Engine rebuild?

[Keith Andrews]

Introduction:
Hi I am a member of the NZ Jowett Club NZ, Nth Division, of some yrs now. In the workshop is a Bradford under full resto,( http://www.steptoe.sytes.net/album01 ) and have purchased another to copy the wood work, which I use almost daily along with our '69 matching #s z28 Camaro.

I am suprised that there is no profiles available for Bradford woodwork, espec as manuals/parts etc are all available for the rest of the vechicle

Since purchasing the new Braddy, I have rebuilt steering, front axles, gearbox etc as everything is rather 'tired' including the engine that puts more gases out the crankcase breather than the exhaust.
At the same time a duel set of everything has been rebuilt for the one in the workshop.
I do have to admit thu, being a ex hot rodder, the temptation got the better of me...the engine bay was quite a mess..so it got a bit of a make over one weekend.


A SB chevy, LPG, I know my way around, vintage Braddy Im in need of info, and advise.

The Bradfords where made and designed for fuel, produced by the Government Petrolium Board, during post war rationing between 1929 and 1953, known then as "pool fuel" This fuel was 1 grade with a octane rating that varied between 67 to 80, and leaded.
Bradfords have a compression ratio around 5.4:1 and a advance curve of 34 deg...more suitable for kerosene.

What I would like to do is update the engine to todays fuel..the lower stuff 91 octane.
Has anyone done this, and if so what mods did you do?
The areas Im looking at are:
Compression: how much can be taked off the heads without interfering with the lifters, and what torque then to use on the head bolts. inserting hardened valve seats
Dizzy curve: Taking out curve to around 36 to 38 deg all in around 2100 to 2500 rpm
Cam: basically stock, the problem here is that as far as I know, noone rebuilds the cams, and all I have is old worn cams. Does anyone have the actual cam specs...lift, lift rate, durations, lobe centers, overlap etc?

Im not looking at 'rodding' or 'suping up' just convert the engine to todays fuel to have it run as it was intended.

Cheers
Steps

[Forumadmin]

Come on you Braddy guys, let us give some answers. Perhaps our intrepid round Aus adventure could test some of the mods!

[pat lockyer]

Kieth just my thoughts on any mods with the CC engine.

First regarding the valves running in cast iron seats, this it seems is ok in the Uk as the failings never really occured with well maintained engines.
We can have the benifit of running Shell optimaxthat runs cleaner, with good valve cooling the timing can be remaped.
This may give more power but staying to the 25bhp!

Any serious alterations to the c/r etc i fear will result in crank breakages do to the inertia loading.

Regarding the heavy breathing from the breather tube the failing of the breather valve can do just that if piston blow bye it is not a prob.

Paul Beaumont may be able to enlarge on mods that have proved ok over the years?.

[Keith Andrews]

Regarding the heavy breathing from the breather tube the failing of the breather valve can do just that if piston blow bye it is not a prob.

I think audable piston slap and around 45/1000 plus updown play of the pistons in the bores has a lot to do with the blow by.

The amazing thing, the other weekend we where on a club run, updown country roads...I was following our club president alsao in a braddy with a good engine...Ken has a bit of a repultion in 'hammering ' along at a quick pace. Even thu my engine is tiered in the extreme I kept up with him. I have never driven a Braddy so fast...We where going up down hills, around cnrs that I doubt I would have been much faster in to 400hp camaro. lol

Im not looking at "more power" but rather redesigning the engine for our 91 octane.
So the crank is the weak point?
I intended to static and dynamically balance, plasti gauge bearings etc..This is normal considered 'race' stuff rather than simply making a long lasting around town engine.
What sort of compression actual (LBs/sq inch)can these little engines take...has anyone messed with the cam valve overlaps in this area?
ie higher compression ratio, actual "real compression reduced by over lap?
I would like to get the orginal cam detailed profiles as a starting piont.

Background..back in 86 the gov was talking about messing with our petrol.
At the time I was right into the Hot Rod sciene, LPG was a simple no no, and took a lot of flak. Till I put the camaro down the strip....
Economically on todays fuel prices it was cheaper to run the camaro than the wifes little toyota on a trip...earlier this yr we rebuilt redesigned cam etc with even far greater results that have exceeded expectations in performace and econonmy.
I built and designed everything from the engine to run at the cooler temps, cam design, carb, valves, heads, dizzy machining /mods etc etc.

The local club guys here (NZ) very supportive..in particular John Wolf and Neil Moore...1st time around I want to get things pretty right and right on for the 2nd engine..I have 4 engines to play with.
To do this I just need to pick the brains of others as much as possiblen from little things to big, theories and ideas.

I do not have much time cause the engine in the current on the road braddy is going to die lol.

[Keith Andrews]

I hope u guys dont mind me making notes, thinking out aloud here...

CAM
I have established the cam profile, fortunately it seems the cam in the engine isa not worn or at least any significant amount.
I assume that Jowett only did release the 1 cam profile

All at zero valve lash in crank degs
Intake open 18* BTDC
Full open 93* ATDC total lift 7.7mm (0.303 ")
Closed 202* ATDC

Outlet open 119* ATDC
Full open 246* ATDC total lift 8.0mm (0.315")
Closed 0* TDC

Can someone confirm the lift is correct to spec please?

This is a very primitive cam profile, thu one can certainly see where that famous bottom end torque comes from.
With the intake opening@ 18* btdc, in effect it opens @tdc
And closing 22deg ABDC it in effect closes @ btdc.
This in effect has the dynamitic and static compression ratios = to each other.
Taking on board the loading of the crank with increased ratio, under these circumstances it is no doubt of concern. Increasing static compression then decreasing the dynamic by delay in the closing of the inlet valve may well be the sol'n to the problem. All modern engines have a far lower dynamic ratio because of this...Dont be fooled by manufactures adverts in regards to 'advertised compression ratio" this generally means squat

Compression Ratio
My numbers do not add up...maybe a non std piston or 'rod???
CC ing the head I get 75cc
Can anyone confirm that this is the std spec please?
Std cylinder volume is 502.5 cc
If Compression ratio is per spec 5.4:1
That gives cylinder volume @ top of stroke + head volume 93.05cc
If the measured head volume is 75cc then the volume at the top of the stroke is 8cc. I have not cc ed this yet but visually 8cc is way off.

From bottom of stroke to top of cylinder is 106.3mm
Top of stroke to top of cylinder is 3.8mm
This gives a stroke of 102.5mm NOT the spec 101.6mm????
Or I have got lost in the calulations lol

The lift above the deck of valves @zero lash not including gasket.
Inlet 5.9mm outlet 6.2mm
Depth inside the head 9.9 mm
This gives the potenual of shaving off approx 3.5mm, which results in a static compression ratio of around 6.6.

I stand to be corrected on anything and open to comments please.
Cheers
Steps

[Keith Andrews]

To continue from answer in another thead to this part of the subject
http://jowett.net/forum/viewtopic.php?p=651#651

Quote:
I know that CB cranks are suspect if you try to overload them. CC is supposed to be more robust, but Personally I only have experience of breaking a CC one!

What was the cause of the break?
I have spoken to many ppl re compression and they all mention the crank...but I have yet to find someone who has actually played with compression, or cam inlet valve closing ABDC.
This part I will continue in the Engine question here to keep continuinty for future reference.

I am making prelimery investgations into alturnative pistions around the 80mm Diam..flat top and dome.
So far OI believe
Suzuki 1100cc motor bike
Some earlier Alfa romao
late 1980s Toyota
VW and porche
early flat head ford/buik v8
May provide posiblities.

I believe I maybe in possesion of one of Neil Moores custom cranks, but will have to wait for him to get home (NZ)at the end of the month..I believe he is somewhere in France rounding around in a few Jowetts.

Steps

[ian Howell]

With regard to pistons for 'flat' engines, doesn't there have to be oil relief or oil supply slots in the 'bottom' side?

Would this mean that it is not practical to use pistons from a vertical engine in flat twins or flat fours?

(Just for fun, I have a remote connection with a VERY interesting restoration project that has a flat TWELVE engine! Actually it was two 'in line' sixes fitted to a purpose-built crankcase, with lots of other innovative ideas too).

[PAUL BEAUMONT]

Firstly to Keith, The CC crank that I know of that broke was probably simply fatigue! it was in my Father's Bradford in 1963. It had spent the previous 3 months struggling through horrific amounts of snow on a rural milk round, and on about the day that the last bit of snow disappeared the crank decided to snap. I have heard that having the timing too advanced (ie before TDC as is current modern practice) will shorten crank life.

I am most interested in Ian's comments about oil slots in the piston. Do you mean the split in the skirt? I was talking to someone who is rebuilding a CB engine last weekend and this subject came up because the pistons have "front" on them and he could not achieve this and the 2 skirt splits at the bottom. I checked a set of new Hepolite pistons that I have and they are identical, so if "front" goes to the front of the engine then one split has to be on top and the other at the bottom - or do I have a duff set??

[Forumadmin]

'Front' aligns the piston in relation to the direction of motion of the crankshaft and not the position in relation to the earth. The sideways forces on the piston skirt caused by the rotation of the mass of the conrod require more oil on one side of the skirt than the other. IMHO! I also read somewhere about how to position the gaps in all the rings for best oil consumption. Sense would dictate on the opposite side to the split; but of course they should not all be in line!

[Keith Andrews]

With regard to pistons for 'flat' engines, doesn't there have to be oil relief or oil supply slots in the 'bottom' side?

All more modern pistons have a row of small holes for oiling...rather than slots...even vertical older engines had slots for oiling in the thrust side of the crank, vertical or horozonal...modern techonloghy design has superseeded this with just holes.

rebuilding a CB engine last weekend and this subject came up because the pistons have "front" on them and he could not achieve this and the 2 skirt splits at the bottom

Do not confuse this oiling slot with a diagonal vertical slot in the skirt, thisa is for expansion of the piston

Would this mean that it is not practical to use pistons from a vertical engine in flat twins or flat fours?

The principle of oiling on modern pistons vertical and horozonal is the same, therefore if using a modern Toyota or VW (it fits) will be ok.

'Front' aligns the piston in relation to the direction of motion of the crankshaft and not the position in relation to the earth. The sideways forces on the piston skirt caused by the rotation of the mass of the conrod require more oil on one side of the skirt than the other.

This sort of confused me at 1st ..I will try to explain another way
In the firing stroke, going down, the piston/conrod is at an angle to the cylinder, theref9ore due to action/reaction and leverage due to the angle with the pistion of rotation of the crank journal..the piston sort of leanns harder on the side of the cyinder wall...this is the case regardless of an engine bet it a boxer, V Or vertical. This is side is the 'front of the cylinder
Also as the cylinder is pushed up the same occurs in the opposite wall, the amount of thrust here is far less then that in the firing stroke down.

Steps

[Keith Andrews]

Somewhere an lost it now..and my glasses..I can even see what im typing lol...Is a comment about setting timing BTDC instread of TDC.

I have seen in my short time with Bradfords, several engines that lack power...this is due to setting up timing gears like a normal engine.
The Bradford timing gears MUST be set as per manual, with valve lash at 12/1000 then valve lash corrected to 6/1000
THIS IS CRITICAL WHEN setting up. Compensating by turning the Dizzy to add degs BTC is just that, the valve timing and uverlap will still be screwed


The cam..which the dizzy drives off is ineffect 'builds in ' around 10 to 12 cam degs fireing BTC.. Keep in mind cam degs are 1/2 crank degs (dont confuse these) therefore like anyother engine We end up firing about 4 to 5 deg BTC.
In my opion and not tested...this is a lot for the low rpm and modern fuels with a faster burn across the combustion chamber than the Gov Pool fuels between 1939 and 1953...Thu on the other hand with low compression/high octane it could balance out to be right
With timing gears SET UP CORRECT a couple degs either side of TDC couldstill produce some small improvement..

I realy do hope Im rexplaining these in an understandable manner??

These explanations are not just credited to me...A long time and close friend, Darrly Critchley of Critchley Automotive in Takanini, Auckland NZ.
Darryl Did his 'time' many yrs ago on on older cars, I have cursed him so many times over the yrs cause he has ALWAYS been right lol
I have a cnr in his workshop where I do my rebuilding
And Dwight Who owns Performance Parts Also Takanini are of great help.
Dwight specialies in American V8 performance, hot rodding, design and build stock, purpose built and race engines...who for well over 25 yrs has been of great help...And who doesnt admit but has a soft spot for my Bradford lol.
Also worth a mention is The Takanin Branch of Beaurepairs (tyre. wheel alignment) where my son works and Chris At Manukau City (Auckland NZ) who is also very supportive. (Has a blown/ NOS custom camaro, V pres. of the NZ Muscle Car club)

Cheers
Steps

[pat lockyer]

To hopefully put this topic in jowett simple terms with regard to piston correct fitment.
The n/s piston should be fitted marked front that will be with the split skirt at the bottom.
The o/s piston should be fitted marked front that will be with the split skirt at the top.
this is more to do with the lubrication than the thrust slap when cold or hot.
Picture to follow if tother end is not bogged down by technics.


Now for those that want to alter the original design that has spaned more than 50 years.

Have you tried the autothermic pistons.
Are you considering the more modern approach in some piston bore methods ie Nikasil or alusil.
Fuel injection and nitro etc.

Are all the changes really necessary i must ask myself.

[Keith Andrews]

Now for those that want to alter the original design that has spaned more than 50 years.

Have you tried the autothermic pistons.
Are you considering the more modern approach in some piston bore methods ie Nikasil or alusil.
Fuel injection and nitro etc.

Are all the changes really necessary i must ask myself.

If one wants to get a Bradford engine "hotted up to the max NOS etc they would either have money to waste or be stupid...
There are serveral other issues with a Bradford that also makes it downright dangerous...Steering, chassis strength, brakes the list goes on.
If one wants HP forget a 2, 4 or 6 cylinder engine go straight cubic inches in the way of a SB or BB chevy ...
The other alternative is to rod with new chassis, drive train etc and widening the body 4 to 6 inches. We do have a 'parts' Braddy as mentioned above, way past resto...this is been considered after the current 2 Braddy restos are finshed. In the 10 yr plan...hopefully before I get to old and reach my use by date

In effect what we have at the moment is a braddy that ran well on 1939 to 1953 'pool fuel' and baddly on modern fuels...Kerosene is a closer match to pool fuel, that is

The purpose of the project is simply to take 1 of several spare engines, that was designed to run on 'pool' fuel that had an octane rating varing between 67 and 80 and of dubiloius content....to run as it was meant to on todays fuel effectively.....
and do it right, which means upping compression, maybe a slightly diff cam profile and dizzy curve...keeping within the strength tolerances of rods, crank etc.
At the end hopefully, we will have, once again, an engine blueprint design to enable us to experiance better how Braddys realy did used to run.

To do this I am drawing on any info, experiances and ideas others may have in there long association with the Bradford as todate.All my yrs have been with LPG and SB chevies rather sucessfully and beyond expectations.

[pat lockyer]

n effect what we have at the moment is a braddy that ran well on 1939 to 1953 'pool fuel' and baddly on modern fuels...Kerosene is a closer match to pool fuel, that is

In reply to the above.I seem to remember that the pool petrol was worse for the Bradfords ie decarbonizing every 8 to 10,000 miles, if you were lucky enough to find the exhaust valvea and seats ok if not the job of valve seat grinding and the fitting of new exhaust valves was common practice. Engines from memory sneezed and poped till warm not like the Bradfords of to-day running just on U/L.
More valve clearance more valve cooling with a proper running motor in more ways than one.

TVO in the old tractors did not suffer from carbon build up with exhaust valve burning.
Same oil used in those days[strange or what]

[Keith Andrews]

Hey great for the pic...So that is a Bradford piston? not a vauxel or some other hybrid?
The pistons in this engine are the same. Being new to Bradford engines I was not sure.

Another question.
Do or have u guys balance braddy engines?
My flywheels, cranks etc (except for the pressure plate) look as if they have never been balanced.
The Camaro even thu it is basically a daily driver (like the bradford) I dynamically got balanced...Flex plate thru to harminc balance including bolts etc, pistons/rods/ bearing all weight matched +- 5/1000gm
When stripped down several months ago (was stolen and thrashed at the police lock up..another story) After 20 yrs and around 150,000 miles the wear was near enought to nil.
Since the cost to dynamically balance was only $NZ 150 for a V8, im thinking about doing the same on the Braddy engine...not as a performace thing but for long lasting/wear.

Pistons?
This week Im going out to look at piston opitions...samples from car/motorbike wreaking yards
So any list of models to look for or look at would be appreciated

Cheers
Steps