Timing trouble....

[blykins]

I'm going to throw this out for reference, not necessarily as a suggestion, but I lock out the distributor on every engine I build and never have timing related starting issues. They all start with a hit of the key and the pump gas street motors run just fine under all conditions.

That's at least as wrong as incorrect valvetrain geometry.   Probably worse.

I've heard that before. Never experienced it, but heard it.

Ever built an engine for a towing application?   Not a sled pull, but something that's hooked to a 12000 lb trailer that's being lugged down at 1800 rpm. 

[machoneman]

Ah, thx for clarifying that Scott. I had thought that vac. advance was off the table from your previous post. And yes, the curve is king so to speak....if one gets it right, the benefits are large indeed.

 
 link=topic=5968.msg65004#msg65004 date=1526232794]

Well said Barry. Yes, one does leave mileage and more on the table otherwise. Funny, but there are zero drawbacks IMO to running a vacuum advance on all but the very hottest engines.   

I'm going to throw this out for reference, not necessarily as a suggestion, but I lock out the distributor on every engine I build and never have timing related starting issues. They all start with a hit of the key and the pump gas street motors run just fine under all conditions.

That's at least as wrong as incorrect valvetrain geometry.   Probably worse.

I've heard that before. Never experienced it, but heard it.

Locked out timing is often OK at WOT.  How much timing are you applying at steady state, light throttle cruise and crowd accelerations?  With locked out timing the answer is either too much or not enough.  Vacuum advance adds a whole "nother" layer of tuning optimization to the equation.  Thats where rotor phasing can get really spiffy - you work with a sweep rather than a fixed position.  OEMs had this figured out a few decades ago...

I'm not talking about a vaccum advance, after the fact...I'm talking about a curve in the distributor. I don;t disagree that for a street deal at part throttle, additional ignition timing can sure help efficiency. I've never found a benefit to a curve in the distributor other than for starting. In my experience, if you need to retard the engine to start it, there are other issues.
[/quote]

[scott foxwell]

I'm going to throw this out for reference, not necessarily as a suggestion, but I lock out the distributor on every engine I build and never have timing related starting issues. They all start with a hit of the key and the pump gas street motors run just fine under all conditions.

That's at least as wrong as incorrect valvetrain geometry.   Probably worse.

I've heard that before. Never experienced it, but heard it.

Ever built an engine for a towing application?   Not a sled pull, but something that's hooked to a 12000 lb trailer that's being lugged down at 1800 rpm.

No I haven't and that's probably where my lack of experience in that sort of area is showing itself.

[Drew Pojedinec]

The bounce at idle is "for real" - you can sometimes see it at idle timing because the springs don't hold the mechanism in position.  One of my friends who is really into such things (distributor machine, and more electronic widgets than darn near anyone on this planet...) also says that the same deal can happen at high RPM when the deal bounces off the stops.  He wants to have the heavier springs and tweaks weight to allow a tiny amount of advance to continue throughout the entire power band so that the weights never bang of the limits.

Funny you mention that.... a lot of the old timer tuners I've chatted with have mentioned that they prefer a comparable setup with heavy springs, where the engine never truly hits max advance.  It's a lot harder to set perfectly on the vehicle that way, would be nice to have access to a distributor machine for that sort of thing.

[Faron]

Just sitting back taking it all in or should I say taking it all in good time , not a fan of locked timing,  great for dyno pulls but the advantages of a correct / proper curve always drive better and get more mpg than Locked IMHO of course 

[cammerfe]

'Back When', the basic set-up for a performance Ford was to use the 10-degree slot in the diz (which gives you twenty degrees of advance in the mechanism) and then turn the diz body to get 18 degrees of initial, for 38 total. With modern combustion chambers you might not need that much total, but lots of initial will make the engine VERY responsive at low RPMs.

KS

[scott foxwell]

Just sitting back taking it all in or should I say taking it all in good time , not a fan of locked timing,  great for dyno pulls but the advantages of a correct / proper curve always drive better and get more mpg than Locked IMHO of course 

That completely depends on the engine and combination. WAY too many variables to make a general statement like that.

[Faron]

really ? 1000+ recurved Dists say otherwise , but since you didn't say it it must not be right