Dear All,

I know its a little bit of a novice question but I need to ask...
Many people are talking about recurving the ignition. How can this be done? Does it mean changing the ignition timing or is it something about mechanically changing advance system or etc?

Thank you for your understanding...

Recurving refers to changing the mechanical advance and vacuum advance so that the engine gets the best amount of timing advance at different RPMs for your particular application. Some vacuum advance cans are adjustable. Mechanical advance is changed by changing springs inside the distributor.

Danny

This is how I went about doing it:

http://www.slantsix.org/forum/viewtopic.php?t=13264


Search for recurve, recurving......

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

thank you for the answers, so I guess I should think of recurving if I have a pinging problem in RPM range? I mostly run on LPG (prophane) which has more than 100 octane so I do not have any pinging problems at the moment. I have shaved 0.045" from the cylinder head and have 2 barrel carter bbd at the moment. In may I hope to buy a cam. Do you think I need to recurve the carb even if I do not have any pinging problems?

As shown in the linked message, usually you try giving the engine more spark advance, sooner and see if performance gets better or if it pings.

Once you find the point of detonation, (spark knock) you back-off a few degrees... that should be the best setting for performance and / or fuel economy.
DD

Read these-

thread one

thread 2

thread 3

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Casually looking for a Clifford hyperpak intake for cheap.

Thanks for topics. Good information.

I also need to fix my mechanical advance on Slant Six (Points-style distributor). Mine is missing one spring completely. No wonder I faced some acceleration problems when advance jumps to 25-30 under 1000 rpm.

I have hard times finding new stock advance spring kits - e.g. RockAuto doesn't list anything but complete distributors (which I think are almost free in your country).

Since it seems that spring kits for six are so rare, I was wondering what is the difference between V8 and Slant advance springs. I think I can find stock springs for V8 from here. What are the dimensions of V8 springs? Does anybody have a picture of stock setting?

Differing from the initial topic, I'm not looking for Advance Curve Kit, just original.

Thank you for your help.

Adrenalin,

If you read the threads you got pointed to you saw I am one of the recurve nuts. I came to recurving only after learning a lot on the forum about slant timing, particularly in the beginning from Emsvitil's graphs. Then of course DI is killer on this topic, not to exclude anyone, now. I realized it would largely be a waste of time and money to get heavy into recurving before I (1) had an engine in optimal running condition and (2) knew what I was trying to get the recurve to do. Just getting advance in earlier to stop ping is good, but you need to know why it is pinging to start with. Don't just lay it to octane or timing.

I may sound like a grinch to you and others may differ, but slants keep me interested because they ARE so different from other engines I worked on for nearly 50 years. They are the epitome of simple appearance that rewards knowledge and responds to tweaking. Just as all the paint on a house won't change the structure of the house, if you have a sorry engine that can't breathe, trying cams and recurving won't address the engine problems at all.

I would get that ignition right, then get the breathing in and out and fuel delivery right, fix the brakes, and then see what dizzy tweaking will do. I am one of the gang who thinks that when you are really ready to do recurving you will know enough to predict a curve you want, create it and know how why your prediction is wrong and adjust. You gotta have good gages, a good tach and my preference is for a wideband sensor to save time....a $300 pop worth every penny to me. Just like racers look for tenths or hundredths of a second, I look for degrees at just the the right vacuum transition point. Until you are tuned to the max, recurving won't help as much as you might hope, yet in good tune, what a help!

rock
'64d100

Thank you for the detailed answer, I totally agree with the concept of what you have mentioned. One should think engine as a whole and recurving is not enough alone. As I have mentioned my goal is to have a Dual barrel, 9:1 CR, Dutra duals, electronic ignition, ported&polished head with backcut valves and a RV15M Cam. From the list above only Dutra duals, RV15M cam and a little more shaving is left (I did not want to risk pinging so left 1mm of shaving for cam application) So I suppose to have a 150-170 hp engine, I hope I can achieve that. Once again thank you for your interest and great help.