7hp valve overhaul

[ian Howell]

Has anyone had recent (Say last five years!) experience of replacing valve springs in a 7hp?

I suspect mine may be a bit weak - does anyone have a rating figure (compression in inches per lb)?

I have a side valve compression tool and valve seat cutters and guide bushes. Valves are OK.

[george garside]

Ian, a simple way of picking out week valve springs is to put 2 of them in a vice end to end so they resemble one long spring. compress them with the vice and the one that closes first is the weeker of the two. Idealy this test should be done with one new or known good spring to compare the others to.

As far as I am aware the spring strength was originally designed to allow some valve bounce above 3250rpm to prevent over reving. in top that would equate to around 50mph. 38 on 4 speed 3rd, and 30 on 3 speed 2nd. It would therefore seem reasonable to assume the springs are ok if these speeds can be attained?

george

[george garside]

Ian, have just noticed you mention a side valve removal tool. Its not needed on Jowett's as the job is done with a spanner and a screwdriver. Similarly grinding in is done using a screwdriver.

george

[Keith Clements]

Our esteemed Paul Beaumont was the club representative at the Club Challenge at the NEC. The task was to beat many others clubs in removing and replacing a valve. Paul was unused to the configuration of a modern head so had an excuse for not winning. Watching him was the only interlude I had in 2 days at the show; but was still multitasking, as I was eating my pastie.

[ian Howell]

George (and Keith): -

Thanks for the info. I suspect (but don't know yet - I haven't actually had a chance to look) that a spring may be broken somewhere.

There is an occasional faint 'tinkle' sound when running (loose 'turn' of a spring?) and very occasionally a sort of misfire -sort of 'poof' sound, like an exhaust valve not closing soon enough.

I know about getting the springs out with a bit of rag but I was prepared for a requirement for an insertion tool to compress the springs to get them in again.

Anyway it only cost 25p at a car boot so it was too good to leave it there!

[Forumadmin]

I had a similar sound on my Subaru. Eventually the engine blew up in a big way. It was a worn big end that caused the piston to hit the valve. When it let go it holed the piston, bent the rod and required a new engine.

[george garside]

At least that can't happen on a sidevalve engine!

Ian, on pre war twins and CA & CB Bradfords there is no need for a spring compressor to either remove or replace valves.

to quote '' valves are removed by slackening off the bottom nut, holding both the lock nut and the bottom nut with spanners and unscrewing the valve, making use of a screwdriver on the slotted head . These instructions apply for replacing a broken valve spring'' Refitting is simply a reversal with the springs fitted uncompressed and then compressed by tightening the bottom nut.

on 1930/33 models without inspection covers in the wings either the wings have to be removed or a special tool used . I have a picture of this somewhere and will post it when I find it. However the 'special tool' is in effect the tip of a screwdriver blade with a handle at right angle to it and should be easy to to make.

The CC Bradford was completely different and used 'normal' colleted valves requiring a compressor. The rag removal was recommended to stop the bits dropping into the bottom of the tappet chamber.

If a valve spring is broken I would expect a veery noticeable reduction in power and the occasional 'poof' may be down to a burnt exhaust valve??

george

[Tony Fearn]

Anyway it only cost 25p at a car boot so it was too good to leave it there!

I also buy the odd 'perhaps it might be useful in the future' items at Boot Sales, but I'd love to see a photo of this, even if as George says, it's not necessary for your Jowett.
Tony.

[ian Howell]

Thanks for the tips George, duly noted. Tony, I'll see what I can do about a photo, but at this very moment contractors are laying wet concrete outside my garage for the base of my workshop extension so I can't actually get into the garage/workshop at all for a couple of days!

[Tony Fearn]

At this very moment contractors are laying wet concrete outside my garage for the base of my workshop extension.

Hello Ian.
I'll bet in a couple of year's time you'll be saying that you should have made it twice the size!
There's somebodies' law that recognises extra space available and our need to fill it to the gunwales.
Tony.

[ian Howell]

Two Years? Why not now!

Sadly I can't do much more as the size of the garden / planning requirements preclude.

I haven't forgotten about the side valve spring tool but now the existing garage is chokker with tut and I can't actually get in at all.

Happy days (daze?).

[ian Howell]

Tony. George and any other 'watchers'.

I am pleased to say that thanks to Webmaster I am now back on the Forum.

Tony:- I will post the picture of the side valve spring compressor, when I can get my computer to speak to the internet again. As predicted, the work shop is not big enough at 9ft by 18ft.

Well there are three welders, a small lathe, a compressor and shot blast cabinet, a pillar drill, a parts cleaner, bench grinder, my Dad's tool chest, 3ft dexion racking, two work benches as well as all the projects currently awaiting attention.

Then, hanging off/on the walls . . .

That of course leaves out the loft which is steadily refilling with spares and 'come in handy' bits.

George:- As soon as I get my car back home from the upholsterers I will have the valve springs out for comparison tests.