Can too little compression for a camshaft cause engine heating

[travis]

How much clearance between the top of the carb and the hood? What does it have for an air cleaner? Was these a/f's taken with the exhaust uncorked and at steady state cruise?

Something is clearly amiss there...could be missing/misfiring as the rpms go up, could be restricted air flow, could simply need carb tuning. I know nothing about these carbs...I'm not a carb tuning expert but I'm thinking some combination of jetting and high speed air bleed tuning is needed here. Do you have another carb you could try?

Did that thing have motorcycle exhaust tips on it???

[topradman]

The fabbed exhaust cone could tell someone has already been busy fighting the overheating.
I don't think I've seen in what car this engine is in?

Some other thoughts that crossed my mind while reading the topic;

- Front air dam / Hood seal over radiator-support;
• As the car only overheats while driving, is it possible to install a (temporary) air dam somewhere under the radiator support, to create a low pressure area behind it. This could help releave and vent hot air from the engine bay better perhaps.
• Most cars have a rubber seal mounted on the inside of the hood, which seals over the radiator/support and prevents hot engine bay air from spilling back over the radiator to the front again.

- Any chance the brakes/drivetrain are/is dragging too much causing the engine to work harder during driving?
What is the engine vacuum while driving a steady speed?

- Perhaps a bit 'very' far fetched; Cylinder wall thickness.
Maybe the walls, even at 0.030" over, are (rusted?) thin (enough) that more combustion heat finds its way into the coolant?
I know it's a lot of work partly disassembling the engine again, but if you have the engine open anyway for some reason soon again, a sonic check could tell something.

I assume fabbed cones were attempt to soften exhaust note as exhaust is pretty loud. Car is a 1941 Willys coupe Outlaw body.

Radiator is well sealed to radiator support, very, very little air could pass through the grill and not have to go through the radiator.

The car will also gather heat when not driving if rpms are raised and held to around highway speed rpm, say 3100.

Engine vacuum is around 15" steady cruise. No brake drag, no drivetrain drag.

When heads were off, cooling jackets are easily observed and very reasonably clean. Engine has maybe 500-600 miles.

[topradman]

There is another method of reducing exhaust reversion, using a very short section of reduced diameter exhaust pipe right at the manifold inlets. Say 1 7/8 dia by an inch long. This will keep exhaust velocity high leaving the cyl but that slight difference will help quell any reverse pulse, limiting reversion. That is a strange manifold.


You briefly mentioned head gaskets. Curious as to cooling flow, series/parallel, could there be any mismatch there?

Another already asked rad inlet and outlet temps.

IR Temp readings of head and block back to front, are all consistent or varied with position?

I agree with the header mods you are describing and that they could help. Anything would be better than what is on this car but chassis would only allow these or iron manifolds. Other option would be for me to make custom headers but customer is at the end of his desire to make this engine work in this car if we incur any more expensive costs ( I know, I know ) and custom made headers are extremely time consuming, thus $$$ to build as I have built several sets and cannot find a way to do them for much under $1000-$1200 and usually lose my ass at those prices.

Head gaskets are series with some 5/16" passages added by the spark plug bosses like a parallel flow but much smaller and smaller than Victor/Renz version which has 1/2" passages there. This is a Gen V block w/Mark IV heads but after a lot of studying on this combo, there are not currently any water movement problems in any portion of the cooling system, I am well confident of that. I changed the gaskets from parallel flow to this version of a series flow previous and it has at least now made the car drivable around town with the ac on ( which keeps e-fan on because of high side head pressure in ac system ). It runs very cool around town, hit the highway and after awhile it begins to gain heat, more and more with speed. Does same sitting still.

[topradman]

How much clearance between the top of the carb and the hood? What does it have for an air cleaner? Was these a/f's taken with the exhaust uncorked and at steady state cruise?

Something is clearly amiss there...could be missing/misfiring as the rpms go up, could be restricted air flow, could simply need carb tuning. I know nothing about these carbs...I'm not a carb tuning expert but I'm thinking some combination of jetting and high speed air bleed tuning is needed here. Do you have another carb you could try?

Did that thing have motorcycle exhaust tips on it???

Plenty of carb clearance from hood, has K&N air cleaner about 4" tall x 16 dia with a filter lid on as well so plenty of air and not over oiled at all.

A/F taken with open headers ( such as they are ) and about 5' of 2 1/2" pipe on either side. They were taken at a steady state cruise.

Doesn't feel like a misfire at any rpm range but exhaust is pretty loud with mufflers off.

Yes, something is clearly amiss!!

I have a 5 gas analyzer that will hopefully be here tomorrow so I can more closely confirm the A/F's as well as use the NOX values to determine if there is any detonation going on and hopefully can come up with a game plan to get this thing finished!????

[ptuomov]

Some suggestions from a novice: is it possible that the early exhaust valve opening, manifold style “headers”, and relatively high camshaft overlap cause the engine to overheat?

At low rpms, some of the cylinders suffer from 180-degree exhaust blowdown interference. That is, when the exhaust valve opens, the victim cylinder running 180 crankshaft degrees ahead of it is still at the overlap when the blowdown pulse arrives at the victim cylinder. That could cause overheating. The problem could be compounded by the early exhaust valve opening, which heats up the exhaust gasses. It could also be compounded by the low compression, which both makes the exhaust hotter and leaves a greater chamber volume for the blowdown interference to pressurize. Finally, retarded ignition would also compound the problem because it would further heat up the exhaust. All of this would also make the exhaust quite loud, like a modern emissions controlled car at cold start when they temporarily advance the exhaust valve opening and retard the ignition timing to light up the cats as quickly as possible.

The reason why I’m thinking about this possibly going on is that twin turbo V8s with log exhaust manifolds and small turbos seem to have similar problems when someone puts in too big cams and installs them advanced. The exhaust blowdown interference causes overheating and detonation and then the computer retards the ignition which does not help the overheating problem...

[topradman]

Some suggestions from a novice: is it possible that the early exhaust valve opening, manifold style “headers”, and relatively high camshaft overlap cause the engine to overheat?

At low rpms, some of the cylinders suffer from 180-degree exhaust blowdown interference. That is, when the exhaust valve opens, the victim cylinder running 180 crankshaft degrees ahead of it is still at the overlap when the blowdown pulse arrives at the victim cylinder. That could cause overheating. The problem could be compounded by the early exhaust valve opening, which heats up the exhaust gasses. It could also be compounded by the low compression, which both makes the exhaust hotter and leaves a greater chamber volume for the blowdown interference to pressurize. Finally, retarded ignition would also compound the problem because it would further heat up the exhaust. All of this would also make the exhaust quite loud, like a modern emissions controlled car at cold start when they temporarily advance the exhaust valve opening and retard the ignition timing to light up the cats as quickly as possible.

The reason why I’m thinking about this possibly going on is that twin turbo V8s with log exhaust manifolds and small turbos seem to have similar problems when someone puts in too big cams and installs them advanced. The exhaust blowdown interference causes overheating and detonation and then the computer retards the ignition which does not help the overheating problem...

THANK YOU PTUOMOV! That is exactly what I have been asking on here! I feel like from the info I have gleaned from this previously assembled and previously unknown engine combo that the camshaft, (Lunati 10110424, although maybe a fine grind for what it was intended for ) is the bad egg in the basket for this engine. Again, 468, CR 8.5:1 or less, little valve open chambered 118cc (or more?) oval port 2.06 in/1.72 ex, 292/292 advertised 230/230 @ 0.050 0.544/0.544 lift, 9LSA, 6IC, along with these shitty designed headers could be an exhaust reversion issue causing heat to gather at cruise rpms of 2800 - 3400?

I don't know how to clean up the pig rich on the carb yet but I will know by tomorrow morning (not a QuickFuel/Holley guy.... yet) and then will see if leaning it out some will help finish the combustion process sooner so maybe I wouldn't have to fire the ignition so early to try for a finished combustion process before valve overlap? Timing is 21btdc + mechanical 19 + manifold vacuum advance +20 = 60!.... and it seems to like it!! I know the more I lower it, the hotter it runs and the worse it runs.

Maybe a cleaner combustion process will help with all this by leaning the carb to some normal AFR?

PS... Lunati guy said this cam shouldn't be a problem for low CR but the cam is listed for 9.5:1 ???

[travis]

I don't think reversion is your issue, but I have been wrong before. Your headers are an unknown to me, but I can't see them being worse than a lot of factory iron exhaust manifolds out there. I've seen, and worked on combos just as messed up as this one (remember when everybody stuck 280 magnums in EVERYTHING?). The cam is too big for the combo, I totally agree with that. Low cylinder pressure is generally going to want a fatter a/f and more timing. If it is going to 10:1 at WOT, then that thing is just ridiculously rich, and the over rich condition at cruise speed...it all adds up to wanting a lot of timing just to run sorta right. I think once you get the a/f and timing lined out, most if not all of the cooling issue is going to go away.

Excessively fat or excessively lean make them loud out of the exhaust. Fat is usually loud and dull sounding, lean is loud and crackly. The cones are one way to quiet them down a bit, but those other tings look like motorcycle mufflers...that's never going to work lol

[user-23911]

How about photos of the plugs?

That usually works.

[CharlieB53]

Have you used the IR Temp and checked temps top/mid/bottom of the different radiators you have tried?

I am thinking frontal area here can contribute to heating. Finding the most efficient design for the heat and water flow you have available.

There has to be something so basic we are all missing it.

Water speed too fast? Is that even possible? Cap pressure? I run into a LOT of bad caps.

[cuslog]

You said you took 5 deg timing out, it got worse, 10 out and it got worse yet -- how about going the other way (adding initial) ? I know you said the timing marks are right but it sure seems (to me anyway) like not enough initial timing or too restrictive an exhaust system.
Good luck, if nothing else you're tenacious.

[ptuomov]

Some suggestions from a novice: is it possible that the early exhaust valve opening, manifold style “headers”, and relatively high camshaft overlap cause the engine to overheat?

At low rpms, some of the cylinders suffer from 180-degree exhaust blowdown interference. That is, when the exhaust valve opens, the victim cylinder running 180 crankshaft degrees ahead of it is still at the overlap when the blowdown pulse arrives at the victim cylinder. That could cause overheating. The problem could be compounded by the early exhaust valve opening, which heats up the exhaust gasses. It could also be compounded by the low compression, which both makes the exhaust hotter and leaves a greater chamber volume for the blowdown interference to pressurize. Finally, retarded ignition would also compound the problem because it would further heat up the exhaust. All of this would also make the exhaust quite loud, like a modern emissions controlled car at cold start when they temporarily advance the exhaust valve opening and retard the ignition timing to light up the cats as quickly as possible.

The reason why I’m thinking about this possibly going on is that twin turbo V8s with log exhaust manifolds and small turbos seem to have similar problems when someone puts in too big cams and installs them advanced. The exhaust blowdown interference causes overheating and detonation and then the computer retards the ignition which does not help the overheating problem...

THANK YOU PTUOMOV! That is exactly what I have been asking on here! I feel like from the info I have gleaned from this previously assembled and previously unknown engine combo that the camshaft, (Lunati 10110424, although maybe a fine grind for what it was intended for ) is the bad egg in the basket for this engine. Again, 468, CR 8.5:1 or less, little valve open chambered 118cc (or more?) oval port 2.06 in/1.72 ex, 292/292 advertised 230/230 @ 0.050 0.544/0.544 lift, 9LSA, 6IC, along with these shitty designed headers could be an exhaust reversion issue causing heat to gather at cruise rpms of 2800 - 3400?

I don't know how to clean up the pig rich on the carb yet but I will know by tomorrow morning (not a QuickFuel/Holley guy.... yet) and then will see if leaning it out some will help finish the combustion process sooner so maybe I wouldn't have to fire the ignition so early to try for a finished combustion process before valve overlap? Timing is 21btdc + mechanical 19 + manifold vacuum advance +20 = 60!.... and it seems to like it!! I know the more I lower it, the hotter it runs and the worse it runs.

Maybe a cleaner combustion process will help with all this by leaning the carb to some normal AFR?

PS... Lunati guy said this cam shouldn't be a problem for low CR but the cam is listed for 9.5:1 ???

I don’t want to make it sound like I know what I’m talking about, but that said, here are a couple of suggestions. Is it possible to fit headers in there? I think that if you are just trying to solve the exhaust blowdown interference issue, then tri-y headers would probably be the most space efficient solution. The “primaries” can be very short like in the BMW headers/exhaust manifolds. Only the secondaries need to be long such that the travel path of the pulse from the offending cylinder to the victim cylinder is very long. In terms of real estate, fitting the two long secondaries is a lot easier than fitting fitting four long primaries.

71122EBB-116F-40CF-B3B6-F42A97069C3C.jpeg

On other suggestions, just throwing this out there, one could test retarding the camshaft and further advancing the ignition timing. It’ll run overall worse, but there’s a chance that retarding the camshaft and thereby making the EVO event later will cool the exhaust and reduce the overheating problem. Just throwing it out there with no real practical experience to support this idea.

[CharlieB53]

Without going back and re-reading the entire thread, I've lost knowledge of WHAT the actual engine temps are. The problem mentioned is boiling fuel in the carb making me think the biggest problem is UNDER HOOD TEMPS.

NOT generally favoring holes in a hood, I don't care much for Louvers. There, I said it. HOWEVER, in those rare cases of small frontal area as in the early Ford's, Stude's, and Willy's, it may be necessary to Louver the hood to provide sufficient air flow through the ENTIRE AREA of the engine bay to provide sufficient cooling.

This has been proved time and again on the Flats. You may be experiencing something like this on the street with this combination.

PROVE IT BEFORE CUTTING THE HOOD. Somehow, manage to lift and prop the hood, even an inch. Use a couple of sticks and half a roll of duct tape, something. And run it, see if it makes a difference.

I certainly hope this works!

[MadBill]

A word of warning re raising the back of the hood: depending on windshield angle and hood contours, it's very possible, probable even, that the region (especially near the center) is in a high pressure zone* and opening up a gap will further pressurize the engine compartment and reduce radiator airflow. *Think about cowl induction.

I have tested a number of cars with bits of yarn taped at the gap and have almost always found them to be drawn into the underhood area. It's a very simple verification test once the hood is propped up.

[CharlieB53]

May we review what radiators have been tried?

I was just reading the section on Cooling at Stewart Components, tech tip #5 on radiators
http://stewartcomponents.com/index.php? ... tion_id=13

Double pass radiators require 16x more pressure to flow the same volume of coolant through them, as compared to a single pass radiator. Triple pass radiators require 64x more pressure to maintain the same volume. Automotive water pumps are a centrifugal design, not positive displacement, so with a double pass radiator, the pressure is doubled and flow is reduced by approximately 33%. Modern radiator designs, using wide/thin cross sections tubes, seldom benefit from multiple pass configurations. The decrease in flow caused by multiple passes offsets any benefits of a high-flow water pump.

A tall narrow nosed vehicle may be a very difficult design, needing very high pump pressure to provide cooling flow for multiple pass radiator cores.

[cjperformance]

What brand and part number cooling fan?
What cooling system pressure?
Im not a fan of just a restrictor in place of a thermostat and definetly not a fan of any of the aftermarket multi pass radiators, i have removed many and cured overheating problems with nothing more than swapping to a conventional radiator. Summer ambient temps here are commonly in the upper 30's and also into the low 40's (degC) so we need good cooling systems.
Also can we have a pic of the fan mounted on the radiator.? Even if the fan is up to task the shrouding/mounting can be make or break in a cooling system.
Cheers