Topic: Single VS Dual pattern cams
From: staunton, va
Registered: Dec 2001
posted 11-20-2002 11:18 AM
Saw this question on another board. We hear how stock ford smallblock heads need a dual pattern cam to offset their lack of flow, but in a mild application like a low 8 or high 7 second car in the 1/8th shifting around 5800 how much would the dual pattern cam really help over the single pattern?
I have heard pros and cons for each, and it seems like everyone talks about how great the dual pattern cams are, but if that is the case then why does ALex like and suggest the comp 270 H/S and the 280 H/S so much? if anyone could help out here, would like to hear from you to Alex on this one.
From: Connersville, IN
Registered: Jul 2001
posted 11-20-2002 09:57 PM
I'm not a expert, but I'll through in my opinion.
You asked about slower cars in the low 8s and high 7s. These car are more likely to have production heads with the bad exhaust flow %. They, in theory, would benifit more from a dual pattern cam. The faster cars would be more likely to have aftermarket heads and also a better exhaust port which may benfit from a single pattern cam.
I know Alex doesn't like to talk about cams on here. I really hope he or someone can answer with more know how.
Grabber Green '70 Mach I 351C 4V
Robbin Egg Blue '79 Fairmont 351C 4V
From: Republic Of Texas!! Temporarily living in KY
Registered: Feb 2002
posted 11-21-2002 07:35 AM
Hydralic Dual pattern cams make logical sense to me. There purpose is to maximize the deficiencies of certain heads (usually exhaust flow) They are economical IMHO.
I have had and seen really good results from them. Especially in Production style heads where you have to spend a fortune in porting to get them to flow.
I have witnessed them used in Fords and Mopes. Both have out-performed the previously installed "standard" style cams at the track.
I am sold. But only on larger hydralic cams for street/strip. It is hard to beat a solid lift cam.
Everything is relative to $$. If you are building a race only car then go roller or solid. If you want both street and strip go with hydralic (split duration) or solid. Just keep in mind that with a solid cam you will HAVE to have an adjustable valve train which means having most stock style FORD heads sent to the machine shop to mill them for rocker studs.
64 Pro-Street Falcon
351C 4V 8.1s in 1/8
79 Ford Bronco 4 X 4 Lifted 6"
400 9.9s in 1/8 :)
70 Plymouth Cuda'
440 Magnum. 2600#
Race Car 6.90 in 1/8
From: Spencer, WV
Registered: Jan 2001
posted 11-21-2002 10:42 AM
The intake duration is the chief factor in the rpm range of a camshaft. Adding a little exhaust time doesn't really affect the nature of the engine that much. Unless it's really low on compression ratio and needs all the cylinder pressure it can get, a dual pattern cam doesn't have any significant drawbacks.
That being said, it's better to have a little extra exhaust timing, than to not have enough.... especially if using exhaust ports that don't flow that well and 'street' exhaust systems.
66 mustang real street
302 4-speed 289 heads
10.63 @ 129.3
From: Lyons, IL, USA
Registered: May 99
posted 11-21-2002 10:51 AM
Sorry Jerry, but I no longer do cams on the racing forum.
The rest of the guys have pretty much covered the question.
I never use a dual pattern cam in a stock/mild SBF personally.
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