4.5 cylinder engine.... :o(

Slothie · Post by **Slothie** » Sun Apr 08, 2007 3:35 pm

First of all, hi to petrolheads everywhere.
i wonder if anyone has any ideas about the problem I have with the rover V8 I have in my trike.
I bought it last year as a "project" (i.e. unworking). I whipped off the cylinder heads, and found that the inlet valve on no.3 cylinder had a valve seat that had 'dropped', and so the valve was never opening. The previous owner had mentioned there had neen a problem with the cylinder after it had overheated, so I wasn't surprised to find this. I managed to clean all the rubbish out from behind the seat with some dental picks and drift the seat back into place. I checked the head against a straight edge and there was no sign of distortion, or evidence of any leaks, so I considered the head to be serviceable. So far so good.
When the winter warmed enough for me to get back in the carport and put the engine back together, I discovered that the timing marks on the engine balancer where in the wrong place (so my first attempt at timing was WAY off). However, by using a depth gauge in No.1 cylinder I was able to establish the correct position for TDC, and presto! it runs. Sort of. On 4 cylinders actually. By feeling the exhaust headers I can tell it is firing on cylinders 3 (yay!), 4, 5 and 6 but not on 1,2,7 and 8. The header for No.7 is warmer than the other 'outer' cylinders but much less so than 3-6, so maybe it's running on 4.5 cylinders!
The engine is an SD1 3500cc engine (engine no 11A49782) and the only odd things about it are that it has a P6 contact type distributor and the inlet manifold has been fitted back to front (i.e. with the thermostat at the back). When I had the engine apart I checked the inlet ports and the manifold would appear to fit properly on backwards!
From looking at the manifold castings it would appear that the middle four cylinders are fed by a different "layer" to the outer four - which is why I thought it might be a fuel/carb problem - but I have no idea which carb feeds which cylinders.
So, do I have a fueling problem, a bizarre timing issue, or some other problem I haven't thought of?
Any help would be most gratefully received!!

Post by **katanaman** » Sun Apr 08, 2007 7:46 pm

I would say you have a fuelling problem. Not sure what the manifold being on in reverse would do but it might mess up the cooling a bit.

ppyvabw · Post by **ppyvabw** » Sun Apr 08, 2007 8:10 pm

Are the carbs jetted differently on each side. I know that on the boxer manifold, the carb feeding ports 5 and 7 is set rich because they fire consequtively. Dont know if it could be the same on the standard rover manifold. Just a thought and probably complete rubbish. switch the carbs over?

Slothie · Post by **Slothie** » Sun Apr 08, 2007 11:31 pm

ppyvabw wrote:switch the carbs over?

That's not a bad idea at all. If the problem 'shifts' then at least I'll know it's the carbs. If it doesn't, then its definitely not the carbs and I've a problem elsewhere! I'll just have to see if I can find my small AF spanners, as there's no way I'll get sockets on all the bolts that hold the carbs on. And I will have to re-route the fuel lines - and the control lines....!

The only other thought I've had is that maybe I torqued down the manifold bolts wrong, or too much, or too little. The valley gasket is a new tin one, and I've heard they are tricky to get to seal up properly. Perhaps I should try it again with some silicone sealant too?

I'm not sure the manifold being on rotated is the problem (although it might be contributing) because the machine has run in the past for some time. But it might explain the overheating problems.

Perhaps the engine maintenance manual I've ordered will help - trouble is it's at my mums and I'm 100 miles away!

Post by **katanaman** » Mon Apr 09, 2007 8:52 am

if you suspect a leak then spray the joints with wd40 and if there is one the engine note will change. I don't think this is your problem though as the dead cylinders are far to distributed and match a duff carb.

Slothie · Post by **Slothie** » Mon Apr 09, 2007 2:09 pm

Hmm.. I was just reading around on this site and came across an excellent post about vacuum and centrifugal advance, and how the vacuum advance is needed to allow the engine to idle... so on a whim I went out to test it and sucking on the pipe causes no (visible) movement in the distributor! I remember having a leaky advance mechanism on an old Manta I had, and that wouldn't idle below 1500 rpm until I replaced the vacuum advance unit....

Do you think this could account for my half-running engine? I can't see how it could be helping so I guess it's off to fleabay to look for a replacement. I might even look for an 35DLM8 dizzy and kill two birds with one stone. I take it will be a drop-in replacement (wiring aside)?

ppyvabw · Post by **ppyvabw** » Mon Apr 09, 2007 8:26 pm

mmm, i've changed my mind about my theory now anyway. I can't remember, doesn't the rover manifold crossover. each carb serves two inner cylinders on one bank, and outer cylinders on the other. doesn't he have a whole bank not working.

about the vac advance, it takes a lot of sucking to make it move, but you can just do it if you suck, put your tongue over the pipe and then suck again.

Slothie · Post by **Slothie** » Mon Apr 09, 2007 9:01 pm

..But if you suck, and the air keeps coming, and you suck more, and the air keeps coming....
I think there must be a hole in it!

ppyvabw · Post by **ppyvabw** » Mon Apr 09, 2007 9:43 pm

oh, well then it certainly sounds like its gone for a preverbial s***e then, adjust your base ignition setting, and if this fixes your half running engine then that is what is causing it, but not sure if its that. it certainly isn't helping though is it.

ChrisJC · Post by **ChrisJC** » Tue Apr 10, 2007 6:57 am

Fitting the manifold in reverse will completely stuff the block / head cooling.

Normally, the water pump will pump the water rearwards through the block. Then it rises up into the heads at the rear, and travels forwards through the heads. Then it passes into the inlet manifold at the front, and then to the thermostat housing.

If you switch the inlet manifold around, the water will pass through the block, rise into the heads and straight out to the thermostat without passing through the length of the head.

Unless the block / heads have been modified (there are bleed holes at the front of the block going into the heads) in some way.....

As for the carbs / duff cylinders, one carb does cyls 2,3,5,8 and the other does 1,4,6,7.

Chris.

Slothie · Post by **Slothie** » Tue Apr 10, 2007 8:29 am

Hmm seems like I have some work to do. I think I'll get the manifold round the right way, sort out the distributor and work from there. It's a pig getting the airlock out of the manifold/heater hose the way it is. I guess its probably why there was no thermostat in the housing - an attempt to "improve" the cooling.

As for the not running thing, from what you say it looks like the carbs are not entirely the problem, as 2 cylinders from each carb are firing OK. I'll report back when I've got the timing sorted out...
Thanks everybody!

Slothie · Post by **Slothie** » Tue Apr 10, 2007 8:43 am

ppyvabw wrote:adjust your base ignition setting, and if this fixes your half running engine then that is what is causing it

Hmm so to see if the engine will start when I get the dizzy sorted, I should add about 10-15 degrees extra advance in to compensate for the non-working vacuum advance? I know it will bork when I hit the throttle, but I'd just like to see it start and run on all cylinders!!

ppyvabw · Post by **ppyvabw** » Tue Apr 10, 2007 3:19 pm

yeah, try that. about 10 or 15 degress. Do you have a timing gun? If you do that though, just let it idle, dont give it any cos it will start pinking, not good. Not sure its that though. block off the vacuum port aswell.

Post by **Coops** » Tue Apr 10, 2007 9:42 pm

Hmm.. I was just reading around on this site and came across an excellent post about vacuum and centrifugal advance, and how the vacuum advance is needed to allow the engine to idle... so on a whim I went out to test it and sucking on the pipe causes no (visible) movement in the distributor! I remember having a leaky advance mechanism on an old Manta I had, and that wouldn't idle below 1500 rpm until I replaced the vacuum advance unit....

Do you think this could account for my half-running engine? I can't see how it could be helping so I guess it's off to fleabay to look for a replacement. I might even look for an 35DLM8 dizzy and kill two birds with one stone. I take it will be a drop-in replacement (wiring aside)?

i have a similar running problem on my efi engine, seems to be half engine at idle but when revs up seems to be better. (my capri work in garage area)
i too have a buggered vac advance unit, i have a new one on its way so if it works will let you know.

Slothie · Post by **Slothie** » Tue Apr 10, 2007 10:32 pm

Hey, theV8kid, I just noticed you're in Newbury - so am I! Small world.

I've managed to hunt down a 35DLM8 at a reasonable price (worked well in february, govnor, honest!) and since I have an irrational desire for contactless ignition I've gone for it. Just have to wait for it now. Still, I have plenty of time to plan what I need to put the manifold back on the right way (cooling problems are one thing I don't need). Even though my trike is not the work of art some of your V8's are, its going to be a problem working out how to replumb the cooling and not make it look a total mess, esp. with my limited facilities/talent!

I'll report back, and once again, thanks to everyone.