tappet vs hydro roller cam
07-18-2013, 02:53 PM
#1
tappet vs hydro roller cam I have a 355ci that currently has a hydraulic flat tappet camshaft.
My question: Are there any fuel economy advantages by switching from a flat tappet to a hydro roller camshaft? The motor makes good power but drinks gas like it was free. My C5 LS6 has a larger cam, bigger valves and still gets "good" gas mileage.
In short this little small block is drinking my cash.
current cam is a 230/230 (@.050) .490/.490.
My question: Are there any fuel economy advantages by switching from a flat tappet to a hydro roller camshaft? The motor makes good power but drinks gas like it was free. My C5 LS6 has a larger cam, bigger valves and still gets "good" gas mileage.
In short this little small block is drinking my cash.
current cam is a 230/230 (@.050) .490/.490.
07-19-2013, 07:43 AM
#3
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an LS is lightyears ahead of anything carbed in terms of fuel economy. not to mention the vette probably has either a 6sp or 4sp auto, which will also greatly help economy. for just saving gas, theres no comparison between carbed and LS V8s.
07-19-2013, 10:51 AM
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I think when GM went to the hyd roller from flat tappet, they quoted the mileage increase as about 2% - or about 0.3 to .04mpg.
The best attribute about roller cams is the ability to run much higher lift per given duration due to the increase in ramp angles. There is a definite limit in a flat tappet cam lift - usually below what heads flow best at any given point. As an example, the roller in my car measures out at 219/219 with .525" lift - and I have seen others that push .550".
The best thing to do for fuel economy is to replace your carb with an aftermarket FI system (one that replaces just the carb) - you may pick up 3 to 6mpg compared to a carb (which are never tuned perfectly at all points on the power curve.
To answer your question, the LS motors get great mileage and power due to the design which promotes volumetric efficiency. A SBC is lucky to get to 100% VE, while I have seen street driven LS based motors push 115% (better than any 4 valve OEM motors). VE is power and efficiency in one concise number.
The best attribute about roller cams is the ability to run much higher lift per given duration due to the increase in ramp angles. There is a definite limit in a flat tappet cam lift - usually below what heads flow best at any given point. As an example, the roller in my car measures out at 219/219 with .525" lift - and I have seen others that push .550".
The best thing to do for fuel economy is to replace your carb with an aftermarket FI system (one that replaces just the carb) - you may pick up 3 to 6mpg compared to a carb (which are never tuned perfectly at all points on the power curve.
To answer your question, the LS motors get great mileage and power due to the design which promotes volumetric efficiency. A SBC is lucky to get to 100% VE, while I have seen street driven LS based motors push 115% (better than any 4 valve OEM motors). VE is power and efficiency in one concise number.
08-10-2013, 07:19 PM
#5
"[QUOTE=Paul Huryk;17556819]
The best attribute about roller cams is the ability to run much higher lift per given duration due to the increase in ramp angles."
And the ability to use oils that have tiny amounts of Zinc.
Al
The best attribute about roller cams is the ability to run much higher lift per given duration due to the increase in ramp angles."
And the ability to use oils that have tiny amounts of Zinc.
Al
08-13-2013, 09:41 AM
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[QUOTE=Big Al;17607618]"True, but nobody was thinking of that in 1985 or whenever roller cams were coming into fashion at Ford and GM.
