Intake risers
- Thread starter firerod
- Start date
In the true sense of the word a longer runner is generally considered better. It is thought that the longer runner has more time to straighten out the intake charge prior to entering the combustion chamber. In all out racing it seems to be better and all of the manifolds that I have built or modified were "long runner" what ever that means! I built two 4" spacers for my flattie. Didn't have any data on the short runners. I liked the look and it put my Stromberg (s) above the generator!
Talkwrench
Well-known member
Any advantage for a singe carb ?
Pete
BANNED
Possibly, if you make the runner long enough. To see any benefit at low rpm the runner needs to be quite long. However, with one carb on a multi cylinder engine you probably won't notice anything.
Intake runner tuning is usually only beneficial on engines with individual cylinder runners. The same holds for exhaust tuning. The "boost" rpm range is also very narrow.
The runners in the attached pic were 15 inches long and were designed for
5200 rpm. The carb was a 650 Holley. The engine was a Ford model B with welded intake ports.
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rick r
Senior Member
There was an extensive article on flatty intakes in Street Rodder mag a few months ago. They dyno tested several flatty manifolds. You might be able to find the article , check out www.streetrodderweb.com
This. I can't recommend JWL's book enough. For a dummy like me, it took me a few times through for it to really sink in, but it is a great resource.
His data takes the fiction out of the internet "facts" that have been floating around.
If I recall, JWL's book stated that a Super-style 2X2 with risers worked best for overall performance. Don't quote me. I'll go back and look to confirm.
Does anyone have an electronic link to this or could they tell me what issue it was in? I'd like to read it.
louisb
Senior Member
That is my plan. Offy super with 3" risers. SoCal Sacramento sells the ones with the dual holes.
--louis
Sounds good. I think you don't want the ones that are the open plenum riser-type. Meaning it is just an open hole vs. two holes simular to those in the take and carb venturi.
This is also an area to check when installing these to ensure they are aligned and, if not, you'll need to port match them. I would assume a mismatch or a ledge created by a misalignment would negate some of the benefits of having risers.
OLD...BILL
Well-known member
CLEARANCE of what
Generator. I'm pretty sure there was never an "official" low rise Thickston. Both the first and second version Thickston's were made with 7" risers. Many got cut down later in their lives to fit under the hoods of various vehicles.
I think I read somewhere that Tommy Thickston believe the "ram effect" his risers gave his intake was the give the incoming fuel a better charge and counteract the poor gasoline of the day.
Not 100% sure and feel to add to my recollection of the story....
BTW: The later Barron hi-rise version was just a reworking of the PM-7 pattern that Frank used after Tommy's death.
ken ct
BANNED
I have a pair like new that are slanted to be used to move carbs back and forth on the manifold about 1" either way front or back. $100 for the pr. about 3-4" rise haven't measured them. free lower 48 shipping.Neet set never seen a pr like this. ken ct PM or email. 4 gaskets included.
Bruce Lancaster
Member Emeritus
Note that you get a bit of extra altitude if you can find an old Offenhauser super dual, one made by offenhauser. On the current repro the carb mounting pads that are above the mold parting line on old ones have been eliminated, and a new mounting area is sort of blended into the basic casting. From pictures (I don't own anything modern) I'd guesstimate the new ones are down about an inch.