A40 - New boots

[MiniMinorMk3]

13 hours ago, Matty said:

Thanks for the info. Well worth considering. Although it's an extra expense, it will pay to do the job properly. 

I was already aware of fuel turbulence problems. I have made up two viton  orings that sit between the carb and the inlet manifold. Do you think that will be sufficient?

The o-rings will help and will be better than nothing. For SU carbs I've seen stub stacks and have used the myself when running a K&N pancake, but I am not aware of any for Weber carbs.

[Matty]

14 minutes ago, MiniMinorMk3 said:

The o-rings will help and will be better than nothing. For SU carbs I've seen stub stacks and have used the myself when running a K&N pancake, but I am not aware of any for Weber carbs.

There are location rings cut into the mating faces of the inlet manifold for the o rings to sit in. I mean, they're basically the misab plates minus the metal plate. But at least they locate. One way to find out I guess 😄

[Matty]

Head stripped and cleaned. Looks in good order. No cracks between the valve seats, seats themselves look good. Will NDT it tomorow cos I can, just to be sure.

It hasn't got unleaded exhaust seats sadly. My go to engine man wants 50 quid a seat. Too rich for me at the moment. Lead additive it is then. It has got one insert fitted. Best guess is a dropped valve at some point in the dim and distant causing damage and necessitating an insert to repair. New stem seals, exhaust valves and a new set of valve guides going in (valve guides are mainly bolloxed).

Before becoming too self congratulatory, I need to put it on the surface plate tomorow and just make sure.

(Edit. The more I look at that pitting around the galleries, the more I'm erring on the side of getting a light skim to clean up.)

 

[Matty]

Also, the head is casting number 12G940, the stamping near the stat reads 12G938. Best I can research is that it makes it an early Sprite or midget head and would've had double valve springs. Could one of our a series experts like @Mr Pastry or @MiniMinorMk3 put me right (I don't have double valve springs fitted)?

[Mr Pastry]

You should use valve springs that suit the camshaft, so there isn't really enough information about what you have to suggest anything sensible.

I think all the 1275 Spridgets had double springs, but Marinas had single springs.  That is with quite mild camshafts of course.  They all revved to about the same limit.   Maybe yours are Marina springs?  Free length 1.95", fitted length 1.383", load at fitted length 79.5 lbs. 

Unless you can find exactly the springs that are designed for your cam, I think you just have to suck it and see,

But put it this way - if you had just stuck it straight in the car, fired it up and driven it, you'd probably be thrilled with it.

 

[Matty]

22 minutes ago, Mr Pastry said:

You should use valve springs that suit the camshaft, so there isn't really enough information about what you have to suggest anything sensible.

I think all the 1275 Spridgets had double springs, but Marinas had single springs.  That is with quite mild camshafts of course.  They all revved to about the same limit.   Maybe yours are Marina springs?  Free length 1.95", fitted length 1.383", load at fitted length 79.5 lbs. 

Unless you can find exactly the springs that are designed for your cam, I think you just have to suck it and see,

But put it this way - if you had just stuck it straight in the car, fired it up and driven it, you'd probably be thrilled with it.

 

Aye, there is some danger I might be over thinking the job a bit.

[MiniMinorMk3]

There are suggestions on the interwebs that the 12G938 was a special head from the MG Midget that had a thicker casting to allow for some porting work to be done.

£50 a valve seat sounds a bit pricey to me, but then everything does these days.

[Tommyboy12]

£50 a seat is a bit much. I paid £25 a seat last year for an unleaded conversion on a 998 head.

12G938 isnt anything particularly special beyond a 940 head but it should have double springs. Given the cam youve got I would consider getting a double spring  even if theyre just standard doubles. It will be fine without as has been said but you might suffer valve float before the camshaft is done giving all its got, particularly with something like a 731.

Minispares hold double valve spring sets for standard setups for fairly cheap. Id probably also be considering them for a lot of other parts too!

 

[Matty]

Today's adventures. Idiot gets up at 6 after getting up at 5 all week.

Transport

A visit to @SiC. Pleasure to put a face to the name! Shame you don't live in Clitheroe instead of Cleeve but we can't have it all 😆. I'll reveal my haul tomorow cos i havent been home long, im having a beer, the kids are already getting on my tits and i cant be arsed taking the sheet off tonight.

visited the Tebay of the south west and stole Si's dinner idea from a recent collection (minus sweet potatoe, bloody awful stuff, what were you thinking 😁).

Final scores on the doors 498 miles, sore arse, new parts. Many thanks Si, great stuff 👍

[Matty]

So, the first look at my new acquisitions, a very kind gift from @SiC. Two sets of Dolomite front seats that Si thinks would suit mine as I'm still on the awful Rover 25 velour. And y'know what, I like em. Whilst they aren't small, they are usefully smaller in every dimension than what's in already. They look period and classy in black cord and black vinyl and they are very comfortable. I've had a quick weigh up and I have enough good bases and enough good backs to make 1 good pair out the 4. Quick going over with a wet vac as well and they'll be sound.

That'll be a job for spring mind, enough to be getting on with this winter.

[Matty]

Back to the engine build. New valve guides and exhaust valves bought this week and new guides pressed in. I made up a guide on the Miller slightly bigger ID than the OD of the guides at a length of 15.25mm which is the deck height I want them pressed in to. Head in the partwash to warm it up, guides in the ice box in the canteen fridge, they went in easy.

so today after window cleaning, i needed to lap the valves in before the head goes for a mild skim this week to cleanup.

Didn't someone say lapping valves in is quite theraputic? No? Thats cos it isnt. Seats have come up well though.

Thank god thats done anyhow. Even god had a day off sunday. Cheers all

 

 

[JMotor]

Good work man!

It'll be great to see how it goes after it's back together.

Agreed with the Dolly seats, they'll look more period in the A40.

[Matty]

3 minutes ago, JMotor said:

Good work man!

It'll be great to see how it goes after it's back together.

Agreed with the Dolly seats, they'll look more period in the A40.

Hopefully it goes well. To be honest I'll be fuckin relieved if it goes at all 😄

[JMotor]

Ach she'll be mint lad 👌.

[Mr Pastry]

It will be absolutely fine.

Just a thought, would it be worth working out the compression ratio while you can measure the chamber volume?  I'm not sure what you should aim for with current fuels, and I wouldn't suggest altering it as it's probably workable anyway, but it would be good to know. 

[Matty]

9 minutes ago, Mr Pastry said:

It will be absolutely fine.

Just a thought, would it be worth working out the compression ratio while you can measure the chamber volume?  I'm not sure what you should aim for with current fuels, and I wouldn't suggest altering it as it's probably workable anyway, but it would be good to know. 

I could do but don't know how. What dimensions do you take to arrive at that?

[Mr Pastry]

I thought you knew everything!

CR= V plus v, divided by v, where V is the swept volume of one cylinder and v is the combustion chamber volume. 

Swept volume is easy of course from the bore and stroke.

You need a burette or a graduated measuring cylinder to measure the combustion chamber volume with paraffin, then add to that the volume of the dish in the piston, plus the volume contained in the gasket.   

[Matty]

5 minutes ago, Mr Pastry said:

thought you knew everything!

I'm only a fitter 😆

[Tommyboy12]

Those head chambers are standard so the compression ratio should be fine. It'll be somewhere between 9.5:1 and 10:1 most probably. Maybe a bit higher if it's been skimmed a few times. It will be fine on modern fuels if it's set up properly. A good rolling road setup will help loads.

[Matty]

15 minutes ago, Tommyboy12 said:

Those head chambers are standard so the compression ratio should be fine. It'll be somewhere between 9.5:1 and 10:1 most probably. Maybe a bit higher if it's been skimmed a few times. It will be fine on modern fuels if it's set up properly. A good rolling road setup will help loads.

Yeah in other news my rolling roads shut down! There is another that does older carb fed stuff in Bury so I'll be going there now.

[SiC]

Stick the car in the back of the truck and drive back down here again to these guys:

https://www.slarkraceengineering.co.uk/

🤣

(I plan to take my Midget there for a rolling road tune-up once I get it back on the road)

[Matty]

35 minutes ago, SiC said:

Stick the car in the back of the truck and drive back down here again to these guys:

https://www.slarkraceengineering.co.uk/

🤣

(I plan to take my Midget there for a rolling road tune-up once I get it back on the road)

Would need extremely long ramps

[Matty]

Bit slow on updates at the minute. Got slowed up a bit by a light head skim and fresh cam bearings. All back from the machine shop now. Been spending time cleaning brackets, engine plates and other tin work and painting where required before the big build up.

Heads done now. New guides, exhaust valves, stem seals, stat, stat housing and studs, some manifold studs, temp sender and bypass hose stub. And obvs a light skim. Painted it yesterday and built it up this aft. Still sneeking round behind bosses back and fitting it in  between jobs 😄

 

[Matty]

Blocks clean and prepped. Need to put new core plugs in and paint tomorow. Also need to work out which stat housing to use. I've got a midget one, bought a mini one because like an idiot I forgot it isn't going back in a midget. So I need to work out which outlet angle best suits the route to my top hose. Which also means I might have fitted the wrong studs 😆. My brain capacity is only so big, sometimes stuff falls out.

[2flags]

Looking good!

[Matty]

7 minutes ago, 2flags said:

Looking good!

Ta! My jobs massively getting in the way of my hobby at present 😁

[kevins]

You mention earlier about using your current 1098 distributor but isn't the new block a A plus engine? in which case I don't think the pre A plus dizzy will fit.

[Matty]

9 hours ago, kevins said:

You mention earlier about using your current 1098 distributor but isn't the new block a A plus engine? in which case I don't think the pre A plus dizzy will fit.

Luckily (or unluckily) it's a pre a plus marina block which came with a 25d the same as the one I currently have.

[Tommyboy12]

Have you acquired a dizzy with a suitable set of weights/curves for the camshaft? It's worthwhile considering that.

[Matty]

4 hours ago, Tommyboy12 said:

Have you acquired a dizzy with a suitable set of weights/curves for the camshaft? It's worthwhile considering that.

It's come with a 25d in it but on accuspark. I hadn't thought about that at all if I'm honest. If it didn't look so manky I'd be refitting it, although I don't want electronic ignition. Thanks for the heads up though. How much difference will it make in reality? Not getting the best out of the cam or it not running right at all?