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MG TD TF 1500 - Spark Advance curves

I'm just a newbie here but does anyone have spark advance curves from a dynomometer test? The original curves were set up for the lousy gas available in Britian back in the 50's. With todays modern fuels some more advance CAN be used, the question is how much. At full throttle, at part throttle? I adjusted the dist. for max revs at idle, 700 RPM and then measured the advance with a timing light. It was 31 deg. A bit much maybe but it is indicative that there is more performance available if we can coax it out (without pinking).
Bob Jeffers

Bob, you might take a look at http://www.ttalk.info/tech/Advance_curves.html
31 degrees is just about right. I set mine (late TD) for 30 degrees at 3,000.
Bud Krueger

To Bud K. Thanks for the link and the clew to to where you set yours. The graph puts all the info in one place. But it is still the original factory info. I'm really looking for newer info with modern fuels. May have to generate it myself by getting an engine rebuilt then taking it to a place with an engine dyno. Expensive!!

Surely someone on this BBS has run an engine on a dyno or rolling road and varied the spark advance for best performance. I have the equipment to modify the advance curve to whatever is needed as shown by the dyno curves. Even to the point of adding vacuum advance if that is what it takes.
Thanks again for the link and info, Bob
Bob Jeffers

I followed Bud's advise when I installed the pertronix in the TF a few years back.
(bought a timming light w/advance feature off ebay for $10.00). 30 degrees @ 3k RPM
yeilded a very nice running car! Currently in for total re-build and the shop has a rolling road & dyno. I will be curious what the results will be and will post them here when I find out. With some luck this should occur very soon!
Cheers,
David 55 TF1500 #7427
David Sheward

Dave, Sounds like I may have hit paydirt! If you can get your shop to run good curves of optimum spark advance I will modify your distributor for you or contribute to the cost of taking the data for the curves (maybe both). You tell me what makes sense. Since I already have a vacuum advance on the TD I would like to get both full throttle data and light throttle data. The difference being the change that should be supplied by the vacuum unit.

Also I will need to know the mod's you have in your engine when the data was taken. Like what is the compression pressure (in effect what has been planed off the cylinder head/off the top of the block). Valve size, camshaft, caburettor size etc. All of this so I can evaluate your data and adapt to my situation.

My TD has been extensively modified, compression pressure runs about 190 lbs/sq. in., camshaft is a Crane cam, the carburettors are 1 1/2in. valves are MKII size, hardened seats, running GJ needles now but plan to change to LS1 this spring, flywheel cut down (almost too much). With the 4.3 rear end gears and 5 speed can easily do 85 MPH. I cruise on the interstates with traffic, not being passed by every Tom, Dick and Harry.

My TF is not so extensively modified, runs about 9.3:1 compression ratio per Stage 3 in the factory modification manuel. Flywheel has been lightened and rear end gears changed to 3.9:1. This also will cruise with traffic but is not as quick as the TD.
Enough for now, Bob
Bob Jeffers

Bob,
I will take a copy of this thread up to Pierre at Upstairs/ Downstairs Motors in Mansfield, Ohio tomorrow so I don't forget. He is the one doing the re-build on engine for me. Somewhere I have some data from a UK source on building a "manual adjustable advance" using a choke cable. I never got around to doing it...but as I recall looked fairly simple to do. I will try to dig that up and send to Bud so maybe he can post it. I need to send a couple of tech papers I have collected to him for posting there.
Cheers,
David 55 TF1500 #7427
David Sheward

Bob, I saw some info that the Boston Area MG Club is holding a Tech Session at a dyno place (N.E. Dyno) on June 4th. Try www.bostonareamg.com for details.
Bud Krueger

Dave Sheward,-- Thanks for the info if you get it to Bud I may try to build one of those spark adjusting gizmo's. I had started to collect bits and pieces to make one but if someone has already done it why reinvent the wheel? This thread is getting interesting!
Bob Jeffers

Bob, the Boston Area MG Club is sponsoring a session at New England Dyno in Worcester on June 4. Here's the sign-up link:
http://www.geocities.com/yellow_mgb/2005_dynoday/2005_dynoday_signup.html
Bud Krueger

I am sure this info on spark curves is available from T type racers. In the UK you can freely buy modified Mini Copper dissy's for the T types, which have been modified to suit modern fuels. The likes of Brown and Gammons sell them.
Henry

The likes of Peter Edney in the UK are involved in race preparation. He may be able to offer some advise if you tell him the setup you have, or even offer to sell you a distributor. Try contacting him through his website, www.peteredney.co.uk
Interested to know if you get some feedback. It seems likely some racers may be reluctant to give too much info away, as that is how they remain competitive! Perhaps you need to get friendly with a few.
Henry

To Henry, Essex ----- Contacted Peter Edney & Co. and they said tell us what you find out? Not too encouraging a reply. Maybe, as you suggested, they are not giving out any info to stay competitive.

I have ordered a T series catalog from Brown and Gammons.
There were no distributors on B&G's website that I could find (but then I'm a newbie).I'll see what is in the catalog when it comes.

Mallory distributors are still available from Moss and they will sell you a kit to modify the advance curve to about anything you want. But it is only mechanical advance, suitable for flat out racing, trials etc. Still since Lucas springs/weights are no longer available that is an avenue that could be followed.

Right now I'm running 1 1/2 in. carbs from an MGA. So there is a vacuum takeoff on what is now the front carb. A small copper tube runs to the other side of the engine and connects to the vacuum advance mechanism from an MGA distributor which I have modified to fit the T series engines. The whole thing works pretty well but I think there is more to be had if proper data is available to set up the curves.
Keep in touch and best regards,
Bob
Bob Jeffers

The B&G part number in my book is 27H 5138 - New 45D type distributor. I suspect it is the same unit that Edney sells. My point is someone somewhere has put in some work to produce this.
Overhere we have quite a strong T type racing community, and I suspect the info is there. Do you have a similar group in the States.
Henry

W.K.F.Woods in his book listed several distributers and their advances for the different cams, compression ratios, AND ocatanes.
Bullwinkle

To Henry, Essex ---- Yes we have several groups of T type racers here in the colonies. Unfortunately they don't seem to disseminate very much info on the engines. My suspicion is that the 45 D dist. has the original curve in it. That I got, it's newer and better info I am looking for.

Bullwinkle----- The book by W.K.F.Woods, What is the title? I don't think I have that one.

One extremely good source of info on distributors I was given was by Bob Gruneau up in Toronto, Canada. He wrote the info for a club newsletter called the Trillium. and gave a lot of info on the cams in the various distributors and measurments to tell them apart. Also the measurements to set up other distributors to work in the xpag/xpeg blocks. The advance curves for various cams and compression ratios was included.

I used this info quite successfully to put an MGA or early MGB distributor into my TD with it's vacuum advance. What I'm trying to do now is get the info to optimize the curves so as to get the most performance I can with the cam, valves and compression I am now running.

Thanks for All the Comments,
Bob
Bob Jeffers

This thread was discussed between 10/04/2005 and 02/05/2005

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