Tune up


IHC in the early to mid-fifties.

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Golden Jubilee
Golden Jubilee

Posts: 539

Joined: Mon Sep 07, 2015 11:14 am

Post Sun Jun 30, 2019 5:13 pm

Re: Tune up

Motor SD240
Dwell 31 @ 750rpm

Valves @ .025 hot
Timed @ 7deg btdc
If you want to hear it run go to my FB page Molcsan Electric.

Now a question you, where do you hookup to take your vac reading
I pull 17c at idle my elevation is 125 feet, seems low but runs just fine va works great..
As I understand it, there are two points for Vacuum "Ported" ahead of throttle where I believe'
the VA is connected , and "Manifold" I connect my gauge at the Manifold same connection
where the vacuum wipers are connected - < is this understanding and hookup correct?

What motor dose yours have ?
Last edited by Harvey on Sun Jun 30, 2019 6:11 pm, edited 1 time in total.

Golden Jubilee
Golden Jubilee

Posts: 4439

Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Sun Jun 30, 2019 6:07 pm

Re: Tune up

There are three vacuums, Manifold which is what it states, and two types of ported vacuum. one is a ported (timed) below the venturi near the throttle plate, when the plate is closed little or no vacuum is at the port, and once the throttle plate passes the port, vacuum is at the port. the third is venturi vacuum, and the port extends to just after the narrow neck of the venturi. this port the vacuum is low and builds with throttle opening and reaches its maximum at high speed- full throttle.
Venturi vacuum can be used to advance the spark as speed and load builds. it also is used to open an EGR valve.
Often the ported (timed) vacuum is used to rapidly advance the timing off idle to prevent a "off idle bog" when the engine is transitioning from the idle to main metering circuits in the carb
Venturi vacuum is more often used for heavily loaded engines that need to run at a broad speed range.
Timed port is more often used on lighter duty engines that are run lean on part throttle to aid in fuel economy.
Many heavy gasoline engine do not run any vacuum advance with the spark curve being based solely on engine RPM. These engines do not lean out the mixture on part throttle opening and sacrafice economy for durabilty. Both the RD/RED and the BD/BLD engines are an example of this.

Golden Jubilee
Golden Jubilee

Posts: 770

Joined: Wed Sep 05, 2018 1:50 pm

Location: Northern New Mexico

Post Sun Jul 21, 2019 2:07 pm

Re: Tune up

Harvey wrote:Motor SD240
Dwell 31 @ 750rpm

Valves @ .025 hot
Timed @ 7deg btdc
If you want to hear it run go to my FB page Molcsan Electric.

Now a question you, where do you hookup to take your vac reading
I pull 17c at idle my elevation is 125 feet, seems low but runs just fine va works great..
As I understand it, there are two points for Vacuum "Ported" ahead of throttle where I believe'
the VA is connected , and "Manifold" I connect my gauge at the Manifold same connection
where the vacuum wipers are connected - < is this understanding and hookup correct?

Whats motor dose yours have ?



On the side of my intake manifold there is a 1/2'' pipe plug. I drilled and tapped the plug and then made a nipple for it so I can hook up my vacuum gauge. When not in use I cap it off.

My truck had an SD240 in it but it was worn out so I currently am using an SD220 in its place. I am using the manifolds off the 240 on my 220 as well as the Holley 1904 carburetor. It all seems to be working well and I'm not lacking for power
56 S120 4x4,

Golden Jubilee
Golden Jubilee

Posts: 8137

Joined: Thu Dec 27, 2012 12:45 pm

Location: Canada's left Coast

Post Sun Jul 21, 2019 7:06 pm

Re: Tune up

I remember my R120 as being adequate powered. Here on the West Coast of BC, much of the real-estate stands on end. The steep grades became a challenge, it could not win, for the SD220. My first iteration was an IHC V8 engine swap. The 304 was a simple bolt in and everything matched up. The V8 powered a IHC/Chrysler 727 three speed automatic. Suddenly the "R" was alive. The brakes became the next minor challenge.
There is something about Old IHC 6 and V8 engines, they sound so good exhausting through a Flowmaster muffler.
I am not a dual exhaust kind on guy, so the 304 had a 4 inch exhaust and the SD220 had a three inch.
I would rather have tools I do not need than to need tools I do not have
“Never argue with stupid people, they will drag you down to their level and then beat you with experience.
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