REPORTS ON A 1914 HUMBERETTE RESTORATION

[Luv2Wrench]

6 hours ago, Mike Macartney said:

Yes Roger, the die was £45 and the tap was £25. As they say "It's only money". They also say "You can't take it with you". Although I am working on a design for a coffin with panniers!

 

 

I've heard you can't take your money with you but you can take your tools... right? 

[JV Puleo]

I hope so. The worst part of traveling is that I feel naked without access to my tools.

[Roger Zimmermann]

13 hours ago, Luv2Wrench said:

 

I've heard you can't take your money with you but you can take your tools... right? 

A few people are even taking their car with!

[Mike Macartney]

What was the first thing I saw when I opened the newspaper this morning?

 

 

I hope it's not an omen!

 

Roger, it is not too much of a problem for you take your, tools and model cars, but Joe would need a few big trucks!

[Mike Macartney]

Since my last post a friend in Australia with a Humberette has emailed to say that his engine has developed a piston problem. Kevin uses his Humberette a lot for rallies in Australia. His next rally is in April next year. I have found some more of the Ford pistons, that I bought for me, so I have now 4 pistons to modify to fit Humberette jugs. Kevin was the first Humberette owner I ever had contact with. I 'met him' via a member of this AACA forum. He helped me a great deal with loads of information when I first got my Humberette. It will be nice to return a favour.

 

 

The damaged piston out of Kevin's Humberette.

 

It's not as bad as the last engine problem he had . . . .

 

 

. . . . when the engine broke a valve.

 

Since his emails and the limited time Kevin has to get the engine back running, I have been drawing out and working through what I need to do to modify the modern Ford pistons. There are a couple of points I need some help with.

 

 

If I am going to fit bronze bushes into the alloy pistons to reduce the size of the gudgeon pin (wrist pins) to the size of the Humberette gudgeon pins. How much larger should the bronze bush be? Presumably the bushes should be a tight fit? I tried looking it up on the internet but I got baffled with too much technical stuff.

 

Here are some photos of my Humberette piston and the Ford piston I am going to modify.

 

 

 

 

[JV Puleo]

I would try for a .001 to .002 press fit in the piston. What is the diameter of the wrist pin? It is likely that an off-the-shelf bushing will be fine as they are usually made to be a tight press fit. You would just have to get an ID that can be machined to fit the Humberette pin. Look for oil holes in the for piston boss...these will have to be drilled after the bushing is in place unless the original Humberette piston did not have them.

 

I should have read your specs first... it looks like a 21mm OD bushing is .012 large. You'd have to take .010 off the OD. That would be doable in the lathe but you'll need a mandrel to hold the bushing. After the OD is machined it should be possible to hold the bushing in a 21mm collet to ream the inside. 5C collets don't compress much but .010 is within their range. You want a tight "push" fit on the wrist pin.

 

I don't know about using circlips...the ID of the clip will probably be larger than the diameter of the Humberette pin. I'd look into those teflon plugs that are used in racing pistons. I forget what they are called but you end up with floating wrist pins which minimizes the wear on them.

 

Another possibility would be to make new, larger pins and ream the bushing in the connecting rod. That would completely eliminate the wear and the larger pins would be better. Those original pins look mighty small to me.

 

A further edit....could you ream the hole in the piston to 21mm. That would allow the use of an off the shelf bushing...then the inside could be reamed to a standard size - like 15mm, the con rod reamed to match and new pins would be easy.

Edited December 21, 2019 by JV Puleo (see edit history)

[mike6024]

On 12/16/2019 at 8:07 AM, Mike Macartney said:

 

PISTON CALCULATIONS FOR HUMBERETTE ENGINE
	STANDARD ORIGINAL HUMBERETTE PISTON			FORD ZETEC PISTON 24003 STD
	Measured	Measured		Measured	Measured
	by Micrometer	by Vernier	Use for Calcs	by Micrometer	by Vernier	Use for Calcs
	inches	inches	inches	inches	inches	inches
Standard bore diameter is 84.25 mm (Ford 84.8 mm)			3.317	3.3386		3.339
Top of piston above top of gudgeon pin hole	N/A	0.901	0.900	N/A	0.900	0.900
Gudgeon pin diameter	0.515	0.515	0.515		0.812	0.812
Half the diameter of the gudgeon pin			0.258			0.406
Therefore top of piston above gudgeon pin centre is:-			1.158			1.306
Height of piston top above top ring	0.138	0.142	0.140	0.294	0.288	0.290
Therefore height of top of top piston ring from gudgeon pin centre			1.018			1.016

 

Below are a few of photos of the pistons.

 

 

 

 

 

 

So it looks like 1.306 - 1.158 = 0.148, or about 0.15 inches so the top of the Ford piston would be too high relative to the wrist pin. 3.76 mm.

 

So the TDC volume would be smaller by (pi/4) (84.7)(84.7) (3.76) in cubic millimeters = 21,181 mm cubed = 21 cc

 

Has it been decided this is close enough? Will the increase in compression ratio be modest?

 

Edited December 21, 2019 by mike6024 (see edit history)

[mike6024]

How is the pin, the OEM pin, held in position in the Ford piston? There is no provision for a circlip. Forgive my ignorance. I don't get it.

 

[mike6024]

On 12/16/2019 at 8:07 AM, Mike Macartney said:

The Ford piston will slightly increase the compression ratio as the extra height of 0.147" which equates to 6.71cc's.

 

 

can you show me how you got this? I came up with something very different.

[Mike Macartney]

Joe, Are these the type of bushings you are recommending?

 

https://www.mcmaster.com/bronze-bushings

 

I have looked on UK sites and not found anything to suit the size of bushing I need. I also looked on the McMaster site above and still couldn't find anything the right size. The bushings need to be able to be made to fit a 13.1mm (0.516") gudgeon pin, which is the size of the Humberette pin. The OD of the bush has to be a press fit into the Ford piston gudgeon pin hole that is 20.63mm ( 0.812"). Yes, I could ream the gudgeon pin hole in the Ford piston to a larger diameter, but still I can't see any 'off the shelf' bushings that are a suitable size. I am happy to machine the bushings out of solid if I have to.

 

I will take a couple of photos to explain why I think the standard size Humberette gudgeon pin can't be enlarged by very much.

 

I am not sure about the 'Teflon piston wrist pin retainer buttons'. There would be a lot of gudgeon pin sticking out of the side of the Ford piston. I will post a photo later that should explain the situation. It is still early in the morning here and I have yet to face the cold weather and get up to the workshop.

 

Yet another chest infection has put me back a bit this week. The antibiotics and steroids have started working, felt a lot better yesterday, now at last I should be able to get up to the workshop again.

 

10 hours ago, mike6024 said:

How is the pin, the OEM pin, held in position in the Ford piston?

 

To answer your question I will have to see if I can find out. Thanks for pointing it out to me.

 

I have just looked it up and here is the answer:

 

Zetec rods are an interference fit with the gudgeon pin (the rod is made red hot so it expands over the gudgeon pin, when it cools off it clamps the gudgen pin extremly tight). The only way to seperate them is to press the pin out which will damage the piston.

[alsfarms]

Hello Mike,  It looks as if you have a thoroughly thought out plan for your piston issue and the pin dilemma.  On another subject, could you take a picture of the front side of the Crestmobile chain drive rear axle.  I have a question that could be answered with a picture.

Al

[Mike Macartney]

2 hours ago, alsfarms said:

On another subject, could you take a picture of the front side of the Crestmobile chain drive rear axle.

 

Al, you will be disappointed with the photos!

 

 

No chains - it's got a differential and shaft drive to the epicyclic gearbox that is bolted to the diff.

 

 

Sorry I can't be of more help to you.

[JV Puleo]

Yes, it does sound as if making them from scratch is the best solution. I would turn the OD and ream the centers. You need a 33/64 reamer (.51562) or you might go up to 17/32 , make new pins and ream the connecting rods. You can get drill rod (silver steel) easily enough and that will do for the pins without any modification.  If the bushings are reamed in a collet the holes in the pistons are probably perfect so it is likely they will just press in and be fine without trying to ream them together although that would also be a good thing to do. To do it successfully you will need a "pilot reamer" but if you are working to a standard size that might be available.

Edited December 22, 2019 by JV Puleo (see edit history)

[Mike Macartney]

Thank you so much for your advice Jo. It is very much appreciated.

 

These photos below may help explain the pistons and gudgeon pins a bit better:-

 

 

The small end is quite small where the bushing is. The photo shows the Ford gudgeon pin sitting on the Humber small end bush.

 

 

This maybe a better view.

 

 

This shows the difference in length of the gudgeon pins.

 

 

This is the Humber gudgeon pin sitting in the Ford piston.

 

 

This shows the amount of standard Humberette gudgeon pin sticking out of the side of the Ford piston. I think the Teflon buttons are out of the question with these pistons.

 

I will have a practise making a couple of trial bushes first to see what accuracy I can get. I was hoping not to change the gudgeon pin diameter from standard, but I could go up to 14mm, like I did with the other end of the smaller con rod. Using a pilot reamer would be good if I can find one at a reasonable price.

[JV Puleo]

The pins are interesting. It looks as if they were intended to float and had brass end to keep from scoring the bores. I don't see why you couldn't use those or make new ones to the same design. The only purpose of the teflon plugs is to prevent the pins digging grooves in the bore so anything you do to prevent that will accomplish the same thing.

[Mike Macartney]

Happy Christmas to all of you.

 

 

It looks as if Santa won't be visiting you this year!

[dei]

NOT a good way to hitch a ride...

 

Reminds me of a song.

 

[Mike Macartney]

On ‎12‎/‎21‎/‎2019 at 9:57 PM, mike6024 said:

The Ford piston will slightly increase the compression ratio as the extra height of 0.147" which equates to 6.71cc's

 

On ‎12‎/‎21‎/‎2019 at 9:57 PM, mike6024 said:

can you show me how you got this? I came up with something very different.

 

Mike, I have worked the calculation through again this morning. The formula I used is Pi x r²  x the extra compression height.

 

Converting the inch measurement's into centimetres we have:

 

radius r = 84.7mm/2 =  8.47cm/2 = 4.235cm

extra compression height = 0.373cm

This time I came up with 8.34cc's

What did you come up with?

[Mike Macartney]

On ‎12‎/‎22‎/‎2019 at 6:15 PM, JV Puleo said:

The pins are interesting. It looks as if they were intended to float and had brass end to keep from scoring the bores. I don't see why you couldn't use those or make new ones to the same design. The only purpose of the teflon plugs is to prevent the pins digging grooves in the bore so anything you do to prevent that will accomplish the same thing.

 

Your post has given me food for thought! Since reading your last post I have been 'googling' the various options available for locating gudgeon pins. They all seem to have their own pros and cons!

 

What are Circlips?

 

Circlips, Retaining Rings and Snap Rings are fasteners that grasp elements or installations onto a shaft or in a dwelling/bore when assembled in a groove.

 

This is what I have always understood as an internal circlip. I have been used to using this type in the past for various jobs.

Internal Circlip Standard

I never before realised that there was a correct way round to fit these circlips. Shiny side to the gudgeon pin. Rough side to the outside. The rough side apparently helps the clip stay in place.

 

Now, I find that there are these, that I have never come across before.

 

Internal Circlip Lugged

 

Axially fitted to bores with grooves, similar to the standard design but with additional equal spaced lugs around the I.D. This feature assists in maintaining good contact with radiused or chamfered components for 16mm to 170mm bore. Well they are out of the question, because they are only available for 16mm diameter bores and above.

 

Snap Rings

 

Axially fitted in shallow grooves as conventional circlips. Often used to retain narrow section components with light side loads. Unlike conventional circlips, special fitting tools (circlip pliers) are not required. I have always found the retaining rings tricky to remove. They seem to be available in both round and square section. The round ones sometimes have 'sticky out bits' to make fitting them easier. They say "the round wire locking ring is nearly bullet proof. It is designed to be used with a pin which has a precision outside chamfer. Porsche has used these locks exclusively in all their engines for years".

 

Buttons or Pin Plugs

 

I believe most aircraft piston engines use these, but they are aluminium. Continental call them 'pin plugs'.

 

 

Teflon style buttons seem to be popular. I believe that these were originally used in engines that were stripped often for inspection. A problem seems to be that the softer Teflon can hold bits of grit that can score the bore.

 

The brass buttons that are in my original pistons I think have been put in by the person who stripped and 'rebuilt' the engine before me. He probably read the same book as me "The Vintage Motorcyclists' Workshop" by Radco. I have used this method with the last two vintage motorcycle engines, where I replaced the original cast iron pistons, with modern aluminium pistons. This is the first engine I have taken apart that has had these 'brass buttons' fitted and they have scored the bores in my Humberette engine! This has put me off fitting this type again.

 

Special Retainers

 

These seem to be very good. They look as if they may be a bit of a pain to remove and fit.

 

Conclusions

 

I have enjoyed learning about the various methods of locating gudgeon pins. If I can find a company to make me new gudgeon pins I think I will go for the standard internal circlip as I should be able to grind a cutting tool to cut the locating groove in the bronze bushes. If I end up having to use the original Humberette gudgeon pins I will possibly make some Teflon buttons to replace the brass ones.

 

I hope you enjoy this Christmas Eve lecture on gudgeon pin 'fixings' as much as I have in learning about them.

 

Now to think through Joe's suggestions and the best methods for me to machine the bushes with the equipment I have.

[Roger Zimmermann]

The last examples are used in the 1956-63 Hydramatic transmissions. The Spirolox have a small rectangular aperture at the ends to facilitate their removal with a small flat screwdriver. The diameter used in transmissions is rather large; I don't know if they would be suitable for a gudgeon pin. The ordinary stamped ring with ears are used on the input shaft at the fluid coupling.

The external snap rings with a square section are used on the output shaft; a specific tool is needed to remove or install them. Sometimes I have to fight a long time to get them away because the tool is slipping...

[r1lark]

52 minutes ago, Mike Macartney said:

I never before realised that there was a correct way round to fit these circlips. Shiny side to the gudgeon pin. Rough side to the outside. The rough side apparently helps the clip stay in place.

 

This is an example of why I follow this thread - I'm learning a lot of things! For example, the rough side versus the shiny side of the circlip - didn't know that.

 

Thanks Mike, you posts are very detailed and informative (and entertaining). 😊

[Mike Macartney]

Many thanks Roger and r1lark for your input. Have a nice Christmas holiday.

 

I have had a very interesting email from my pal in Australia with details of the electric starter motor conversion that was fitted to his Humberette by a previous owner.

 

All very ingenious.

 

 

A starter ring shrunk onto the flywheel for the cone clutch. He is not sure what vehicle the starter ring is from, but it has 96 teeth, which may, or may not, be a clue.

 

 

It appears to fit over the top of the gearbox where it is open where the clutch is, in the photo below.

 

 

It took me a while to find a photo of the gearbox (transmission). I have now taken over 2,500 photos of the Humberette, during the past year and half, that I have been 'playing' with the car.

 

The starter motor gives me yet something else to think about!

[JV Puleo]

I suspect the bores were scored before the brass caps were put in the pin. I don't get the feeling the last person to have your engine apart was what I'd call a meticulous workman.

[Mike Macartney]

I think you are correct there, Joe! What do you think they originally used to hold the pins in place? The bores were quite badly marked in the position where the pins are.

 

I would mention something about farmers or butchers, but since I have 'met' Al and Ted, on this forum, I now realise, that not all farmers and butchers are like the old fashioned small farmers that I came across, in the past, in the UK, when I first moved up to Norfolk from London in the 1970's! One local farmer, who brought a Rolls Royce into us for some repair work, had hacked out a section of his rear bumper and arc welded a ball hitch to it so that he could take his pigs to the local market in a trailer. I suppose it was better than having the pigs trotting about inside the car!

[alsfarms]

Merry Christmas Eve to you Mike.  It is great to see, chat, and learn of your plans regarding the Humberette.  Sometimes, I get overly busy with "things" I my world, that makes it so I can't respond and comment as often as I would like to.  I wish that we all just lived down the street from each other so we could drop by to philosophy, tease and help.  Second best is this forum medium, that allows us to chat literally around the world from each other.  I like all aspects of the antique automobile restoration process and you are doing it all, (and to a very competent level)!  Keep up the good effort.  Your project will be very tidy and should bring you lasting satisfaction when complete!

Al

[JV Puleo]

Take a look at the inside of the piston for signs of an attaching system. Most often it was a split pin or a clamp or a pin that screwed into the piston and passed through the piston pin. In 1914 it was believed that the pins should be tight so there was always some means of securing them, which often failed, hence the scoring.

 

You can make perfectly good new pins from drill rod (silver steel)... you can even drill them out to lighten them a little. It does not have to be hardened and it already has a ground finish. The hole can be reamed .001 to .0005 undersize or exactly to size - it doesn't make much difference but this should make doing the inside of the bushings much easier and give you an "as new" tolerance.

 

The original owner of the first RR I worked on was a sheep farmer in New Zealand. He often carried sheep around in the back seat...and said they'd made him the money to buy the car, they ought to be able to ride in it once in a while!

Edited December 24, 2019 by JV Puleo (see edit history)

[alsfarms]

all I can do is smile.....farmers have generally needed to do what they can do......sometimes others would scratch their head in wonder or confusion at what they see!  I could share some "whoppers" on this subject for sure!  Those stories are for another time!

🙂

Al

[mike6024]

9 hours ago, Mike Macartney said:

The formula I used is Pi x r²  x the extra compression height.

 

Converting the inch measurement's into centimetres we have:

 

radius r = 84.7mm/2 =  8.47cm/2 = 4.235cm

extra compression height = 0.373cm

This time I came up with 8.34cc's

What did you come up with?

 

Using those numbers:

 

3.1415 x 4.235 x 4.235 x 0.373 = 21 cc  which agrees with my result. So your calculation agrees with mine, you just punched the numbers into your calculator wrong.

 

Bring this up because I am concerned it may be too much of a difference.

 

[chistech]

8 hours ago, Mike Macartney said:

I think you are correct there, Joe! What do you think they originally used to hold the pins in place? The bores were quite badly marked in the position where the pins are.

 

I would mention something about farmers or butchers, but since I have 'met' Al and Ted, on this forum, I now realise, that not all farmers and butchers are like the old fashioned small farmers that I came across, in the past, in the UK, when I first moved up to Norfolk from London in the 1970's! One local farmer, who brought a Rolls Royce into us for some repair work, had hacked out a section of his rear bumper and arc welded a ball hitch to it so that he could take his pigs to the local market in a trailer. I suppose it was better than having the pigs trotting about inside the car!

We had a customer who would come in twice a year with an old two stroke Saab wagon (I’m not sure of the brand but believe it was a Saab), and he had his pigs in it. Man that car stunk! The car was old and in rough condition including the motor and at least a couple times the motor would only start and run backwards. I know one time he left the yard in reverse moving forward. Merry Christmas my friend.

[Mike Macartney]

14 hours ago, mike6024 said:

Using those numbers:

 

3.1415 x 4.235 x 4.235 x 0.373 = 21 cc  which agrees with my result. So your calculation agrees with mine, you just punched the numbers into your calculator wrong.

 

Bring this up because I am concerned it may be too much of a difference.

 

Ooop's. I just tried the calculation on the same calculator this morning and it came up with 152cc's! ? ! ? I then did the calculation on an Excel spreadsheet and it comes to the same amount as you calculated. Thanks for pointing out this problem. I think the calculator is heading for the bin!

 

I'll check what difference it makes to the compression ratio, but not with the calculator!

[Mike Macartney]

18 hours ago, JV Puleo said:

Take a look at the inside of the piston for signs of an attaching system.

 

I'll take a look and see if I can find any evidence of anything. Thanks for the suggestion on making the gudgeon pins myself.

 

It sound if farmers where the same world wide and not just in Norfolk!

[alsfarms]

Good Morning Mike,  I presume and hope that you and the Missus had a delightful Christmas!  We sure did.  I like the concept of using "Drill Rod" for the grudgeon pin bushings.  That stuff is TOUGH!  I have used it for specialty products also but learned that you certainly do not want it to get hot during the machining process or you are done machining....it gets harder than the back of a hard headed persons head!  One of my favorite "Farmer" stories involved a Great Uncle who MANY years ago, had his Model T out on the desert west of us about 40 miles.  The poor old "T" started to bang a connecting rod.  Before it completely failed, he stopped, drained out the oil, took off the offending rod cap, cut the leather tongue  out of his work boot, fit in the cap, cranked it down, loaded the oil again and drove home very slowly.  Sometimes we farmers are the "mothers of improvision" for sure.  I noted elsewhere that maybe Mike needs a bit of a nudge! 🙂 .  If Mike and Jane get a chance, it would be nice to see a delightful couple seated in the newly re trimmed Humberette body along with the top up so we can all see just how cozy you two can get.  That may just give some of us the "drive" (play on words) to set some good New Years resolutions.  And this is a biggie New Years as we are kicking off a brand new Decade.  Lets make our time count and boy am I talking to me!  Keep up the good work on the bottom end of your Humberette engine!

Al

[alsfarms]

Mike, I just checked out your couple of action pictures of you and your Crestmobile on the London to Brighton Run a few years back.  Some of us can only dream of such things, and you get to enjoy...good for you.

Al

[Mike Macartney]

8 hours ago, alsfarms said:

Some of us can only dream of such things, and you get to enjoy...good for you.

 

It is called determination! I had always wanted to do the London to Brighton run since I was around 8-years old. When I retired I started buying cheapish vintage motorcycles and restoring them. After a few years of messing about with motorcycles I had a few quid's worth. I don't have holidays, play golf, go out for expensive meals or wear posh clothes. I thought I was running out of time to accomplish my dream. I had a look to see what veteran cars were available and how much they cost. After some time I found an advert of somebody selling the Crestmobile in Belgium. It seemed to be about the cheapest veteran car available. I contacted the guy and said that I could not afford to buy the car at present until I sold some of my motorcycles. He asked what motorcycles I had and I sent him a list. He agreed to swop the Crestmobile for a couple of motorcycles and the balance in cash. Jane and I borrowed a trailer, took the Ford van, with the bikes in the back and trailer over to the continent on a day trip and came back with the Crestmobile. It had been in a open barn for about eight years and looked very sorry for itself. I then applied to enter the run and worked my socks off to get the Crestmobile running and presentable for the run that November. Most things are possible but you need to prioritise what you actually want to achieve.

 

 

Collecting the car in Belgium.

[Roger Zimmermann]

Interesting story...Anyway, you certainly had no trouble to travel with that light vehicle on the trailer, especially traveling so many miles. We had more difficulties when my '72 de Ville was transported from the customs in Zurich to Bienne (about 100 miles) because the car was a tad too far back, plus the weight from the spare parts in the trunk! At more than 40 MPH, the trailer began to dance...

[alsfarms]

Hello Mike and Roger,

It looks like you have both had some epic adventures!  Thanks for sharing the stories with us.  Mike, the crest mobile is a dainty  and pretty early automobile.  You must be happy to have in stored away and waiting for the next adventure!  What is even better, the Humberette will also be in the great looking and fine running mode just waiting to serve you at your "beck and call".  Do you have a solid resolution for your wrist pin (other side of the pond nomenclature) issue?

Al

[Mike Macartney]

Since before Christmas I have been suffering, yet again, from a bad chest infection. So far, this time I have managed to keep out of hospital!

 

Yesterday, I thought I felt a bit better and ventured out to the workshop, to have a bit of a clear up, before starting to do some proper work on the engine. After a half an hour I was knackered and had to pack up. At least, being confined to the house I have managed to some planning of the work and I have at last done the calculation for the compression ratio using the Ford pistons.

 

HUMBERETTE ENGINE WITH PISTONS THAT WERE WITH IT
BORE VOLUME CALCULATION	mm	cm/cc's
Bore Diameter	84.250	8.425
Bore Radius	42.125	4.213
Area of bore( pi R squared)		55.77
Stroke Length	90.00	9
Therefore Volume of One Bore C7 x  C8 (Vd)		502
Number of Cylinders	2	2
Therefore Volume of Two Bore's C9 x C10		1004
Measured Volume of combustion chamber (approximate)		180
Compression Ratio
Guessing that the compression ratio of the era maybe around 4.5:1
CR = (Swept volume Vd + combustion camber volume above piston Vc) divided by combustion chamber volume Vc)
Therefore: Vd +Vc equals		682
Therefore: Existing Compression Ratio CR = (Vd + Vc)/Vc		3.8
THE FORD ZETEC PISTON DETAILS	mm	cm/cc's
Bore Diameter	84.70	8.470
Bore Radius	42.35	4.235
Area of bore( pi R squared)		56.37
Stroke Length	90.00	9
Therefore Volume of One Bore C7 x  C8		507
Number of Cylinders	2	2
Therefore Volume of Two Bore's C9 x C10		1015
Extra height of Ford piston above Humberette piston	3.73	0.373
Therefore the extra volume that takes up is		21
Therefore the new Combustion chamber volume Vc = 180cc -21cc		159
So now  Vd +Vc equals		666
Therefore: New Compression Ratio CR = (Vd + Vc)/Vc		4.2

 

 

Now that surprised me. I thought it would have made the compression ratio a bit higher than 4.2:1

[Roger Zimmermann]

Take care of your health! Glad you are feeling better.

[Mike Macartney]

Thank you Roger. I'll do my best. I don't think the damp weather at this time of year does me much good. Perhaps I would be better staying in the warm and start doing some model making!

[Roger Zimmermann]

1 hour ago, Mike Macartney said:

 Perhaps I would be better staying in the warm and start doing some model making!

Then, I could be able to help you more than with your present project!