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Issues with Hot Restarts
https://www.slantsix.org/forum/viewtopic.php?t=61134		 Page 1 of 1
Author:  SpaceFrank [ Sun May 14, 2017 2:03 pm ]
Post subject:  Issues with Hot Restarts
My LeMons-racing Dart doesn't like hot restarts after it's been sitting. It will fire right up when cold, and if you shut if off hot it will fire right up if you try to start it immediately. But if it's hot and has been sitting for more than a couple minutes, you have to crank it forever before it will fire up. This has given us problems when doing fuel and driver stops at LeMons races. It doesn't seem to make much of a difference whether you pump the gas, hold the pedal down, or do nothing.

Since the problem only presents itself after the car's been sitting for a bit, I can't help but think it's related to heat soak. We've got a 350 cfm Holley 2300 on an aluminum 2-bbl intake with an aluminum adapter plate and a 0.5" thick phenolic spacer. We have performed the "fuel line mod" over the valve cover. The carb is tuned a little on the rich side, but I think the problem existed even before we went up a few jet sizes.

We're currently running Dutra duals, with no wrap or anything on the pipes. The problem existed even with a stock manifold, but it's possible it's gotten a little worse since adding the Dutra exhaust. We use a giant aftermarket aluminum radiator and a plastic 6-blade mechanical fan from Autozone with no shroud. We intentionally have the back of the hood adjusted so it sits a little high, in an attempt to help pull air out of the engine compartment, but I'm not sure if it helps.

The engine runs very cool even under race conditions. I think we normally run a colder than stock thermostat which keeps us around 180 on the track. It'll creep up to 200 if you come off the track and sit idling or drive around slowly. It would not surprise me at all if the under-hood temps get very high when the car sits still after racing.

Any thoughts? The problem may be getting worse as the engine gets more worn out and loses compression, but I just did a leakdown test and she's still looking pretty healthy, all things considered.
Author:  DusterIdiot [ Sun May 14, 2017 3:42 pm ]
Post subject:  Choke?
Did you eliminate the choke or set it to full 'LEAN' during race time?

Did you pull the the heat flap in your rear modified dutra (or do you have dual duals?)

Does the leading edge under the hood have a rubber gasket or air dam?
Quote:
plastic 6-blade mechanical fan
You should upgrade to electric, or find a stock late model 5 blade clutch fan.
Author:  sandy in BC [ Sun May 14, 2017 3:44 pm ]
Post subject: 
I had similar symptoms with the Desoto in Mexico.

On the Costa Grande the ambient heat and endless grades had the entire car amazingly hot. The engine temp was fine (giant rad).

If I parked the car for 10 mins the engine temp would rise to a worrisome level. Everything seems like its about to explode. Getting fuel worried me enough to get everyone out of the car while we were at the pumps. We had to park the car in the shade for 20 mins with doors open and hood up before resuming our journey.

The car is EFI so it started fine. I'm sure the return fuel system helps.

My suggestion would be an electric water pump and electric fan setup to drive off heat while you fuel and change.

If you have a electric fuel pump with return line leave the pump running.

For sure open the hood and doors while you pit.
Author:  my5thmopar [ Sun May 14, 2017 4:32 pm ]
Post subject: 
You're describing the exact issue I had with my 72 Dart. I'll throw out a test for you. Try this the next time you're testing. Hold the accelerator just enough to open the throttle blades. Just push real slow so you don't pump a bunch of fuel down the throat. While holding try to start. If it starts, I won't be any help to fix it. I discovered the issue and wasn't able to resolve it. I just ended up pushing the accelerator to avoid hot start.
Author:  SpaceFrank [ Sun May 14, 2017 4:53 pm ]
Post subject: 
The Holley's choke has been removed. The heat riser flap in the modified rear manifold is still there, and it appears to work fine, but now that you mention it I've never checked to make sure it opens fully when hot. I've got the car warming up to check this right now. I know the flap in our previous manifold turned freely and snapped shut when cold, but I also can't say for sure if it opened properly when hot.

We don't have any kind of rubber gasket or air dam under the front edge of the hood. In fact, we could probably add more gasket material around the radiator, now that I look at it again. There's a bit a of gap on one side that could let incoming air come around the rad rather than through it... but I'm not sure if that matters for this issue.

Sandy, those are all good suggestions, but unfortunately they're of limited utility for us. Per LeMons safety rules, the kill switch has to be off during fueling, so no electric pumps or fans can be on. Granted, we could turn the power back on while we're belting in the new driver, so that might help some if we had an electric fan or pumps.
Author:  SpaceFrank [ Sun May 14, 2017 4:59 pm ]
Post subject: 
Okay, the car's been idling out front for about 10 minutes now, and I can report that while the heat riser valve does open up some, it doesn't open all the way. It just kinda dangles halfway between fully open and fully closed. If you hit the throttle, the increased force of the exhaust flow does force it open more, but still nowhere near fully open. I'm guessing I need to replace the spring.

Another thing I'm noticing is how many exhaust leaks we've got. I think we've finally got the manifold surface sealing well with the Dutras on a Victor Reinz gasket, but both flange gaskets are leaking along with the heat riser "hot box" gasket. I'm sure that's contributing to high engine bay temps as well. The stamped steel hot box gasket is hammered garbage as we all know, and I've never had luck with the stock flange gaskets either; sooner or later they always blow out. I may have to shell out for the Remflex gaskets in these locations.
Author:  DusterIdiot [ Sun May 14, 2017 5:11 pm ]
Post subject:  Yep...
Quote:
Another thing I'm noticing is how many exhaust leaks we've got. I think we've finally got the manifold surface sealing well with the Dutras on a Victor Reinz gasket, but both flange gaskets are leaking along with the heat riser "hot box" gasket. I'm sure that's contributing to high engine bay temps as well. The stamped steel hot box gasket is hammered garbage as we all know, and I've never had luck with the stock flange gaskets either; sooner or later they always blow out. I may have to shell out for the Remflex gaskets in these locations.
Getting this sealed will help greatly.
Quote:
I'm guessing I need to replace the spring.
If you are racing it, and not using it to get to work daily... you may as well wire it open and leave it...
Author:  DadTruck [ Sun May 14, 2017 6:04 pm ]
Post subject: 
Quote:
Remflex gaskets in these locations.
Frank, I have a new remflex heat box gasket that I will never used,

PM me a ship to address and I will get it going your way no charge,,

consider it my contribution to a slant six LeMons effort.
Author:  SpaceFrank [ Mon May 15, 2017 12:09 pm ]
Post subject: 
Thanks, DadTruck! I just sent you a PM.
Author:  SlantSteve [ Mon May 15, 2017 1:36 pm ]
Post subject:  Re: Issues with Hot Restarts
Quote:
We're currently running Dutra duals, with no wrap or anything on the pipes. The problem existed even with a stock manifold, but it's possible it's gotten a little worse since adding the Dutra exhaust. We use a giant aftermarket aluminum radiator and a plastic 6-blade mechanical fan from Autozone with no shroud. We intentionally have the back of the hood adjusted so it sits a little high, in an attempt to help pull air out of the engine compartment, but I'm not sure if it helps.
Personally I'd get rid of the hot box completely if your only racing. A set of headers would help reduce heat soak to the intake and carb,yet still provide plenty of heat for atomisation. Alternatively wire the flap full open as a minimum and grind off all the underside of the intake where all those little stalactites hang down into the hot box to reduce surface area to reduce heating.
That big plastic fan must cost you some power,plus raising the hood at the rear?? That was like an old 80's thing......problem is it's one of the highest pressure areas of the car and you actually reduce air flow by doing it,the air enters through the raised rear area and reduces the pressure differential between the engine bay and the front of the car,hence reducing airflow.
I'd drop the hood down to where it should be,ditch the plastic fan, for safety and for power and fit an electric fan,even turned off it will increase airflow by reducing restriction under racing conditions and then run it when parked to ventilate the engine bay.
If your keeping the present headers,at least wrap the pipes if not the cast iron headers to reduce heat too. Cold air induction might also help,maybe use the cowl air to feed the intake? im not sure of the rules in your category,but beware of excess lengths of rubber fuel hose,aka fuel line mod, some scrutineers over here will frown on anything rubber over 6" long if it's not braided AN hose,just keep an eye on it over the exhaust area for any deterioration with the extreme heat from racing,maybe even use a braided hose and fire sleeve or a teflon to be safer...or just run an electric pump with safety switch and keep the hoses right away from danger areas?
Author:  BamaFan95 [ Mon May 15, 2017 2:02 pm ]
Post subject: 
My '85 Dodge Ram Slant Six does this too. I do the same thing my5thmopar said, holding the throttle partially open. It runs like crap for a few seconds once it starts and then eventually smoothes out. Never have been able to figure it out.
Author:  DadTruck [ Tue May 16, 2017 2:21 pm ]
Post subject: 
Quote:
new remflex heat box gasket
went in the mail today :D
Author:  rich006 [ Tue May 16, 2017 3:48 pm ]
Post subject: 
Image

From the sun visor on my 1974 Dart. I don't know how relevant it is to the original post, but apparently it was well known to Chrysler that the throttle should be partly open for hot restart on a stock 1974 slant.
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