Advise Please Big end knock

[carmadmike]

Hi all and what a loverly day here in Poole Dorset
I have just fiited a new cam to my 2500 engine in my vitesse. After I first started it up I had the timing 180 degrees out and it back fired. Then I had the timing to far retarded so it tryed to fire when the piston was before top dead centre and made the engine sound like it had siezed but it didnt.(if you no what i mean). When I got the engine to run it developt a knocking sound like a big end has gone. Would the timing being out have damaged the big end when it tried to fire when the timing was to far retarded. If I put a strobe on it, it sounds like it knocks twice as fast  than the strobe flash so points to big end. When I put a long screw driver on the skirt of the block where the sump is I can here the knock very loud. so also points too big end. I cant here it with the screw driver when placed on other aeras of the engine like the cam chest. So I 90% sure the noise is no1 big end.
Now
when I take the engine out to investigate should I
1, strip and clean the hole engine (head of pistons and cam outagain) and replaced main and big end bearings with crank regrined or
2, just dismantle the engine so I can get the crank out to repair leaving in the pistons and head. the engine was fully rebuilt last year All advise welcome What would you do. Thanks in advance Mike.

[Steve Cureton]

I wouldn't have expected trying to start it with the valve timing out to knacker the big end (happy to be corrected) but you could have caused other damage (piston hitting valves) which might explain the appearance of being seized. If you're convinced it's the big end then I would drop the sump and assess the damage before deciding the best course of action.

[MarkB]

The engine sounding seized is caused by the timing being out valve or ignition. It's happened to me several times over the years. The engine backfiring wouldn't have caused any damage in itself, and not sure if 180 degrees out would allow the valves to hit the pistons. If the big ends weren't making a noise before hand, I would have thought it unlikely to be a big end. Obvious stuff like enough oil, oil pressure, is all ok? I would also check fuel pump lever, distributer drive etc. before I stripped it again.

Mark

[thescrapman]

Are you sure it is not your new cam knocking??

Last thing you did has to be prime suspect

Cheers

Colin

[Clive]

I had a similar thing on my 1500 engine I built up. It came partially assembled, and I finished the job.
Terrible knocking noise. Turned out to be the timing gear on the end of the cam, held on with bolts and spring washers, no locking tab :o
Luckily no damage done, and a tab fitted and no more issues. However, I was convinced the noise was from the middle of the engine somewhere...

[carmadmike]

Hi and thanks for the answers
Steve
it wasn't the valve timing that was out that was OK it was the ignition timing that was out. It fired when the piston was on the way up probably about 25 degrees bftdc. which stopped the piston travel dead. could it of damaged the big end by squashing it and leaving play in it. I think I will take the engine out and put it on a stand to assess the damage I'm getting to old to crawl under the car.
Mark
The timing was out 180 degrees to start with but then i still got it one tooth wrong on the distributor drive gear. which made the piston stop dead on its way up. The valve timing was OK so the valves wouldn't hit the pistons. If the piston has been stopped dead on its way up could it of dented or squashed the big end bearing to leave some play in it to knock. the oil pressure is about 40 psi at 2000 revs and the car drives ok apart from the knocking noise.
Colin
When I put a long screw driver on the bottom of the block it sounded louder than on the bulge of the camshaft. I think it will have to be engine out time to take a look. Thanks Mike.

[herald948]

Yet another possible cause of the "knocking" is having any two plug leads reversed! Years ago I managed to do this (without noticing) on a GT6 Mk3 I was selling to a friend. He was aware of the sound and the fact that it still seemed to run quite strongly if not "perfectly"! He did let me know a few days after getting the car back to his house that he had found plug leads 3 & 4 to be reversed; once he fixed that, the car ran beautifully!

I wouldn't have felt quite so, uh, incompetent if it hadn't been only a few months previous that I had spotted and fixed the same problem on a Herald I had gone to look at and test drive!  ??)

[carmadmike]

Hi just checked the leads and they are OK. I started the engine again and the noise wasn't there at first until it had warmed up a bit. I then restarted it after about half an hour and the noise had disappeared. I was thinking of changing the oil again as it is about 1500 miles old and putting in an additive to see what happens. can the oil thin with fuel when it was running in as it burnt some.

[carmadmike]

Just drain the oil and found the sump plug with metal on it is this usual for first oil change after rebuild.

[Nick Jones]

Seems to be quite a bit....... If its very fine "fur" then might not be excessive for a first start with fresh bores and rings.  If it's run before then I'd say that's too much.  If it's got actual lumps that you can feel with finger tips that's too much also.

On the knocking..... are you using a Vitesse sump?  If you are, the front two BEs of a 2.5 will clout the sump at BDC and make a very scary noise.  Can also happen to a lesser extent if you have already "relieved" the critical areas of the sump but not made the dents quite deep enough.....  BTDT on a 1500 with 1300 sump.....  :B

Nick

[carmadmike]

Hi Nick
Its very fine fur with no hard bits and was the first oil change from rebuild new bores and rings.
On the sump side it is a vitesse sump with dents in to clear the big ends. it didnt knock before the cam was changed.
Rebuit engine last year with KSC2R cam but found it to top end. engine didnt knock. Changed cam to 308778 with lift on inlets from chris wittor but didnt change followers as they were new about 1500 miles old. The noise sounds much louder at the bottom of the block at the front by no1 conrod and no noise at no6 conrod.  When you listern to the cam chest on the side of the block thre is a slight noise at the front and no noise at the rear. Could the sump be amplifyng it ? and it is the cam as Colin said. Also should I have changed the followers ?.

[Nick Jones]

Magnet deposits probably ok for first 1500 miles on a fully rebuilt engine - I'd suggest that a first oil change at about 100 miles would be better though - as most of the major "self-adjustments" will have occurred well within that.

Conventional wisdom says that you should always fit new followers with a new cam or at least reface the old ones (though opinions definitely differ on whether the latter is a good idea!).  It also says that a new cam should be run at 2000 rpm from first start for 20 minutes.  Also, if planning to re-use a cam and followers they should be carefully labelled so they can be matched up to their original lobes when refitted.

I've always stuck with conventional wisdom and so far so good.

What you are describing does not really sound like cam noise.  I still like the sump theory (obviously I'm biased because it's mine).  The reasoning is that although it did not make contact in your previous installation it may have been close.  You now have a different sump gasket (maybe thinner) and the engine has quite likely been resting on it's sump, been dragged on its sump or even set down with a bit of a thump on its sump.  It's heavy b*gger and the sump is only sheet steel, so it could now be too close.... maybe.  Obviously, if your engine has been sat in the car the whole time (which it may have been for just a cam change) then I'm talking tosh and can be safely ignored!

Another question:  Big ends usually make more noise under load unless they are really far gone so I'd expect no (or very little) noise at idle or at 1500 - 2000 rpm steady state, but a distinct "brrrrr" on snap throttle opening.  This would also likely be worse once the oil has warmed and thinned.

Nick

[carmadmike]

Hi Nick
Today I have changed the oli for Millers classic perfomance 20/50 mineral oil and put in 750 ml of slick 50 engine treatment.
Took it for a 5 mile spin and when I came back the noise has disapeared apart from a very faint ticking sound that I can live with.
The engine feels alot smoother and has even quitened down the top end rattle of the rockers. so I will leave it at that for the moment and see what its like in a few weeks. Thanks for all the advise from you all Mike.