Stripped thread on 3.0 air injector

Mark McClure · 09-18-2006, 07:19 PM

Hi,

Hit a bit of an issue yesterday. After putting the car on the dyno for the first time I had a flat out session up a hill on the way home. Just before the top I blew one of the plugs blocking off the air injector. It looks like the thread is stripped.

Does anyone know what thread diameter is used on the 3.0 79 SC heads. I will see if it can be repaired with a helicoil and some jbweld.

Thanks

Mark....

ChrisBennet · ChrisBennet's Garage

M10x1.0

cstreit · cstreit's Garage

Are you sure JBWeld will handle the heat though?

sww914 · 09-19-2006, 07:33 AM

I've had an exhaust stud JB welded in for 2-3 years. The hole was stripped out except for the 2 top threads, and I didn't have time to fix it properly before a race, so I JB'd it in and hoped for the best. All is well.

Henry Schmidt · Henry Schmidt's Garage

Just go to the hardware store and buy a 1/8 - 27 pipe plug.
It will thread into the existing hole and should stay indefinitely.
If you are nervous about it falling out use red or green Loctite.

Mark McClure · 09-19-2006, 08:23 PM

Thanks guys.... I will go to the local specialty fasterners store for the pipe plug.

Is this self tapping? or do I need to run a tap into the hole? Si there a metric equivalent?

Thanks

Mark....

Henry Schmidt · Henry Schmidt's Garage

In this application (stripped threads) you will find that these plugs will thread in beyond your stripped threads to engage the threads deeper in the hole.

Even though the pipe plug (tapered threads) is not metric the threads are amazingly close. This is not a plug to use of you intend to reinstall air injection in the future.

Mark McClure · 09-20-2006, 05:27 AM

Henry, can you confirm the size 1/8 -27. Do you mean 3/8 with a pitch of 27?

I did not think of driving the grub screw further into the hole. Thanks for the advice. If we drive further into the hole why not use the M10x1.0 grub screw?

Mark......

Henry Schmidt · Henry Schmidt's Garage

1/8- 27 pipe plug.

This is a tapered plug that will lock itself in place. If you use a 10x1.0 plug what would stop it from going all the way through?

We use these plugs all the time without issue.

Mark McClure · 09-20-2006, 06:04 AM

Thanks Henry - will get one tomorrow.

I have just rebuilt the engine and put in on the Dyno for the first time. I know that Dyno's are all different but I only managed 200rwhp. engine is

3.0 79 sc
10.5:1 JE's
GE80
EBS springs
ITB's
EMS Stinger ECU
Twin plug
Ported heads
SSI
Monty

I though that it would be a but more potent! The torque is good and we have limited it to 7300rpm. What do you think of the results.

Thanks

Mark....

cstreit · cstreit's Garage

200 RWHP (235 crank) sounds a little low... but not outrageously so. I would have guessed closer to 250 crank HP. Can you post your dyno sheet? How's your air/fuel?

Henry Schmidt · Henry Schmidt's Garage

211 DIN RWHP and 268 Ft /lbs of torque
10.5:1 JE pistons
40 mm ports
DC 60 cams
Shuffle pins
Knife edge
46 mm PMO
1 1/2 " headers

eapcpa · 09-21-2006, 07:40 AM

Another nice motor Henry. Does the drivers side air duct behind the distributor need to be modified for clearance? If so can you post a picture? I am not to the point where I can test fit mine.

Mark McClure · 09-25-2006, 04:47 AM

Thanks Henry......took awhile down at the shop. The young guy had no idea the old fella went straight to the box and gave me the grub screw.

Retapped the whole thread locked and screwed.....sounds dirty!

All is good.

Chris I will put it back on the Dyno in a few weeks after I replace the TPS sensor and post the Dyno sheet in a new thread. The more feedback the better.

Nice motor Henry........make my backyard rebuild look like a ..........well a backyard rebuild!

Cheers

Mark......

Henry Schmidt · Henry Schmidt's Garage

The tin is from a 930 Turbo.
It is possible to modify a stock piece from an early 911.

PJMARKOW · 09-25-2006, 02:07 PM

Hi Mark,

Sounds like your getting that engine running OK. Is it run in yet? You could be down a little if the rings etc haven't seated yet. Did you use the dyno at Autotech? My car registered 230Kw at the rear wheels on that dyno (3 litre turbo, K27, Kolkeln, headers, 7.5:1 JEs, .8 bar), but I'am sure it's getting more now that it's completely run in.

Cheers

Mark McClure · 09-26-2006, 04:59 PM

Hey Paul,

Yes almost there......did quite a bit of road tuning and then went to see Peter.......Changed quite a bit. Also found a TPS issue which made tuning hard. I will replace the TPS, once we identify what it is! and try again.

Have been driving the car all week, goes OK but I expected more.

Your car is really driving the horses........!

Wil give you an update soon.

Mark.....