mopardude318
Well-Known Member
I thought I would try out the 725 Road Demon on my hot street 318. My brother had one brand new in the box sitting on the shelf, so why not try it out and see if I like it. This is the one:
http://www.summitracing.com/parts/dem-4402020ve/overview/
What I had on there before was a single feed Holley 650 spread bore with a 1 inch square bore adapter:
Throttle response and fuel mileage seemed to be pretty good with this carb. Overall I was very happy with it. However, I developed a vacuum leak which seemed to be a carb base gasket leak. While I had it off, why not try the Demon.
Knowing the reputation that Demon carbs have with metal shavings in a brand new carb, we decided to take it apart for a rebuild, and deburr and clean all the castings.
Upon removal of the fuel bowls, first thing we see, metal shavings imbedded in the gaskets!
Look at all the crap on these gaskets!
Here is everything cleaned, deburred, all holes chamfered, threads tapped, rough edges filed, etc etc. I tell you what, we found ALOT of metal shavings everywhere. In the metering blocks, fuel bowls, main body etc.
Now that it's all back together, for the install I needed carb studs, a new dual feed fuel log, float bowl/metering block gaskets and a gauge!
Here it is installed, I had to shorten my existing fuel line 2 inches where it comes from the pump, and put a 90 on the filter, and make up that short run to the fuel log using XRP -6 hose and fittings.
I had to shorten the throttle cable and of course adjust the kickdown again.
It is definitely more low profile than the other carb with the adapter plate.
The engine seems to run even better and is also very responsive. I only drove it around for one day for a few hours as we just completed the swap.
One thing I did notice after installing the fuel PSI gauge was my fuel pressure! My mechanical pump has been putting out nearly 11 PSI at idle and would settle to 9.5. Most likely too high, as I recon this would force fuel past the needle and seat. I may try a different fuel pump or use a regulator.
The pump I have is a Carter Strip Super Mechanical pump, which is most likely more than I need, or too much.
http://www.summitracing.com/parts/crt-m6270/overview/make/dodge
Anyways....I'm open to any thoughts, comments or suggestions you may have.
http://www.summitracing.com/parts/dem-4402020ve/overview/
What I had on there before was a single feed Holley 650 spread bore with a 1 inch square bore adapter:
Throttle response and fuel mileage seemed to be pretty good with this carb. Overall I was very happy with it. However, I developed a vacuum leak which seemed to be a carb base gasket leak. While I had it off, why not try the Demon.
Knowing the reputation that Demon carbs have with metal shavings in a brand new carb, we decided to take it apart for a rebuild, and deburr and clean all the castings.
Upon removal of the fuel bowls, first thing we see, metal shavings imbedded in the gaskets!
Look at all the crap on these gaskets!
Here is everything cleaned, deburred, all holes chamfered, threads tapped, rough edges filed, etc etc. I tell you what, we found ALOT of metal shavings everywhere. In the metering blocks, fuel bowls, main body etc.
Now that it's all back together, for the install I needed carb studs, a new dual feed fuel log, float bowl/metering block gaskets and a gauge!
Here it is installed, I had to shorten my existing fuel line 2 inches where it comes from the pump, and put a 90 on the filter, and make up that short run to the fuel log using XRP -6 hose and fittings.
I had to shorten the throttle cable and of course adjust the kickdown again.
It is definitely more low profile than the other carb with the adapter plate.
The engine seems to run even better and is also very responsive. I only drove it around for one day for a few hours as we just completed the swap.
One thing I did notice after installing the fuel PSI gauge was my fuel pressure! My mechanical pump has been putting out nearly 11 PSI at idle and would settle to 9.5. Most likely too high, as I recon this would force fuel past the needle and seat. I may try a different fuel pump or use a regulator.
The pump I have is a Carter Strip Super Mechanical pump, which is most likely more than I need, or too much.
http://www.summitracing.com/parts/crt-m6270/overview/make/dodge
Anyways....I'm open to any thoughts, comments or suggestions you may have.
