Underbonnet heat - Best Anything I missed ?

[morgan]

Hey team.

Just a quick sanity check of the obvious. Pretty sure I know the answer.

New engine in, fitted, simply lovely. Couldnt be happier.
Usual age-old problem of underbonnet heat build up when stationery.

5mph and over - will sit 180 all day long.
Parked up with bonnet open (heat escape) will hold 180 all day long.
Close the bonnet and it will climb 40deg inside 10 mins. Not boiled it but must have been close.

Big ally rad , good water pump, proper coolant, fan, shroud - its all good.

I am pretty sure my core issue is 2fold -
1 - Headers. Whilst ceramic and lovely, headers get hot.
2 - No vac advance. Got a vac can, but the baseplate locked down and mechanical only (15-34 or whatever)



So - My thinking is I have 3 options -
- Get the vac can working - Car makes good vacuum so should be doable - but I know vac cans can play funny with non-stock ignition curves and I DONT want to touch the curve - its been set so nice. Its possible that adjusting the can might combat this; anything could help I guess.
- Wrap the headers. I think this is more 'moving the problem' - its still fundamentally that the idle fumes are too hot due to timing - but it should help.
- Fit a nice big leccy fan and accept that in traffic, on it goes.


As I say, my problem is really just 'Heat in the bay' - but I'd like to not panic about hitting more than 10 mins of traffic.



Anything obvious I have missed ?

[sublimemike]

You could get the headers heat coated, may help a bit. I suffered with this for ages, then I changed the hood for one with a scoop and It went away but I guess you won't want to do that. I run a fan controller now with a 50 amp merc fan like Alkiller did when he was on the forum for belt and braces.

[sublimemike]

Oops! I see the headers are already coated

[Dave999]

(sorry bored at work so i rambled on a bit..... )

first check your radiator cap seals....

standard spec for my little car is 16LB cap, you will find loads who say 7lb is enough, our chums in the US seem obsessed with this... certainly is not good enough for mine.
you can run at speed with the cap loose or ineffectual and it stays cool until most of the coolant is gone from the heads
but you would certainly notice a problem as soon as you get stuck in traffic... as i found when the centre of my cap rusted out and the spring made a break for freedom

14- 16 lb cap just make sure your pipes are clamped on well...

with standard pulleys water pump and fan speed should be fine. no cavitation or periods of over pressure.

spin the pump too fast and you can get very high pressure in the top hose and radiator top tank that vents via the cap very slowly on each journey that maintains that high rpm,and then a few weeks later when going to the shops you boil over and get stuck. modern cars have the filler cap on a pipe to the bottom hose side of the equation.. the sucking side, the vented or return cap sees the lowest pressure in the system...... which is why the coolant return type set up works well.

idle mixture? lean runs hot.

but you would know it was lean enough to cause excess heat because it would not run right, the heat associated with lean ness tends to be more of an issue at high rpm, you would have persistent drop out of some cylinders, at idle and pulling their ignition lead would make no difference to RPM.

Rich runs hot
massively rich, and again would lose a cylinder or two, nasty plugs, and the end of the tail pipe would be black, you can't burn great clods of lumpy mixture so it would be splattered all over the drive or up the wall of the garage.

but just a bit rich will run hotter, mainly due to the flames going down the headers and heating up the engine bay sections of the exhaust and then of course everything near by, this much richness won't cause obvious poor running, but you could reduce the heat going into the headers by starting the fire a little bit earlier

initial timing:- by changeing this....!

set initial timing to a little bit more and tune for maximum vacuum and rpm then set idle speed to sensible again with the throttle stop.
if you have to do some processes because it automatic you may need a friend to look after the idling in neutral idling in drive carry on.

or if you don't want to move the dizzy or get into springs and limiting
you may be able to combat by adjusting vacuum advance on your vacuum can, to the smallest setting then plugging into unported vacuum, your plenum will act like a cushion so the pulsing won't be too great.

that will pull in some advance at idle, doesn't cost nuffin and may improve things.
you may run cooler and lift off the throttle engine breaking will be reduced. meaning better fuel economy, less hard-back-on-the-throttle action, to get going again, basically around town it will feel like someone removed a couple of foot from the length of the car.

the advance it adds will be gone by about 1500 rpm

if it makes no difference add a little more
should be obvious from your timing gun because your lines won't line up anymore because its pulling in more initial advance
at idle it may put up with 40 * or more, as soon as you hit the throttle, it will be back on the mechanical curve.

i don't know about your carb? does the idle mixture adjustment effect quantity of pre mixed fuel and air or just the amount of fuel? quantity and ratio plays a part. are you adjusting a fountain into a stream or air or is it like a foam party? i have a foam party it complicates matters.

i.e is it adjusted with a screw or do you need air bleeds and jets or rods and jets and worry about emulsion consistency as as well? i know nothing about holleys....

do you have a gunson color tune or an AF meter/sensor

gunson, tune to a blue white flame at idle on the second one back on one side and the 3rd one back on the other
then check a bulkhead cylinder, they run the hottest

Af meter tune to 14.1 its got alcohol in it these days 14.7 was for 4 star.

big electric fans Mmmmmm these cars sold in texas, in florida in mexico, in australia, in south africa
clutch fan is a good reliable fan. fan work would be an elastoplast over the issue, yeah would be ok, but you aint fixed the issue, you just hid it. do this last


Dave

[morgan]

Now THAT was a 'full Dave'.

Yeah; the point on 'texas summer' is one I make a lot - these cars should cope.
I've found a couple of things in the interim -my shroud gap is too large - I always knew it was , but I hadnt realised if the gap is too big round the fan it will just recirc the air in the bay. So thats a thing.

Great shout on the rad cap - Its a cheap thing to try - I might even have one in the box-o-spares.

I really dont want to fudge around with the mechanical advance of the initial (its pretty high anyway, like 16-18 I think) as mr Billadeau set it all up on the dyno - jets, curves, the lot - and she is in a lovely place. But the vac could be a thing in my mind. Each 180 degree on an adjustable vac can should take 2-3 deg out so its worth a go I think.
At the moment though, sucking on a tube doesnt move the baseplate at all - so wondering if its been locked somehow. I need to get a pump on it and get some proper suction. Or just run the car up and point the timing gun at it of course... I feel there should be some help to be had here.

Some great suggestions sir, as always. Thanks.

[Dave999]

i have no shroud and a decent gap... but i have a smaller engine and more space...

can you feel the draw through radiator from the front
just hang kitchen towel down the front of the grill and give it rev if it sucks the towel in to the grill its sucking ok reversion would blow it out

if the dizzy curve is good, and dyno set, do not mess with that... so just off idle to max rpm is dialled in mechanically, and you will still use that curve.

set to TDC with rotor at no.1 position
put a ding into the edge of the dizzy directly below the line in the middle of your rotor arm contact

use a craft/stanley knife blade to mark the dizzy base position against the block. nice thin precise scratch better than a fat marker pen
don't move anything when its out and put it back in exact same place

then you can investigate your Vacuum stuff without worry.

may just be that it has had so many 180 Degrees wound in that it now doesn't move i.e the spring inside is in coil bind

what it is at the mo. in regards to initial and what it needs could be different 15-18 sounds reasonable but carb headers headflow cam/lift CR all play a part.

all you can do is try....no guarantees it will work BUt it might...

dave

[morgan]

OK - lengthy conversation with engine builder; long story short to get me through break in I now have a monster electric fan setup.
Twin fans, 2800CFM - sounds like a hovercraft !
Good news is they do the job. The sheer heat they throw out from under the car is insane. But they do the job.

Trouble is (ok, it is super hot weather currently) you have about 5 mins in slow traffic before we leap from 180 to 210. Like I say; fan blasts it out but I recognise its a band aid - the core problem is the insane levels of heat. Rad cap seems good. Thermostat seems to work.

Reading round the issue whilst I continue to work on vac-can advance etc there are ac couple of other things.
- Filled up today - she is doing ~7mpg (usually 10-14). So thats a thing. Fuel = heat.
- The US forums all suggest that new built engines produce a lots of heat until they properly bed in. This has done like 75 miles. SO I think I need to get another 900 on it before drawing any serious conclusions.
- The US forums also suggest that ceramic headers during break in is a bad thing. Mine are ceramic TTIs.

So I *think* I have a bit of a perfect storm.
- Super hot weather.
- Brand new engine heat
- Ceramic headers
- Fixed advance (not vac).

Monster electric fans will save me whilst it beds in, so the new plan is keep fettling with the vac, let the thing bed in, and ENJOY IT - god it drives good...

[Dave999]

ah didn't know it was all new.... yes a new motor is basically polishing itself into a broken in state...

the ceramic headers during break in thing, is about the first 20 minutes when you break in the cam, can make the headers glow red hot whilst you find a nice advance and throttle position to keep it chugging at 2000 rpm. if they get red hot the coating comes off.
Basically you don't normally do 2000+ rpm for 20 minutes standing still.....

so is you fuel consumption worse than the race motor or better?
Or is this a more "RACE" motor than the last one?

if its tamer than the race motor and is using more fuel when its doing much the same style of driving, where is it going?
rich at idle can make it run hot in traffic

do you have a AF ratio gauge?

do you have a locked out distributor, no mechanical curve?

Dave

[Blue]

Those flexible rad hoses are not good for flow and can trap air, treat yourself to the correct moulded ones.

[Blue]

I also fitted a FlowKooler water pump to an engine recently and was stunned by how much volume it moved, I will also use those in future.

[morgan]

Funnily enough I have one of those in the cupboard.
The one on there is a new 440source one I think - but I can easily swap it over.
Rad hoses - will do. I assume the ally rad inlet is somewhere near position of a stock rad ?

[morgan]

Dave -

Engine has been broken in on the dyno prior to tuning runs, so essentially ready to go. So my headers are not doing the cam break in - should be good.

Its not a wild build - designed to be far more streetable than the last. 475hp and 515lb/ft@3,200. Should be just right.
Mech advance 18-34ish (although I admit I have not got a gun on there yet - i will do so at the weekend).
All nice stockish parts, Edelbrock ally heads etc, 750 carb. Nothing wild.

But yeah, super thirsty and super hot - but I think getting some miles on and sorting that vac-can will help.
I've not actually overheated it yet, but the under bonnet is immense unless you keep moving. Wild fluctuations - 180 on a steady run and anything up to 220 when things slow down. The monster fans bring it down to 180 but the you can feel the heat being blown from under the car like an F1 diffuser !

I really think I am just being super sensitive. Its a brand new motor. Its been set up really nice. I just need to get some miles on it, make sure the flow is good, and get that vac can working to try and pull it in at idle (which is where the heat is made).
Hopefully the MPG will sort its life out too...

PS - The HEI modules are working good

[Blue]

Funnily enough I have one of those in the cupboard.
The one on there is a new 440source one I think - but I can easily swap it over.
Rad hoses - will do. I assume the ally rad inlet is somewhere near position of a stock rad ?

Yes the stock hoses usually fit that style of ally rad.

[Dave999]

read something somewhere a week or so ago making a point about the size of the passages in certain pumps
looking at the pump from the front there is a cast in bulge to one side that is a pipe into the block
some have a flattened angle to them some are more rounded.

general consensus was that the more rounded one had a bigger internal bore and flowed better

flow cooler were supposedly designed with the big bore
mancini and 440 source had smaller bore

seemed to be linked to the style of impeller the casting was designed for
presume both had the design of the casting based on orginal chrysler parts

given that the whole system is designed around a pressure difference between inlet and outlet i'm sure there will be good reason for the differences.

i.e restricted flow in one area causes a greater pressure difference between inlet and outlet and that will impact flow speed through the restriction, it will be faster.
less restriction potentially means slower speed flow but its a bigger tube so volume is higher. In theory you end up in the same place.

dunno enough about thermodynamics and flow dynamics to know which could be better or worse, but keep in mind most car radiators are perfectly able to cool the motor provided there is some flow. over pressure would be a problem as mentioned previously, it slowly lets the coolant out via venting without any noticeable symptom until much later on

its what drove the development of different water pump gearing by mopar for race cars, stop blowing pipes off and stop venting at the cap when RPM and heat production conspire to be more than cap pressure.
nothing to do with flow speed, coolant can't go too fast i.e 20 half filled trucks going twice as fast a 10 full trucks shifts the same amount of coal... both can do that all day long provided they can dump their coal.

at idle you are over filling your trucks or they can't dump.


Dave

[Dave999]

if you start it and let it run at idle wit the radiator cap off do you see movement of coolant once the thermostat opens. or does it all start to pile out over the top of the filler spout? would imply a potential lack of flow in the radiator....
your big fans work so there is definitely some flow...
which would imply that your thermostat at least opens.

you could try doing this with the front jacked high see if there is big air bubble hiding somewhere, you would hear it bubble through.

this might seem like i'm teaching you to suck eggs, when you had the mechanical fan on was it bolted on the right way round? i.e the physical fan part on the spacer or on the clutch

do you run with the bypass circuit connected up? connected as standard it can mask a restricted flow in radiator or a sticking thermostat. its designed to allow an engine to live in both circumstances and get you home with resteicted cooling capability.

i think ive run out of ideas now...

Dave