Type 4 svda improvements /mods

[K70]

Hi,
I have fitted a new svda to the 2.0 type 4, the one with the blue plug connector for the hall unit.
It's better than the original worn out one with no overheating, in reliability sense for the moment anyways.
95% drives fine, good low end torque, no flat spots.
I'd like more top speed, just a little bit more.
Are there any tips for improvement please!?
The motor is stock 2.0 with dual dellorto DRLA 36.
As per advice on here 8 degrees idle /28 flat out btdc.
The engine checks out OK on compressions and decent service items=plugs, cap leads and valve adjustment.
The brakes are serviced and tyres checked.

Ps safe way to connect tacho remembering it has hall ignition needed pls. 2 old hand held meters, no instructions...

[Bruce.m]

What rpm are you topping out at?

The CU motor has smaller valves I think and a shorter duration camshaft (Than the 914 & 411 cars). So the power will taper off sooner in the rpm range.

[Piledriver]

Make sure to hook that up with the right Bosch coil driver, the Vanagon distributors hall sensor cannot drive a coil, and replacement parts don't exist.

From memory its the same setup Golfs of same years ran, so you have far more choices than just Vanagons if you need a hall module/connectors etc. The connectors at the distributor tend to disintegrate. There are 2 different distributor connectors in that era but the modules are electrically interchangeable.

I personally would find a dual vac dizzy for a T1/T3/T4 and stick points or a pertronix in it, possibly driving the OG Bosch coil driver, as it is a great high current coil driver. Carry a spare pertronix module if using it to drive the coil directly. Just set it so you have 28 degrees timing at 3500 RPM without vacuum connected, and lock it down. The vac can will add up to 20 degrees more timing under low load conditions. This is a feature, as you will run cooler and have better mileage at cruise. (must have ported vacuum port)

On the distributors wearing out, I just gutted the one from my Cabby with 180K showing, converted it to a 72-1 wheel (rc truck steel spur gear and a touch of TIG to fill a gap) had ~zero side play and I only had to shim the end play down. None of the pile of distributors I have seen had any significant side play on the main shaft, just bad end play or worn bushings for the weights occasionally. The one on my Squareback has >500K on it, has a 36-1 wheel in place of the guts for the last ~12 years but ~zero side play. (on a T4)

[K70]

Thank you Piledriver.
The point about distributor wires was 100% correct.
Tiny delicate wires easily ruined and a shutter wheel passing or touching.
Once I fixed them temporarily it ran OK.
People rebuild an engine and put all the old rubbish back onto it.
That distributor had been on 40 years and round millions of times.
The grey fibre spacer washer fell off in many peices soon as distributor was pulled.
Now sorting out timing ‐even though new distributor in exactly same place as old, need to keep it there at about 40 degrees btdc (hoses on ?!) For good performance. Tickover guessing 1200rpm +.
28btdc =hardly 70mph.

[Piledriver]

You want a max mechanical advance of about 28 btdc on a T4, then the vacuum advance will take it from there, depending on load..
Without vacuum advance (or programmable with pressure/vac sensor) you will have very high egts and cht, as timing will be greatly retarded at cruise, and it will have far less "pep" in off idle area.

[Bruce.m]

Pile. How much vac advance can the type4 take? At what point do you add advance (70% MAP?) and at what rate / progression do you add it?
Cheers

[Piledriver]

Varies, but low loads and very lean mixes seemed to like a lot more timing than many would consider.

I ran two variations on the engine, straight 1700 914with the slight dome, .028" deck (no head gaskets, no base shims) and 1700 heads, and 1800cc 2L Porsche heads (much different chamber design/plug location/valve and port sizes,, cut for 49cc chambers but heads got step cut so deck was ~.060" , did seem knock proof

1700 cr worked out to ~8.4:1, 1800 a bit less, both ran web 73 cam..(will probably go back together with 96mm flattops closer to 9:1 CR)

Probably easiest to dig out timing/AFR target tables, back at the beginning I was running iridium "pulse" plugs that actually allowed running at 22:1 AFR at cruise, dropped CHT by 75 F easily vs stoich... those are sadly NLA and the cheaper replacements work no better than NGK or Bosch triple electrodes, can manage ~18-19"1 AFR at 70 MPH cruise with conventional plugs. (AB tested with the pulse plugs back when avai;lable)

Actually experimented long ago fabbing "pulse" plug wires using RG6 coax, but that was pre-efi and it torched the distributor cap/rotor in minutes..Would likely work better on LS2 truck coils or such.

[K70]

That's gonna take a while for that serious info to register with me. I reread till it goes in.
I am rechecking soon but it is slightly rich. plugs look happy. Probably at 34-36* hoses off.
45* hoses on. maybe.
Not hot at all and runs eager, good compared to stock.
No off areas in drivability.
And I did not mess about with the drla jetting, no change from 1st install.
I've a infra red heat gun reads to 350f I can get readings.
Read something about lean means less timing req -
but I've no oil temp , head temp gauges nor AFR and lambda sensor. so that kind of guessing could be expensive.
Was lead to believe svda and clones lazy and low on mechanical advance. It probably is meant as replacement on waterboxer vanagons with Bosch electric ignition.
Probably in a light 914 36 deg not exactly crazy.
Anyways I want a decent exhaust from stock even though it works OK so that will lean main jet .
Ps so NGK B6ET will work fine? Some gains?

[K70]

OK I reread that, thank you!
Are there any other distributors I should be considering?
On another post on here a vanagon owner was recommended type 1 distributor from cb with the vw hall system or pertronix, from cb performance.
If I find a good oe type 1 distributor , could this be adapted and carried as a spare pls?
I am finding worn out oe type 4 distributors (no parts available even for rebuild etc ,according to vw factory since 2010) or endless Chinese universal copies.
So German or Mexican type 1 could be useful?
The new emergency Chinese one is worn after about 10 drives in 10 months.
Ps I'm at about now 32-34deg hose off ,plugs together.
Just trying to get nice idle and carb balance .