What are people using for timing lights?

[jferrante]

Adding to my necessary tools for my car - was curious what people were using for timing lights?
Getting some backfiring at low RPM's so want to check.
Thanks

[RSTarga]

Check your points

[jferrante]

Originally Posted by RSTarga

Check your points

Check the gap with dwell you mean?

[Jonny H]

I do a lot of ignition timing work and use an Equus 5568. Good mid price timing light. Soft rubber case. Has a bendy middle which sits nicely on the 911 rear slam panel.

Careful using the 'advance' feature. This uses the measured RPM to hold off the strobe. The light can be a little slow to respond which gives you misleading readings if the engine is changing speed quickly. I never use the feature.

I have managed to burn the strobe out on one though. Like I said, I do a lot of timing work!!!

[RSTarga]

yes, backfires at low rpm's are sometimes caused by the wear on the fibre bar of the points. They close up. Put some new ones in and check the dwell, then set timing. Last timing light I bought was at Sears.

[jferrante]

Originally Posted by RSTarga

yes, backfires at low rpm's are sometimes caused by the wear on the fibre bar of the points. They close up. Put some new ones in and check the dwell, then set timing. Last timing light I bought was at Sears.

Got it - new to all this. Reading some old threads - looks like the 78-83 didn't have points? is that correcT? I have a 3.0 out of an 83

[rwest]

I have this one from Sears, it has RPM too which is very handy when setting idle.

Sears.com

[Jonny H]

Originally Posted by jferrante

Got it - new to all this. Reading some old threads - looks like the 78-83 didn't have points? is that correcT? I have a 3.0 out of an 83

More likely an air leak in the CIS causing the backfire. Take the air filter off and you'll see five slot head screws. If even a single one of those screws turns and will not tighten, then your air box is blown.

[jferrante]

Originally Posted by Jonny H

More likely an air leak in the CIS causing the backfire. Take the air filter off and you'll see five slot head screws. If even a single one of those screws turns and will not tighten, then your air box is blown.

Thanks Jonny - in my reading I also have found this is common.

[jferrante]

Just ran out 2 of those bolts were not tightening - guessing these airboxes aren't cheap? throwing a WTB up now since I want to get all the old parts fixed on this thing

[Jonny H]

Don't succumb to the pop off valve BS. Most folks who have minor backfire issues (like you had) just don't know that their air box has failed already.

When fitted, the cracked box now blows open the pop off valve and they rejoice, thinking it has 'saved' them. It hasn't, their box is still cracked.

Further more, you can't reliably glue ABS with epoxy, so installing a valve can cause further back fires when this joint fails. In this case, this wonderful device 'saves' the airbox from an event that it actually caused. Brilliant!

So what causes the airbox to crack in the first place? Most likely heat, vibration and age. Yes it can be down to a lean mixture or timing issues. There is documented issue with fuel pooling in the bottom chamber which was resolved on later cars.

If you buy the current Porsche air box, it has the mods that stop the fuel pooling issue. Probably about $300 over there.

[jferrante]

Originally Posted by Jonny H

Don't succumb to the pop off valve BS. Most folks who have minor backfire issues (like you had) just don't know that their air box has failed already.

When fitted, the cracked box now blows open the pop off valve and they rejoice, thinking it has 'saved' them. It hasn't, their box is still cracked.

Further more, you can't reliably glue ABS with epoxy, so installing a valve can cause further back fires when this joint fails. In this case, this wonderful device 'saves' the airbox from an event that it actually caused. Brilliant!

So what causes the airbox to crack in the first place? Most likely heat, vibration and age. Yes it can be down to a lean mixture or timing issues. There is documented issue with fuel pooling in the bottom chamber which was resolved on later cars.

If you buy the current Porsche air box, it has the mods that stop the fuel pooling issue. Probably about $300 over there.

Great info thank you

[rwest]

I'll tag on what Jonny posted and agree that the pop off valve isn't something I put in on my new air box for exactly the reasons he stated.

I also wouldn't buy a used box since I also agree that with age the box gets brittle and is more likely to crack from a minor backfire. The spider inside should really help stop backfires as well.

Lots of threads on testing for vacuum leaks, do a search to find them- adding 5lbs of air into the port that feeds the brake booster and then spraying soapy water at every joint and look for bubbles.

[jferrante]

Originally Posted by rwest

I'll tag on what Jonny posted and agree that the pop off valve isn't something I put in on my new air box for exactly the reasons he stated.

I also wouldn't buy a used box since I also agree that with age the box gets brittle and is more likely to crack from a minor backfire. The spider inside should really help stop backfires as well.

Lots of threads on testing for vacuum leaks, do a search to find them- adding 5lbs of air into the port that feeds the brake booster and then spraying soapy water at every joint and look for bubbles.

Love this place thanks - will pressurize the system

[rwest]

Check this thread out.

HELP! have to let the car warmup???

[rwest]

Here's a great one as well.

CIS Troubleshooting for Dummies

[jferrante]

Thanks was going through both of them - track tomorrow will get to this stuff on Sat. thanks all