I'm getting unexpected results when trying to time my engine. So a few questions arise: Is my 1600 type 1 likely to be a an AD type engine and how can I tell? My timing pulley has no marks, but I've marked TDC. Looking from the rear of the bus, is Before TDC clockwise or anticlockwise? I have an SVDA distributor, so presumably set timing with the vacuum plugged. Apologies if these are daft questions. Bus runs well enough, but is tricky to start and I want to eliminate timing once and for all.
Send me an email address and I’ll send you an idiots guide to timing. (No offence!) tomorrow morning.
Thanks, found a stamp on the generator stand which confirms its an AD. email: georgerunner95@googlemail.com Cheers, Mark.
There MAY be a timing mark on the inside of the pulley where the belt runs . If you're still unsure it's worth buying a new pulley with the degree marks or just buy a used original pulley with the cut marks on , a 1600 pulley should be about a tenner .... Gary at CoolCampers will have a good one . Sent from my SM-G960F using Tapatalk
When you say “unexpected results”, what do you mean? I only ask because way back if I timed my engine at idle to 7.5° BTDC, at revs it was almost off the scale. Setting the timing to 30° BTDC at revs, meant that at idle it was basically 0° and a bit rubbish. It turned out to be a knackered SVDA distributor (proper original Bosch too) and replacing the dizzy sorted the problem completely. Just out of interest, why is an AD engine of interest in this situation?
I looked up the settings for timing and got a list which gave different settings for different types of engine. Just needed to be sure I had an AD, in case it had been changed in the past.
So what exactly are the issues you`re having apart from no timing marks ?? (to me the lack of accurate timing marks IS the issue ..) 99% of 1600s with a half decent dizzy will run well set at 7.5* BTC giving around 30* on maximum advance , but with that accuracy you`ve got to start with an 100% accurate TDC measurement and if you`ve got points they need to be spot on - guesswork could wreck an engine if you`re unaware of the warning signs .
I've never seen a pulley without a timing mark or heard of such. It would be a useless object? This lack of ze mark, self-marking of ze TDC and ze subsequent undetailed "unexpected results"... very un-german, I wonder... Just throwing it out there, but you do know there are 2 TDCs? One on the exhaust stroke, one on the firing stroke. Might you per chance be both looking for and marking the exhaust stroke one? If you did, first try looking 180 degs round the pulley for the timing mark of which I am 99.999999% sure there will be one, or put your lead on No. 3 lead and use that.
I set the TDC myself, using a pencil in no. 1 plughole. The engine seemed to pick up and idle more smoothly (faster) when I moved it away from the 7.5 btdc setting. Hence the question about which way was 'before'! Its really a crisis of confidence... Anyway, I'll go back to first principles. Re-check TDC after having a very close look for timing marks in case I've missed them. Static time to 7.5btdc. Block off the vacuum and check that I get roughly 28 deg of advance at 3k rpm. If OK and if necessary, reset idle and mixture. Drive it to check and then try a cold re-start.
It is good you found TDC so you know which marking you need to use on the pulley for 0 degrees, as there are several around. In general the only aircooled 1600CC engines that have timing set at other than 7.5 degrees typical at idle are either very old ones, or some for the USA market where they have dual vacuum lines for the DVDA distributor, one timing advance and one emission control timing retard line. For those the idle timing would be 5 degrees after TDC retarded by the emission control line vacuum. (but as soon as you touch the throttle it advances to 7.5 BTDC just off idle so it can accelerate at all) Its the 28-30 degrees BTDC at 3k RPM that is critical - a crummy idle is nothing compared with melted pistons (one way to tell if your timing is too advanced apparently is that there will be little bits of aluminium on the spark plug electrodes ) Indeed an engine will run faster and smoother if you advance the timing - I have used a really old outboard motor where the speed control in fact rotated the coil in the magneto around the flywheel rather than adjusted the throttle. Its why timing by ear is not a good idea as it leads you to picking the smoothest idle rather than the Lean Best Idle down at around 850 rpm, . As you set the timing, you may have to adjust the carburettor air bypass to tweak the idle speed, and the idle mixture screw to keep it running well. Its also worth checking that the engine picks up off idle - I have noticed sometimes that slightly unscrewing the smaller mixture screw a part of a turn once you have set the idle up can make the engine stumble less when you test open the throttle. Other factors to check is that when the choke is warmed up, that the throttle plate completely closes and the choke stepped cam is not quite touching the adjustment screw. Then the bypass and mixture screws work properly as they arent fighting a too large air flow down the main throat of the carburettor (like having an air leak somewhere .) If you let it rev over 1000 rpm at "idle" then the distributor starts adding centrifugal advance. Setting up a warm idle at 1000 rpm can result in chugging to a standstill when it cools down again. If its hard to start, that may be user error (flooding it by stomping repeatedly in frustration on the accelerator for example, one push to set the choke should do.. ) or absence of correct auto-choke operation or carburettor issues rather than timing advance. Air leaks can also cause poor idling.
Thanks Mike, that explains why the revs picked up when I moved away from 7.5btdc. The point about 28-30 at 3k rpm is well made and I'll keep an eye on that. I'll go through the process, just to be safe, but I'm beginning to think choke, carb. etc. as I'm careful to only 'press once' when starting. It runs well once its started, so that may implicate the choke I suppose.
That's all well and good ASSUMING your TDC is bang on , otherwise it's all guesswork... The pencil is close but no cigar - I tried myself but couldn't get anything 100 % certain so mashed the middle out of a spark plug and made a guage . You could of course just buy a good used pulley with marks ... Sent from my SM-G960F using Tapatalk
Just to add to any confusion (sorry), but worth knowing that not all compatible, original VW pulleys are equal. There are at least 2 different diameters which may both have the same, correct TDC and 7.5* marks for your engine. I was always led to believe that the larger diameter (approx 180mm) pulley is correct for a 1600 van, identified with a 'D' stamped into it. Bear in mind it's a very long time ago that I needed to know this stuff so worth waiting for others opinions.
