21 replies to this topic

[j0-rdan]

Hi guys,

 

I am totally stuck with an engine issue and really need your help. Please bear with me as I try to give as much information as possible below:

As some of you might know I have recently taken on the challenge of giving my 1275 engine a bit of a rebuild. This was a result of the car developing an odd fault while being used as a daily driver for a short period of time. When acceleration was very gentle everything appeared to be fine, however under medium or hard acceleration the power had really disappeared and this was accompanied by a rasping sound. The best way I can describe this would be the usual engine noise and then at around 2500-3000 rpm it seemed like someone had started gunning a moped with holes drilled in the exhaust!

 

The engine is a 1275 (early 1990’s), with stage 3 head, Hif44 carb, 1.5:1 roller rockers and electronic points. Previously it had run 88bhp with Peter Baldwin. When I started investigating I found cylinders 2 and 3 were low on compression.

 

So in response the engine came out at Christmas, head gasket had blown between 2 and 3 so fitted a new bk450 gasket. While I was at it I changed the exhaust manifold gasket too. I also took the opportunity to add/change the following:

- MED verto ultra-light stage 1 balanced flywheel and clutch (This also identified it was time to change the clutch arm, which was an absolutely nightmare to get out)

- Gearbox oil seal kit

- New valve stem seals and gave the head a good overall clean up (reseated valves etc.)

- Swiftune SW8 billet camshaft and rebuild kit (including cam followers/oil pump)

- ARP Washers for main caps (200-8530)

- Minispares Cross Pin Diff (C-AJJ3385)

- Duplex timing chain conversion kit

- Assortment of gaiters/fitting/gaskets/seals/bushes

 

So this weekend I was ready to take the car out for its maiden voyage and I am heartbroken to report despite everything the original issue remains!

I tried my best to assemble as much information as possible so let me summarise below:

• Compression is now back to normal (always been high since fitting st3 head) 160 psi across all bores but cylinder 1 which was 170. This went up in 3-5 stages to reach the maximum
• When front wheels jacked up and engine run through gears the noise has gone no matter the revs or acceleration. So only occurring under load
• I thought this may indicate a carb issue so pulled mine off and replaced with a spare Hif44 I have and although the running was a bit rougher it was clear the issue remained and makes me pretty sure it is not the carb

 

So what am I left with? I am totally stuck and feeling defeated. Any advice would be very gratefully accepted as I do not know where to go from here.

Edited by j0-rdan, 15 August 2016 - 02:23 PM.

[R1mini]

I would look to see if your exhaust/engine is touching metalwork under acceleration, check/replace all bushes on any engine mounts/ steadies you have.

 

Just a thought!

 

Cheers

David

[nicklouse]

some loose nuts and bolts rattling.

[Carlos W]

Was there any damage to the head or block due to erosion caused by hot gasses travelling between cylinders?

[Broomer]

The fact the noise is accompanied by a loss of power it can't simply be a few loose bolts or a worn engine steady?

What ignition setup are you running ?

[R1mini]

The fact the noise is accompanied by a loss of power it can't simply be a few loose bolts or a worn engine steady?

What ignition setup are you running ?

 

I didn't see that bit, I shouldn't skim read stuff

 

David

[nicklouse]

The fact the noise is accompanied by a loss of power it can't simply be a few loose bolts or a worn engine steady?

What ignition setup are you running ?

 
I didn't see that bit, I shouldn't skim read stuff
 
David

was not the power loss sorted and just the noise remained? that is how I read it.

[Spider]

I'd say you have a sticky valve and / or possibly a floating valve guide.

 

You maybe able to spot this by taking the rocker cover off and having a look at the valves and guides, you may need to rock the engine over a couple of times to be able to look properly through the springs.

 

I would recommend against running it until this is resolved, there is a good risk of breaking the valve and having it go where it shouldn't.

[j0-rdan]

Thanks for the responses. Power loss is still very much there unfortunately

Not really sure what to say on the ignition front, lucas coil and electronic points on standard distributor. New cap fitted not long ago. I sort of feel this could be the issue as it is one of the few areas not switched out for new/better parts. Seems strange that it is only under load though and the power loss is dramatic.

[j0-rdan]

I'd say you have a sticky valve and / or possibly a floating valve guide.

 

You maybe able to spot this by taking the rocker cover off and having a look at the valves and guides, you may need to rock the engine over a couple of times to be able to look properly through the springs.

 

I would recommend against running it until this is resolved, there is a good risk of breaking the valve and having it go where it shouldn't.

 

Thanks, I think I am going to need to get it on a rolling road to replicate the noise under load. Just revving the engine while stationary won't do it so happy to make a list of things to check for when I get it there.

No problem in regards to keeping it off the road until it is sorted.

Edited by j0-rdan, 31 May 2016 - 11:22 AM.

[Spider]

 

I'd say you have a sticky valve and / or possibly a floating valve guide.

 

You maybe able to spot this by taking the rocker cover off and having a look at the valves and guides, you may need to rock the engine over a couple of times to be able to look properly through the springs.

 

I would recommend against running it until this is resolved, there is a good risk of breaking the valve and having it go where it shouldn't.

 

Thanks, I think I am going to need to get it on a rolling road to replicate the noise under load. Just revving the engine while stationary won't do it so happy to make a list of things to check for when I get it there.

No problem in regards to keeping it off the road until it is sorted.

 

 

If it is as I am thinking, and it's an exhaust valve, it may well need some heat to get it to do it's 'trick'.

 

I've seen this a couple of times over the years now, but been lucky enough to see when it was cold what was going on, even though it didn't do this trick until some RPMs and load was applied.

 

It also may not be this, only a suggestion.

[nicklouse]

Ohh that would sound like a broken spring giving valve bounce?

[Dusky]

I've had an advanced airleak /mixture problem wich did the same, only on full throttle in 4th. Sounded like hitting a hard cut rev limiter

[mk1leg]

what needle are you using I used a BBC in my 1380 with sw5...........

[blacktulip]

Is your dizzy advancing properly?