View Full Version : Helicoil or Drill and tap?

01-06-2010, 08:15 PM
I got a broken bolt on an alum intake manifold it is the left bolt for the TStat housing. So I got it out by drilling with a carbide dremel bit. I retapped it to the stock size, after taking out the junk. But the bolt is loose as I put it in. It can get tight enough to hold it, but if I torque it down too much it will probably strip the alum.

So should I drill smooth and retap with a larger tap to use a larger bolt or should I Helicoil to use the same factory bolts? Ive never helicoiled before though.

01-06-2010, 08:25 PM
I would go ahead and use the larger bolt technique.....:D

Or go with a keen-sert....

01-06-2010, 08:30 PM
Retapping would be easy but so are helicoils. I've used them a several times for blower inlet and oulet holes, and have not had one failure. Keen-serts are the ulitmate way to go for strength but are a little pricey.

Super XR7
01-06-2010, 08:32 PM


01-06-2010, 08:40 PM
I've been told helicoils work good up until you need to remove the bolt again, then you would need another helicoil sometimes. Anyone hear this?

01-06-2010, 08:44 PM
I've been told helicoils work good up until you need to remove the bolt again, then you would need another helicoil sometimes. Anyone hear this?

Thats what I am afraid of. Helicoiling coming off in the future. That area has a high leak probability and chances are I will have to take it off multiple times.

01-06-2010, 08:58 PM
If you have the intake off, drill and tap that sucker. If not, helicoil it for now.

I also heard there is another option (that Big-E might be referring to) that a lot of Cadillac Northstar owners are using to repair their aluminum blocks after the threads are destroyed when the heads are removed for HG repairs. Timeserts (or time serts) are what they are called. Price prohibitive, but supposedly the best thing for repairing damaged threads in aluminum housings.

01-06-2010, 09:03 PM
All the info you need on keenserts

http://www.carrlane.com/Catalog/index.cfm/27025071F0B221118070C1C512D020609090C0015482013180 B041D1E173C3B2853524B5F

I've never had a helicoil come out of a blower top bolt, and those are regularly removed.

01-06-2010, 09:25 PM
Just use red loctite on the helicoil itself, then it will be locked in the manifold pretty good incase you need to remove the bolt again.

01-06-2010, 09:51 PM
Had to helicoil all four stud holes on the single plane hi-rise intake on the SBF in my RX7 due to a buddy trying to be superman when tightening the nuts on the carb studs. only complaint I would have at all is the tool it comes with has a plastic handle that stripped when I was trying to tap the holes. it has a square hole that the square end of that tap fits into but it didn't last long. I have a tap/die set so it wasn't really a big deal but a ~~~~ none the less.

helicoils will be stronger than the original too.

01-06-2010, 10:01 PM
If you install the heli-coil properly, there should be no issue with it pulling out. Keenserts are very good as well. Those thermostat housing bolts shouldn't be all that tight anyway. Folks tend to over tighten them which leads to the warping of the thermostat housing and leaks.

For a lasting repair, I'd definitely go with some sort of insert that isn't aluminum.

01-06-2010, 10:42 PM
Anyone know what size helicoil kit do I need too keep the same bolt?

01-06-2010, 10:57 PM
Pretty positive its M8x1.25

Super XR7
01-07-2010, 07:42 AM
Ricardo, If you are going to use SS fasteners you should get Nitronic-60 helicoils which have good anti-seize properties.


01-07-2010, 03:27 PM
Helicoil. As had been said tapping the aluminum isnt the way to go. I had to do a helicoil in my head as one of my bolts snapped inside....The bolt didnt come out all that pretty either...Heli coil has been doing great since

01-07-2010, 03:41 PM
I will be using the factory bolts. I found a kit at the parts stores but it looks like the insert is somewhat short. Is this going to be enough? Its maybe a 1/4 deep.

01-07-2010, 05:11 PM
The inserts are short. I worried the first time I did one as well....It will be fine

Kurt Sunday
01-07-2010, 06:49 PM
Same thing happened to me. Helicoil worked fine.

01-08-2010, 08:11 PM
fyi, I've used helicoils in the vacuum industry and I've never seen one come out. It was proper proceedure to spec them out on nearly all bind threaded holes in aluminum vacuum chambers. "Set" the coil by breaking the tang at the bottom once it's inserted and it'll stay in there for good.

If you want to tap to a larger size, I could lend you the taps, but the next standard size jumps to a 10mm. Having two different size bolts is a P!TA. Helicoil is the way to go. Get the kit with the tap, coils and insert tool. It's worth it. Having a standard size like 8mm x 1.25 in your toolbox will def come in handy down the road, seeing as a crap ton of the bolts on the car are that size.

01-11-2010, 01:40 PM
How about just drill/tapping and putting some studs in there? That's what I did. :cool: You'll have to go a little bigger, but since the threads on mine weren't too bad, I used the studs off an extra inlet plenum (for the TB), plus a few washers that I did a little grinding on.