Aaron R.

I did a lot of research on my hot start problem by using search and browsing old threads. I got some good advice there, but I still have a problem.
1985 305, 1200 miles on complete rebuild. Brand new Edelbrock 1406 and Performer intake put on with engine rebuild. Runs good. New Summit HEI. 12 degrees initial timing advance. Electric fuel pump regulated to about 6 psi. 180* high flow thermostat. Clutch driven fan. Everything on the engine is new.

When the car has warmed up (180+) and I shut it down it floods within 5-10 minutes. To restart it I have to floor the gas and crank it for about 5-7 seconds. It always restarts, but it's annoying that it won't start right up and the cloud of blue smoke is abnoxious.
Usually if I shut the engine down for only a couple minutes (like to fuel up) and restart it fires right up no problem. I don't even have to touch the gas pedal. Same when it is cold. Fires right up. But if I let it sit hot I have to floor and crank it.

I wrapped the fuel lines in insulation; no change. Blocked off the intake heat risers at the heads; little or no change. Added a 1/2" wood spacer under the carb. That helped some, but not enough. It keeps the carb only about 5* cooler than the intake manifold.

The car runs fairly normal temps. The guage is pretty accurate and I have verified it with a new infrared handheld temp gauge. When I run down the road on an 85* day the engine runs around 180*. If in town with traffic temps climb 200-210. When I shut the engine off, the engine temps slowly rise about 20 degrees. I have verified this with the guage and infrared. Currently I have no underhood insulation. Not sure if that would help absorb some of that heat, but I know the engine and the carb both get about 20* hotter from heat soaking in after I shut off the car.

Sorry for the long winded explanation. Any help would be appreciated, especially if you have had this problem with your 1406 before and managed to fix it!

camaronewbie

12 degrees initial might be too high. 6psi on carb might be too much as well - I'd try getting the fuel pressure down to 5 or under, and readjust carb settings on timing of about 8 or 10 at most. My 350 carbed is set at 10 timing, and I'm wondering if it's a little too high. My fuel pressure is set to about 5psi (same carb as you).

Are you using a return-style regulator? Is it the in-tank fuel pump? If you paid under $50 for it, it's not a return-style, and I've always read that a return style reg must be used with the in-tank fuel pump - so may be a fuel issue.

Aaron R.

I have experimented with 8, 10, and now 12 degrees initial advance. All seem to behave about the same.
I had the pressure down around 5 and experienced some slight surging issues at mid throttle, so I bumped it up to about 6. It made no difference in the way it starts but the surging seems to be minimized.
The pump I am using is externally mounted back by the fuel tank. The regulator is a Holley with no return.

camaronewbie

I'm certainly no expert - those were just my thoughts. I the end, every engine is different and each like it's own timing and fuel pressure settings.

I have issues with mine, but not starting - when mine gets above 200, it wants to bog down instead of accellerate. Maybe my issue is a similar problem as yours, but I haven't tracked it down to any particular problem yet, other than my engine just doesn't like to get hotter than 200. Today I installed a 160 stat hoping that would cool it down a bit - but I noticed it stil climbed to 200 at a long light. Next I'll try a better than stock fan - think the stocker only pulls 1250 cfm, and for $130 I can get one that pulls double that.

Then, a dyno tune is in order, because mine just seems to be very hot and that could be timing, tuning, or any number of issues - and after 2 years of fooling with it, I'm obviously no good at tuning it myself

Aaron R.

Thanks for the suggestions.
I wish I was an expert. I probably would have this issue fixed by now.

pancherj

I am not too familiar with the Edelbrock carb. I had one years and years ago. However, fuel shouldn't be pushing into the engine after it is off. Most of the aftermarket regulators drop the pressure to zero rather quickly. Factory ones are a different story. I would look for float too high or just an internal leak in the carb. Also, fuel boiling could be an issue (sounds like you were already addressing that).

As for initial timing advance...12-16* is good for a typical small block. The more you retard initial (8* or worse), the HOTTER the engine will run. Over advancing would do the same thing, but it would have to be WAY too advanced. Also, make sure you have the air dam below the radiator. Our cars are bottom feeders, they get the majority of the air for the radiator from street level. If you don't have that plastic air dam, the airflow will seriously be reduced.

Aaron R.

I do have the air dam in place.
I think it is a boiling fuel issue. But I am running out of ways to cool the fuel. The other day it was about 85* outside and when I got home I checked the temps. As soon as I shut it down the carb was about 140*. 10 minutes later it had risen to 160* from heat soak. I don't know if that is enough to "boil" the fuel, but things are going to get really hot when it is 95-100* around here.

pancherj

That seems pretty hot to me. Along with the spacer, you can make a heat shield under the carb out of some aluminum or steel sheet metal. I have also seen guys make shields that go between the valve covers and the inner fenders. This is to keep the radiant heat from the headers down below the intake level.

Aaron R.

I think most of the heat is soak from the engine, not radiant exhaust heat. I have stock cast exhaust manifolds with the thin heat shields on them. The carb has to be absorbing most of its heat from the intake. The intake and wood spacer stay about 5* warmer than the carb at all times, telling me the heat is soaking up through the intake to the carb. It seems more like transferred heat, not so much radiant heat. Frustrating, because like I said the engine runs about the right temps. I'm about to the point of drilling holes in my thermostat and cooling everything WAY down. I have done that on other vehicles before, but then I have to deal with the hassle of swapping out t-stats every time the weather changes.
If I can't fix this right I think I will eventually just go to a fuel injection system. No wonder manufacturers got away from carbs. Stupid things are finicky.

five7kid

iTrader: (14)

These cars were known to have hot issues. That's why they came out with the vapor lock kits.

Why do you have an Edelbrock carb on it? What distributor are you using?

ASE doc

I have issues with Edelbrock carbs anyway but that aside, its interesting to note that it starts right up when cold. I assume it has an electric choke. The choke setting may be good for a hot start and when you fire it right back up after shut down the choke hasnt had time to cool so its not an issue. But after sitting a few minutes the choke cools down even though the engine is still warm. Thus it way overfuels the motor on start up. If this is the case, Youll need to back the choke off some. It will make cold starts a little more work but hot starts will be more normal. Hope this helps.

83T/A

I just put a new Edlebrock 1406 on mine too.I am having the exact same issues.Cranks fine when it is cold and even if I shut it off for just a minute.If it sits very long I have to hold the pedal to the floor.Car is running a manual fuel pump due to an engine swap.Thought it might have something to do with this and that maybe there were some lines or return lines in the wrong place.It is very frustrating.Seems the hotter it gets outside the worse it is.It even tries to die sitting at a red light.Where does one get one of these vapor lock kits?

Auggie

OK, lets do a little mech. fuel pump 101. The fuel pump is run off of the camshaft which runs at 1/2 the speed of the engine. When you stop at a light the needle and seat in the carb closes therefore fuel stops flowing. Because the fuel pump arm is operated by the camshaft it still moves up and down (slot in diaphram shaft) but the diaphram stops moving. When the diaphrem stops moving so does the fuel which is now being heat soaked and turns from a liquid to a vapor. This is knowen as vapor lock and is the reason that you need a return line even on elect. fuel pump applacations. When the engine is at idle even though the needle and seat have closed fuel will still flow through the fuel pump return line (smaller ID line) keeping the pump cooler. High performance fuel pumps have stiffer return spring for higher RPM. I use the stock L69 pump. The return line also helps when the hot engine is shut off and the heat starts soaking into the carb building pressure that will be bled off through the fuel pump return line. There is a bulltin out for a small elect. fan that is used to cool the carb and I did see someware that there is a alum. plate that is placed under the carb to bleed off the carb heat.

Auggie

ASE doc

Good description of mech fuel pump function.

For those who have spent money on new mechanical, returnless pumps, there is an inline filter available at most any parts store that has a 3rd port for vapor return. The vehicle's existing retrurn line can be used for the vapor return to tank. This is an inexpensive alternative to installing a three port pump.

naf

iTrader: (7)

With ASE on this one. First check that the choke is not closing when you go to hot restart. If it's closed, manually open it before cranking to see if the problem goes away.

The OP had the LG4 which would have come with the mechanical pump WITH return line, although these were still susceptible to vapor lock, vapor lock 'shouldn't' be the issue here-unless the fuel is boiling out of the carb and not in the lines. The needle/seat should isolate the carb from anything that's happening downstream. Why swap to an electric pump? Was it an attempt to cure this issue?

Rule out the choke before going any further.

Auggie

Yes the N&S will isolete the fuel in the carb float bowl unless the fuel hot soaks in the float bowl (reason for the fan) and turns into a vapor which would allow the N&S to open.
If there is no return line the residual fuel pressure in the fuel line would then shoot fuel into the float bowl area and possiably flood the engine. Just a guess??

Auggie

five7kid

iTrader: (14)

The fan has a thermal electric switch in the return heater hose at the water pump to turn the fan off when the engine temp goes down. The power to the fan only comes on when the ignition is off. So, in stop & go traffic, the fan won't do you any good.

Also, "vapor lock" is the vaporization of the fuel in the pump supply line. Since liquid will boil at a lower temp when the pressure is lower, the mechanical pump trying to suck on hot fuel in the supply line lowers the pressure on the liquid, turning it to vapor. The pump can't pump vapor, and the carb can't run the engine on vapor.

While I've got the floor, note that a mechanical pump does not "pump" when the cam lobe moves the lever. The lever depresses the spring, and the spring "pumps" the fuel out the outlet. The outlet has a relief valve (indicated in the illustration above but not annotated, nor is the relief valve spring shown) that controls the output pressure, and if the outlet pressure is above the relief valve cracking pressure, the spring won't depress the diaphragm.

Auggie

Yup, and years ago you could buy high performance fuel pump springs for rebuildable fuel pumps. I am not sure if they are still avaiable??

Auggie

naf

iTrader: (7)

Under normal conditions the Needle/Seat should still close once the float rises with incoming fuel. The pressure in the line can, however, get high enough to force the needle off the seat regardless of float position. This is unlikely in most cases because the fuel tank has a pressure relief valve that should release pressure in the fuel system prior to this happening. Failure of the pressure relief valve CAN cause this but can easily be ruled out by leaving the gas cap loose on shut down and prior to a hot re-start. A crimped return line could possibly cause a similar problem, though I'm speculating here as I haven't seen an instance of that.

Keep in mind that hard hot re-starts can still be a problem even though fuel, air and spark are present. Too much fuel, too little air or weak spark can make it difficult to start. Rule out the simple stuff first.

InfernalVortex

iTrader: (4)

I had that problem for a month after I got my car together. I was using a kind of rubber (Push-loc I think it was called?) line that apparently didnt insulate heat very well. It touched the top of the waterneck and valve cover, or got very close.


This caused me problems:


I then changed it to this:


Problem went away, I thought it looked ugly so now it looks like this:



Different brands of gas boil at diff temperatures, try another brand.

Also, feel the fuel bowls with your hands. If they burn to the touch tehy're way too hot.

Since I have my fuel pump on a switch, I could just run the car off of the fuel in the bowls for a minute before I turned the pump on. What would happen to me is I could crank the car up fine, and it wouldnt flood out and die until I hit the fuel pump switch and it pumped the new boiling fuel into it. It would then start spewing fuel straight out the bowl vents as the floats suck in the boiling fuel. Would strand me for 20 minutes and a time and was not safe at all. But it did help me narrow down that the fuel was boiling in the fuel lines, not in the carburetor itself.

ASE doc

Holley and Edelbrock both still make a rebuildable mechanical pump. I just saw them in JEGs catalog the other day. There were other brands also, in fact JEGs even markets one by their own brand name, its probably a reboxed Holley.

zcam96

What raidiator hose are you using. I recently switched to carb and am haveing a hard time finding a good upper hose.

mh82camaro

hey bud...i have done similar things...same intake , same carb, 160 t-stat, wrapped fuel lines, carb spacer, edelbrock carb heat absorber, i have a stock mech fuel pump with return line, same problem...i tried everything i knew how to do...but yeah same issue...when this motor gets hot and sits or very very at drag strip etc...it wants to stall going down road. but when cold...fine...same as you...what did you ever figure out ....i am curious?
thanks

mh82camaro

aaron r

scooter500

iTrader: (1)

I was able to solve my heat problems by installing a small pusher fan somewhat above the center of the center of radiator and behind stock wire bracing. Also connected a separate fuse, relay and an adjustable switch to allow the fan to independently turn on/off according to setting on switch. The small pusher fan kicks in when I'm stuck in traffic and keeps the engine from soaking up too much heat. Fan stays on maybe 10 minutes after the engine is off until the car is at a reasonable temp. 6, 8... 10 amps max so not much of a concern as far as the battery is concerned. The original single 16" fan is still there and works but the pusher fan was what made the difference for keeping my car reasonably cool while driving in traffic and also immediately after parking it on on a hot day.

There was a primary metering jetting change to the original ccc carb made about 1/2 way through 1986 to prevent hot soak conditions like you're describing (Delco part 17082634). Maybe there is something similar for your 1406 carb?

mh82camaro

if you don't mind me asking what kind of fan did you use and the switch...never heard of a switch like what you are using...i like the idea...i thought of doing this but wasn't sure if it would work...glad to see it does... by the way i don't have a stock carb ....1406 edelbrock and i don't have a electric fan on it right now only the visious fan...thanks for the help though

scooter500

iTrader: (1)

It's been a while but IIRC I used an 8" Zirgo ZFB8 - Zirgo Ultra High Performance Electric pusher fan and know I used adjustable Zirgo switch. From an old post it was a "Zirgo ZFSWA" $24.95 fan control switch (180* - 240*), a new $6 30 amp relay, a $3 20 amp fuse holder w/ wires, $3 of black & $3 of red 16 gauge wire, some $3 14-16 connectors, & then use electric solder to connect it. This was the kind of fan switch that had a copper probe that is put in/under the radiator hose w/ some blue sealant to get a tight seal. Anyway, I put the switch in a case from Radio Shack to allow mounting near radiator.

mh82camaro

yeah this is has been a problem for me in this car forever....i was just wondering and see if anyone else has had this problem...i have upgraded ignition system..due to i hear heat is a issue, i have heat wrap on the fuel lines going from trans area ..and next to headers, i bought the heat spacer to put below the edelbrock 1406, it does have a vicious fan (no fan clutch) flex a lite fan, 10degree of initial timing, 160 thermostat,stock fuel pump with return line. my ideas were installing a additional fan pusher fan?, rerouting fuel line from pump to carb? wrang more of the fuel line in heat insulation sleves? just trying to see if anyone else has some ideas,
what it is doing is when it is hot like everyone else...i have to hold down the gas pedal to get it to start..throttle it a little bit then it will start and run...when it gets really hot it wants to stall at the stop signs...etc...or when you slow down to make a turn...it cuts out...stall...so then you have to once again hold the pedal to the floor keep cranking it...then it fires....it gets so agravating...so any and all ideas will be appriciated...i am considering the fan idea?

scooter500

iTrader: (1)

mh82camaro,
besides adding a small pusher fan what about a better water pump?. I tried a Robert Shaw 3-hole thermostat but went back to a regular one after installing a a stage 1 pump by Stewart and my cars been gtg. Apparently the Robert Shaw 3-hole thermostat is a must for the stage 2 or higher water pump.

mh82camaro

thats what i am talking about scooter...thanks...just trying to see what all you guys ahve done...to see all my options or what could be the best repair to solve this problem...i was thinking about adding on of those carb heat shield kits from mr.gasket...any of you guys use them..do they work..do they help..thanks

chas0218

You could always try running a lower thermostat. I have a 165* in my 383 and my temps stay right at 180* or around 165* on cold mornings. When I shut her down the temp rises to 200* but as soon as I turn the car on and get some of that cooler anitfreeze thru her it drops extremely fast.

I am also running an aftermarket autometer gauge so I know its a lot more accurate than my stock gauge. The stock gauge reads a needle width above 100* when my autometer reads 180*.

I never had any hot start problems after my 165* thermostat and re-routing my fuel lines. Make sure your fuel line is routed away from the exhaust and engine where possible.

IROC315

iTrader: (9)

Interesting thread. I am having the same issues on a 1990 truck I converted to carb. The 1406 was cheap so I used it over a quadrajet. I used some rubber line coming from the mech pump I used. I lifted the bed and put in a carb pick up in place of the stock pump. I am going to try some of the things I've picked up in this thread. I also have a ford taurus fan I am planning to put in to replace the stock manual fan. I'll definitely keep these in mind when I get started on my Iroc soon.