New member hello & APD rebuild

[`Gordonhbm]

Makes absolute sense. When fitting do you do this with spring pins in place and the suspension an max droop?

[yantofullpelt]

Hi you may want to consider that when new your A.P.D. would have been fitted with 19 inch wheels although a lot of owners run on 17s
Great to watch your progress and sharing it with us. I really enjoy mine and have done now for over 30years
I believe that the apd was Austin’s £100 car unless someone on here knows different,

[Goldnrust]

I just checked and, according to RJ Wyatt's book, I think my car would have been £102. The APD the £100 Austin in 1934, but had gone up £2 by 1935! Damned inflation! haha.

I hadn't twigged that my car would have had 19" wheel originally. I had presumed that all 7s were moved to 17s by 1935, given that the APD was the last high frame car in the range? Either way, I've got 5 good (and 2 rough!) wheels here, so I'll stick with the 17s for now.

[Goldnrust]

I probably should have been finishing off the brakes... but I've got side tracked by an empty work bench, now the majority of the suspension and brakes are back on the car, and could not resist starting on the gearbox.




When I initially drained the gearbox, all I got was water, no oil. So I presume the oil had been drained at some point previously, this left me a bit worried. I had liberally sprayed it down with WD40, but I still feared for the bearings and other components that were hidden out of sight. As you can see above, it didn't look pretty in there, no carnage to see but plenty of old fashioned dirt.

With some guidance from the helpful article on the Cornwall Austin 7 Club website, I had the gearbox stripped down with relative ease (not withstanding the evening when I'd misread the instructions as I was trying to do this at 11:30pm after a busy day!).



Inside the case looked even more dirty and I seem to also have a collection of spring washers! I wonder when those were lost, a while ago I bet as some were buried under the dirt, not just sat on top.



The gearset looked equally grim, though after a bath and a scrub was looking much better for itself. I think that layer of old caked on dirt and oil had actually protected all the steel parts from the water and there was really no corrosion to be seen anywhere inside the gearbox, which was a huge relief. I'm not hugely experienced with assessing synchros, but they didn't appear to be bottoming out, and there was no sign of rocking when the two tapered pieces were held together, so I believe that's all looking promising!



Though initially feeling a bit rough, after a thorough clean up I was happy to reuse the bearings.

While cleaning I made the mistake of pushing down a bit hard on the 1-2 sychro assembly, and it popped apart, with 6 spring loaded ball bearings flying across the shed in opposite directions! I found 5 of them, but the 6th was nowhere to be seen. Helpfully they appear to be standard 1/4" ball bearings and I had a plenty of those left over from overhauling my BSA, and some with some fiddling and help from a jubilee clip, I was able to get it put back together!



The inters haft bush was swapped out for a bronze bushing replacement, as I believe is common practice.

I also discovered a broken detent spring, on the 3-4 shift fork. Due to the sideways load applied by the helical cut gears, this would have likely had the car popping out of 3rd, which I believe is not unheard of with these boxes. I fitted new detent spring and balls to all 3 shift forks as a precaution.



I considered trying to convert the oil scrolls on the input and output shafts to modern lip seals, as suggested in the Cornwall A7 club article, but I decided in the end to pause on that for now. I'm still a beginner on the lathe, a mistake would be difficult to fix and I also don't want the project to 'creep' any further than it is already doing. I'll see how big the puddles are under the car and decide if I want to have ago at it another time!

Anyway, now I was ready to reassemble with some new gaskets, which was fairly straight forward. Looking much cleaner in there.



And finally reinstall the clutch release bearing, which had been cleaned and packed with fresh high temp grease, and installed the clutch fork with new taper pins.



Excellent. I should get back to rolling about on my back under the car dealing with the brakes shouldn't I... but there's a clear bench again now and the engine sat there on the floor just waiting for some attention...

[Ruairidh Dunford]

Impressive progress - keep the updates coming.

[Goldnrust]

Thank you!

Ok, so full of enthusiasm from the gearbox (tentative and untested) success, it was time for a bit of engine inspection / autopsy, everyone's favourite. This is where I might be needing a bit more advice from you all, as I have some decisions ahead of me.



One very small sidevalve engine ready to be pulled apart.

Like the gearbox the engine was full to the top with water, as I have drained what I can and sprayed wd40 where I could but I fear water is still trapped inside it. At the very least is it going to need stripping down and giving a thorough deep clean. Hopefully the silver lining of this will be the ability to run a modern oil with detergent in it, without the fear of blocking oil passageways and jets with chunks of dirt.

Having followed the disassembly handy guide in Bill William's book, I managed to get it, mostly, all pulled to pieces a couple of nights ago.



That's the easy bit, and now starts the careful measuring and decision making of what can go back in and what must be replaced.

Starting looking at the crank, I had a good look for cracks around the 4th journal by eye and didn't spot anything, so that's something! haha. Whilst doing that, the first thing that strikes me is that the rear main bearing seat has been knurled. I presume a repair where a previous owner felt the rear main bearing race wasn't tight enough on the crank? It took a reasonable amount of careful drifting off, so I presume the fix has worked!



The main bearings themselves feel good, a bit dirty I think but they are nice and tight, with very little play. The front angular contact bearings hold the crank nicely when nipped up together with no 'waggle' as Bill William's book describes it.

The rod journals look really good to me, especially given the rudimentary oil filtering in the 7 engine. Breaking out the micrometer, and checking several points on each journal, I'm getting 1.290 - 1.291" across the whole crank, so that's great news. Presuming that the 1 5/16" crank is precisely that as standard, i.e. 1.312" ,that would suggest the crank has been ground -20.



The rod bearings also look very fresh, I presume they would have had to be remetalled when the crank was ground? They all measure 1.293", so a good 0.002 - 0.003" oil clearance.



So far I couldn't be more pleased really!

The camshaft bushings and bearings look good, but there's an odd bit of wear on the lobes. It's only on the one side (closing I think!), but it's on all of the lobes. No idea if this is 'normal'?



Taking a look at the bores, and things aren't terrible, but they aren't looking as nice as the bottom end.



This is cylinder 1, pretty representative of them all. Don't be distracted by the water marks and staining, that's to be expected when it was flooded and none of it can be felt with a finger nail. The wear lip at the top of the bore can just about be felt though.

I've measured the bores at 2.230 - 2.231". They seem pretty round and consistent, not showing any ovality and only that 0.001" top to bottom.

The pistons are labeled +30, and measure at 2.224-2.226" at the base of the skirt. Given the +30 pistons, those numbers seem a seem a fraction low to me, so I will double check the calibration of the micrometer, but thats not super important. What counts is the 0.004-0.006" piston to bore clearance which a fair chunk bigger than the 0.0015" I've seen suggested for these split skirt pistons.

I've only checked the top rings so far, but they are all 0.017 - 0.020", which is a lot bigger than the 0.004-0.007" kind of specs I've seen suggested.

I think it's fair to say it wont be long before it's due at least a set of rings, and depending on the accuracy of my measurements, either some new +30 pistons or a rebore to +40 and pistons.

I still need to get the valves out, I'm waiting for a suitable spring compressor as the one I have won't work with the side valve engine, but on first impression they look 'ok', nothing too scary. I can see the the valve chest is going to need some serous cleaning as it appears that when a previous owner painted the cylinder block they did it with the valve chest covers off and theres black paint over all the valve gear which is now flaking off and could definitely cause problems if it got into the oil galleries.

One thing I've not removed yet is the oil pump. I've knocked the top cap off from the crank case, and removed the nut holding the drive gear on, but haven't been able to remove the drive gear itself to release the oil pump. Is there a knack to this?

So now I need to make a plan as to where to go forward from here. I have, on the one hand, not driven an Austin 7, and so would like that chance and to see if I actually like it (I think I will!) before I pour any more money than I have to into it, so I could throw the engine back together with just a clean up and some gaskets knowing that it might burn a little oil and possibly be a bit down on compression with those worn rings.

On the other hand, it can be false economy to ignore these issues and right now I've got an engine in bits on the bench so it's only the money stopping me from making those fixes, it will be a lot more work to pull the engine again if after the first test drive it's clear that it's worn out.

To complicate matters, I have decided I would like to do some performance upgrades, a dangerous rabbit hole I'm aware! My car hobby journey started with bolting a turbo on to the side of my mx5 less than 6 months after learning to drive and I've done engines swaps and all manner of other performance modifications over the years. As I've gown older I've realised the fun in driving a slow car fast as opposed to driving a fast car slow, but I do still want to be able to have enough power to enjoy driving with spirit. 

I can live with my 17hp Fiat 500 cruising at 50mph on a flat road, doing 55-60 at a push with a tail wind (not that I don't have plans for modifying that engine also...), but I believe my 7 engine would be more like 12-13hp standard? And cruise at more like 40mph?

With that in mind I have already scored a '37 high compression cylinder head on eBay, had plans to fit 3/4" radius cam followers, double valve springs, an SU carb and go to town with the die grinder in the ports (And then pray the stock crank lasts till my budget could stretch to a phoenix one!). Doing all this on a worn engine could well be counter productive. 

Any advise would be welcomed! Do we think those ring gaps and bore to piston wear means I'd be silly to even just put it back together with the high comp head and worry about the rest of my plans when I can afford to do the engine build the 'right' way? Are my modification plans even feasible with a stock crank or am I asking for disaster?

Lots to think about, while I continue to strip down and clean parts!

[Alan]

It’s fairly simple to improve the power output of a standard engine, but if you do, Be aware that reliability decreases with power output. The real skill in building hot A7 engines is in getting them to hang together. But, for a reasonably exciting road car, I’d fit the 37 head, forget the double valve springs but use the flattened tappers. Then I’d do a little bit of block porting - just remove the sharp edges really. Then, finish with a decent inlet and four branch exhaust manifold and SU carb. That will give you over 20hp if it’s done well.

[AustinWood]

If you decide to change pistons I'd advice the new slipper pistons. A big improvement over the originals that have 4 rings.
The joint between block and crankcase tends to leak so best to fit the silicone gasket that is now available. Also that joint has been known to give trouble, pulled studs etc, so best to avoid the double valve springs. Many people discard the oil baffles which are a fiddle to fit and don't do much.

[Howard Wright]

Hi Goldnrust

I’m also enjoying your thread which seems to involve new posts virtually every day (where do you find the time!). it reminds me of my faltering steps into Seven reconstruction!

My own advice regarding more power follows that from Alan and Jim. However I would also recommend getting the crank, flywheel and clutch cover plate dynamically balanced. Also balance the weights of the con rods and pistons. It really makes for a smoother engine with confidence to rev that little bit higher.

Cheers

Howard

[Goldnrust]

Thanks everyone for the helpful input.

Low 20s horse power sounds exactly the kind of thing that I think I'm looking for Alan, so that's good to know. And yes I'm well aware I will sacrifice reliability to get there. I've a collection of broken engine parts in the shed to remind me of the past 15 years of modified engines!

I had presumed that the double valve springs would be a 'common sense' mod, having read about the single valve springs not being happy above 4,000rpm? but I had not considered that being side valve it would put load on the crank case. So thank you, and I will take that advice to stick to the standard single spring set-up.

In terms of making sure the engine hangs together, are the oil system modifications (mentioned in guides like this one from the 750mc https://www.750mc.co.uk/ugc-1/1/52/0/the..._garre.pdf) of boring the oil pump bigger and modifying the cam bushes to reduce oil loss worth while in an engine of this level of tuning? Or would that be overkill?

Makes sense about balancing, Howard. The flywheel and clutch assembly is a heavy old thing, I'm sure there would be a gain to taking some weight out of it... it's a slippery slope isn't it! I tend to try and find time in the evenings when I'd otherwise just be sat on the sofa. I try to get out to the shed 2/3 times a week after the kids are asleep and all the chores are finished!

I think I am leaning towards 'doing it properly', having the bores taken out to +40 and fitting some new slipper pistons. As someone mentioned on another forum, if I were to just chuck it back together as it is and it turns out I love driving the car then having to pull the engine in a few months time to do it right when it keeps oiling plugs would be very frustrating, and if I didn't bond with the car then selling it with a properly rebuilt engine will be easier. My wallet won't enjoy this plan though!