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How to make it go faster
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1935Hillman



Joined: 06 Apr 2010
Posts: 257
Location: Hampshire

PostPosted: Sun Dec 16, 2018 12:00 am    Post subject: How to make it go faster Reply with quote

Here's one that will hopefully bring forth some interesting responses.
How does one go about making a prewar sidevalve four go faster ? It is a question that regularly crops up among members of our Aero Minx register. The 1185cc ally headed fours are easily capable of 70mph when 'on song' but must surely be capable of more. A 100mph Aero tourer cannot be impossible.
Let us know what you think please
Many thanks
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Penman



Joined: 23 Nov 2007
Posts: 3965
Location: Lancashire

PostPosted: Sun Dec 16, 2018 12:21 am    Post subject: Reply with quote

Hi
Well in the fifties we used to put longitudinal checkered stripes on them. Laughing
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jp928



Joined: 07 Jun 2016
Posts: 241
Location: Australia

PostPosted: Sun Dec 16, 2018 2:34 am    Post subject: Reply with quote

Being maybe excessively practical...See if you can dig up any reports from the period of hotting up that specific engine, and if there were failures. First area I would look at is head - does the chamber have any squish area? this will be opposite the valve area, part of the roof being flat and almost level with the head face - squeezes the mixture into shooting towards the plug and improves burning. Look up side valve head work by Harry Ricardo. Will probably need changes to ignition timing to take advantage. Then look at exhaust etc.
Be aware that you may be exposing weaknesses in the design or build somewhere.
jp 26 Rover 9
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ukdave2002



Joined: 23 Nov 2007
Posts: 3380
Location: South Cheshire

PostPosted: Sun Dec 16, 2018 10:16 am    Post subject: Reply with quote

The restricting factor with many side valves is the small valves with no option to increase the size.
Forcing air in with a supercharger is an option, there are some relatively cheap smog pumps that can be used as a supercharger on smaller engines.

The Aisin AMR 500 is a popular choice, they can be bought used for a couple of hundered quid, loads of examples on the web where folks have fitted them.

Dave
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Kleftiwallah



Joined: 27 Oct 2016
Posts: 222
Location: North Wiltshire

PostPosted: Sun Dec 16, 2018 11:07 am    Post subject: Reply with quote

Penman wrote:
Hi
Well in the fifties we used to put longitudinal checkered stripes on them. Laughing


And a disk brake sticker to 'adjust' for the increase in speed!

Cheers, Tony.
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alastairq



Joined: 14 Oct 2016
Posts: 1101
Location: East Yorkshire

PostPosted: Sun Dec 16, 2018 11:31 am    Post subject: Reply with quote

The biggest issue with any [naturally aspirated] sidevalve is the ability to get decent amounts of mixture into the cylinder.
Sidevalves are naturally 'self-governing'...in that they hopefully run out of the ability to breathe at higher revs...[before crank or rods appear to snap]....

There is a trade-off between raising the compression ratio [the easiest way of increasing torque], and increasing the engine's ability to breathe to gain higher revs.

The higher one goes with compression, the more restricted the transfer passage becomes [twixt valve and cylinder]

Standard cylinder heads are usually pretty good as they are.

The point is.....the attempt to increase top speed is limited by how high the engine will rev [and sustain those revs]...

Supercharging is the most effective way of simply increasing the output of a sidevalve......as ukdave has mentioned. However, that also brings it's own issues [increased heat, increased risk of detonation, etc]

I am not familiar with the Hillman sidevalve [being more au fait with the Ford sidevalve]..but, aside from supercharging, I would first get the engine up to optimum tune as standard. Then one is not stressing the rods, bearings or crank unduly.

My advice?
Begin with the ignition system.

See if you can get hold of a hall effect kit for the distributor [Sparkright, or Distributor Doctor]

This will stabilise the ignition timing over the rev range....something points cannot do accurately.

Then find out what the maximum ignition advance should be [from factory]? Set that up for the rev point where it should be ''all in''. This needs a strobe timing light, and timing marks on the crankshaft pulley...these may need to be made yourself? Mark TDC first [tippex? Or better still, tippex and a filed notch].....put a fixed timing point on the block....might be a visible crack or bolt or anything.
Measure the outside diameter of the crank pulley, then do the simple calculation for the circumference , and work out how long a length, over the circumference, the maximum advance [in degrees]will be, and tippex the circumference for that distance....this will make the maximum advance easier to see with the strobe.
The timing a tickover will be whatever it ends up as...might need to adjust carb idle speed to suit?

If the total advance doesn't actually come in at the revs specified, then check out any mechanical advance weights and springs in the distributor. They may be sticking, or the springs may be too strong..might try some weaker springs first?

Once the sparks are happening at the right time, consistently...then I'd have a look at the valves.
First, one needs to find out the maximum intended lift of the valves. Then see if your valves are giving that?

Pull the head [which you will be doing anyway].....and using a dial indicator, measure the valve lift. I don't know how Hillmans adjusted their valves.....but what you're after is the minimum factory stated valve stem gap, that gives the correct valve lift....often the gaps are set as a singe figure, regardless of whether the cam, the followers, or the valve stem itself, are exactly to factory specs. Whatever gap you end up with, it must not be less than the factory stated gap...but could be more......as long as the correct [or nearly so] valve lift is achieved....and they're all pretty much equal across the cylinders. It is a simple job to do.

Once you know the timing is set to spec, and all the valves lift as the designer intended....then look to improving the intake system.
Check each intake port [valves out at this stage] and, using burrs, remove any sharp edges your fingers detect inside.
I don't know how much each port can be increased in size, as I don't know the block thicknesses....so best left as-is.
Then consider changing the inlet manifold for one that can be used with twin SU carburettors. This may need making!
Twin 1 1/4 " SUs ought to be about the biggest size that'll work.
[Although I am considering making a manifold to take a single 1 1/2" or 1 3/4 " SU for my Ford engine.....to make keeping the fuelling in tune easier]
Swap any mechanical fuel pump for an electric one.....a basic Facet [solid state] pump is adequate, and easy to hide...remove mechanical pump and blank off hole..or turn it into a crankcase breather.

All the above ought to make the standard engine more peppy.....won't increase top speed much though...that'll be down to how high the power band goes....what final drive gearing you have, diameter of wheels, etc.

Also, if planning to mix with modern traffic on its own terms, oil pump, type of filtration, might need looking at...as well as making damned sure the radiator and cooling system passageways are clean and clear.

Remove the engine fan , and fit an electric radiator fan. That'll divert some horsepower to turning the wheels as well.
Overall, I suspect you may be aiming at just over 40 bhp, simply with careful work.

On the car itself, get rid of [or junk] any unnecessary weight......leave the picnic basket at home.
Don't opt for over wide tyres....even radials will sap more horsepower than crossplies.
Brakes?
Whilst they should always be top-notch, if they are manually adjusted, set to factory specs, then back off one click!! You don't want even the slightest bit of rubbing.

Fit a small rev counter as well.....one of those Chinese 6 quid one's off eBay is good enough...although I don't recommend wiring up the light, it'll startle you come darkness falling!
The rev counter will allow you to discover the best gearchange points too.....[rather than relying, as I do, on my ears]
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47Jag



Joined: 26 Jun 2008
Posts: 1458
Location: Bothwell, Scotland

PostPosted: Sun Dec 16, 2018 12:33 pm    Post subject: Reply with quote

The limiting factor as I see is always going to be the rear axle ratio. As the car stands, in top gear, note the road speed in relation to the engine revs (using Alistairs’s suggested rev counter) and from that calculate the required engine speed to achieve your 100mph target. I reckon it will be close to 7000rpm. The only thing I see missing from Alistair’s advice is the need to balance the engine to enable safe running above 5000rpm.

Even with a Chevy V8 fitted you wouldn’t see 100mph.

Art
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alastairq



Joined: 14 Oct 2016
Posts: 1101
Location: East Yorkshire

PostPosted: Sun Dec 16, 2018 12:38 pm    Post subject: Reply with quote

Quote:
The only thing I see missing from Alistair’s advice is the need to balance the engine to enable safe running above 5000rpm.


It ought to be fine as is....it may not breathe enough to get to 5000 rpm anyway? Smile
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Dellow Mk2, 1951 built, reg 1952.
Ford Mustang coupe, 1967, 6 cylinder auto.
Fiat 126 BIS
Cannon special [1996 registered. Built in 1950's]
----------------------------------------------
Ford Pop chassis, Ashley 1172 bodyshell, in pieces.
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ukdave2002



Joined: 23 Nov 2007
Posts: 3380
Location: South Cheshire

PostPosted: Sun Dec 16, 2018 1:39 pm    Post subject: Reply with quote

In the world of Morris 8's engine and drive train, the Achilles heel's are the diff and half shafts, if the engine was modified to produce more power a beefier axle would be required.

Dave
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alastairq



Joined: 14 Oct 2016
Posts: 1101
Location: East Yorkshire

PostPosted: Sun Dec 16, 2018 1:45 pm    Post subject: Reply with quote

Ford Y types had a [known by Ford] weak rear axle....as well.

I'm not sure the sort of power increases a gentle fettling would achieve, would worry the back axle?

I am suggesting stuff which basically makes the engine as efficient as the standard equipment allows....
_________________
Dellow Mk2, 1951 built, reg 1952.
Ford Mustang coupe, 1967, 6 cylinder auto.
Fiat 126 BIS
Cannon special [1996 registered. Built in 1950's]
----------------------------------------------
Ford Pop chassis, Ashley 1172 bodyshell, in pieces.
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peter scott



Joined: 18 Dec 2007
Posts: 5996
Location: Edinburgh

PostPosted: Sun Dec 16, 2018 8:38 pm    Post subject: Reply with quote

Fit a blower.

Peter
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Ray White



Joined: 02 Dec 2014
Posts: 2787
Location: Derby

PostPosted: Sun Dec 16, 2018 9:22 pm    Post subject: Reply with quote

One thing that has so far been overlooked is the question of adding a vacuum advance to your distributor. Considerable benefits can be obtained by advancing the ignition at lower throttle settings - something your basic distributor's centrifugal advance system is incapable of doing.
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47Jag



Joined: 26 Jun 2008
Posts: 1458
Location: Bothwell, Scotland

PostPosted: Sun Dec 16, 2018 11:52 pm    Post subject: Reply with quote

The originals post’s request was to create a 100mph Aero Minx. Assuming the ability to achieve 70mph with the current state of tune. I‘m guessing that it won’t be pulling more than 4500rpm at that speed. Extrapolate that to 100mph it would have to be capable of 6500rpm.

While in Canada I had a similar problem with a 1966 Mk1 Austin 1800. It’s gearing was something like 14.5 miles/1000rpm. I balanced & tuned the engine to stage 3 MGB specs and it would wind to over 7000. I also fitted the ‘new’ higher ratio crown & pinion which raised the revs/mile to about 15.5/1000rpm. Even then it was only capable of just over 100mph. It got there really quickly though. The ribbon speedo was indicating off the scale but the numbers don’t lie.

Art
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Ray White



Joined: 02 Dec 2014
Posts: 2787
Location: Derby

PostPosted: Mon Dec 17, 2018 12:14 am    Post subject: Reply with quote

47Jag wrote:
The originals post’s request was to create a 100mph Aero Minx. Assuming the ability to achieve 70mph with the current state of tune. I‘m guessing that it won’t be pulling more than 4500rpm at that speed. Extrapolate that to 100mph it would have to be capable of 6500rpm.

While in Canada I had a similar problem with a 1966 Mk1 Austin 1800. It’s gearing was something like 14.5 miles/1000rpm. I balanced & tuned the engine to stage 3 MGB specs and it would wind to over 7000. I also fitted the ‘new’ higher ratio crown & pinion which raised the revs/mile to about 15.5/1000rpm. Even then it was only capable of just over 100mph. It got there really quickly though. The ribbon speedo was indicating off the scale but the numbers don’t lie.

Art

Back in the day I recall the Riley 'One point five' could be made to go indecently quick as well. Razz
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colwyn500



Joined: 21 Oct 2012
Posts: 1728
Location: Nairn, Scotland

PostPosted: Mon Dec 17, 2018 9:17 am    Post subject: Reply with quote

alastairq wrote:
The biggest issue with any [naturally aspirated] sidevalve is the ability to get decent amounts of mixture into the cylinder.
Sidevalves are naturally 'self-governing'...in that they hopefully run out of the ability to breathe at higher revs...[before crank or rods appear to snap]....
est gearchange points too.....[rather than relying, as I do, on my ears]


This and the entire subsequent is excellent advice and really concisely written...clearly a man of experience!

Alastair has summarised everything I have seen contributed on the Fiat Forum over ten years of reading up on how to get more from my two cylinder car. Very Happy
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