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Exhaust Manifold gets very hot.


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As I said a week or so ago, I have recently started the engine on my TR3a for the first time.

 

Today, having fixed a couple of coolant leaks and thoroughly cleaned the wrapping on the exhaust manifold, I started it up again and let it run at 2 to 3 thousand rpm for about 15 to 20 minutes.

 

Its a Phoenix tubular manifold and I noticed that down in the down in the middle where all the pipes come together and where it is impossible to wrap, the manifold was glowing cherry red. is this normal? Presumably the rest of the manifold is equally hot but because it is wrapped, it isn't visible?

 

This apart, everything seems OK. Once I had run in the camshaft, I balanced the carbs, set the idle to about 900 rpm - much below that it was a bit lumpy - and checked the dynamic timing which seemed pretty much spot on.

 

I have a bit of a brake problem which I'll cover in another post, but I would appreciate some re-assurance that its normal for a tubular manifold to get red hot when the engine is running at a fast idle.

 

PS what sort of oil pressure should I be looking for? Mine seems to be just over 50 psi whatever the revs, even when the oil has warmed through. I assume that is the point at which the pressure relief is operating, I didn't touch it when i rebuilt the engine, is that about the right figure?

 

Rgds Ian

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I've had a SAH/TriumphTune mild steel (not stainless) system for many years and it's never glowed red. Maybe wrapping only part of the system is causing local hot spots. Doesn't sound right to me (but then I wouldn't have wrapped any of it in the first place!).

 

Oil pressure on rebuilt engine is 70psi hot (50-60 at idle) using Penrite HPR30 (20W/60) after 13000 miles. But how accurate are the oil pressure gauges now? Don't worry unless it drops any lower or starts making noises or burning oil. :rolleyes:

Edited by BrianC
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You could possibly adjust your pressure release valve to get a bit more pressure at 2000 RPM (about 70). Tubular manifolds do get very hot, although when I had them on my GT6 I only saw them cherry red hot when thge timing was a bit off. I have always wondered with exhaust wraps whether they would create a very hot spot at the first unwrapped section.

 

Andy

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Hi Ian,

Tubular manifolds are thin. The hot gas coming out of each port heats its associated tube and then cools for a moment - roughly 4:1 ratio cold/hot.

However at the point where it all joins you have continuous hot gases.

Normally the gases are less hot than where they exit the port, but!!, you have lagged the only place they can cool.

Therefore you have very hot gases at the joining of the four pipes. = red glow.

Keeping the heat in is very good. But it appears that you are too hot to start with.

 

Roger

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I'm with John and Ashley. Last winter, after rebuilding my engine (camshaft faillure), the first start up suffered from a to far retarded ignition. Point is, with retarded ignition, the car will start and run pretty decent as long as it's in the workshop. And it sounds pretty normal too! The only give away on my car: fumes and smoke bellowing out of the exhaust, setting off the fire alarm inside the workshop!

 

Menno

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Thanks All,

 

So the general consensus is that I need to retard the ignition.

 

No problem but just so I don't do it wrong, the distributor rotor arm is rotating anti-clockwise so I need to rotate the body of the dizzy clockwise to advance the ignition - correct?

 

Rgds Ian

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Try setting the static timing first with a light bulb, by the book. That's your first step. The overall idea is, that it's best to advance the timing even a little more due to the modern fuels. There's a lot of info on the forum about that.

 

Menno

 

EDIT: here's some useful info: http://www.vtr.org/maintain-index.shtml, about 1/3 down, under Electricals > Ignition System > Setting the Ignition Timing on a TR.

 

M.

Edited by Menno van Rij
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Ian

You don't need to retard the ignition, if there is anything wrong, it's that the engine is already too retarded.

 

The best thing to do is use the timing marks to set it by the book. Guessing desnt work.

 

Ash

 

My mistake, I meant advance!

 

I have set it by the book and checked it with a strobe against the timing marks I made on the (new) pulley when I re-assembled the engine. It is currently at TDC when the engine is running at about 900 rpm.

 

Rgds Ian

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