type 4 motor

[Piledriver]

You can "fake" ported vacuum using manifold vacuum with a throttle operated valve, some OEMS did that (along with a temperature operated valve in some cases. Adds complexity, and unneeded complexity is the last thing you want to add.

I actually drilled a set of italian 44IDFs to get a proper ported vacuum advance signal once.

Most dells have one.

He's genuinely trying, so we'll provide all the help we can.

I still don't like draw through carb, unless its very low boost and just for looks, and the builder truly understands all the limitations//issues...
...uneven fuel distribution being the dead herring in any draw-through package, a single wideband at the collector only sees the average AFR, given the engine layout each hole can be all over the place, and even change when cornering.

[GARRICK.CLARK]

Hi Guys. I have been trying to overcome issues with this turbo set up for 2yrs on and off. 1st try at fitting a turbo.
I have had some good results apart from the backfiring issue which it always had. I've gone from blow through to draw through swapped fuel pumps tried all different timing combos and still cant get a flat accelerator pedal without a huge manifold backfire. I no its an inlet backfire as the blue silicone air filter to carb joint is black on the inside.
Never heard of rotor phasing before till Bugssy mentioned it so thanks for that. not got round to checking that yet but I have read up on it and looked on you tube and one of the side effects to the rotor being in the wrong position is inlet manifold backfiring and mine certainly has that. Also its the only thing I've not checked.
Yeah Pile and Clonebug have been patent so a big thanks to them and others for advice given.
I'll put my engine spec up as it is now.

Type 4 1911
Web 86A cam
7.5.1 comp. Tight deck.
42x36
kidney shape chambers
Big inlet ports
Max size oval exhaust ports
Matched to ports stainless 1 piece header.
New 2" SU carb.
8mm fuel pipe all through.
3psi fuel pressure at idle, rising rate FPR014 fuel reg under boost, reg returns fuel to tank.
Chinese 034, Petronix 3 module with matching coil and leads. German dual vac. New German cap and rotor.
14 initial 30 max timing. No vac advance only boost retard. 35 plug gap, big blue spark.
GT 2256S Turbo =2" oulet into 2" T section inlet manifold. Pressure taken from the actuator goes to a Vibrant pressure box. Out pipes on this box go to boost gauge, water injection, (dual vac can with one way valve fitted) ( fuel reg with one way valve fitted).
AEM Water injection. 1 small nozzle fitted to the inlet pipe in the middle of the T section part of the inlet manifold.
NGK BP8ES plugs. Changing to these plugs stopped the over run I had when key was switched off.
PLX Air fuel monitor. Sensor fitted 8" from turbo. No silencer apart from a small Vibrant resonator.
I really think the rotor phasing is the backfiring as it stops when I advance it further. But then it over advances it and starts to ping.

I've got a German 009. I'm gunna lock it out and set it at 24 then check the phasing, should the spark happen on the leading edge of the rotor or in the middle of the rotor and not to either side of the rotor with a big gap so the spark has to jump across it. also I think my rotor has copper the full width of the rotor. Should this copper piece not be narrower.

[Buggsy]

Thanks for the info Garrick. Do a search for "Volksnut SU" in this forum. Volksnut was practically a legend for his success with SU carbs in a draw through set-up. Smooth running and plenty of power. Look in particular for jet needle tapering, and whether or not he ran boost reference to the diaphragm. Don't think so, but it has been 12 or 13 years since he posted. I can't remember the details anymore.
Your dynamic compression is very low with that cam and compression, but that is not your backfire problem. You should be practically ping proof with compression that low. We'll address that later.
Let me think on this a little more, and I'll get back to you.
Rotor phasing. When the magnetic pointy thing on the rotor points at the sensor on the pick-up, the rotor should point at the terminal in the cap. Just that simple. Easy to check.

[Clonebug]

Try tightening the plug gap to .024-.028. That could possibly be an issue.

As Buggsy says your compression will be quite low but you might also have airspeed velocity problems with those larger valves and big inlet ports......

[GARRICK.CLARK]

Bugssy, Yeah i'll do a search for volksnut = SU and see what comes up.
I lowered the static comp so I could up the psi. You no how it is, 7psi ,then 8,9,10 etc. I'd be happy at 15.
Clonebug. I'll reset the plugs to 24 and check the spark colour.
I went basic today. locked a German 003 dizzy. So gunna set it at 24.
Then check the phasing of the rotor.
Just wondering were to drill a hole in the cap to get a look at the spark while its running. It might have to be on the side of the cap.

[Clonebug]

Why not let the 009 run as stock and use the MSD to retard the on boost advance????

[GARRICK.CLARK]

I've not got an MSD yet. I locked it so that I can check the rotor phase with a dizzy that couldn't advance. once I no that's ok I'll unlock it and just limit it to 24

[Piledriver]

Actually... You'd either let the 009 run to 30-32 and let the MSD retard under boost, or JUST lock the 009 at 24 and live with the continuously retarded timing and a bit too much crankng/idle timing.

...You could do the same with the vac can distributor, and have proper advance under light load.
There are ways to make it work only under vacuum...
A stocker is somewhat more likely to be "right" vs. a 009, and the mechanical advance bits work the same.

Have you done leakdown+compression tests and have a baseline?

[GARRICK.CLARK]

When i refitted the vac dizzy, I just guessed were the timing would be, put the strobe on it and read 30* at idle. My guess is the low static comp makes it able to turn over without bucking. It ticked over smooth too. I lowered timing down to 14 as that's were its supposed with the cam duration of 290 that I have. The idle then wasn't as smooth at idle. I'm hoping the 24 will be ok. With the locked 24, if it still backfires it cant be timing related as its just timed at 1 locked timing number that many people use and no advance/retard to confuse it so to speak.
Yeah it might not be optimum for the street but its not a daily.

Not done a leak down yet.

Valves were only recently lapped in and tested for seat leakage with fluid. Clearance is good between valves n piston tops, so they cant kiss n bend the valves. I did have that once.

[Buggsy]

Hi Garrick,
There is no reason to drill holes in your distributor cap, or lock your distributor just to check rotor phasing. The reluctor and rotor turn on the same solid shaft. All you have to do is take the cap off and look at it. When the protrusion on the reluctor ring is aligned with the electromagnetic pick-up, the rotor should be pointed at a terminal in the cap. You can check it in less than a minute.
After reading your last post, I think I have found the root cause of your problem. Your setting the initial timing with vacuum lines attached, aren't you? That is something you never do on a standard ignition system. Making the situation worse, you have manifold vacuum going to the distributor, instead of ported vacuum.
Let me know if this is case. Then I will know what to tell you to do next.

[GARRICK.CLARK]

Hi Buggsy. It's not got a reluctor like an MSD does . I've got a Petronix 3 module . It just fits in the same place as the old points. There isn't 1 of those magnetic rings like on the Petronix 1 either, just the 4 cornered centre shaft that the points used to ride on. It must get a signal from the 4 cornered shaft.

[Piledriver]

Also, have you absolutely verified TDC mark on pulley?

A lot of stock pulleys have other marks than TDC, and a lot of the aftermarket pulleys are stuffed.

I once ran around for the first ~week or so tuning with my base timing 27 degrees advanced... Once i figured out I had the wrong mark i realized the motor was pretty much knock-proof. Ran OK too...

[GARRICK.CLARK]

Well. Out of curiosity I drilled a couple holes either side of the dizzy cap. I can see that the spark is ok. I can see that the spark does jump to the cap terminal, but its not that far.

[GARRICK.CLARK]

Hi guys. I haven't logged on to this for a while but I'm back with an issue.
I'm trying to feed extra boost into my motor. I can get a flat throttle at 1 bar and all is good, I'd like 1.5 bar going through it but any thing after 1 bar and the motor starts missing. Plus
I'm still locked at 24 and use the dual vac can in retard mode only . It works ok.
I do use water/meth.
Afr is at 12.
Is there a limit to what an 36mm valve oval port will flow. I have maxed out the port size with out any welding.
I thought a type 4 motor could be boosted to destruction. Its only more psi and fuel isn't it.

[Piledriver]

The spark can blow out under boost, try narrowing your plug gap first.
What ignition setup?