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manifoild glow
smart51 - 31/10/06 at 05:44 PM

I've just fitted my engine after some repairs and done a few shake down miles. When I got back I lifted the bonnet to look things over and noticed once of the exhaust headers glowing slightly red. I've never noticed this before, even doing emissions for SVA.

What causes one header to glow and not the others? too rich? too lean? I've had problems with compression, which seem to be fixed, but it is one of the problem cylinders that is glowing.

DIY Si - 31/10/06 at 05:51 PM

That would normally indicate a lean(er) mixture in that cylinder. If all of them are like that, I'd suspect a timing issue.

Winston Todge - 31/10/06 at 06:32 PM

What was the compression issue in the end?

Chris.

smart51 - 31/10/06 at 06:57 PM

quote:
Originally posted by Winston Todge
What was the compression issue in the end?


They said they soaked it in WD40 for 2 days and with oil in the bored, redid the compressin test and got the figures up quite a bit. Their engine building chum said that he thought that the rings were gummed into the grooves in the pistons. I don't see how gum would pull the rings in from the cylinder and hold them there. It turned over normally when I got it back. After quite a fight I managed to start it by suqirting WD40 down the carbs when crancking.

I've done about 4 miles since fitting, in traffic so I havent excercised it fully. Im not sure it's 100% but it runs. I'm just concerned about the manifold doing something new.

Peteff - 31/10/06 at 07:23 PM

Is there a kink/sharpish bend in the exhaust where it gets hot? If it's running and sounds alright I'd be tempted to keep running it.

viatron - 31/10/06 at 07:32 PM

Gummed rings can cause low compression, the rings are sprung and if they get gummed up and cant expand the slightest wear cant be taken up by the rings expanding out to seal against the cylinder. This is normally not a good sign however as it would indicate either very poor servicing ie irregular oil changes or very very rich running causing crud to build in the ring landings. A good fix is a good dosing of redex for a few days straight into the bores via the plug holes, im talking a good amount too! Then turn the engine over with some rag over the empty plug holes, quite often the mess that comes out is very revealing, on first start after this the smoke will put an army smoke grenade to shame!!! An oil change may be a wise precuation as well as the redex can leak past the rings into the sump.
HTP

Mac

jon_boy - 31/10/06 at 07:54 PM

dont piston rings expand when theyre hot, hence they were stuck in the groove from cold......could be wrong here

gazza285 - 31/10/06 at 08:27 PM

On the right lines, the pistons expand in the bore too, as do the bores themselves. The theory is that at normal working temperature every thing has expanded to fit perfectly with each other component, hence the need to run with a thermostat, and when the engine is cold the rings can be stuck in the piston and so away from the bores, leading to blowby and low compression. Tjis could be why the workshop recommended towing the car in gear to allow the bores to heat up with friction and so expand the bits to reduce blowby.

02GF74 - 1/11/06 at 07:54 AM

quote:
Originally posted by gazza285
On the right lines, the pistons expand in the bore too, as do the bores themselves. The theory is that at normal working temperature every thing has expanded to fit perfectly with each other component, hence the need to run with a thermostat, and when the engine is cold the rings can be stuck in the piston and so away from the bores, leading to blowby and low compression. Tjis could be why the workshop recommended towing the car in gear to allow the bores to heat up with friction and so expand the bits to reduce blowby.


Good tip about the redexs by the way - it came to me a day ago too!

Hmmm, did wonder about the rings but surely if they get stuck, they would stick in the engine when its cold and give problems when hot ans everything has expanded? i.e. good compression when cold but bad when hot?

Maybe worth doing a comp test when hot?

re: glowing red manfold - is there anything physically different about the one glowing? whcvih cylinder is it? you would expect the 2 cetrnal one to run hotter perhasp but they all should be about the same....

thunderace - 1/11/06 at 09:39 AM

by puting wd40 down the boars you increase the comp i rebuild wetbikes and find i can get a false reading of around 180lbs by sticking some 2stroke down the boars when its true reading is around 110lbs until its run in.

http://www.wetbike.pwp.blueyonder.co.uk/

smart51 - 1/11/06 at 11:46 AM

quote:
Originally posted by 02GF74
re: glowing red manfold - is there anything physically different about the one glowing? whcvih cylinder is it? you would expect the 2 cetrnal one to run hotter perhasp but they all should be about the same....


It is cylinder No. 2 It has a bit of a bend in it, less than No. 1 but more than No. 3. The carbs haven't been touched. I was just wondering if low compression or bad piston rings could cause this.