Initial engine break-in setup — running rough

[Moseley]

Unless my eyes are deceiving me, that push rod looks fairly beaten up as a result of coming off the rocker arm - the tube is mushroomed at the end, and possibly looks bent? Also, the nut looks right at the end of its ‘slack’ travel on the adjuster compared to the others - points towards having had the gap set when the cylinder is not actually at TDC.

Is the push rod the same length as the others? Have you rolled it across a flat surface to check it isn’t bent?

 

[ozziedog]

@ozziedog you're bang on here, the trouble I've got is that I'm now getting so excited after waiting so long to drive this thing that I'm starting to rush and squeeze jobs in during my lunch breaks while it's still light. Hopefully, there is no internal damage...

Should be ok, I’d just have a good look at the pushrod and roll it along something dry and flat like your kitchen work top. Might be a good idea to do it when the long haired general is out too Then a quick wipe around with some kitchen roll. I’d pop the other side off too and then you can do the adjustment doing the opposite game. I’d put a few bob on that motor was only running on two cylinders. So give all the leads a little fiddle with on both ends and re set the valve clearances/ lash.
Ozziedog,,,,,,,, then we can get somewhere

 

[Mechanoid]

If you had a bent valve then you wouldn't get the correct cylinder pressure. Do a compression check on that cylinder. The other thing you could have done while the rocker shaft was out is to put a straight edge along the tops of the valve stems. If they are are all touching the straight edge, the chances are that the valve isn't bent. If No. 4 valve stem is below the others then it is most probably bent. However, do a compression test to set your mind at ease!

 

[philstar]

After a short delay fixing the T4 I have now performed a compression test on the engine, and it's not good reading.

All cylinders are showing within less than 5psi variance, but only at 25psi

I tried a different connection on the tester and managed to get 50psi on cylinder #4 before running out of time, but even if this were replicated across the other three cylinders, 50psi is still too low for a brand new engine isn't it?

Assuming the tester isn't faulty, what are my options?

To confirm, this is a newly rebuilt engine (all-new top-end assembled by myself), end float is fine, standard 1600cc. It sounds great and revs freely (past a hesitant flat spot slightly above idle, as discussed earlier), there are no oil leaks. I haven't yet driven it on the road.

It does have an electric fuel pump so I might repeat the test again with this disconnected just to see if it makes any difference but I can't see it making up for nearly 100psi.

 

[Dirty Harry]

New engine has to brake in and compression increases as the bores get smoother en piston rings gave to bed in too.

 

[philstar]

I forgot to block the rear vacuum port on the carb which won't have helped things

I have now re-assembled everything and got it running again and it does seem better, though there is a backfire if I rev it high and hard from idle. I have tried pulling off a number of times up a slight slope on my drive and it hasn't come close to stalling, so I think I'm going to fix the rest of the bits to get it road legal then get it insured and give it a road test.

If I'm still concerned I might take it to a garage where they can perform a more accurate setup.

I'm still not convinced about my butterfly valve/choke setup (Thread: Stepped cam set up) as it seems that even if I hold the cam fully open, the butterfly valve isn't quite vertical, and it is "loose", so I can then stand it up straight with my other hand.

 

[philstar]

Finally got the bus insured today and took it out for a quick 2-mile test drive—there was no stalling at junctions etc, no huge oil leak, but it's definitely lacking power and doesn't want to pull past 30mph or up any semblance of a hill. I think I need to re-check everything (tappets, timing, compression) before I go again.

Never had so much adrenalin running through my body, that's 11 years' worth!!!

 

[ozziedog]

I’m laughing here because you’re so excited. Mines only running on three at the moment and I can’t get organised to go and fix it and I’ve still got a zillion jobs before the start of the season and the season has started
A fresh built motor will be down on ponies but not by that amount that you’re telling us of.

Ozziedog,,,,,,,,, that’s a lot of adrenaline for sure

 

[philstar]

After another MOT fail on the T4 and loads of welding I'm finally back on the bus.

First of I set the valve clearances again—they were all fine.

Then I attempted to set the timing with my new timing gun... got it bang on for 7.5dbtdc on idle, however, I am getting ZERO advance whatsoever when I give it any kind of revs. It revs sweet as a nut all the way up to 4000 rpm (once it's warm), but the pulley mark stays over to the right and doesn't budge (air cleaner removed, vacuum hose unplugged from carb and capped, corresponding carb connection capped, both connections on manifold capped).

I performed another compression test (albeit with the engine slightly warm) and once again it's spitting out 25psi.

I was hoping to have this bus for my own wedding (in 3 weeks' time) but I really don't think it would make it.

What's my next move? Do I abandon all hope and pull the engine, perhaps aim for BugJam?

 

[sparkywig]

Does it advance will all the vacuum connections attached?

 

[philstar]

Great question—I don't know, today was the first time I've used a timing gun! I'll connect it all up and try, might not be able to get on it until Saturday though. What will that test tell me?

 

[sparkywig]

If you're using a vacuum advance distributor it wont advance unless it's connected to a vacuum source.

 

[ozziedog]

Pop the dissy out, and just check that you have some advance in there that isn’t seized, like the dissy internals, should move freely.

Ozziedog,,,,,,,, I’ve had that on mine.

 

[davidoft]

Double / triple check you’re setting the valves in the right order

How / what method are you using to set the valves ?

Are you sure the leads are on correct ?

 

[NigelDenham]

Do you have a dual-advance distributor fitted? If its an original Bosch vacuum only you wouldn’t expect any advance with hoses plugged. If it is dual advance (later Bosch and pretty much any aftermarket one with a vac can) definitely check the mechanical advance, you should be able to rotate the points plate ten or so degrees by hand.
25 psi seems really low. I mean really low. Sure the gauge is working ok?

 

[philstar]

Thanks all—I appreciate your time and thoughts!

I have an SVDA fitted with electronic ignition, it was only a cheap one bought from eBay or MegaBug about 12 years ago, but it's barely done any miles at all. I've seen Accuspark ones on eBay for £70 (https://www.ebay.co.uk/itm/182163969108) so perhaps I should replace it? It idles lovely and revs up nice, I'm just not getting any advance at all—my intention is to time the engine for maximum advance, but perhaps I am following the guide for a 009 dizzy by mistake?

I'm not confident about the compression tester—it's a cheap one I inherited so I might just buy another one to rule that out. 25psi is ridiculously low...

Lead order has been checked, I set the valves using the "TDC then rotate 180 degrees backwards" method. I removed the rocker arms and refitted to check everything.

 

[NigelDenham]

I’ve a couple of svda’s, old Bosch and recent pertronix. Both behave about the same, I time (with vacuum hose removed and capped) to 30 degrees btdc at max mechanical advance- all in by about 3,500 rpm by the readout on the timing gun, then they both drop to 7 or 8 degrees btdc at idle. Connect the vac hose back on and the advance goes up a degree or so at idle.
So it looks like you get around 22 or 23 degrees mechanical advance (which I guess is all an 009 would give you), and the vacuum advance adds another 10 or 12 when needed?
My engine seems really picky about carb (34 pict-3) and timing settings, yet a friend has a 1600 tp in his split screen with the same (but really cheap chinese) carb and 009 distributor and his runs beautifully no matter what you do to it! These things are so old and have so many non-standard bits by now I doubt any two run the same…..

 

[philstar]

I've tried sucking on the dizzy vacuum pipe and it takes all my might to move the advance even after lubricating everything and manually opening/closing it to get it as loose as possible, so I either need to strip it all down or bite the bullet and get a new one. At least that's likely one issue solved.

I have a new compression tester arriving today so as soon as I get that I will run a test and confirm if the other tester is faulty.

Could be taking the engine out tonight!

 

[philstar]

It was the compression tester! Getting over 145psi on all cylinders now using the new one!

What a relief.

I suspect the dizzy was sticking so I wasn't getting any vacuum advance OR any mechanical advance. I've got a spare 009 I can throw in tomorrow for a test drive while I get an SVDA sorted.

...happy days...

 

[NigelDenham]

It was the compression tester! Getting over 145psi on all cylinders now using the new one!

What a relief.

I suspect the dizzy was sticking so I wasn't getting any vacuum advance OR any mechanical advance. I've got a spare 009 I can throw in tomorrow for a test drive while I get an SVDA sorted.

...happy days...

Sounds like you’ve got to the bottom of things!