Lobsided Jowett not balanced at all.

chapman · Post by **chapman** » Fri Apr 03, 2009 4:40 pm

Looking at these oil temperature figures you have no problems
The only difference different temperatures on each side of the engine makes is that you may need a different mixture from each carb to balance it to get smooth running but if the oil stays at 65c then there is no danger of engine damage
I also believe that Jowett radiators are not good enough for modern traffic conditions and if you ask Dennis Sparrow his racing radiator is vastly different to the standard model

Keith Andrews · Post by **Keith Andrews** » Fri Apr 03, 2009 8:39 pm

I also believe that Jowett radiators are not good enough for modern traffic conditions

That beleif is not just jowett, goes for most old models even Chevy
And the main culpit for this is

1/ manually clean rradiator cores..which should be done as routine when building and engine.

When we put new engines together we do oil pump water pump, oil filter, water hoses as a mayyer of ruotine but for some reason the radiator just gets a flush...this may clean most out, even partly un block some cores, then we fire up the new engine, those odd bits of sealant fall off , hit a partly blocke core ans stay there.
Also to keep in mind is the spring in the bottom hose to stop it collapsing under low pressure...these coorode, generally breakup before the bottom hose is replaced...and the peices jam in cores...no flushing removes these.

Oh bottom hoses, if they are soft, when under higher rpms and more suction from the water pump, they can squeeze up restricting flow, flow down and engine cools...Seen people chase hot running and this turned at to be the culpit many times over the years...AND sometimes leading to a manual clean of cores.

Post by **Forumadmin** » Sat Apr 04, 2009 7:48 pm

The chances of a Javelin water pump sucking in a plastic bag, let alone a squiggy hose are fairly remote. If anything the hoses are on the high pressure side, the head being the constriction.

Did about 5 miles in traffic today in the Javelin and water temps seemed fine. Air temp was just under 20C.

Will try the fast run again tomorrow and have a look at the spark plugs. If that does not show anything, I think the heads will be off again.

My odds on the cause now are 50% head gasket/liner sinkage, 30% head crack, 20% weak mixture. Anyone want to run a book?

Keith Andrews · Post by **Keith Andrews** » Sat Apr 04, 2009 9:16 pm

If 100% sure the radiator is not restricted,
I would be running a HC check on the radiator, try
up the total cruise timig 3to 5 degs
then would drop in jets known to be a little on the rich side.

In that order, simply becuase of ease of adjustment.

Odds I would lay with the HC check...cracked head or head gasket.

Post by **Forumadmin** » Sun Apr 05, 2009 12:20 pm

Have ordered Sealey Combustion Leak Detector Fluid for rad check.

Fitting bigger jets requires actually finding some. Will do that if heads prove to be OK.

Keith Andrews · Post by **Keith Andrews** » Sun Apr 05, 2009 9:13 pm

The local garage workshop should be able to do the check in 5 mins
Generally workshops dont charge for basic testing like HC/ battery and the like.

Post by **Forumadmin** » Sat Apr 11, 2009 11:46 am

Made up an adaptor for the radiator cap yesterday. Made a cylindrical rubber bung to fit under the top bit of an old rad cap. Made a hole through this and put a 3 foot length of clear tubing through. Put some indicator fluid in tube and waited for the steam to just start coming up tube. Checked air tight by squeezing hose. Fitted a syphon bulb used for battery testing on end of tube to keep sucking the gas from the rad through the liquid. Liquid stayed blue showing it did not detect any CO2. Anyway the liquid did not move up the tube that it would do if the cooling system was injected with combustion gas. The rad water stays perfectly clear with no brown film and no bubbles.
This test was not absolutely conclusive of no head leak IMHO. But I am a doubting Thomas.

Then ran the engine at very high revs when there is a staccato barking through the air intakes. Sounds like a Formula 1 engine! A similar sound but a more pronounced bark when dabbing the throttle at these very high revs. Not a very good test for the engine; but I am getting desperate.

Will try the road test again this weekend when it stops raining.

Keith Andrews · Post by **Keith Andrews** » Sat Apr 11, 2009 9:23 pm

Liquid stayed blue showing it did not detect any CO2.

The indicator fliud should be one to detect HC not COx...and there are diff indicators for deseil and petrol.

Post by **Forumadmin** » Mon Apr 13, 2009 11:45 am

Not been able to find any fluid to detect HC. Do you know one? Only found gas analysers with an HC probe which is what was done the first time by my friendly garage. Will take car there again this week if they have a slot.

Took car out for two 10 mile runs yesterday with three passengers but on normal roads (that is no extended runs at 60 mph plus). Car did not overheat. However, this was with the heater off. So am investigating if the heater is upsetting the system. Very unlikely I know.

Still not really happy with the sound and power with foot down; gets up to speed but makes a lot of noise doing it. Yet another symptom to investigate. May start swapping known good parts from Jup!

Keith Andrews · Post by **Keith Andrews** » Mon Apr 13, 2009 8:56 pm

with the sound and power with foot down; gets up to speed but makes a lot of noise doing it.

This often indicates incorrect advance curve, can be to far retarded or advanced, and/or leaning out.

Post by **Forumadmin** » Tue Apr 14, 2009 10:34 pm

The fluid I have detects CO2 in the same way as the Lisle stuff. I have found no evidence that the Lisle fluid detects HC (Hydrocarbon). The Sealey fluid allegedly reverts back to blue by passing atmosphere through it. I guess CO2 level is so small in atmosphere the O2 reverses change from yellow that indicates presence of combustion gas.

Looking at http://www.freepatentsonline.com/6806092.html the Lisle patent also shows CO and Co2 as the detected gasses. Tells you what the fluid is made of. Any chemists out there?

There are some who suggest on the web that HC is a better test; but I can find no fluid to do the test only the HC probe on a gas analyser. The garage may not be too happy at sticking it in the rad as contact with coolant destroys probe!

There seems to be a different Lisle fluid for diesel whereas the Sealey fluid says it does both. Surely the combustion gases are the same; just more Hydro Carbons in diesel.

Post by **Forumadmin** » Mon Jun 01, 2009 11:40 pm

A few more episodes in this saga have transpired without a report.

I took the car to a specialist who gave the water system a pressure test to see firstly if it held 5 psi (when not running, but hot) and, secondly, did not increase in pressure when running at full chat to check for gasket leak. All was OK. System holds pressure; so attention focussed on carburation. As I said I was inquisitive about why the car seemed to run out of steam (or as I thought petrol ) at high revs which also caused a bark in the engine note. Carb bowls were dry after a run which could be insufficient petrol or evaporation from hot engine. (May revisit that as Mike Smailes said modern petrol suffers from vaporization.)

I first took the car for a test drive as a baseline on a known route of two miles through town, up a hill and onto a fast dual carriageway, down a hill, roundabout and back again. The problem on full power occurred and overheating up to 95C started on return (ambient was 25C).

Filled up with superunleaded and did a test run. Not much different but did seem to run 5C cooler. (May try some octane booster this week)

I had tried an electric pump previously; but it was not reliable so this time made a better job of it. Changed mechanical for electrical pump. Next test drive seemed a better engine note with no gasping or barking. However still intermittent misfire.

Returned changed ignition coil. Then noticed loose wire on distributor. Another test drive all OK except still overheating at prolonged 60mph plus..

I had chatted that day with Mike Smailes who had supplied the Dell Orto carbs. I was thinking of changing jets but he said he had only ever tried 1.42mm jets. He did offer lots of other suggestions.

Surprisingly the overheating stops immediately you decelerate and even cools down when waiting at traffic lights. OK the electric fan may assist there; but at 60mph the air flow should be even greater unless something weird is happening with venting of bonnet. I know of the tales of negative pressure below the windscreen that my heightened bonnet may be upsetting.

Anyhow this week's test is to revisit the distributor; the current one is professionally reconditioned (hopefully to proper profile) and replaced the electronic ignition in a vain attempt to find the problem.

One other possible change is to move the electric fan thermostat that may be impeeding water flow in top hose.

You may recall I had severe problems with the original air filter causing carbs to completely loose it at 70mph through the standing wave transmitted via the air box. This I cured by fitting two paper pancakes in the space in the bonnet. There is a chance that the interference may only be reduced and there is still some residual upsetting the DellOrtos above 60mph.

My final thought for today is the pintel valve that favourite butt of all problems. Could be at 60mph the blow by the pistons is too much for the carb/crankcase balancing system.

Keith Andrews · Post by **Keith Andrews** » Tue Jun 02, 2009 1:43 am

Some observations...

Filled up with superunleaded and did a test run. Not much different but did seem to run 5C cooler. (May try some octane booster this week)

Higher the octane the slower the burn, the more advance required, slower the curve.
Is the curve over advanced? tuned by ear? doing so is slow death for any engine.
When one retards the advance there is a piont where performance and econony drops off dramatically withing a couple degrees.
When one advances the curve, it ildles very smooth, seems to run very smooth, and power/economy doesnt drop off any significate amount untill it is well in the danger area of slow death, high HC and NOx emissions....and when extreme, auditable pinging...note detonation occurs well blow audable pinging
Find the piont of drop off of power, retarding then set just above this....no more!

I was thinking of changing jets

Higher the octane , the lower the SG ofd the fuel, and therfore require bigger jets...keep in mind we are running far higher octanes than what the "pool fuels" upto 1954 (hi 60s to mid 70s octanes on todays ratings)
Therefore factory jets will tend to run the engine lean and hot

Surprisingly the overheating stops immediately you decelerate and even cools down when waiting at traffic lights.

Not suprising..a carb is in fact 2 carbs in one...a circuit for idle and another for off idle...hence why adjusting idle mixture has such a small effect to be considered NIL when off idle... there will be enuogh adjustment in idle mixtures to compensate for the SG of the higher octane fuel, but not so for the power circuits

OK the electric fan may assist there; but at 60mph the air flow should be even greater

Correct, there is no way a fan can push as much air thru the radiator as if travelling at 30+ mph... hence why many engines have thermo fans..they dont need the fan to turn when moving.

One other possible change is to move the electric fan thermostat that may be impeeding water flow in top hose.

These old cars, including Chevies into the early 70s, where way overbuilt in the pump capacities, radiator etc...hence why if run without a thermstat they cabn run hot....because the coolant passes thru the radiator to fast with the exit temps too high....If one uses modern std thermostat in a chev, it will also run hot because the hole diameter is slightly smaller and the shut off doesnt move as deep...the simple fix is a 3/16" hole drilled in the thermostat....is not much but all that is needed.

I think from you descriptions each of the areas...coolant restriction, timing, jets on its own maynot be a cause, but combine them and the overall is the problem.

Post by **Forumadmin** » Thu Jun 04, 2009 8:53 pm

I think you misunderstood the thermostat for electric fan. This is the sensor bulb about 5mm diameter inserted in top hose, not the thermosat in the water pump outlet. I think teh water pump stat has a large enough hole in it to provide bleed when cold. This was a Jowett service mod.

Otherwise advice on carbs is sound. Usually I set advance to 21deg at 300 rpm which was what was best on the race engine on the rolling road. MAy not be correct for ths engine though!

Then take out for test drive and drive up an incline on half throttle at 50mph ; Adjust until I get pinking and then back quarter turn on micro adjuster. These days find petrol varies so much that adjustment is sometimes necessary after a fill.

Let you know tuning results this weekend.

Keith Andrews · Post by **Keith Andrews** » Thu Jun 04, 2009 9:53 pm

Usually I set advance to 21deg at 300 rpm

That is way over advanced...
What one has at idle means squat...other than having enough for a reasonable smooth comfortable idle.

What is important is what is in the curve under power.
An internal comustion engine, in broad terms ( and varies depending on dynamic compression rato/ fuel octane, and to a far lesser extent to chamber design) is around 36 degrees total, at about 3000 to 3500 rpms, and a graphed curve, a nice epipitial curver around 35 to 40 degrees.
Hence the correct way to set dizzy timing on a given curve is to take the rpms up to just above 'all in' (with VA disconnected) and set total degrees.)

An intial of 21 degs (I do not know how many crank degrees in a jowett dizzy) will be giving a curve that is way too high, and a total way too high for under power.
This can cause weird things to happen like auditable detonation, midway up the curve, not always all the way up.
Setting the shape of the curve is done by changing spring weights, and idealy with AF sensor, or portable fuel anyliser, road testing or using these tools on a chassis dyno.

To illustrate a very fast curve, on a 105 octane fuel and CR 10.5:1 to 11:1(LPG) with low duration cam (bottom end) one needs about 6 to 12 @ 500 TO 600 RPMS (idle) light springs that come off just above this (650 rpms)
18 degs@ 1500 rpms , 26 degs@2300 32 degs (all in ) 2600 to 2800 rpms
This all the way up is way over what a low compression, low octane fuel (about 90/95 ) requires....running on such a curve has pistons coming up and still firing loading rods, bearings etc, cause fires to early

Too high an intial loads starter motors eventually melting the soldered joints in soleniods and armitures causing hard starting and eventually, when hot , the 'dry joints' in the armiture to have the starter motor just click, as if dirty terminals.

Think of the curve at any given piont in the rpm range like this...
Shooting a deer at full run...get the lead time right and the shot will be right on target (heart or head shot) drops the deer in its tracks
A little off, the deer will drop 100 m away( longer walk)...and maybe still have to take another shot to kill it.
Further off, you still get the deer but have to spend a day tracking down..
Way off, you dont find the deer but after a few days the deer dies anyway, and you dont find it.
Too much lead or to less and you miss altogether
Each piont in the curve has to be spot on to fire with correct lead time for max explosion to take place at TDC.

To recurve for modern foels one has to change the springs rather than just move the curve up and down changing the intial.
The more advance the leaner the fuel, leaner the fuel, higher temps

I assume you are not running a VA...A VA introduces more advance, with 3 parameters
1/ the Vac range it works in
2/the amount of degress in that range
3/The strength of the spring in the canister (VA curve shape) thu this is far more tollerant when setting up and can generally be discarded.

I think you misunderstood the thermostat for electric fan. This is the sensor bulb about 5mm diameter inserted in top hose, not the thermosat in the water pump outlet. I think teh water pump stat has a large enough hole in it to provide bleed when cold. This was a Jowett service mod.

I was referiing to the "thermosat in the water pump outlet."