1968 Hillman Minx Estate - 08/10/21 - Road Trip!

[mrabody]

Jan 11, 2012 18:18:53 GMT Seth said:

Ditto on the heads. I thought I'd try out what tools I've got on one of the ports. There's a ridge with a sharp step about an inch in from the manifold face so I smoothed that a bit...



..and there's a nasty ridge particularly on the inside radius above the valve so I've blended that in a bit too.



Just following some leads for the more major machining now.

Seth,

If you go to the homepage for the Sunbeam Alpine Owners Club of America and check the top righthand corner you'll find a link to an article about Dave Vizard's recommended mods to the combustion chamber on a Rootes alloy head.

www.sunbeamalpine.org/

[mrabody]

And a Special Tuning Guide for the Series II Alpine can be found here:

rides.webshots.com/album/239960975SWErVQ

[Seth]

Thanks for all the number crunching Shahin. I had noticed discrepancies myself between values given in different sources. I had also wondered about how they quoted the same comp ratio for 1725 ally and iron head engines when apparently using the same pistons with different size combustion chambers.

Thanks for the links MrA As it happens I've just bought a copy of the Vizard cylinder head book off Ebay - yet to arrive! From looking at the link it seems as though his mods are slightly different to the Holbay ones.

[PaykanHunter]

Feb 8, 2012 12:22:45 GMT Seth said:

had also wondered about how they quoted the same comp ratio for 1725 ally and iron head engines when apparently using the same pistons with different size combustion chambers.

Seth,
So as I mentioned I believe they achieved same CR(8.4) with the different pistons, is that also your conclusion here?

[PaykanHunter]

From August 2010 issue of Retro Cars Magazine. ;D

For bigger images visit my post:
www.paykanhunter.com/2012/02/while-you-were-sleeping.html

[Seth]

Feb 9, 2012 16:36:08 GMT PaykanHunter said:

Seth,
So as I mentioned I believe they achieved same CR(8.4) with the different pistons, is that also your conclusion here?

Nothing I have indicates that so I'm still not sure but it could be a possibility. Thanks for the RetroCars Scans. I've already got some of them

I'd not been using the car much and about a week after the RR Jumble opened to bonnet to find the battery and inner wing covered in rusty water and a lack of the wet stuff in the radiator. The thermostat cap I'd been hoping would last 'til the engine change had finally given up the ghost at some point between home and Stevenage. Anyhow, I had a good second hand one from the 1725 bits and so I kept the NOS one I bought soon after getting th car (knowing this was a likely trouble spot) for when I finally do the engine. The bolts undid fine so it was about a 10 minute job.



Engine progress has been slow but I'm sort of getting there. I finally picked up a head gasket set the other week so I've got on with the head work. I had already cleaned up the edges of the combustion chambers where there were weld beads showing but it was now time for the mods.

Gasket paid down and lined up. Permanent marker used to 'colour in'.



Leaving me with...



The small Vizard book I mentioned is ace! Really good technical discussion and fullsize combustion chamber diagrams. I traced the relevant one and then stuck it on a bit of card.



Then by making holes for the valves to poke through it could be used as a template to scribe around.



Leaving nice clear lines to work too.



I did this one first about a week ago to try out tools etc and cleaned it right up after the re-shaping.



Then today I did the rest, leaving them a bit rough for now.



But now I am in a quandry again. I've done a quick and dirty measure of the chamber size and on a 1725 with flat pistons these will have too high a compression ratio. Really they are designed for a standard engine with the comp ratio brought back up by skimming the head. A look at the photos of the Holbay head I saw a couple of months ago shows that they are opened up even more - around the exhaust valves and that whole area by the spark plug and that'd still have the 9.6:1 or thereabouts.

But, the chambers as they are now, with a light skim, would be a perfect size for the 1500. So I think I might be going back to plan A and convert the original engine to ally head configuration using this head and the 1725's cam, and manifolds.

Standard ally twin carb 1725 power is quoted as 79bhp. Standard 1500 iron head is 54bhp. The Vizard book suggests an increase of 11-15bhp from the head alone. Considering the extra breathing and cam change (and comparing figures across the range of engines) I reckon that should put the 1500 up to 75, maybe 80bhp, a healthy increase. I could always bolt the 1725 crank/rods in at a later date and open the chambers up more to suit.

[PaykanHunter]

Seth,
Your Plan-A means that this will be the only documented 1496cc engine with Ally Head, I would love to know what your final CR would be! I'm here to Help!...

If you give me some measurements of your grinding area, I could build a CAD model Volume quickly and give you your Clearance Volume, then you could have a relatively accurate CR and even HP! ;D Let me know!

Sample:

[bazzateer]

Whenever I pop over to RR I can always rely on Seth to have something interesting to catch up on!

[Nathan]

^ LIKE

[Seth]

Thanks guys. Pretty picture Shahin!

I've done a spreadsheet with all the various combinations of parts that I keep meaning to add a bit to and post up. A 1500 with a standard ally head would give a comp ration of 9.24 according to my calcs. I'm actually going to aim for a bit lower than that, around 9 so that normal unleaded fuel is OK. I'll measure the chambers the old fashioned way with a syringe and a sheet of perspex as its impossible to make them to a definite measurable shape. I'll also have to bear in mind how much I intend to get skimmed off the head once I've finished the re-shaping.

Only documented alloy1496? Someone else must have been as daft as me in the last 40 years and done it before. I bet there's an article hiding in an old Hot Car or something.

I finally got down to the dungeon again earlier this week and picked up all the 1725 bits I think I need to do the swap so once the Herald is MOTd I can get on with it.

[PaykanHunter]

Could you please share your calculation? How did you come up with 9.24?

[Seth]

Shahin, here's my workings. All the original figures come from the Rootes factory manual.



The only one that doesn't really tally with quoted figures is the standard alloy 1725 compression ratio which I have at 9.2 whereas it is stated in the manual as 9.2 I don't know where this discrepancy comes from.

[Seth]

Well, its taken a while but I've finally finished the home mods to the cylinder head. Its partly taken ages because I've had to experiment to find the best way for doing things and tools to use. The chambers all looked much the same but on measuring there was 2cc difference between the largest and the smallest. Doesn't sound like much but it would result in a difference in compression ratios by 0.4. So lots more grinding/shaping/polishing went on until I managed to get them all the same give or take some minor measurement error.

Even mearsuing took a bit of time to develop a method. While I have read about filling the chambers with fluid it wasn't as easy as I thought it might be. I started using a petrol sort of fluid and the reason for using something like that is that it has low surface tension. But I was sealing the valves by smearing the seats with grease, and also the join between my perspex sheet and the head itself. The fluid had a tendency to leak though, as it would dissolve the grease so I kept getting unrepeatable results. Eventually I reverted to water which was a heck of a lot less unpleasant to use as well. The surface tension meant I had to keep an eye out for the bubbles and make sure I could expel all the air.

Here's the perspex sealed on to a chamber. There's two holes, one for eh syringe and the other to allow air to escape. Once the chamber was nearly full I'd have to position it so that the remaining air pocket sat under the small hole.



I used a 10mm syringe, four fills getting the chamber almost full, then reverted to a 5ml syringe that is graduated by 0.2ml. Here the chamber is nearly full and you can see the bubble under the syringe/air hole.



Anyway, as I said, there was quite a lot off faffing around but I'm pretty pleased with the end result.



Ports all got smoothed too, and sharp edges radisued where necessary.



The chambers are 41.8cc give or take. Plugging this into my excel sheet, adding the head gasket allowance and removing something to allow for a .010" skim gives me a comp ratio of 9.32:1 Higher than I was originally planning but then I was chatting to a friend last night who suggested that ally head engines can generally run higher ratios due to the quick heat transfer they have. So the 9.32 should be fine on regular fuel - its only a smidgen more than the standard 9.1 of an ally head 1725 and less than the Holbay.

[Em]

Very clever stuff!

I seem to remember from my school days that a drop of bleach in the water kills the surface tension...

Looks like you've sussed it though!

[tonybmw]

Top Work Seth, all very clever stuff

[PaykanHunter]

Excellent Work Seth!...

[Mystery Machine]

Inspiring stuff Seth.

I'm not going to pretend for a minute that I understand all of it, but I certainly sit here in awe of how you go about it, your methodical approach and the way you get your results. It's just brilliant to read (even for a dumbass like me).

I love this thread....and this car.

[stealthstylz]

I find porting heads quite fun, even the measuring bits. Basically Bruce the static compression ratio is determined by the stroke of the piston (how far it travels from top to bottom) and the cylinder volume at both points. Most work on the combustion chamber is done by removing metal, and hence increases its size, and in turn drops the compression. By measuring the size of the combustion chamber afterwards you can find out how much compression has been lost, and skim the head accordingly to raise it back up.

[Seth]

Engine work is kind of progressing in that I have some more of the bits needed, have cleaned some other things up etc, but needing the car and the horrendous weather means I haven't yet taken the plunge and pulled the engine out. I did finally get around to fitting a working oil pressure gauge at last a couple of weeks ago so that I could determine the current state of play. Once properly hot after some motorway work it settles to about 50psi at speed, dropping to 20 at idle but that's not bad.

Picked up some more wheels today that may or may not work their way on in future. GR8 4 BONNEVILLE!



They're Austin Devon 16s with 4 1/4" stud pattern and having got them cheap I think I'll be hanging on to them until I find some use for them.



Whaddaya reckon? Banded to 5.5" ish wide and Nankang 165/50s?

In other news, I received a phone call the other night ('analogue social networking' I've decided to call it) such that I otherwise wouldn't necessarily have heard about this as I don't have a Facebook account.



Cool I suppose to have an image of my car broadcast to and appreciated by such a wide but specific internet audience evn if I'm a bit embarrassed by its condition at the moment. Thanks to those RR'ers I recognised as leaving supportive comments. I wondered whether S|W would have expected various Iranian connections ;D - though it was quite fascinating to see the various places in the world this picture got shared to. Obviously I can now also measure my life's worth by the number of 'likes' it achieved so that's good* too.

[slammage]

Very cool Seth, love seeing how this unfolds throughout the years, inspiring stuff indeed!

Gav