Hank,
Great comments and pics on head porting. I'm porting a set of Brand X right now and it got me thinking about stuff.
On the Offy vs Clifford, here are the 2 best runs with each intake. Results are corrected for car weight (down to a gallon of gas) and weather (Temp, Barom, RH altho it was all pretty constant)
Intake....Carb....60foot....0-60mph.......1/8 et/mph
Clif.....600AFB.....2.580...10.127.......11.266 at 62.383
Clif.....390Hol.....2.585...10.469.......11.318 at 62.870
Offy.....450Hol.....2.582...10.208.......11.238 at 62.506
Offy.....390Hol.....2.574...10.487.......11.284 at 62.277
That's why I called it a "tie", to me all these are SO close, how would you pick? So I'd go by price $$$ in a nice climate like ours, or go with the Offy for its cold weather driveability for a cold-weather capable car.
EDIT, FYI these tests were done with weight~3050lb (includes me), 250cid stock + 4bbl about 170hp, 1.82 powerglide, 3.08 open rear (no traction problems for sure)
Deuce Coupe,
I see what you are saying but as your tests proved the Offy showed a 2.9% gain in a roll on comparision, were most driving is done for an everyday street car, were not @ W.O.T. all the time as your test are done in. Also Tlowes dyno tests, wide open throttle.
Part throttle tests will show an advantage in the lower RPM range also towards the Offy.
That is one area that most all intake manifold comparisons are done with the throttle wide open.
That's great, but like I said, we are not @ wide open throttle all of the time, & when you have too big of port runners, port velocity suffers, meaning you lose low end torque & that is where the Offy has shown below 3000 RPM, the Offy does make better low end torque.
The Offy is better for lower RPM street everyday driving.
The Clifford is better above 3000 RPM.
It all depends on your combination also on which one will work better for your application.
They are two different manifolds for different applications,
The RPM ranges are different for both.
Just looking visually, they look to be much different in design.
I would never recommend one, of these two intake manifolds for any type of application.
I would want to know what the person is looking for power wise, type of driving, what RPM range the engine will be operating in, etc.
While others seem to think the Clifford is the only choice in a manifold between these two.
That's fine, they have an opinion, & so does everyone else.
If you ever install too big a camshaft for your engine, the Clifford manifold will fall on its face down in the lower RPM range.
Meaning, if your engine combination is off, the Offy is a more forgiving manifold.
I believe my best mileage was done with the Offy also, it gives a better signal to the carb.
And you are correct the Clifford took longer to warm up, but it did not bother me too much.
Maybe in colder climate, it just might make you mad.
IIRC, Tlowe never published the max HP & torque between both manifolds with the same camshaft/engine combo.
I heard they were pretty close.
I have not used the intakes on a 292, just 250's only.
I think a 292 engine w/the 4.120" stroke can handle the larger runners of the Clifford.
I think if the tests DeuceCoupe were done w/a 194 engine the results would had had wider gaps between the two intakes (favoring the Offy), & if your 250 was overcammed the results would have been in more favor of the Offy, which I have done with my testing, but not on purpose, I was just overcammed for the compression & gearing I had.
Later got the combo better matched.
I never tested on a completely stock engine like DeuceCoupes.
MBHD
