TR2/3/3A Pre-Ignition On TR3A

[Quelch]

Hi Everyone, I have just statically set the ignition timing on my TR3A with the radiator removed (3/8" BTDC on the crankshaft pulley mark) During the first road test the car was pinking really badly going up any sort of hill. I've retarded the timing 1 complete turn on the vernier (in increments of 1/4 turn) and I'm still getting a lot of pre-ignition noise. Does this sound normal & should I retard it even more? What fuel do these engines run on best? I am using regular gasoline, should I be using premium? For the record the car is fitted with a TR4A cylinder head with SU HS6 carbs, 86mm pistons and a Crane XR700 electronic ignition. The auto advance springs in the distributer are new (moss) and the vacuum line to the carbs is not leaking. Many thanks Neil.

 

[Geo Hahn]

Neil,

I have two 4-cylinder TRs. To the casual observer the engines are quite similar but I find the TR4 requires premium fuel and careful tuning to avoid ping/pink/knock. The TR3 OTOH seems like it could run on lamp oil. Nothing (even California off-brand sub-regular) causes it a problem.

I would try premium and see how that goes. Also, you don't mention whether you are using brand-name gas. Some may feel it does not matter but my perception is that some brands have superior additives (e.g. Shell & Chevron) that (among other benefits) reduce knock.

 

[TomMull]

My TR3A likes high test as well but substantial pinging is a bit of a concern. I'd crawl under and confirm the static timing. https://www.macysgarage.com/myweb6/ign-timing.htm

Tom

 

[Geo Hahn]

...I'd crawl under and confirm the static timing...

Certainly take nothing for granted. On the TR that seemed so fussy I even confirmed the accuracy of the timing marks by making a piston stop out of an old spark plug...

and making a composite photo of the position of the mark as the piston hit the stop in each direction...

 

[TR3driver]

Cool photo, Geo!

The owner's manual says "Use only Premium fuel of 95 octane or higher" and my TR3 seems happier with premium. YMMV, especially in Canada where you can buy real gasoline instead of the "reformulated" stuff they sell around here.

I also consider the 4 BTDC timing figure as just a starting point. From there, I find the point where I can just force the engine to ping (by getting it good and hot then lugging it in 4th gear) and back off from there by one division on the vernier. There is a comment in the owner's manual about backing off the timing if it pings with the stock setting.

 

[CJD]

I agree. The vernier adjustment may not be retarding the ignition enough to make a difference...until you get the distributor turned closer to begin with.

 

[Bruce100]

You are sure the distributor drive gear is oriented correctly, right?

 

[Quelch]

Thanks everyone for your input. I'll try the premium gas and also the plug stop idea to establish how accurate the timing mark is. Many thanks again, Neil.

 

[Lukens]

I'm going to ask a dumb question here: why don't you just retard it until the ping stops?

 

[Don Elliott]

I suggest that Lukens has a great idea. In my case for my 1958 TR3A, I just rotate the distributor body till it starts and idles nicely. Then I warm it up and take it for a ride. If it pings in 4th gear when I stomp on it at 1500 RPM, I pull off the side of the road and adjust it till there is no more pinking or pinging. BTW, my TR is very original with 1991 cc and normal compression ratio. I run with Shell 87 or ESSO 87 octane because I have the least problem with these concerning ethanol. I also add 4 ounces of Marvel Mystery Oil of Lucas Upper Cylinder Lube every tankful of gas. Don Elliott, Original Owner, TS 27489 LO, Montreal - 55 years this May.