Escort mini-update...

[GasSavers_RoadWarrior]

Just filled up, 34 mpg, w00t! (Bear in mind this is the auto) Best before that had been 32, which was a single long highway trip on most of the tank with 3 second truck drafting. On "normal" tanks I was swinging from about 29.5 to 31, depending on amount of city and drafting. This 34mpg tank, no drafting, nasty 40mph gusty winds for 1/4 to 1/2 of it, and it was I think still tuning out the rich. Before I blew the HG and messed with the head, it got one freak high of 36, saw 34s with non ethanol gas and acetone, but 32 was normal/average. Since then we've had mandated ethanol, which since I wasn't driving it for the changeover I don't know it's impact on Wile-E (Marvin may actually like it better)

[GasSavers_RoadWarrior]

Got a backlog of 7 receipts entered in the gaslog, need to keep it up to date dammit... just realised I did get a 33.5 a few tanks ago, but I'm thinking I got draft practically the whole tank.

[GasSavers_RoadWarrior]

So Friday showed 34mpg on the fill again, still haven't been real happy with overall smoothness, felt like I was missing something, suspicious of PCV system, so replaced valve, bung and rejigged the elbow. Runs a little different again, not so snarly lower down but took some lumps out higher up...

Put in a dose of RWs homebrew seafoam equivalent (Varsol/Isopropyl) with a touch of methanol as well... Trying to get my cylinders declagged after apparently misfiring on and off for weeks.

[BumblingB]

Glad to hear your doing better. I sold my auto wagon a few months ago after it dropped a valve. I can't help it but there are tons of nice Escorts that are local on Craigslist with dropped valves. I can overhaul a 2.0 Escort in my sleep now. Took a few tries to get everything perfect.

[GasSavers_RoadWarrior]

'tis the season for dropped valves, hot weather, cooling system failure, calcification, or thermostat problems provoke it. I've got nearly new rad, newer waterpump, newer coolant sensor, newer rad fan, new thermostat in there and good premix antifreeze (Then I don't have to stress about what water to mix in it) So I hope Wile-E is sound there.

Can't find good mpg figures for 2nd Gen auto wagons when driven for mpg, wanna know how well I'm doing. The manuals do great, the SPI autos seem to do better too, auto hatches and sedans seem to get around 32-34.

[GasSavers_Erik]

So what usually causes a valve to drop?

For low speed driving- I always thought that it all started when the head of the valve became bent slightly off center so the valve stem bends a tiny amount in order to seat evenly in the head recess and eventually fatigue cracks in the stem allow it to come apart.

What do you guys think the root cause of dropping a valve is? Overheating the engine and the stem scuffing/seizing in the guide? Is this the event that initially bends the valve stem and sets it up for failure? Overrevving and contact with a piston during valve float (for interference engines)?

My idea on the cause is from hearsay on the internet so correct me if I am wrong.

[GasSavers_RoadWarrior]

IMO on these motors, cylinder #4 overheats first, valve seat starts dropping out, valve contacts it hard, damaging valve, then varying degrees of carnage ensue according to when the owner notices.

[GasSavers_Erik]

I see- so when you inspect the damage, the valve seat for the dropped valve is usually cocked sideways or otherwise not in its factory position.

Or does the seat drop completely out and bounce around in the cylinder when the valve head is lost?

[GasSavers_RoadWarrior]

Could do either, either crack out from valve impact and fall out around the valve, and hammer the snot out of the piston and head, stay attached and break the valve head, or the valve could snap further up and fall in. Might first show as a light "funny tapping" and if ignored progress to "running REALLY rough and sounds like someone is beating crap out of the motor with a hammer". In case of light "funny tapping" it might only have bent or stretched the valve slightly and only fallen out a little... which shouldn't require too much work to get fixed... new seat and valve, vs having to weld up holes in the head replace piston and rod... maybe other parts... BUT cheaper to make sure the cooling system is A-okay as it greatly reduces the odds of it happening.