I need race engine overhead cam help
I need race engine overhead cam help
(OP)
I am restoring a 1974 Lancia Stratos factory race engine based on a Ferrari V6 engine. This engine has 4 valves/cylinder and 4 overhead cams. Displacement 2470cc with 10.5 compression. Horsepower around 300 at 8,700 RPM.
My question is this, the original cams the intake opened at 38 degrees BTDC, close at 74 degrees ABDC. Exhaust open 74 degrees BBDC and close 38 degrees ABDC, duration 292 degrees with overlap of 76 degrees. The cams were damaged and were sent to a cam specialist to repair and they changed the values to the following: Int open 21 BTDC, close 51 ABDC. Exh open 53 BBDC, close 19 ATDC. Duration 274 both intake and exhaust. Overlap 40 degrees. How will this change effect the performance of this engine?
My question is this, the original cams the intake opened at 38 degrees BTDC, close at 74 degrees ABDC. Exhaust open 74 degrees BBDC and close 38 degrees ABDC, duration 292 degrees with overlap of 76 degrees. The cams were damaged and were sent to a cam specialist to repair and they changed the values to the following: Int open 21 BTDC, close 51 ABDC. Exh open 53 BBDC, close 19 ATDC. Duration 274 both intake and exhaust. Overlap 40 degrees. How will this change effect the performance of this engine?





RE: I need race engine overhead cam help
From my point of view, the change would make the engine much more "streetable" if that is what your after. It's the wrong direction for a race engine, IMO.
Rod
RE: I need race engine overhead cam help
RE: I need race engine overhead cam help
RE: I need race engine overhead cam help
292*
38/74 - 74/38
106* LSA
108* IN CL
104* EX CL
252*
21/51 - 53/19
106* LSA
105* IN CL
104* EX CL
These two cam profiles are worlds apart. The new 252* profile (not 274*) will produce massive low end and give you no reason to rev past 4000 rpms. IMHO, those cams are junk now with the regrind. Even if you could put adjustable cam gears onto adjust your center lines, it still wouldn't perform like the original lobe grinds.
RE: I need race engine overhead cam help
It also depends a lot on what minimum lift the cams are measured from.
The earlier closing of the intake might induce detonation.
Lift was not specified, but will have a significant effect depending on the flow of the heads at original and reground lifts.
Regards
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RE: I need race engine overhead cam help
Regards, Sandy Cormack.
RE: I need race engine overhead cam help
RE: I need race engine overhead cam help
You can buy new cams.
You can have a competent cam grinder build up your cams with Stellite then regrind to your spec.
You can have steel billet made into new cams to your spec
Regards
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RE: I need race engine overhead cam help
Regards