underhood heat

[oldbee]

If I remember right ur 9* stamp on the mechanical is 18* on the engine,so now you need to either set initial at +_ 18 to get to 36* total w/o vac adv. I'm also wondering if the cam is degreed in correctly? Sounds like a bunch of minor errors bunching up.

 

[Yatzee]

I could use some schoolin' on fine tuning my RB.
I built this motor in the spring and did the cam break-in afew months ago and it now has approx 500-700 miles on it (speedometer/odometer is closer to kilometers when I checked against a gps). First oil change last week to dino 10w40 with a zinc additive. No surprises thankfully!
A few days ago on Saturday, I attended a Fall cruise with the local mopar group, which included some beauties (I'll post some pics of these if you wish). Well the temperature was over 90F and I thought I was in for some trouble! I almost cancelled but gave it a shot. Turns out I was the only one of the group that was affected by the scorching heat. Yeah, I know 90F is nothing like you south western guys are living with, but it is nasty for up here!

Car is/was running fine and the temperature gauge generally sits in the middle and drifts upward until the stat opens and it usually falls back to the middle. This has been consistent since I started driving it in August. I do not have aftermarket gauges yet, but seems normal for it with the 180 stat.
Driving along the open roads was fine as the outside temperatures started to rise. As we pulled into the first town, some light traffic slowed things down for a few minutes and the temperature started to rise on the gauge a bit, but nothing alarming. The engine however, was now stumbling a bit and eventually stalled in the parking lot for our first stop. Started easily to park though.
We left but the car had not cooled enough and I noticed it stumbling as I waited in line at the stop sign. It hesitated as I turned but got moving. The temperature gauge showed slightly higher than normal but was dropping as I drove at about 50 mph. First stop sign, waited about 30 seconds for my turn and stalled. Started but was sputtering a bit. I continued to drive for a bit until I slowed to stop at the side of the road where it stalled. It would start if I floored it, but would sputter when I put it into gear. It even started to diesel when I turned it off. Temperature gauge was a bit higher than normal, so I figured I had heat soak going on and vapour lock?
I managed to get it into the shade to let it cool, even though it did not boil-over or overheat. Once it cooled and started up again, one of the mechanics with us, adjusted the idle screws a bit which seemed to help the rest of the journey.

Yesterday, I ran the motor in the shop (which was about 85F) and the heat that was coming off of the rad/fan was incredible. Even with the hood open, I could not touch any metal parts on the engine like the coil or chrome covers, etc., without getting burnt. Even my chrome timing light became so hot that I had to wrap it with a rag. The temperature gauge was again slightly higher than normal and was not overheating. I assume the rad is doing its job to cool the motor, but I'm wondering if the engine is just running too hot.
I have a few questions:

How does the timing affect the engine temperature?

Could exhaust manifolds be too restrictive for certain cam designs and cause excess engine heat, besides the heat they climb too?

While a shroud should help with temperatures in traffic, can it make any difference with engine compartment temperatures?

Here's the engine specs and some analysis info.

Ah yes, the under hood temps. If you have decent size headers, a good deal of combustion heat ends up out back, if you have cast manifolds it stays up front. Same goes for a small exhaust system with tons of bends. An electric cooling fan with 2500+ cu. ft. per minute will push that amount out under the car even at idle. I mount my spare "cowl induction" hood on the car for the heat of summer and even though it's only a two inch rise the amount of hot air that comes out is amazing. For your info, I run 16 BTDC static and 34 all in and overheating has never been an issue with these timing values.

 

[Glenwood]

If I remember right ur 9* stamp on the mechanical is 18* on the engine,so now you need to either set initial at +_ 18 to get to 36* total w/o vac adv. I'm also wondering if the cam is degreed in correctly? Sounds like a bunch of minor errors bunching up.

So is the 9* x2 counterweights?
The cam was spot on according to the degree wheel when I installed it.

 

[threewood]

I'll clean up the plugs and have another go at the timing. I was thinking I would have to replace the counter weights in it to get the mechanical in range. How do you know if vac advance is needed or not?
.

The counterweights stay the same. To limit the mechanical advance the slots in the 9L plate are shortened up. Right now you have 18° mechanical which may be fine as long as you don't go over 18° initial.

If you are driving it on the street vac advance is needed. You will get better mileage and better overall performance from your motor. You can test is with a vacuum pump and it should be adjustable with a small allen wrench in the vac nipple.

 

[Ron H]

I want to re-read the posts as there's some tips in here I want to check out as I still think my rebuilt motor with slight cam upgrade and bunch of other heady internals and headers is running a bit hotter than I think it should (around 210). I went to a 7-blade fan and a shroud that has helped; brought temp down around 10 degrees. Fan sits 1-inch from rad that's pretty stock. Some say my original rad is still too wimpy for the motor. Yeah lots say a shroud is important to direct air flow at motor otherwise it disburses air all over the place under the hood where you don't need it. Yeah, timing effects temp as does carb mix; lean creates more heat. I reckon you're good with proper functioning rad...no possible clogging, etc. Check your rad temp at top and bottom as it should be some 30 degrees or so cooler at the bottom for functioning rad. You have a hi-per water pump? Assume you have no tranny excess heat issues that otherwise could be contributing to floor heat.

 

[Tim Wenum]

Summit racing sells a universal fan shroud- made by spectre.
3 inch is part number SPE-4348. They also sell a 5 in. It ties through the radiator. both are 20 inches long

 

[mopar 3 B]

5/16 fuel line? Try some 3/8 and lean the secondaries if needed. What you are doing is equivalent to using a plugged fuel filter. It going to run hot untill its completely broke in. Find some hiway and go somewhere. Like a couple of hours.
Also never mentioned anything about the aircleaner. The carb maybe set fine. Lack of air will make it run rich and hot.

 

[miller]

I believe Ron H is making some real good points.

My 2 cents...
I've always figured a motor with 500-600 miles on it, is broke in. All it's going to be.

Was going to comment on your fuel line routing, but you beat me to it. I will say, think you'd be better off using 5/16" steel tubing, though. Route it about like you have it, but with a air gap, a little off the motor itself.
I made all of my fuel lines, using 5/16" brake line stock, and my little tubing bender.

It's been mentioned, both fuel mixture, and timing, can make heat, if not set right. Oh, yeah, those plugs are big time rich!! I had an issue like that once...wound up being the lousy plug wires I had. It would be worth, hooking a plug up loose, to ground, to see if your getting a good spark. But, I'd sure get that carb mixture corrected, either way.

Cam, aka valve timing, should have a little valve overlap, on the exhaust stroke. It simply allows a little fuel into the chamber, before the exhaust stroke is finished, cooling as it does. Just trying to say, the correct mixture, and timing work together, and have a big effect on the temps the motor is going to run at.

Assuming you have a spring in the lower radiator hose. Right?
Two things, on the radiator, that might be worth trying. Need to make sure it's getting good flow. Kill two birds with one stone. I'd see how the motor acts, with NO thermostat. With it out, and radiator cap off, fire it off, just idling, and look at the flow through the radiator. Should be a steady flow going across, but no real fast. Coolant needs enough 'time' in the radiator, to actually get cooled.

 

[Glenwood]

The counterweights stay the same. To limit the mechanical advance the slots in the 9L plate are shortened up. Right now you have 18° mechanical which may be fine as long as you don't go over 18° initial.

If you are driving it on the street vac advance is needed. You will get better mileage and better overall performance from your motor. You can test is with a vacuum pump and it should be adjustable with a small allen wrench in the vac nipple.

To test with a vacuum pump, I assume this is done while running to see what it advances to at increments of vacuum pressure? I've been reading up on vacuum advance last night and think I understand it a bit better now, although I'm not sure if it should be on the ported or manifold outlet of the carb. I read that ported vacuum for vacuum advance is not helpful for idling when the mixture is leaner, because of low vacuum with non-stock cams. My vacuum is at 15, so it probably doesn't matter in my set up. Is there any issue with the vacuum advance on full time manifold vacuum? This would put the idling timing upwards of 20-30* btc.

 

[Glenwood]

I want to re-read the posts as there's some tips in here I want to check out as I still think my rebuilt motor with slight cam upgrade and bunch of other heady internals and headers is running a bit hotter than I think it should (around 210). I went to a 7-blade fan and a shroud that has helped; brought temp down around 10 degrees. Fan sits 1-inch from rad that's pretty stock. Some say my original rad is still too wimpy for the motor. Yeah lots say a shroud is important to direct air flow at motor otherwise it disburses air all over the place under the hood where you don't need it. Yeah, timing effects temp as does carb mix; lean creates more heat. I reckon you're good with proper functioning rad...no possible clogging, etc. Check your rad temp at top and bottom as it should be some 30 degrees or so cooler at the bottom for functioning rad. You have a hi-per water pump? Assume you have no tranny excess heat issues that otherwise could be contributing to floor heat.

I was fascinated by the tiniest rad I've ever seen on a lumpy 340 Duster that was with us. It looked like a stock 18", two-core without a shroud and a flex-lite fan that was a few inches from the rad. I know small blocks are supposed to run cooler, but I was surprised he had no issues on a hot day like it was.
Like I said, the the motor wasn't really overheating, but I image the heat being thrown off the rad under the hood was over the edge for the edelbrock while idling. I'm hoping that there will be less heat being thrown off of the rad when I have the timing and carb set up properly. Perhaps a shroud will help to direct that hot air under the motor better.
I've not had issues with the tranny other than some leaking from the cables and speedo oring. I will invest in a trans cooler in the future however. Good point about the tranny causing more heat at the floor though. Could very well be contributing, although the tc is only about 2400 and hopefully not too high for stop and go traffic on a hot day.

 

[moparnation74]

I believe Ron H is making some real good points.

My 2 cents...
I've always figured a motor with 500-600 miles on it, is broke in. All it's going to be.

Was going to comment on your fuel line routing, but you beat me to it. I will say, think you'd be better off using 5/16" steel tubing, though. Route it about like you have it, but with a air gap, a little off the motor itself.
I made all of my fuel lines, using 5/16" brake line stock, and my little tubing bender.

It's been mentioned, both fuel mixture, and timing, can make heat, if not set right. Oh, yeah, those plugs are big time rich!! I had an issue like that once...wound up being the lousy plug wires I had. It would be worth, hooking a plug up loose, to ground, to see if your getting a good spark. But, I'd sure get that carb mixture corrected, either way.

Cam, aka valve timing, should have a little valve overlap, on the exhaust stroke. It simply allows a little fuel into the chamber, before the exhaust stroke is finished, cooling as it does. Just trying to say, the correct mixture, and timing work together, and have a big effect on the temps the motor is going to run at.

Assuming you have a spring in the lower radiator hose. Right?
Two things, on the radiator, that might be worth trying. Need to make sure it's getting good flow. Kill two birds with one stone. I'd see how the motor acts, with NO thermostat. With it out, and radiator cap off, fire it off, just idling, and look at the flow through the radiator. Should be a steady flow going across, but no real fast. Coolant needs enough 'time' in the radiator, to actually get cooled.

All great points.....

The last MP unit I had I pitched that and installed the firecore RTR system....A better distributor with more functionality provide 2 important tools...
1. Hotter spark
2. Lots of adjust ability

The 2 problems areas in his set up is the carb and timing.......Also, adding to the fact the crappy fuels we have and the hotter burn point....

Those areas need to be straightened out first before addressing the coolant situation....

 

[Glenwood]

Summit racing sells a universal fan shroud- made by spectre.
3 inch is part number SPE-4348. They also sell a 5 in. It ties through the radiator. both are 20 inches long

Thanks for the tip! I looked at these a while back but wasn't sure how it would help as it doesn't seem to utilize the entire rad surface. I am not a fan (no pun intended) of fastening it through an aluminum rad. I wonder how long the rad will last with the shroud vibrating on it.

 

[Glenwood]

5/16 fuel line? Try some 3/8 and lean the secondaries if needed. What you are doing is equivalent to using a plugged fuel filter. It going to run hot untill its completely broke in. Find some hiway and go somewhere. Like a couple of hours.
Also never mentioned anything about the aircleaner. The carb maybe set fine. Lack of air will make it run rich and hot.

Thanks for the suggestion. I would think that a larger line would be needed if it was starving for fuel when accelerating. I'm not sure I understand how the larger tube size would help against heat soak though. I'm surrounded by highways here, and the trip on Saturday was 160 miles mostly all highway. I'm hoping it is now fully broke in.

good point about the air cleaner. I had a 65 breather on it with a 14"x3" filter, but the bottom is the same dia. as the filter, so it is unsilenced. We were thinking that the hot air is getting trapped inside making matters worse. I switched to the chrome top for fully open to test with. Maybe time to cut the hood and add a MW scoop!

 

[Glenwood]

I believe Ron H is making some real good points.

My 2 cents...
I've always figured a motor with 500-600 miles on it, is broke in. All it's going to be.

Was going to comment on your fuel line routing, but you beat me to it. I will say, think you'd be better off using 5/16" steel tubing, though. Route it about like you have it, but with a air gap, a little off the motor itself.
I made all of my fuel lines, using 5/16" brake line stock, and my little tubing bender.

It's been mentioned, both fuel mixture, and timing, can make heat, if not set right. Oh, yeah, those plugs are big time rich!! I had an issue like that once...wound up being the lousy plug wires I had. It would be worth, hooking a plug up loose, to ground, to see if your getting a good spark. But, I'd sure get that carb mixture corrected, either way.

Cam, aka valve timing, should have a little valve overlap, on the exhaust stroke. It simply allows a little fuel into the chamber, before the exhaust stroke is finished, cooling as it does. Just trying to say, the correct mixture, and timing work together, and have a big effect on the temps the motor is going to run at.

Assuming you have a spring in the lower radiator hose. Right?
Two things, on the radiator, that might be worth trying. Need to make sure it's getting good flow. Kill two birds with one stone. I'd see how the motor acts, with NO thermostat. With it out, and radiator cap off, fire it off, just idling, and look at the flow through the radiator. Should be a steady flow going across, but no real fast. Coolant needs enough 'time' in the radiator, to actually get cooled.

Always good to hear from you Miller! How's that wrist doing?

The fuel line is copper/nickel with a sock on it, as close to the carb as I can get. I tried to keep it of the motor as much as possible. It is a tight squeeze around the distributor!
I'll work on the timing and mixture today, which is supposed to be the last very hot day this week up here. We'll see what testing reveals. Anyone ever try to make a cardboard shroud for testing purposes? Could be a 'cool' experiment or end up shredded all over the shop lol.

Yeah rad hose has a spring and looked to be okay during all this 'fun'. I think flow is okay as the motor did not overheat. It may be heating up too much and the rad is handling it somewhat well, so we'll see what happens with getting things set up properly before I mess with the stat.

 

[miller]

Questions...

Exactly how many turns out, on your mixture screws? Baseline, starting point should be 1 and 1/2 turns.
With only one carb, should be fall over easy. No chances of a vacuum leak?
I prefer using a tach, but that said, what happens when you (gently) turn the mixture screws all the way in? Motor should die.

 

[miller]

Always good to hear from you Miller! How's that wrist doing?

Yup, thanks, and good to hear from you, too! Not worth a flip, on the wrist. I'm a big boy, get by one way or the other. (I'm not easy!)

So, you don't have all that rubber fuel hose, that's in the pics? Or, am I seeing things wrong?

 

[Glenwood]

All great points.....

The last MP unit I had I pitched that and installed the firecore RTR system....A better distributor with more functionality provide 2 important tools...
1. Hotter spark
2. Lots of adjust ability

The 2 problems areas in his set up is the carb and timing.......Also, adding to the fact the crappy fuels we have and the hotter burn point....

Those areas need to be straightened out first before addressing the coolant situation....

Funny you mention the firecore. I don't have one of those, but I've had this distributor and I was thinking about using at some point. I don't know the brand as there aren't any markings, but I bought it and a 440 from a guy who races a bb dart. He was shedding all of his bb parts for a planned modern hemi swap.
I figured I'd get the current system set up properly before I introduce an upgrade, in case there's issues with it. Don't want to start chasing my tail by changing things.

 

[Glenwood]

Questions...

Exactly how many turns out, on your mixture screws? Baseline, starting point should be 1 and 1/2 turns.
With only one carb, should be fall over easy. No chances of a vacuum leak?
I prefer using a tach, but that said, what happens when you (gently) turn the mixture screws all the way in? Motor should die.

They were about 1-1/2 to 1-3/4, but I have to check again and sort of start over when I'm ready to start it up today (after much more coffee!).
Don't think I have a vacuum leak, haven't seen anything yet to make me suspicious. Motor stumbles with one turned in, but haven't tried both. I assume you're thinking that if it doesn't die with both in, there's a vac leak?

 

[Glenwood]

Yup, thanks, and good to hear from you, too! Not worth a flip, on the wrist. I'm a big boy, get by one way or the other. (I'm not easy!)

So, you don't have all that rubber fuel hose, that's in the pics? Or, am I seeing things wrong?

its a silicon sheathed insulated sock. the only rubber is for the filter and inlet to the pump.

 

[miller]

Motor stumbles with one turned in, but haven't tried both.

Just one at a time...seems it's good.
I'd start with the mixture screws at 1 1/2 turns. Even that could be too rich. Motor wants what it wants. But, it's a whole package deal...timing, fuel, air...all working together.

Using a tach, peak RPM, in the middle of the range. RPMs will fall, too rich, or too lean. Then, simply 'match' the two screws exactly. But, must be done with the carb in it's idle circuit! Just means, if idle speed goes too high, re-set it, and start all over again.