Okay I'm going out on a limb here popping mid- high RPM's

[Bug53]

I have a 1600 DP that I just put a set of KS Kadrons on with EMPI manifolds.
Sparxwerks SVDA.
Fuel Pressure at 1.5-1.75
Timing at 32 (vacuum line plugged)
130 Mains, 60 idles.
Good compression.
Idles smooth as silk, make good power with aggressive throttle.
Not too much stumble but its there along with the popping between 1800 -3500RPM.
I have gone up with jets, I have gone down with jets, I have done the accelerator pump mods to give a bigger shot, I have synchronized carbs to NASA levels of accuracy with the balance tube both on and off.
Checked with a Uni-syn both ways too.

Here's the question.
Could this engine be off by one tooth on the camshaft and still run at both ends of the spectrum but go to snap crackle pop at no load rpm's between 1800-3500. It really cracks and misses at the higher end.

[Vanapplebomb]

Often times I have found this to be ignition related. Classic weak spark symptoms.

First thing I am usually suspicious of is the condenser (if you have points)

Then, check the coil. For points, 3-4 ohms primary, 8K-9K ohms secondary.

How do the spark plugs look?

Points clean/gapped? (or ignition module functioning?)

Check spark plug wires. Unless they are resistorless, 3K-5K ohms is common… same with spark plugs with a built in resistor.
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1800 Type 4 Berrien 295

http://www.thesamba.com/vw/forum/viewtopic.php?t=487021

[Bug53]

It has made no difference with two standard distributors and a pertronix which also was used.
I have a Bosch blue coil which I will measure the resistance in.

[Dougy Dee]

Low battery voltage will result in odd things happening with ignitions.

[Lingwendil]

Sounds like ignition related for sure. My new engine was like this, and the timing light showed massive timing scatter on the 009 when revved. Swapped in a different distributor after fiddling with the 009 on it, timed it, and it went away entirely.

Could be voltage related, quick test is to power the coil directly from the battery terminal on the alternator.
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73 super beetle thread http://www.thesamba.com/vw/forum/viewtopic.php?t=649622 Back on the Road!

Modify your Kadrons for SVDA http://www.thesamba.com/vw/forum/viewtopic.php?p=8115884#8115884

Cast iron VJU4BR8 SVDA reference thread- https://www.thesamba.com/vw/forum/viewtopic.php?t=...mp;start=0

Need replacement filters for original Kadron aircleaners? WIX #42087 is a perfect fit, as is Napa Gold #2087!

[johnnyvw164]

Didn't someone recently post a picture of EMPI manifolds that were way off center? Could that be the issue?

[VW_Jimbo]

It may be a weak or broken valve spring. I had one on an intake valve one time that drove me crazy for months! Look at the valve springs for a crack. You need to get up close and personal with it.

I just had 2 bad coils that produced popping at higher RPMs.

I also had fuel filters cause this because of a lack of fuel volume.

And then there is jetting. You could try stepping up the idle jet. That jet is still in the game a little bit. Maybe it is a little bit off.

Next thing is, what is the compression ratio of the motor?
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Jimbo

There is never enough time to do it right the first time, but all the time necessary the second time!

[mikedjames]

I just swapped a distributor with points and condenser for another one after having hesitation and stumbles around 50 mph in my bus, and having to give it a lot of gas to go at any speed - so that the AFR went down from 12.5:1 to 10.5:1.

It was great after the swap - really all I did was swapped a shiny looking new condenser for a dirty old condenser ; the old one ran well, the new one was bad.

A few months back I had swapped in that new condenser and it ran well, but it degraded over a few thousand miles until I started doubting making it through a 200 mile trip.
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Ancient vehicles and vessels

1974 VW T2 : Devon Eurovette camper with 1641 DP T1 engine, Progressive carb, full flow oil cooler, EDIS crank timed ignition.
Engine 1: 40k miles (rocker shaft clip fell off), Engine 2: 30k miles (rebuild, dropped valve). Engine 3: a JK Preservation Parts "new" engine, aluminium case: 26k miles: new top end.
Gearbox rebuild 2021 by Bears.

1979 Westerly GK24 24 foot racer/cruiser yacht Forethought of Gosport.
1973 wooden Pacer sailing dinghy

[airschooled]

If the engine runs well in any RPM, the cam teeth are most likely fine.

Are the carbs ported for vacuum advance? Hook that up, if you can. Here's a quick and free test to see if that will help:

In the driveway on a warm engine, advance your timing 6-8 degrees and test for pops by revving through the offending range. Any better? Vacuum advance will help. No change? Look elsewhere.

Make sure to set the timing back before putting the car back on the road and loading up the engine.

Robbie
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Learn how your vintage VW works. And why it doesn't!
One-on-one tech help for your Volkswagen:
www.airschooled.com

[Bug53]

[Bug53]

[Bug53]

Solid 13 volts at idle 14 volts with the revs up a bit.
Spark is strong will jump an inch to the distributor cap while each is individually pulled and re-inserted.

The only common denominator on this engine now are the EMPI piece of crap manifolds one of which was bad from the get go, replaced by Kaddie Shack and plug wires which are all new in April and wire core, not resistor wires.

I am thinking of re-working the manifolds and smoothing out the bores and ridding of the slag puddles and rough sand texture. Also lowering the web where they mate further down the tubes.

[67rustavenger]

[Bug53]

[raygreenwood]

And.....you noted this issue is with NO LOAD.....between 1800 and 3500 rpm.

What exactly do you mean by "no load"?

Do you mean steady state, flat land cruising.....that kind of no load?....or.....
Driving along at that rpm range and taking your foot all the way off the pedal in gear?

If its the 2nd one......it could be as simple as an exhaust manifold leak or a muffler joint leak. Ray

[Bug53]