Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing "Modern" Tuning

Okay Fellas,

Over the past week I think I've finally gotten my '60 Mog back on the road and I'm just working on fine-tuning the carbs. I had the carbs rebuilt by someone else which turned out to be a huge headache and then rebuilt them again myself. They are not leaking at all, and as far as I can tell the vacuum advance is working normally (I can see it move the distributor plate when suction is applied). The car has a TR3 engine with 87mm piston liners and the stock H6 SUs, now running the richer than stock "RH" needles. The engine was completely rebuilt by a reputable TR expert with a new waterpump and MorganSpares aluminum radiator and bellows type block off thermostat. It was also converted to a lead-free head with hardened valve seats.

Over the past month I have also converted to negative earth, switched over to an alternator, welded up a custom manifold-back exhaust with a slightly larger diameter, and installed a wideband oxygen sensor to track AFRs. I also picked up an el-cheapo infrared thermometer to check manifold and radiator surface temps. This seems a little bit more technologically advanced than when the car was built.

When warmed up, the original temp gauge reads about 1/3 way between the normal and hot marks. My handheld thermometer reads about 155F (68.5C) on the aluminum end tank next to the water inlet, and the top radiator hose reads about 165F (73.8C) I attribute this to the shiny aluminum reflecting the laser. The exhaust manifold reads in the 550F (285C) range when warmed up and idling.

At cold idle the AFR is around 12.0, warm Idle it rises to around 13. At throttle while driving and WOT I'm getting around 12.5 with a split second spike into the 15's on overrun from WOT. When using the piston lifting pins, the idle does drop slightly and the engine runs poorly which would normally be indicative of a slightly lean condition, even though my AFRs are on the richer side.

The car otherwise seems to run and idle well. I just didn't know if anyone with more experience with tuning carbs could look at this data and say "looks okay!" or "Oh gosh, it's bound to blow up" before I go out driving more. I'm probably being a bit OCD about this.

Happy Motoring!
Read

Well I'm very old school, from memory of SU's the basic settings are 1 1/2 - 2 turns out for the jets as a starter. Then adjust to get smoothest and fastest idle, making sure they are done independently or on some set ups doing one will alter the other. Out for rich and in for weaker. tHrottle stops can be get approximately right by listening with a piece of hose or a vacuum gauge, dash pots must use thin oil not engine oil and Pistons should fall with a good clonk. All this of course is probably way out of date as a method and assumes everything else is ok with the engine and you don't have air leaks or worn spindles. The only guide to getting it right then was an engine that would idle nicely, pull well and a check of plug colour after a good run. All old hat now I guess.

I always set my SUs up as follows:
Assuming needles are unworn!
Check needle lengths are the same.
Set the jets just below the bridge of each carb. Just a mm or so.
Set the throttle levers to move at exactly the same time and synchronise the choke levers.
Then warm up. Recheck the airflow using a tube or gadget.Adjust if necessary. Check both at idle and with some revs. Finally test the mixture. Adjust both jets by exactly the same amount. I used a tyre tread depth gauge which is ideal for measuring jet position. Make sure the dash pots fall freely. I would experiment with dashpot oil to find the best option. I've used 20/50, 3 in 1, and Red ex with varying results.

Hi Read,
Unless you've changed the cam for a hotter one I would suggest going back to standard needles to see if it runs properly then experiment with richer needles, just a thought....
Have you had a look at the myriad of TR websites in the U.S.? The Teri Ann Wakeman site, www.tr3.info from memory may be a good place to start , best of luck and keep us informed!

Thanks Taffmog!

The place that built the engine recommended a needle on the richer side, but I could swap the "SM" back in and see how she does!

Also thanks for the link