Blocking Hear Riser

[topfuel724]

Engine is a 59A in a 1940 Coupe. 276" with Fenton headers, Harman-Collins Cam and Magneto, Ford of Canada aluminum heads, Offy intake with 2-97's by Uncle Max.

I recently had the intake off and decided to block the two heat risers in the block with some steel 3/4 inch freeze plugs. Everything went well and the plugs tapped in firmly just just below the block surface.

The strange thing is that since doing this it seems that the exhaust noise at the tail pipes is much louder than it was before. I wouldn't think that this would be the case but has anyone experienced this before?

[deuce_roadster]

Isn't that the reason that is done, to make the exhaust sound different?

[flathead4rd]

You are correct.

[Merc Cruzer]

Yup, that is one of the effects of blocking the heat risers. I think , tradition has it, you were supposed to use the "year of the car penny" to block them.

[ford38v8]

If you are familiar with the mechanics of a muffler providing Noise Cancelation, that was what was happening with the heat risers before you blocked them. Now, with no crossover to cancel each other, your exhaust has a crisper sound to it. Let the good times roll!

[RalphG]

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Here we make sure to clean out the heat riser passages any time its apart. Helps prevent carb icing and improves cold performance. Straight pipe gives me plenty of good sound.

[Ol' Ron]

I did tha when I was younger 60 years ago. but I don't do that anymoew because I can't find the right pennys.
Gramps

[topfuel724]

Thanks to all for the replies. I knew that blocking the hear risers in the block would allow for a denser charge of the mixture in the intake manifold but did not realize that the exhaust tone would change. Also I did not have any 1940 steel pennies to use.

[Ken/Alabama]

Originally Posted by topfuel724

Thanks to all for the replies. I knew that blocking the hear risers in the block would allow for a denser charge of the mixture in the intake manifold but did not realize that the exhaust tone would change. Also I did not have any 1940 steel pennies to use.

Could be because there were no 40 steel pennies. Use copper.

[5851a]

Originally Posted by Ken/Alabama

Could be because there were no 40 steel pennies. Use copper.

Only 43. OT My Grandfather said that later on the bars downtown hated the steel pennies and would throw them over the back of the old bars to keep them from coming back. Said they looked like nickels after dark.

[Conrad Rossi]

I didn’t know either it would change the sound of the exhaust either. Nor the year of the car penny “requirement". Will start looking for 1946 pennies.

-Conrad

[aussie merc]

brass welch plugs do the job if you dont get snow good idea if you do i wouldnt do it as its use is to heat the inlet manifold [a double edge sword ] helps heaps when baby its cold outside but can cause endless issues when its hot with todays fuels

[ford38v8]

Originally Posted by aussie merc

brass welch plugs do the job if you dont get snow good idea if you do i wouldnt do it as its use is to heat the inlet manifold [a double edge sword ] helps heaps when baby its cold outside but can cause endless issues when its hot with todays fuels

For this reason, the best compromise is to drill a ⅛" hole through each of the two plugs. Copper pennies of the year of manufacture do the job very well, as the metallurgy is compatible as well as the year.

[kiwi nz]

I can remember about 45yrs back a fellow club member had a Ford Pilot with sixpences in the heat risers and straight pipes with no mufflers. On a winding road coming down from the hills you could hear him coming from miles away. Accelerating on the straights and backing off on the down hill.

No other car in existance could ever have that sound.

Geoff Kiwi

[blucar]

During the early to mid 1950's, blocking the hear risers on a flat head Ford was a common event if you wanted two rattle the neighbors windows and have the law after you.
I don't know where the penny thing came from, probably from the same guys that used large washers in lieu of thermostats, or cut every other blade off of the water pump impeller. All of these tricks made the engine run faster due to less drag in the cooling system... Ya sure.
In my world we cut a strip of shim stock, .030/040, about 3/4" wide, loosened the intake and slid the shim material between the block and the gasket at the heat riser, tightened the bolts up and let the good times roll. Then when we had all the fun we could and every beat cop in town was looking for us we would stop the car, get out the roll of steel wool, a couple of sixteen penny nails, stuff the pipes with steel wool slid the nail into the pre-drilled hole in the tail pipe and went our merry way to the local stroll or drive-in burger joint. Oh The Good Ole Days, Almost Brings Tears To My Eyes.
After we had our fun for the night we would pull the nails out of the pipes and head home, within a few mile the steel wool would burn out. Next morning a few minutes work would have the shims stock out and the manifold snugged down... Everything was quiet on the western front. Time to go to school...

[pistonbroke]

I had to block off the risers in my 46 Cadillac flathead and now I seem to own a hotrod instead of a cruiser. the pipes are a lot cracklier. All the kids want me to rap them off. As said above, If you don't like it a balance tube is a option. Tim

[Merc Cruzer]

Like blucar described in his post, I used the strips of metal to block off my heat rises on both sides.

[petehoovie]

Originally Posted by Merc Cruzer

Like blucar described in his post, I used the strips of metal to block off my heat rises on both sides.

[Gene1949]

And then there are guys like myself who could care less about period correct pennies or a "cool factor". We block off the majority of the passage to cut down on the heat soak on the carburetor while sustaining the cold startup drivability.
Luckily, I grew up with guys that weren't concerned with "being cool" and focused on actually improving horsepower and drivability.

[Merc Cruzer]

Originally Posted by Gene1949

And then there are guys like myself who could care less about period correct pennies or a "cool factor". We block off the majority of the passage to cut down on the heat soak on the carburetor while sustaining the cold startup drivability.
Luckily, I grew up with guys that weren't concerned with "being cool" and focused on actually improving horsepower and drivability.

Gene1949,

The exact reason I blocked mine off was too cut off the heat going to the carburetor, I did the metal tabs with the edge bent up, rather than the penny's, so I could install and remove them with needle nose pliers, after just loosening the bolts. Just in case I didn't like it. 13 years later and they are still in. Here is the before and after blocking off the heat riser, at the same location.