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1500 Spitfire engine tap/rattle


Conor L
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In need of some advice here folks, If you've been reading my built thread over in the projects section you may be aware that when I had my rebuilt 1500 engine running there was a strange noise that randomly went away however a noise has developed again. The noise occurs when holding the revs at 1500 rpm goes and goes away when you hold them at 3000 rpm but if you blip the throttle there's a noise at the rpm drops past the 1500 mark. I had a little listen around with a long screwdriver which highlighted a tap coming from just underneath the engine number, so I removed the rocker shaft (which stripped 1 of its studs, thankfully nut end), removed the push rods and using a magnet checked the cam followers using a magnet which highlighted the rear 3 followers were sticking. So I sprayed some engine oil down there and worked the followers with the magnet until sliding nicely, reassembled with new stud, set valve clearances and replaced the cover gasket. Fired it up this afternoon and the noise is still there however listening around with the screwdriver has confirmed that the noise under the engine number has gone. Timing chain area is quiet and the bottom end seems normal too. I just can't pin point this noise and I'm very tempted just to pull the engine out and rip it apart again. I'll leave some videos showing what I'm talking about any advice as to what I've done wrong is most welcome.

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I have not followed all of your epic restoration saga so some of these points may have already been covered.

I agree that from the clips it sounds like the rocker gear.  Once after rebuilding a Ford engine, it soon became very noisy.  On re-checking the valve clearance the gaps were far too large.  Some how it had bedded in on being run. Re-setting the gaps minimised the noise and after that the gaps remained correct.

My car came with shiny gauze filters but would not run correctly, running out of power as the revs rose and the mixture became weaker.  This was rectified  by fitting standard pleated paper filters direct to the carbs without the air box.  There was still a problem in hot weather while idling as the hot air was drawn from over the exhaust manifold.  I managed to get a used air box and some tubing to restore the setup to standard which remedied the situation.

The screwed plug blocking the manifold vacuum take off point does not look right.  Is it sealing?

Graham

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Thanks for the replies so far guys much appreciated! @Colin Lindsay the manifold gasket is new along with the studs and nuts, am I right in thinking that of air is escaping then it would also be sucking it in also so would spraying water or oil around the gasket show if that was an issue? @Iain T I did change the cover gasket incase the rockers were fouling the cover however I will run without to see if this highlights anything 👍 @gbostock funny you should mention that as the 2nd time I had the engine running the valve clearances had become way out, after resetting all was fine and the engine ran pretty quietly until this new noise, I'll recheck before I run it without the cover. I have been reading about the pancake filters not being a good choice I do still have the original air box however it's not in the bests of condition with some real deep pitting. Is there some sort of inbetween filter out there as I do prefer the look of the shiny filters over standard probably because I'm young. Bit of a story behind that manifold I sent the original away to the club shop for a stainless water pipe to be fitted however when it came back it was damaged, after a few conversations the club kindly agreed to send out their display manifold in exchange for my damaged original. After fitting it all back together with the new gasket I went to put the plug in and turns out the threads in the manifold were no good hence why it's sat at a funny angle this is something that needs sorting which will be done when the car goes back for the rest of the body panels.

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I had my head modified and skimmed and fitted new rocker gear and pedestal shims. When I started the engine it was like a machine gun. I took the cover off and noticed one rocker was hitting. Like you I fitted a new gasket which gave me just enough clearance. When the weather is a bit better I'll check the rocker arm angles to see if the shim is too thick. 

Iain 

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I've just spent the past couple of hours in the garage and checked some of your suggestions so I've rechecked the valve clearances rocker 1 was a bit loose but the other 7 were fine. Started the engine and ran it up to temperature (noise still there) switched it off, took the rocker cover off and tried to restart it... nothing. gave it slight throttle and it started but didn't seem to happy about it and promptly died and wouldn't restart so I put the cover back on and it fired straight up which is a bit odd. I feel the noise is slightly louder now. Not sure why I did this but before I came in I removed the spark plugs and turned the engine by hand. I'm pretty sure this isn't normal but I can't see going back through pictures what I've done wrong as everything was done by the book, the engine was an unknown but had been rebuild at some point in its life with a crank grind and rebore to +20 and in all honesty it wasn't that worn.

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I've been thinking about what @NonMember said about resonance because when I had the engine running in the chassis the exhaust was only roughly fitted and the rear box was held up by a jack and this noise has only really occured since fully bolting it to the car. I bring up the exhaust because I remember the down pipe being very close to the gearbox bellhousing/rear engine place (stainless tubular manifold fitted) so I'm wondering if the down pipe is hitting that and the noise is going through the manifold because I does seem louder on that side of the engine around where the manifold runs 🤔

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9 hours ago, Conor L said:

took the rocker cover off and tried to restart it... nothing. gave it slight throttle and it started but didn't seem to happy about it and promptly died and wouldn't restart so I put the cover back on and it fired straight up which is a bit odd.

That's not entirely surprising. The crankcase breather system vents through the rocker cover to the carburettor "constant depression" chambers. If you run with the rocker off, this makes for a huge air leak that throws the mixture way off.

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When you took the rocker cover off did you see any marks on the inside where something hitting? That's an easy find! 

However judging by your last video and your comment I would look for something tapping the exhaust or the exhaust hitting. 

Iain 

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Blocking off the breather pipes seems such an obvious thing to do with the cover off... D'oh! In my defence it was late at night aha. Been outside this morning fighting with the exhaust took the whole system off apart from the manifold (down pipe joint was blowing anyway) as can be seen in this picture the exhaust is clearing resting on the bellhousing 

20210115_114036.thumb.jpg.1ab1e48c28cb6000bda9dd781ca63fe6.jpg

no matter how much I bent it I couldn't get it any further away (manifold was sourced from Paddocks) so I put it all back together loosely, aligned it the exhaust as best i could, tightened all the joints and started it up noise still there even when I lever the manifold away from the bellhousing and that downpipe joint is still blowing (always seemed to have issues sealing that up) it is entirely possible that the manifold is just badly made/formed which wouldn't surprise me being an aftermarket part. Are there any flaps in them at all that could've come loose? 1 think that I did take note was the noise was quieter from cold and after about 3 minutes would suddenly get louder, much thinking to be done.

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12 minutes ago, Conor L said:

that downpipe joint is still blowing (always seemed to have issues sealing that up) it is entirely possible that the manifold is just badly made/formed which wouldn't surprise me being an aftermarket part. Are there any flaps in them at all that could've come loose? 1 think that I did take note was the noise was quieter from cold and after about 3 minutes would suddenly get louder, much thinking to be done.

Ok - seal the downpipe joint; use exhaust paste as well as a gasket. It will eliminate any noise from there.

Have you tried listening from the silencer end while the engine is revved? You may hear a change in note from the exhaust pointing to something along the system. If the noise gets worse as the engine warms, this may point to something expanding with heat - again, manifold or exhaust. If the exhaust is resting on the bellhousing, is this due to the manifold curvature, or are your exhaust straps too short? Can you lower it any at the engine end?Just a few thoughts...

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22 minutes ago, Conor L said:

the exhaust is clearing resting on the bellhousing

If it's not easy to move it away, the best fix for that is to fabricate a bracket to clamp it to the engine back-plate. That stops it moving so it can't "hit". It also reduces stresses on that pesky downpipe flange with the gasket that won't seal because it keeps being stressed.

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Thanks for the pointers chaps! I've had it running for about an hour and a half this afternoon and have driven it around my close a couple of times, engine pulls really well and plenty of low down torque which I like so I feel the engine is healthy which is good my mind can rest a bit now. In terms of the exhaust I have this manifold supplied by paddocks.

0017875_exhaust-system-sports-manifold-ssteel-spit-13001500jpr476_550.jpeg.591855a52407bc1133b9469037864e5b.jpeg

This is the type of downpipe joint I mean rather than the standard flange with 3 studs which like you say can be a pain. I'm not sure whether it can be dropped at all as it fitted tightly on the head studs. I did purchase a fitting kit which came with the bracket for the diff and 1 which I assume could be for the gearbox using a standard set up so I'm going to investigate whether that can be used on the tubular manifold. Another thing to note is that with my head under the car the noise is much clearer than on top you can really hear the rattly sounds around where the blow is which is just behind where the manifold is touching the bellhousing so fingers crossed I can use the spare bracket on the tubular manifold to slightly push it away, stop it blowing and hopefully no more annoying rattle!

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most 421   631 collectors manage to leak , and stainless it much tougher to clamp does not compress well

some are just not designed to have clamps as expansion needs to  accommodate wild pipe expansions

the only cure on my 631 was to slot and add weld clamps due to space limitations 

 

vit6_631.jpg

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I'll order up some Mikalor clamps and hopefully manage to come up with something to space the exhaust from the gearbox. Hopefully these clamps will finally sort the blow as no matter how much paste I use it still won't seal. Haven't really looked into it much today have been fitting the interior instead but I will update as soon as the clamps have arrived. I managed to miss @Iain T comment yesterday (apologies) when I removed the valve cover there was no obvious sign that the rockers had been hitting the cover. @Anglefire the twin box is a nice set up and sounds really good. My manifold and centre pipes were new however my rear box was 2nd hand which also needed modification to allow it to fit straight.

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New Mikalor exhaust clamps arrived yesterday so seeing as the weather was actually dry today I thought I'd tackle the exhaust, back section off, down pipe piece off and I also slackened off the manifold too on the head, managed to bring the 1 pipe down a bit so at least there is now clearance between it and the gearbox, new clamps fitted, exhaust roughly fitted to aligned and tightened everything up... Grrr noise still there! Exhaust isn't hitting anywhere and I can fit a flat blade screwdriver between the exhaust and gearbox think it's safe to say now that the exhaust can be ruled out. There is no obvious note change at the tail pipe end either. Interestingly though it's definitely louder underneath the car around the engine area as this video shows. I don't have the funds at the moment to pull the engine out, strip it down and have it inspected due to being made redundant again thanks to this blooming virus just before Christmas but I think it's looking more likely that this will happen.

20210121_152105.thumb.jpg.79eed1f07eb1eae35e9de5c5d0dd96f6.jpg

 

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