blocking off the heat risers?

37fordtruckguy

37fordtruckguy

Member
while working on my truck with my grandfather he was telling me that since I have a aluminum intake manifold I don't need the heat risers because it transfers heat better than cast iron. I know that they were meant for preventing the carbs from iceing over in a cold climate, but it barely get below the 40's even during winter. My question is what are the drawbacks and advantages? Other than it being more raspy sounding from what I heard.
 
I dunno about the sound,I tried them blocked off in the 33 and went down the street ,came back and took them out,it sounded terrible.
lawrie
 
I had a 49 Mercury. blocked off the heat risers, didn't see any difference with performance, the engine would pop back when let up on gas and gave it very nice sound.
 
>>>My question is what are the drawbacks and advantages?>>>

Try it. You might like it. I use thin shimstock so, depending on the season, I can slip 'em in or out by loosening/re-tightening the bolts a bit rather than taking the manifold off. To do this, you gotta grease the gasket pretty good so it doesn't stick to the manifold or block.

Jack E/NJ
 
For general street driving the engine needs the heat risers to be open.. Blocking the heat risers in a EV8 engine is a racing modification and/or a modification to make the exhaust have more rap, noise.
 
Its mainly for street use. What makes me want to do it was that the fact that the base of the carbs are hot enough to burn me when I try adjusting the idle mixture screws.
 
Yeah, that seems pretty hot. You could try different thickness heat-dissipating or -insulating spacers if you don't wanna mess with blocking the risers off.

Jack E/NJ
 
Don't forget that the wheat penny needs to be the same year as the motor for good luck...this was what my dad used to do on his 36 while in high school..used to say it sounded cool too
Randy
 
I've got a big box of those wheat pennies if you need a pair the same year as your car.
They were my grandfathers collection that I inherited. Love to see them go to a good purpose.
 
If your carb is getting that hot, you may want to try a phenolic spacer made for that purpose. I think Speedway have them.
 
Iv got some bad news with the flathead now. since I decided to block off the heat risers i though it would be a good idea to do the valve lash and other inspections. I found a nice long crack in my number 2 cylinder on the intake, also i have a tad amount of oil sitting in each of my intake ports is that normal?
 
>>>I found a nice long crack in my number 2 cylinder on the intake, also i have a tad amount of oil sitting in each of my intake ports is that normal? >>>

Other than the crack, do you see any evidence that the #2 cylinder is running any differently than the other seven cylinders, eg appearance of spark plugs, combustion chambers, compression check, coolant leak, etc. As for the tad amount of oil in the intake ports, sounds like a bit is leaking around the guides or gasket --- if it's not using a lot of oil, I wouldn't worry about it.

Jack E/NJ
 
I blocked off mine in the 53' Merc and it does change the sound for the better. I like the shims since all you have to do is loosen the bolts and slide them in. If you don't like them just loosen the bolts and slide them out. The big difference is the heat riser temp to the carb. Cold starts it is a little rough until it warms up, but after that no issue what so ever. First temp without the riser blocked off, second temp with the riser blocked off.
 

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I have an alumn. Offy dual intake on my 8BA. It would get hot enough to boil the fuel in the carbs bowl after shutdown, creating a flooding issue when start up, and leaking the fuel out between the gasket and the phenolic spacers. I used the thin metal shim stock to block off the risers. pretty much remedied the problem.
 
When using a shim. Do you put the shim between the gasket and the intake or the gasket and block. What thickness shim stock do you use?
 
Either way --- mine seems to slip in and out and get at easiest on top of the gasket. Can go partly or fully in/out to adjust heat transfer --- and of course sound 8^). Just use the thinnest shim that'll be stiff enough to slip in and out. Mine was 0.010". And use liberal amounts of grease on all 4 surfaces to avoid gasket sticking.

Jack E/NJ
 
Another Barn member told me to use 22 gauge (.025+/-) metal stock and cut out small tabs
1 1/4" X 1 1/2 " then bend a tab at the long end to help with the installation. Loosen the intake manifold bolts, put grease on both sides of the tabs and slide them in under the manifold and on top of the gasket, then retighten the bolts. That way if you don’t like the sound or for any other reason you can just loosen the bolts and slide it out. The only drawback is in the winter the car will run like crap until the block heats up.
 

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When I rebuilt my 42 Merc engine, decided to put 2015 pennies back in. Maybe they'll still be there long after I'm gone - and somebody will get a kick out of seeing them when they pull the manifold. I've sure enjoyed seeing some of the 'Wheat Pennies' that others had put in blocks long before I got them. I consider it a bit of a 'future gift' - kind of like a 'time capsule' in an old building.

2015-07-18 17.26.23 copy.jpg

2015-11-07 18.30.55 copy.jpg
 
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