Uncle-Pekka Posted February 28, 2016 Report Share Posted February 28, 2016 I've been running my car now many years with a shot heat riser... Manual close open and leaking valve. Now that the manifold is off for winter overhaul I consider removing the riser and putting blind shut off plate in between the exhaust and intake manifold. I run my car only at summer and warm weather. Do I need the heat riser at all? Quote Link to comment Share on other sites More sharing options...
TodFitch Posted February 28, 2016 Report Share Posted February 28, 2016 Depends on your climate/weather and if you let it idle until warmed up before driving. . . I find that on cool (not cold) mornings, especially when the humidity is up, a working heat riser helps on cold start drivability. YMMV. 2 Quote Link to comment Share on other sites More sharing options...
greg g Posted February 29, 2016 Report Share Posted February 29, 2016 I have run mine without a heat riser for years. From temperatures of 10 degrees F and higher. I do let it warm up a bit on those types of days, never had a stumble or carb icing problem. I do have the heater return hose zip tied to my after market dual intake manifold so that might help but only when the heater is in use. I have a sheet of thin stainless steel between the manifolds with a gasket on each side. Quote Link to comment Share on other sites More sharing options...
Uncle-Pekka Posted February 29, 2016 Author Report Share Posted February 29, 2016 (edited) Thanks, What I plan to do is the same as Greg has done. Aim to get rid of the exhaust leaks due to worn out riser mechanism. With a bit of a luck I will up grade to double carb set up with 3+3 headers within an year or so... In that case I also need to run without heated intake, because the twin carb units I'm considering do not support exhaust heating. Edited February 29, 2016 by Uncle-Pekka Quote Link to comment Share on other sites More sharing options...
greg g Posted February 29, 2016 Report Share Posted February 29, 2016 now that I reflect on the procedure, I remember having the flapper welded in the horizontal position, and then having a spot of weld or braze put on the exterior of the pivot to seal that against potential leaks. It has been 12 years so details are getting sketchy. Good luck with your project. What are your plans for sourcing your manifold/headers? 1 Quote Link to comment Share on other sites More sharing options...
Uncle-Pekka Posted February 29, 2016 Author Report Share Posted February 29, 2016 Good luck with your project. What are your plans for sourcing your manifold/headers? Well, I already bought split headers from George Asche (the freight to Finland is lenghty story, incorporated to a car import project, looking fwd to see them in March...) The intake #1 choice would be vintage Edmunds, shared 1st place the new AoK production. However, these are not currently available, thus there is a secret plan B, which will only be published if successfull... The coming summer 2016, I'm mentally prepared to run the original factory setup with the leaks mended. If I get lucky, I just might upgrade "in the middle of the season"... Quote Link to comment Share on other sites More sharing options...
Don Coatney Posted February 29, 2016 Report Share Posted February 29, 2016 Well, I already bought split headers from George Asche (the freight to Finland is lenghty story, incorporated to a car import project, looking fwd to see them in March...) The intake #1 choice would be vintage Edmunds, shared 1st place the new AoK production. However, these are not currently available, thus there is a secret plan B, which will only be published if successfull... The coming summer 2016, I'm mentally prepared to run the original factory setup with the leaks mended. If I get lucky, I just might upgrade "in the middle of the season"... If you bought the George Asche dual setup I believe you will find the heat riser flap welded in place to make a true exhaust split eliminating the heat riser. Quote Link to comment Share on other sites More sharing options...
Uncle-Pekka Posted March 3, 2016 Author Report Share Posted March 3, 2016 ^ @ Don, Well, I bought 3+3 headers (original cut in two parts) from G.Asche, thus for sure there will be no heat riser once I get them installed. The intake, however, is yet an open case. As told I've been looking the new twin carb AoK, but it's not available yet. 1 Quote Link to comment Share on other sites More sharing options...
Don Coatney Posted March 3, 2016 Report Share Posted March 3, 2016 Open intake is fine. No matter how many carburetors you run the manifold is full of enriched fuel air mixture. When an intake valve opens a vacuum or low pressure area is created inside the manifold and the enriched charge will move to the low pressure area as the piston moves downward. No two intake valves are open at the same time. Quote Link to comment Share on other sites More sharing options...
Merle Coggins Posted March 3, 2016 Report Share Posted March 3, 2016 Open intake is fine. No matter how many carburetors you run the manifold is full of enriched fuel air mixture. When an intake valve opens a vacuum or low pressure area is created inside the manifold and the enriched charge will move to the low pressure area as the piston moves downward. No two intake valves are open at the same time. With that logic why would you need a split exhaust? No two exhaust valves are open at any one time either. Quote Link to comment Share on other sites More sharing options...
Don Coatney Posted March 3, 2016 Report Share Posted March 3, 2016 With that logic why would you need a split exhaust? No two exhaust valves are open at any one time either. In my case I wanted dual exhaust due to the unique sound. 1 Quote Link to comment Share on other sites More sharing options...
Plymouthy Adams Posted March 3, 2016 Report Share Posted March 3, 2016 don't forget Don..your increased lift and duration makes this a bit more HUFFIER than the stock block... Quote Link to comment Share on other sites More sharing options...
Don Coatney Posted March 3, 2016 Report Share Posted March 3, 2016 don't forget Don..your increased lift and duration makes this a bit more HUFFIER than the stock block... I believe the split exhaust increases engine "breathing" and power output but I have no documented proof. Seat of the pants estimates was a selling point to the unscrupulous route 66 repair shops that installed a throttle return spring with less tension and told the owner his or her vehicle accelerated much faster with less foot pressure. Documentation is required today. 1 Quote Link to comment Share on other sites More sharing options...
Plymouthy Adams Posted March 3, 2016 Report Share Posted March 3, 2016 there is no need to show documentation when not claiming a stated value in net HP.....to say its a kick in the pants is enough..the weak throttle spring is common to the punk who thinks his new four barrel throws him back when if fact it stumbles greatly then recovers..the loss of the stumble is never factored in by these guys...time slip will show it though.. Quote Link to comment Share on other sites More sharing options...
dpollo Posted March 3, 2016 Report Share Posted March 3, 2016 Now that is a really good question. Short answer..... a split exhaust sounds great. and while that may be a feeble attempt at humor here is another. Sometimes when valves get sticky more than one is open. It surely fouls up performance ! Quote Link to comment Share on other sites More sharing options...
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