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Posted by: second wind Jan 21 2018, 02:46 PM

Hello out there......my car just got back on the road due to a bad coil and it was tricky to find as it still sparked the plugs....just not under compression. During wrenching we altered the timing and it is at 33 degrees btdc now. Car starts great and has tons of low end.....kind of stops pulling at 5,000 rpm with slight knocking. Replaced seemingly healthy vacuum lines to distributor and high end improved a bit and some knocking sound lessened. What are your experiences with not being at 27 degrees and what are the risks? Thank you very much. BTW.....not driving car for months is depressing and now driving is really a blast!! No wonder we are here.
gg

Posted by: Dave_Darling Jan 21 2018, 07:34 PM

Run higher-octane fuel to try to control the spark knock.

Knocking will kill your motor, given time. Air-cooled engines seem to be even more vulnerable than water-cooled, likely due to less-perfect cooling on the heads.

--DD

Posted by: gereed75 Jan 21 2018, 08:06 PM

Not sure why you would want to run higher than specified. The specified advance is designed to optimize power for any set of engine design parameters (stroke, cam timing etc) advancing timing past the spec leads to higher internal cylinder pressures and corresponding higher stress on bearing and higher CHT’s and less power. There might be some gain for slightly advanced timing and higher octane than specified but not much.

Increased risk of knock, bearing wear, higher CHT’s and less power. Why bother?

Posted by: second wind Jan 21 2018, 08:39 PM

Hey guys....thanks for response....just went out and car revs to 5,400 with strong pull and no knock.....maybe it is not really 33 degrees.....I wish it would stay like this forever but somehow they never do.....OMG is this car running great....trying to avoid the fly in the ointment.....when will it show up? Sure fun when running so well....perfect idle and tons of power....maybe I will just shut up and enjoy...
gg

Posted by: Vacca Rabite Jan 23 2018, 09:10 AM

Figure out what the timing is as accurately as possible. I've had very good luck with using variable advance timing lights just using the "0" (or the TDC line) as my timing mark.

Time the car where it seems to be happiest. If you hear knocking under load, back off a few degrees. Too much timing will increase head temps, but so will too little. You want to find the sweet spot where the engine is happy. IIRC, for most engines that's between 27 and 32 degrees. After 32 degrees there is a problem that needs attending for a long living engine.

Zach

Posted by: brant Jan 23 2018, 10:12 AM

you can get away with higher timing numbers at altitude.

however you look to be in California... I'm assuming sea level?
you really need to accurately time that car
and getting closer to 27-29 is a really good idea
or race gas at 10$/gallon

Posted by: gothspeed Jan 23 2018, 10:23 AM

Does anyone run 'locked out' timing on their type 4? I have seen it done on many other car engine configurations. Many magnetos are 'locked out'. But I have not yet seen any threads or talk about it here on world.

Posted by: The Cabinetmaker Jan 23 2018, 01:50 PM

Time it where it should be. 27° btdc. It sounds like you are guessing about the 33°. If your just guessing and you are wrong you might be at 40 or 20. The engineers did not "guess" when they decided on 27.

Posted by: infraredcalvin Jan 23 2018, 02:25 PM

Get yourself a good AFR meter. You’re running lean at high rpms. The recent cool weather (dense air) is helping your car run better. You will see in increase in the knocking as it warms up again.

Unless you want to continuosly tweak timing, and fuel mixtures, find a compromise when the weather is warm. Chances are it will be close to factory recomended 27 deg.

Posted by: pete000 Jan 23 2018, 03:17 PM

A digital programmable 123 Distributor is a great thing ! See the group buy thread.

Posted by: brant Jan 23 2018, 03:40 PM

when you say "locked out" do you mean to lock the advance plates?

We used to run a locked advance distributor on a type 4 race car
Literally had a sheet metal screw locking it

but you need advance and retard on a street car.

on a full race car that only runs in a power band between 5,000-7,000 rpm you don't need anything but full advance.

it would bog and run crappy at low rpm.
starting isn't fun either

Posted by: gothspeed Jan 23 2018, 06:05 PM

Cool, thank you for the info

Posted by: Rand Jan 23 2018, 06:47 PM

Monitor your temps if you are going to play with timing. Get a head temp gauge if you don't have one. Advanced timing raises head temps. Retarded timing raises oil temps. If any of your temps are pushing their range, something needs attention.

Posted by: second wind Jan 26 2018, 09:25 PM

So what was I thinking??? I am back to 27 degrees timing and cars runs really nice and maybe I am seeing things but seems to run cooler....oil temp wise. Cylinder head temp seems like before. Glad to be back in spec for many reasons.....thank you all for your help!
gg