4 valve Rajo and an OF.
Forum rules
If you need help logging in, or have question about how something works, use the Support forum located here Support Forum
Complete set of Forum Rules Forum Rules
If you need help logging in, or have question about how something works, use the Support forum located here Support Forum
Complete set of Forum Rules Forum Rules
-
Topic author - Posts: 5256
- Joined: Sun Jan 06, 2019 7:21 pm
- First Name: Allan
- Last Name: Bennett
- * REQUIRED* Type and Year of Model Ts owned: 1912 van, 1917 shooting brake, 1929 roadster buckboard, 1924 tourer, 1925 barn find buckboard, 1925 D &F wide body roadster, 1927LHD Tudor sedan.
- Location: Gawler, Australia
4 valve Rajo and an OF.
A friend has a speedster fitted with a pair of swayback NH Holley carburetors. In rebuilding the exhaust system, he is looking to simplify the setup. The car has a 4 valve Rajo head, but the camshaft is unknown. Nor has he any knowledge of the pistons used without pulling plugs and having a look. I have a good OF Stromberg carburetor on the shelf, and it would be a simple matter to make a new inlet manifold to suit it for his application.
The questions are;
Will an OF be sufficent to give optimal road performance for a 4 valve Rajo equipped car?
Will it out perform the current NH's, which are rigged such that the second carburetor only comes on line under heavy throttle?
Allan from own under.
The questions are;
Will an OF be sufficent to give optimal road performance for a 4 valve Rajo equipped car?
Will it out perform the current NH's, which are rigged such that the second carburetor only comes on line under heavy throttle?
Allan from own under.
-
- Posts: 1057
- Joined: Thu Feb 21, 2019 1:20 pm
- First Name: Joe
- Last Name: Bell
- * REQUIRED* Type and Year of Model Ts owned: 24 Fordor
- Location: Tiffin Ohio
- MTFCI Number: 24066
Re: 4 valve Rajo and an OF.
Not enough air and fuel, it will run it but restricted on air flow for the size valves in the head. I have the twin NH's on mine and do like the way it performs, you need an equilizer tube between the two carbs to make it work right. Just my thoughts!
-
- Posts: 979
- Joined: Mon Jan 07, 2019 5:42 pm
- First Name: Stan
- Last Name: Howe
- * REQUIRED* Type and Year of Model Ts owned: 2
- Location: Helena, MT
- MTFCA Number: 19133
- Board Member Since: 1999
Re: 4 valve Rajo and an OF.
IMHO, the OF is not carb enough for the setup. You would be far better off with an MB-1 Stromberg, a 4 series Zenith or a couple other sidedrafts. OS-1 Stromberg's are good and depending on the RAJO model, some people run OS-2 Strombergs or HP5A Zeniths on them. If you are stemwinding you don't want either one of those, they can be hard to start. They also can be difficult to get to idle well with that big a carb. HP5A's with a venturi reducer will work but there are HP4A's or HP4U's that are great for those, they will start well, idle well, and will make use of about everything a 4 valve RAJO will do.
-
- Posts: 327
- Joined: Fri Jan 04, 2019 10:18 pm
- First Name: Harry
- Last Name: Lillo
- * REQUIRED* Type and Year of Model Ts owned: Speedsters, racers, depot hack, coupe
- Location: Calgary
- MTFCA Number: 13996
Re: 4 valve Rajo and an OF.
I realize the initial question related to the flow capability of the OF carb with a 4 valve RAJO.
I have run OF, Winfield as well as NH singles on a hot flathead engine. In my opinion as single OF will not flow enough to keep the 4 valve happy.
I am just finishing up a 4 valve RAJO engine and have some similar questions.
The engine has a 290 cam, 1 :1 rockers, log manifold and DU4 spark.
My choice is a pair of Windfields.
I am also interested in knowing how the progressive linkage worked on the present setup.
A good friend had a nice twin carb log manifold on an overhead. He started out running a single rear carb until he finished rebuilding the second carb. The engine ran way too warm and he could not resolve his heating problem until he got the second carb on. The front two cylinders were running way too lean and 3 and 4 too rich.
I have considered progressive linkage to run on one carb until I need more jam, but am reluctant to do so because of this experience. Any experiences from others on this?
Harry
I have run OF, Winfield as well as NH singles on a hot flathead engine. In my opinion as single OF will not flow enough to keep the 4 valve happy.
I am just finishing up a 4 valve RAJO engine and have some similar questions.
The engine has a 290 cam, 1 :1 rockers, log manifold and DU4 spark.
My choice is a pair of Windfields.
I am also interested in knowing how the progressive linkage worked on the present setup.
A good friend had a nice twin carb log manifold on an overhead. He started out running a single rear carb until he finished rebuilding the second carb. The engine ran way too warm and he could not resolve his heating problem until he got the second carb on. The front two cylinders were running way too lean and 3 and 4 too rich.
I have considered progressive linkage to run on one carb until I need more jam, but am reluctant to do so because of this experience. Any experiences from others on this?
Harry
-
Topic author - Posts: 5256
- Joined: Sun Jan 06, 2019 7:21 pm
- First Name: Allan
- Last Name: Bennett
- * REQUIRED* Type and Year of Model Ts owned: 1912 van, 1917 shooting brake, 1929 roadster buckboard, 1924 tourer, 1925 barn find buckboard, 1925 D &F wide body roadster, 1927LHD Tudor sedan.
- Location: Gawler, Australia
Re: 4 valve Rajo and an OF.
I suspected the OF might be just a bit lacking on a 4 valve Rajo, but had to ask. What about a pair of OF's? Thank you for your list of alternatives Stan. I'll have to list them in my little black swap meet book and keep my eyes open.
The owner had a new set of headers made to tidy up what was on the car when he purchased it. When these were fitted, the car ran like crap, lacking power and response. On checking, I found that the throttle linkage on the first carb was fouling on the header and he was only getting 2/3 throttle!
Now he wants to tidy up the whole thing. The current intake manifold has the NH's in line with the two ports on a tube manifold which places them almost down on the frame rail. This car still runs on gravity feed. However, the runners to the carbs are around 8" long. Those runners, and the balance tube are 1.25", with the balance tube almost up at head port height, but the runners necked down at the carb end.
He wants to drop the rear tank down to near the original height, and is prepared to run a fuel pump, so we were looking at making a new intake manifold and eliminating some of the length of the runners, reducing the size of the balance tube and lifting the carb/s at the same time. Looking for guidance here.
I was surprised to read that the pair of NH's would do the job. The progressive linkage set-up is interesting. Until around 2/3 throttle, only the front carb is working. The path to the rear two cylinders is quite tortuous, but apparently it works. With loads of throttle the second carb comes in. There is a rod with an adjustabe stop connected between the two carbs. As the first carb is asked for more, the rod slides and the stop engages to open the plate on the second carb. I have not seen/heard the car running to see just how much the second carb contributes. If it works well, a good tidy-up of the linkage mechanism may be all that is needed.
Allan from down under.
The owner had a new set of headers made to tidy up what was on the car when he purchased it. When these were fitted, the car ran like crap, lacking power and response. On checking, I found that the throttle linkage on the first carb was fouling on the header and he was only getting 2/3 throttle!
Now he wants to tidy up the whole thing. The current intake manifold has the NH's in line with the two ports on a tube manifold which places them almost down on the frame rail. This car still runs on gravity feed. However, the runners to the carbs are around 8" long. Those runners, and the balance tube are 1.25", with the balance tube almost up at head port height, but the runners necked down at the carb end.
He wants to drop the rear tank down to near the original height, and is prepared to run a fuel pump, so we were looking at making a new intake manifold and eliminating some of the length of the runners, reducing the size of the balance tube and lifting the carb/s at the same time. Looking for guidance here.
I was surprised to read that the pair of NH's would do the job. The progressive linkage set-up is interesting. Until around 2/3 throttle, only the front carb is working. The path to the rear two cylinders is quite tortuous, but apparently it works. With loads of throttle the second carb comes in. There is a rod with an adjustabe stop connected between the two carbs. As the first carb is asked for more, the rod slides and the stop engages to open the plate on the second carb. I have not seen/heard the car running to see just how much the second carb contributes. If it works well, a good tidy-up of the linkage mechanism may be all that is needed.
Allan from down under.
-
- Posts: 663
- Joined: Fri Jan 04, 2019 11:15 am
- First Name: Tony
- Last Name: Bowker
- * REQUIRED* Type and Year of Model Ts owned: 1914 touring
- Location: La Mesa, CA
- MTFCA Number: 32
- MTFCA Life Member: YES
- Board Member Since: 2005
Re: 4 valve Rajo and an OF.
I have an OF on the speedster and on the 14 touring and I think they the very best carb for the T.
However I have close friend with a four valve rajo and we have tried number of carbs with varying degrees of success. All were trial and error and it’s been a fun ride over the last 5-6 years. However I can state categorically that the OF at 1 1/8” is too small for the full performance you can get with the four valve Rajo. Right now the rajo has a Stromberg M1 at 1 1/4” and the owner thinks it’s both the best looking and best performance carburetor he has tried.
So there in a nutshell is five years of playing with different carbs, we may be wrong, we may be last but it’s been great fun getting here.
However I have close friend with a four valve rajo and we have tried number of carbs with varying degrees of success. All were trial and error and it’s been a fun ride over the last 5-6 years. However I can state categorically that the OF at 1 1/8” is too small for the full performance you can get with the four valve Rajo. Right now the rajo has a Stromberg M1 at 1 1/4” and the owner thinks it’s both the best looking and best performance carburetor he has tried.
So there in a nutshell is five years of playing with different carbs, we may be wrong, we may be last but it’s been great fun getting here.
Tony Bowker
La Mesa, California
1914 Touring, 1915 Speedster, 1924 Coupe.
La Mesa, California
1914 Touring, 1915 Speedster, 1924 Coupe.
-
- Posts: 209
- Joined: Sat Jan 05, 2019 9:24 pm
- First Name: Warwick
- Last Name: Landy
- * REQUIRED* Type and Year of Model Ts owned: 1916 LHD USA Touring 1916 RHD Canadian Touring 1916 Pickup
- Location: Trarlagon Victoria Australia
Re: 4 valve Rajo and an OF.
Allan, My Rajo 4 Valve came with from what I can remember was a fairly big SU carb. It had a very simple inlet manifold and used pretty simple throttle controls off the standard rhd control shaft. It serviced the big inlet valves well. SU's are readily avaialable. Search 4 valve Rajo on the forum. there was good coverage fairly recently of a chap with a 4 valve Rajo that initially had twin NH carbs then swapped for 2 bigger accessory carbs. Thing ran very quick when sorted. http://www.mtfca.com/discus/messages/59 ... 1462740130
-
Topic author - Posts: 5256
- Joined: Sun Jan 06, 2019 7:21 pm
- First Name: Allan
- Last Name: Bennett
- * REQUIRED* Type and Year of Model Ts owned: 1912 van, 1917 shooting brake, 1929 roadster buckboard, 1924 tourer, 1925 barn find buckboard, 1925 D &F wide body roadster, 1927LHD Tudor sedan.
- Location: Gawler, Australia
Re: 4 valve Rajo and an OF.
Warwick, can you recall if the SU mounted with 2 or 4 studs? 2 studs = 1 1/2". 4 studs = 1 3/4" or 2". A single carb is much easier to work with!
Allan from down under.
Allan from down under.