too.
As AndyG says, sometimes a helicoil insert can go "wrong" when you are threading it in, but you can pull them out (it "unwinds") the insert, then run the tap down the thread again to clear it, and put in another insert. Looking down into the threads with a good torch will let you see if they are nice and even and well seated. Don't forget to knock off the tang when you are happy, and make sure you get that out as well. Again, compressed air is your friend.
When all done, run a bolt into each thread to be sure it goes right down easily. If you are buying new bolts, usually worth running down them with a good die to clean them up - I am always surprised at how much comes off the threads of a new bolt when you do that.
If you want to chat about it, PM me for a mobile number, happy to talk.Header tanks - you can't beat a bit of bling.Comment
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Great advice Wilf on compressed air and running bolts as a trial before installation.1973 Tahiti Blue, TV8, ZF 4 SpeedComment
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Hi Wilf, many thanks for info, if I get stuck I will PM you for advice. Thanks again Andy. Really appreciate your help. SteveComment
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The main thing is go slowly clean the tap very often or you will bugger the thread and use penalty of cutting fluid, slowly slowly catchy monkey"The UK,s 2nd Most Easterly Stag" Quad Exhaust- ZF 4 Speed BOXComment
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The biggest tip I can offer is :- don’t try to get the helicoil to be as deep as the original thread depth.
the helicoil taps are available as 1st to bottom.
however, they are all tapered.
so if you fit the helicoil and there is some of it tapered, the standard bolt will lock in the taper, before it’s clamped the manifold down.
best to fit a 1D helicoil or 1.25 D or 1.5 D that isn’t tapered.
it’s possible to trim the helicoil length by grinding.
the kit that I’ve used, amongst others is this
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Anyway, be sure to check the bolt engagement depths before proceeding with any fitment.
Some people also recommend wurth brand inserts / timeserts.Comment
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Last edited by Philip Wardle; 1 February 2025, 09:36. Reason: Table for minimum drilling depth addedComment
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Excellent many thanks everyone for all your help and information. Really appreciated. Cheers SteveComment
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Below is a link to a thread (pun intended
) I did a few years back when I helicoiled my heads. Has pics to show the steps.
Now Stagless but have numerous car projects
So many cars, so little time!Comment
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