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So, I've had great input regarding the 351C in my 1973 Cougar XR-7 convertible. It's come a long way. No more overheating (wrong thermostat was in there from last "mechanic" to work on it), had points system removed and replaced with electronic system and had new Edelbrock thunder series 650cfm carb put on, yet I still struggled with hot starts. Engine started beautifully when cold, but it still was terrible when starting warm (mind you the temp was still just over the "C"). The engine would turn over and over and just rumble to a start rather than starting cool. This is with a new high torque mini starter, new battery, and alternator...meaning the engine is turning over at full speed. So, I decided to try a carb spacer. I ordered a square bore 0.5" spacer made by Edelbrock from Summitt Racing and put that between the Holley single plane intake and the carb. The gaskets are all in place and I am 99.9% sure there are no vacuum leaks. That brings us to today...things are better with the carb spacer, but still far from perfect. What I am wondering is if there are adjustments needed with the carb? There is a fuel filter that stays choc full of fuel, so I don't think it is a vapor lock issue with the fuel line. Could it be an issue of the carb "flooding" when the vehicle is shut off? If you turn the car off when it is warm, then immediately turn the key, it fires right back up, but let it sit for ten or fifteen minutes, it is difficult to start. I am planning to go back to the shop that installed the carb - they have a good reputation - but I wish I had some idea as to what could be going on. The only other symptom present is that the car hesitates sometimes when you floor it. Push the pedal hard and it will hesitate...any input would be greatly appreciated. I want to believe that it is something simple! Thanks, Tyson
 

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That sounds like fuel is leaking from the carb. and into the manifold, remove the air cleaner and watch for gas vapor coming out, that is a sign of leaking somewhere, I have a holley that did the same thing untill I changed it , and no more hard start.
 

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Did you have to change the whole carb? This carb is brand new - not that new parts can't have problems. So what you're saying (I apologize, but I am something of a novice and am learning) is that after I've run the car for a while I should turn it off, remove the air cleaner, and look for gas vapors? Thanks again for the input. Tyson
 

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Did you have to change the whole carb? This carb is brand new - not that new parts can't have problems. So what you're saying (I apologize, but I am something of a novice and am learning) is that after I've run the car for a while I should turn it off, remove the air cleaner, and look for gas vapors? Thanks again for the input. Tyson
You are correct, After trying everything I know(which is right much about Holleys) the only cure was a different carb. I don't know much about Edelbrock but you have a over flow of fuel problem. I sent a new carb back to holley two times and it never got fixed.
Edit, One thing you might try is lowering the floats a little.
 

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So, I've had great input regarding the 351C in my 1973 Cougar XR-7 convertible. It's come a long way. No more overheating (wrong thermostat was in there from last "mechanic" to work on it), had points system removed and replaced with electronic system and had new Edelbrock thunder series 650cfm carb put on, yet I still struggled with hot starts. Engine started beautifully when cold, but it still was terrible when starting warm (mind you the temp was still just over the "C"). The engine would turn over and over and just rumble to a start rather than starting cool. This is with a new high torque mini starter, new battery, and alternator...meaning the engine is turning over at full speed. So, I decided to try a carb spacer. I ordered a square bore 0.5" spacer made by Edelbrock from Summitt Racing and put that between the Holley single plane intake and the carb. The gaskets are all in place and I am 99.9% sure there are no vacuum leaks. That brings us to today...things are better with the carb spacer, but still far from perfect. What I am wondering is if there are adjustments needed with the carb? There is a fuel filter that stays choc full of fuel, so I don't think it is a vapor lock issue with the fuel line. Could it be an issue of the carb "flooding" when the vehicle is shut off? If you turn the car off when it is warm, then immediately turn the key, it fires right back up, but let it sit for ten or fifteen minutes, it is difficult to start. I am planning to go back to the shop that installed the carb - they have a good reputation - but I wish I had some idea as to what could be going on. The only other symptom present is that the car hesitates sometimes when you floor it. Push the pedal hard and it will hesitate...any input would be greatly appreciated. I want to believe that it is something simple! Thanks, Tyson
tyson You not the shop needs to adjust the carburator. i bought a new holley carburator a few years ago and i had a similar problem. what i learnt was the mechanic i was using could not possible adjust the carburator correctly because holley carburators are trial and error adjustment type of carburators. you cant just expect to buy it new let the mechanic put it on and then start driving it everyday. that wont work with holley it will work with edlebroch. so what i did when i had that problem was i studied the dvd disk that came with my carburator. it tought me everything. How to adjust power valve, how to adjust floats , how to set floats and so on i basically tought myself how to adjust the thing and now mine is set it has been working fine with no problems for the last four years. i made adjustments, drove it some came back and made more adjustments and so on till i got it right you need to do the same thing....hope this helps
 

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Have you replaced the gas cap recently? Is it a California car the the emssion crap in the tank?
 

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What are you using for fuel? Today's oxygenated fuels boil at a very low temp. I have pulled carbs off hot engines and I found the fuel boiling when the air horn was removed. Keep in mind the carb was in my hands and was not to hot to hold. If you are using oxygenated fuel try a tank of non oxygenated fuel if available and see if it helps. Also does your cat have a three line fuel pump aka has a return line? If not the residual fuel pressure in the fuel line will exaggerate the problem by refilling the carb as the fuel boils off. If none of this applies to you it could be a defective carb or float level problem.

Bill
 

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Discussion Starter #8
Hello...as always I really appreciate the info. It isn't a California car, and I haven't changed the gas cap recently. I think from what I've heard above it is certainly an overflow of fuel problem of some kind. I am going to see about insulating the fuel line to minimize the impact of warm or hot fuel, but I think the culprit here is the carb. I don't want to spark tremendous debate, but I began reading a little more about carburetors, specifically Edelbrock vs Holley, and it sounds like this is more common with Edelbrock because of the smaller fuel bowls. It sounds like the Holley is more finicky and needs more tuning over time whereas the Edelbrock could be a little more set it and forget it, but if this is a problem that I'm going to have to deal with forever with Edelbrock, I'm switching!
 

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I've never had a problem starting my car under any conditions. Happy Edelbrock carb owner.
 

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So what electronic ignition system did you put in? Pertronix? Or did you go different dizzy and new box set up? Be sure that you have full voltage to the pertronix if that's what you have. then I'd start looking at timing, then look for vac leaks, then start looking at carb. It sounds to me like you haven't had something right from the begining, and have not nailed it down yet. To keep swapping things is counter productive. If the carb is new and around 650 CFM then it's probably sized about right - it may or may not need some tweaking, but likely is not your starting problem.....the hessitation thing could be carb or timing/advance. Note a few things: if it's vacuum advance - then be sure you are hooked up to a ported vacuum port on the carb (IE not constant vac), that will ensure it's not advancing when you are trying to start. Then set you intial timing (with advance unplugged and capped off) as long as there are no vacuum leaks you should be able to easily start it at this point. If not - keep digging until it will consitantly start. Once you clear that hurdle, start working on how well it runs......
(just for giggles you can pull a plug and see if it's "wet" when you have this trouble - could indicate whether you are flooding too)
 
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