1946 TC valve clatter question

[Lynn Dykgraaf]

Happy Friday Folks,

My 1946 TC serial number 1943 is back on the road. A winter spent taking care of many years of neglected service work and worn-out parts has made a local driver out of it. The list of attended too items is as follows,
-New cooling system. Non-pressurized is a revelation to me.
-New rebuilt starter
-New rocker assembly
-Joe Curto rebuilt original 1946 carbs. (An aside, they do not have plungers to retard the piston and enrich the mixture.
This was quite the surprise as I have never met an SU without one).
-Inspection of all fluid sources and topping off as needed.
- Sourced and purchased a correct reproduction alloy valve cover to replace the disaster that came with the car.

The numbers all match, including the correct head casting numbers.

Here is my question. The valve cover that came with the car showed a 12 Thou hot valve adjustment value. My TC should be a 19 Thou hot adjustment number. The valve clatter seems pretty loud/harsh to me. I have had British motors since the 70's so am pretty comfortable at getting correct settings and car/bike running as it should. The list included multiple TR3's, 4's, a TR6, 3 Sprites, One 100-6 Healy, One MGA and multiple Triumph Bonneville and Bultaco bikes. Is it possible my TC motor has a later camshaft that requires a 12 thou hot adjustment? How could I tell without a teardown? Acceleration is pretty week. It seems to run pretty lean at the moment as well.

I'm proceeding slowly and thought it was time to see what everyone thinks. My MGA and the Sprites were never even close to hard accelerating, but the TC seems particularly lackluster. Having never had a TC I have no reference point to work from so I am looking for some experienced thoughts on the question.

Looking forward to the comments.

Lynn Dykgraaf
Lake Stevens, Washington State. USA

[Steve Simmons]

First of all congratulations! The car looks great.

As for the camshaft, after so many years it's highly unlikely the original camshaft is still with the car. The valve setting will depend on what camshaft is currently installed, and it could be one of many aftermarket varieties. My method for setting the gaps when I don't know what's in there is to start with 15 thou and see how it sounds. The TC will sound similar to most other British cars when they are right. You should hear them, but not loud. In my experience, being a thou or two off won't dramatically impact performance. So if it sounds ok at 15 then I leave them there. If they are still loud, try closing them a bit until they simmer down. I do very much doubt there is a 19 thou cam in there. I don't recall the last time I saw one of those. Maybe someone still makes them, but they certainly aren't the most popular option. The only other thing you could do that I can think of would be to remove the timing cover and upper gear, and see if there is a marking on the front of the camshaft. Not worth the effort in my opinion.

[Tom Lange, MGT Repair]

Agree with Steve - if the engine in your car has EVER been rebuilt, is most likely to have the .012 cam in place. Your valve cover is not original to the car if it heralds a .012" setting. I would also adjust your brakes, to be sure nothing is dragging.

If your car is still a slug, I would send your distributor to either Mark Medynski at British Vacuum Unit, or Jeff Schlemmer at Advanced Distributor, for a complete rebuild. Then set the timing to no more than 32 degrees at full advance, and be prepared to feel the difference!

I find it quite astonishing how much better a car will run with the original distributor, rebuilt by one of those gents.

Tom Lange
MGT Repair

[Lynn Dykgraaf]

Could not agree more with both sets of comments. Both of you pretty much confirm what I feel is likely to be correct for this motor. 19 is way too loud. 15 a reasonable starting point for getting to correct.

I have a paper trail that came with the car for work and parts going back to 1950. Nothing about an engine rebuild but inquiries and hand written replies into building a more powerful motor as well as a hand drawn cam profile diagram. Lack of paper to support a rebuild makes me wonder. EVERYTHING else was kept so why not rebuild receipts?

Here are the results. Completed a hot head valve adjust to 15 thou yesterday. New silicon gasket and sealer required over night cure before restart. Just fired it up on a fully cold motor. Valve clatter much reduced. Raining like crazy hear today so will need to wait for a short drive. Added two additional flats of enrichment to carbs as well and will get after checking the timing next.

Thanks for the input.

Lynn Dykgraaf
1946 MG TC #1943
1958 TR3A TS-22436LO

[i.thomson]

lynn, there is a way of checking which cam is in there by measuring valve opening and closing pionts but I do not have it to hand just now. Perhaps someone else will come up with it for you. I disagree that there are no new 19thou. cams out there though. I believe there are so it's best to check. For a start though I would check the timing. Modern fuel demands more static advance than when the cars were built so the official TDC timing is now too far retearded. Most people use between 5 and 10 de. BTDC nowadays.
good luck
Ian

[Norman Tuck]

A very good article on how to determine which camshaft you have can be found at: http://ttalk.info/CamshaftID.htm .

Good luck, Norman

[Lynn Dykgraaf]

Norman,

I really liked that article and that kind of activity just puts a smile on my face. I only wish I knew of it when I had the front of the car apart for a cooling system overhaul.

Current update.
- Distributor sorted and timing now correct. Thanks to all who contributed to that process. Picked up 100 at idle rpm and
smoothness. Currently set to 2 degrees BTDC at 950 RPM. Will dial back idle to earlier setting once next step completed.
- Looked into records to find out last time cap, rotor, points, wires and condenser replaced and could find nothing. So full
tune up kit on order. Once that arrives and installed, I will adjust and re-time the system. Followed by a double check of
carb balance followed by mixture adjustment for best running.
* Just a little aside here. My 1946 carbs have no plunger to retard and enrichen the mixture on acceleration. We'll see
how that affects the fine tuning process.

Lynn

[i.thomson]

lynn, the early carbs had no damper in the dashpot, relying instead on the heavy piston to give the required enrichment on accelleration. Pre-war SU carbs were the same. The spring and damper came in later when the piston was made of lught aluminium insread of heavier brass. As to replacing the electrical components I would be wary of modern replacement plastic parts, especially the cap and rotor arm. If they are in good condition I would continue to use them on the grounds that the old stuff was of superior quality to that found nowadays. Modern condensers/capacitors are problematic also. I try not to replace too many things at once, having created too many problems which didn't previously exist.
good luck.
Ian

[Ray White]

Here in the U.K. there is one guy who we all know can be relied on to maintain high standards.

http://www.distributordoctor.com

Does Martin Jay ship to the States? Sorry, don't know. You will have to contact him.

[Steve Simmons]

Yes, he does. I get my points and condensers from Martin. Quality stuff.