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Custom duals vs tube headers
https://slantsix.org/forum/viewtopic.php?t=64312		 Page 1 of 1
Author:  slantsix64 [ Sat Dec 14, 2019 4:24 pm ]
Post subject:  Custom duals vs tube headers
Hey guys so I have already some split exhaust manifolds that I had cut and welded, pretty much like dougs duals he made, the heat riser was welded shut but make contact under my aluminum offy intake, the slant runs really well good decent mileage constant 22mpg all around city and highway, I came across some Clifford shortie headers for dirt cheap, wanted to give them a try I know they do not provide heat but I'm going to add a flange on the bottom of my intake to take make it water cooled.



My question is how much H.P would I gain over the split stock logs vs the shortie headers, also mpg will it remain the same if I add the water cooled flange under my intake, thanks for taking time to read, oh here's a picture of what I have now, and the car is a 64 dart 225 with 833 3.55 gears 9to1 edelbrock Avs 500 Howard's 473 lift camshaft, also have a head I ported and installed bigger valves laying in my room.
Author:  Reed [ Sat Dec 14, 2019 6:49 pm ]
Post subject:  Re: Custom duals vs tube headers
Quote:
[H]ow much H.P would I gain over the split stock logs vs the shortie headers
Not much that you would notice on the street.
Quote:
, also mpg will it remain the same if I add the water cooled flange under my intake
You will likely encouter cold driveability and it will take longer for the intake to heat up. I would expect you to lose a few MPGs.

Headers are OK for a race car, but generally a bad idea on a street car. So is welding the exhaust flap shut.
Author:  Dart270 [ Sun Dec 15, 2019 3:45 am ]
Post subject:  Re: Custom duals vs tube headers
The headers will get you more HP over about 4000-4500 RPM. The warm up period will be a bit longer, but if you use a water warming jacket under the carb the difference should be pretty small. If you take a lot of short trips, MPG will probably suffer. MPG warmed up on the hwy will probably be a bit better, but hard to say.

Lou
Author:  slantsix64 [ Sun Dec 15, 2019 9:22 pm ]
Post subject:  Re: Custom duals vs tube headers
Quote:
Quote:
[H]ow much H.P would I gain over the split stock logs vs the shortie headers
Not much that you would notice on the street.
Quote:
, also mpg will it remain the same if I add the water cooled flange under my intake
You will likely encouter cold driveability and it will take longer for the intake to heat up. I would expect you to lose a few MPGs.

Headers are OK for a race car, but generally a bad idea on a street car. So is welding the exhaust flap shut.
Thanks for the reply, Reed, to add more detail im in SO California, also i forgot that yes the exhaust manifold is welded flat shut and not touching the bottom on the intake there is about 1/4 inch gap, this helped alot with heat soak in the summer with my offy four barrel, in the winter car starts up fine with the manual choke warms up almost the same as before now with the extra pipe i created a little more heat which is a plus cause my car always ran cooler than the thermostat rating when i did the swap to the duals mileage stayed the same if not gained a little more mpg than the stock exhaust system.
Author:  slantsix64 [ Sun Dec 15, 2019 9:37 pm ]
Post subject:  Re: Custom duals vs tube headers
Quote:
The headers will get you more HP over about 4000-4500 RPM. The warm up period will be a bit longer, but if you use a water warming jacket under the carb the difference should be pretty small. If you take a lot of short trips, MPG will probably suffer. MPG warmed up on the hwy will probably be a bit better, but hard to say.

Lou
Lou thanks for the reply!, yes as i stated before to Reed, i actually have no direct contacted with my heat riser that is welded shut flat there is a 1/4 gap before it hits the bottom, im running the offy aluminum intake so if i add a hot spot under the intake with the water coming from the cooling system it should help, just would take a bit longer to warm up, and would probably be better than my current exhaust set up. Im going to give it a try honestly, i picked up the headers for 60 bucks if i dont like it ill put my old system back on.. Plus i like how cool the slants look with those tube headers!!!!
Author:  Dart270 [ Mon Dec 16, 2019 5:21 am ]
Post subject:  Re: Custom duals vs tube headers
Sounds great. I ran Clifford shorties for many years in SoCal on a 64 Dart Slant. No issues...

Lou
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