Building a hot vintage engine with Jonny69

Jonny69

Jonny69

Jonny69

Man of Honour
Man of Honour
Joined
3 May 2004
Posts
17,705
Location
Kapitalist Republik of Surrey
Note: Some images are missing because bandwidth on my has been exceeded. I am currently moving images about...

About a month ago the engine in my old Pop expired. It was kind of expected because it had stood for about 15-20 years before I had it and I just put some petrol in it, cranked it over and it ran. Well it was getting slowly worse, lots of noise from the top end and it was weeping a bit of water. Then I took it on a long run on the motorway and the obviously very perished rear seal gave up and I was losing oil out the back.

The decision was taken to convert it to a later lump, out of a car called a 100E because it's a fairly easy swap onto the original gearbox and it's free extra horsepower for the same displacement, 1172cc. Plus I had one that was overbored, cammed, flowed and breathed on and it was going to liven the car up quite a lot. Given a bit of time I realised I really haven't got enough time to do it when my Anglia needs some time so a quick change of plan and I decided to work the original lump. It would all need a rebuild anyway so it's not much more to slip in a cam, do a bit of flow work and get the head ground down for some more compression.

So I'll be needing some vintage speed equipment. Aquaplane inlet manifold, check:

aquaplane1.jpg


Aquaplane exhaust manifold, check:

aquaplane2.jpg


Twin carbs, check:

carbs.jpg


A trolley full of junk parts, check:

trolley.jpg
 
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And now I need to do much head scratching because everybody who knows anything about these engines is now dead so I'm pretty much on my own!

Saturday afternoon me and a mate hoiked the old engine out the car. Literally took the radiator out, took the grill shell off the front of the car and lugged it out with a tow rope and a chunky luggage strap. This is the offending item:

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I have a spare engine I picked up for £30 that I'm using as a test bed. I was hoping it might be a runner but it has had water in it and the valve guides are shot but it's a good block to experiment on:

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That's half a shopping trolley it's sat in, they make great engine trolleys. Please note: Sainsburys charge £1 for their trolleys but they are free at Waitrose. I stole mine from Sainsburys because I feel by not charging me Waitrose has trusted me not to steal their trolleys. I will honour that trust. Sainsburys on the other hand has made me feel like a petty theif so I honoured that too and nicked their trolley. And very nice it is too.

Here's my hot 100E engine. Head off and I'm going to be taking the cam out as it's the same fit for both engines. This one is a re-ground high lift item. Note how the valves are next to the bores, it's called a sidevalve engine and most vintage engines are this design:

07-07-07_1719.jpg


First on the priorities is to increase the compression. These old engines have super low compression so they can run on ultra low grade petrol. The Pop engine is 6:1 and the later 100E engine is 7:1, both are too low really and it can be increased by machining the head down. With the extra lift of the cam I need to be sure that the valve isn't going to come into contact with the head if I start machining the face, because it's going to decrease the height of the chamber:

09-07-07_1837.jpg


I've measured it in the 100E block and it comes to 9.5mm, direct lift from the cam so it will be the same in the other engine. Next because the inside of the chamber is rounded at the top I need to know I have enough clearance at the sides of the valves when they are open:

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Here's checking the standard lift, I measured to be 7.35mm so my reground cam is quite bumpy in comparison:

09-07-07_1840.jpg


I discovered something interesting. Earlier engines were only 950cc and had a smaller combustion chamber to suit the lower displacement. The stud pattern on the head is the same throughout the range so an easy way to get some more compression I figured is to use an early head on a later engine. Also I'd have to take some 4mm off the metal which is going to make it very thin and probably prone to cracking. The early head would only need about 1mm maximum thus leaving me plenty of metal left.

Here you can easily see the difference, it's about 1/3 smaller which will instantly take it up from 6:1 to around 7.5:1 I worked out. Early head is on the left, later one is on the right:

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It's a lot more shallow so I have to check I will have enough clearance once the face is ground. It comes in somewhere between 10mm and 9.5mm so it's going to be close once the headgasket is on.:

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I'd also better check it's the same width in case the valves don't fit in across. All ok, the valves are 58mm across and the chamber is over 61mm:

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On the chamber on the right hand side where I've cleaned it up you can see there is a bulge either side of the spark plug hole. I am going to get this machined down so that it is flush. That way I can take a bit more meat off the face of the head and hopefully get it up to about 8:1 compression which is plenty for a sidevalve:

09-07-07_1854.jpg


Ooh I'd better quickly check it actually fits on the studs, phew that's a bit of luck!

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So here's a shot straight down on the bore on my spare engine. I'm going to be doing some flow work here to improve the efficiency. There's a sharp edge on the side of the bore and the plan is to round that off in the area under the combustion chamber. This is an old well proven trick from years gone past and I am going to follow that advice. Gas flows over a smooth curve easier than it does a sharp edge, it's quite simple:

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So it's too much for me now, I need to see a mockup...

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And finally I decided to get the head off the engine I'm going to be using. This is a matter of clubhammering the hell out of it, driving wedges in the side, wriggleing and more hammering. It gets well rusted onto those studs. Here I've numbered the valves so they all go back in their correct holes. I'll be regrinding them but it helps if they go back where they came from:

09-07-07_1942.jpg


So tomorrow I'll be talking to my mate who is going to grind the head and a week later I should be able to fit it. This week with a bit of luck I'll be cleaning it up, flowing it and screwing it back together.
 
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Would it be worth knocking up a little water pump for it? An ancillery one, driven by a belt, just to cycle it around and stop the block hotspotting.........Just a thought?

Shouldn't be too tricky, either....Or you could use a leccy one :)
 
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I can remember porting an old side valve Briggs and Stratton in my youth...fun days. You can actualy get tuning parts for them now. ISTR ditching the headgasket entirely and lapping the head to the block with valve grinding paste. Might be a bit trickier with the pop engine ;)

Interesting that inlet and exhaust valves are the same size on the Ford, wonder if that was purely to make the valves cheaper to produce?
 
Jonny69 said:
Spare me your scientific mumbo jumbo, I can't be bothered with all that modern trickery :D
Click to expand...

lol :cool: top stuff mate, look forward to the rest of it

Dogbreath said:
I can remember porting an old side valve Briggs and Stratton in my youth...fun days. You can actualy get tuning parts for them now.
Click to expand...

junior dragsters run Briggs based motor, can get 3.75" bore billet block, heads, forged cranks, alky carbs etc to make around 75hp off one!
 
Dogbreath said:
Interesting that inlet and exhaust valves are the same size on the Ford, wonder if that was purely to make the valves cheaper to produce?
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They aren't quite, the inlet is a tiny bit bigger than the exhaust but my mobile doesn't take very good pictures, probably because it's a telephone not a camera. You can get oversize inlets but because they are so close it's only 1mm bigger so for the grief and added expense of getting new seats cut it's not worth it in my opinion.
 
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