H20 timing

[Flyman666]

I have a H20 stroker
Mild cam ,header , when I had the SU’s on I had timing set at 16* BTDC. Car runs great original H20 timing from there book says 7 *BTDC I now have DCOE 40’s on the car. I haven’t touched timing but now no vacuums advance What should I have timing set at ?
Ps ; electronic ignition

Thanks

[Daryl Smith]

H20 or R16 head? (different combustion chambers)
Dish or flat top pistons?
Squish?
Compression ratio?
Standard Plug or extended nose?

Lots of variables here.....
'best' timing would need dyno tuning, and a curve likely quite a bit different than stock.
'good' running I'll let those with actual experience with that setup step up.

IF you are inclined....you can run a vacuum hose from each runner to a single homebuilt 'manifold' then from there to the stock distributor to get back some of your vacuum advance...Alvin might have a picture or two...

[Flyman666]

Thanks Daryl
R16 iron head Flat top Pistons im not sure on the compression and standard plugs

[Nissanman]

Vacuum advance needs to be from a ported source at the throttle butterfly not from the engine side of the butterfly.

[Gregs672000]

I'm not an expert but I have spent a lot of time creating (with the help of a really good dyno tech) a timing map for my car (crank-fired by Mega jolt, high compression engine).
The advance curve is built into your electronic distributor, so it's not adjustable beyond setting initial timing which should change your final timing advance, which is probably around 34 or so degrees when set at 17 initial. As i understand it, vacuum advance is more about fuel economy. When the engine is not under load (cruising) it advances the timing a bit to give the engine more time to burn the fuel and help it be efficient. The timing is reduced when you add load by opening the throttle plates. I've also been told that "bigger carbs like a bit more initial advance" and thus Nissan set the Solex equipped U20 at 20 degrees initial (probably influenced by the cam profile too as there's more overlap vs an A cam). Too much initial advance may cause problems further up the rpm range if it over advances and causes the engine to fight itself.
Given your likely compression ratio (under 9 to 1 with the flat tops?) and your new ability to compensate for fuel ratio at different loads and rpm with the Webers, I'm pretty confident that you could run 20 degrees initial and not experience any problems. If it were to ping a little you can 1) richen the ratio a step depending on what rpm range (slow speed, then richen the idle circuit, high rpm then the main jet, or try the next step up accelerator pump jet if it pings when you hit it. This is assuming your jetting is close to begin with!), or 2) run higher octane fuel, or 3) simply back the timing off a couple degrees. As mentioned, some Webers and similar came with (or could be added) a port on the carb for vacuum advance, but it must be in front of the throttle plate, not from the manifold as that's the exact opposite of what you want.
On any modified engine, the only way to truly know would be to run it on a dyno as Daryl mentioned where they would adjust timing to find max torque at full advance, and where that happens is based on cam profile, carb main venturi size, carb jetting, timing and a few other factors. More advance is not always better! Your cam probably has more lift and duration. At lower rpm the overlap results in more of the fuel being dumped out the exhaust because the valves are open longer to help it breath at higher rims. Advancing the initial timing may help it burn more of that fuel and be more responsive at lower rims, but it's also under some load off the line, so it can be overdone.
It sounds like you enjoy playing with the engine. I highly recommend a wide band air/fuel meter to set your carb jetting (game changer for me, but I've done a lot to the motor and it's less forgiving with the high compression), or talking to other Weber equipped R16 owners to compare notes on jetting, cam, physical location etc, or get really good at reading spark plugs. Or contact a local dyno and see what they charge to help you set up or confirm timing and jetting (they usually offer air/fuel ratio as an option, charging for it of course!). You'll learn a lot with just a single pull and may be able to extrapolate some adjustments from there with more street testing. It would give you a solid baseline from which to work.
More than you want to Do? Then try 20 degrees initial, watch your plugs for color, listen for ping and see how she Feels! BTW, the extended nose spark plugs (NGK BPR6ES) tended to make my motor ping. The BR6ES has a recessed nose.
Hope this long post helps!

[Flyman666]

Thanks a bunch Greg. A wide band is in near future. I need new exhaust from the collector back. Anyway
But for now I will try advancing the timing to 20’ and see what happened.
Dyno time will have to wait till I stop spending bank on the car for a while. Lol

[Flyman666]

And I put Weber’s on the car. Because my last name is Weber

[Daryl Smith]

"Vacuum advance needs to be from a ported source at the throttle butterfly not from the engine side of the butterfly."
Nissanman is correct here in that your distributor is set up for ported vacuum advance with an SU carb. A quick google search will bring up some good explanations of ported, manifold, and no vacuum advance, and how they apply.

"As mentioned, some Webers and similar came with (or could be added) a port on the carb for vacuum advance, but it must be in front of the throttle plate, not from the manifold as that's the exact opposite of what you want."
Actually, that placement would just be atmospheric pressure, ported vacuum is at the venturi, right by the throttle plate...Greg and I are both used to crank fired systems which use manifold vacuum....I have seen systems as mentioned with vacuum lines from each port, whether it was ported or not, I don't know, however, I don't know if the vacuum 'quantity' would be as high on this as it would with the SU setup since each cylinder has it's own throttle plate. It may be that the available vacuum is lower, and manifold vacuum works just fine?? OR maybe there are 'ported' outlets on the weber carb you can use...?? A google search on DCOE's with vacuum advance should bring up some relevant info.

"The advance curve is built into your electronic distributor, so it's not adjustable beyond setting initial timing which should change your final timing advance"
Unless you have a totally programmable electronic distributor, the advance curve is controlled by weights and springs inside the distributor and can be adjusted. The professionals associated with these adjustments are few and far between these days, but they can be found. Not sure about parts (springs/weights) tho....There may also be vacuum canisters that could provide more/less vacuum advance if needed. Considering the cost/time involved tho....Greg is probably more right.... ...unless you are racing.

So...Greg has pretty much laid out the easy strategy for your timing, a little experimentation would be good, but, starting with an initial of about 20* as he has said, and cap the vacuum canister on you dizzy. **However you need a way to limit timing to the stock maximum, or thereabouts. Just adjusting the dizzy to 20* initial will also raise your max timing 4*, which may cause pinging/damage....be careful.

Vacuum advance helps with milage, emissions, and throttle response. Personally, I wouldn't run without it...actually can't with the EFI system, but, wouldn't anyway if I were to run a distributor.

[Gregs672000]

Thanks Daryl, I forgot the EI dizzy is still mechanical! DUH!
Regarding the vacuum advance port on a Weber, I've seen one on a set of 40s on a Ford 2 liter escort (formula Ford engine) in a Fiesta. Worked great.

[Gregs672000]

Looks like the 152s have a provision for a ported vacuum per quick search.

[Daryl Smith]

NP, Greg, we all get a little hasty in our replies at times, myself included....
RE: BPR6ES plugs.....Have you tried them since switching away from the dizzy? I haven't had any issues with my 1600 or 1800 engines, but they were lower compression. You may indeed have a problem with them because you are running such high compression (11:1?), or, you may be able to back off the timing a degree or 3. The projected nose plug moves the spark kernel slightly further into the combustion chamber, theoretically allowing for a quicker burn of the mixture by being more 'centered' in the mix. Less timing BTDC means less negative work, more efficiency....possibly more power.
Of course, again, there is the possibility it is too much for your engine....

Flyman,
notoptoy is the guy to talk to as far as adapting the dizzy for your setup. Surprised he hasn't spoken up here yet. He's been building these dizzy's for a while, and should be able to help you out with what you need.
Not a lot out there on adapting vacuum advance with these carbs.

Would the U20 solex dizzy (no vacuum adv.) bolt in and work on this setup? The timing curve would likely be workable...Anybody?

[Gregs672000]

Yah, I was a bit quick in saying the 152s come with some kind of ported vacuum (that was per a Z website from someone who had messed with them a lot as I gathered). I've since looked further and there's really not much out there that I can find. Since I've seen it done I know it can be, but doing so may actually require some modification (drilling in the right spot?). And in the end, it may not make a lot of difference. Until I went to the megajolt, I didn't run vac advance for 30 years. I had my EI dizzy curve modified to a max of 8 or so degrees additional advance, limiting total to 28. I removed the vac advance canister. The ability of the megajolt to pull out timing under varying load at specific rpm is critical to my motor (11.7 to 1) to run safely on 92 pump gas, not so much for a lower compression engine (BTW, thanks again for encouraging me to go the megajolt route!).
I think I tried the extended nose plugs with the megajolt, but I can't be sure as its been a long time. What you said was totally correct from what I can find, but it may be that I decided to stick to the standard plug as it didn't solve what ever issue I was addressing, which most likely was ping. If I had free access to a dyno...
So, getting back to the original post... as you can see, you can start going down many rabbit holes. I don't believe the "Solex" engines had a different advance curve and they set the I initial timing at 20, ultimately adding 3 more degrees total without any dire consequences. Without a dyno, I think the best way will be to make sure jetting is good (glad you're getting the wideband!) and then trying a few degrees advance and comparing butt dyno feel will be the way to go. A dial back timing light would be helpful to to know how much total advance you're running. Play and have fun!

[Gregs672000]

Just to beat a possibly dead horse... here's a link to a diagram of the 152 showing the location and cover for the vac advance port (http://www.carburetion.com/diags/45DCOEDiaginfo.asp) Part #48. Per the post, some come drilled, some don't. Regardless, it would require routing some vac lines to each throttle and then combining those to a single line to the distributor. For the megajolt, which uses manifold vacuum to measure engine load, I used the existing ports on the solex manifold and fed them into the unused and now sealed manifold coolant tube, which helps to create a uniform signal (I had blocked off all the coolant to the manifold at the head years ago per Bob Sharp). From there it goes to the megajolt which comes with a MAP sensor.

So, if your carbs are already tapped, it would not be hard to create something similar and run the vac advance on the dizzy. Worth It? Hard to know! For my high compression engine, critical.

[Gregs672000]

Been reading more... some say a combo of all 4 would create too strong a signal. Maybe tying 2 instead of 4? Sounds like it's becoming more effort than its worth...

[notoptoy]

I would suggest doing away with the VA (just don't connect it to any Vacuum source), set your initial timing at 16-20 BTDC (Depending on the curve in your Dizzie). I have an H20 with SU's and a VA and I run 16 BTDC with no ping or knock. The solex set-up does two things, eliminates the VA, and locks the breaker plate so there is no float. With these I suggest 20 BTDC and the DCOE's are most similar. Then experiment with the timing a few degrees either way to see what fits your driving style - just avoiding Pinging or knocking.