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MG MGB GT V8 Factory Originals Technical - Cam Selection
|Iím currently building a 3.5L Rover V8 based on the 1980 SD-1 engine. As expected, I found a couple of cam lobes worn down to nubs, so Iím evaluating my options for cam replacement. The engine is stock except for the block hugging headers and the hotwire fuel injection.|
I would appreciate hearing about others cam selections, especially those with very similar engine configurations. I would like to keep my stock valve springs. Does anyone know at what lift the springs come close to binding? Whatís the best compromise between RPM before the valves float and lift?
|The stock springs are good for .370" lift and not one fraction of an inch more. |
FWIW, I have a 4.2, but I put in a new cam a while ago and the car goes like a raped ape; it is Erson grind TQ20H:
intake opens 39 deg/ closes 73 deg (so, duration 292)
exhaust opens 81 deg/ closes 31 deg (so, duration 292)
The car has the big Vitesse valves and of course aftermarket valve springs (double ones in my case). The car only get 14mpg in perfect tune, so that's a downside of this setup.
|My choice for a stock 215 was Crane 900531. Intake 260', exhaust 268', valve float with new Crane springs- stock replacements- 6500 RPM's. Spring #99891.|
This is a mild upgrade, not a wild bumper. Stock engine, 4 bbl version, runs fine on 87 octane gas, reasonable gas milage, slight lope at idle, plenty of power, but definitely not a hipo engine.
D & D has several cams, including a clone for the hot Skylark 210 hp engine. You might want to talk to Dan after he gets back from Fall Carlisle this weekend.
If you decide you want to go realy wild, talk to Woody Cooper at the Wedge Shop. He likes the Erson cams & has several custom grinds for the 215/3.5.
|I looked at Crane's website and they say this cam requires machining of the head. Bigger spring pocket?|
You say "valve float with new Crane springs- stock replacements- 6500 RPM's". Does this mean you just replaced the springs without doing anytning else?
Thanks for the help.
|What kind of cam has a race like lope?|
... most any cam with a really long duration ... which isn't always much fun around town. Let's get one thing straight: when hot-rodders running BBCs get that huge lopey sound and have the thing idling at just a few hundred rpm, they are almost always running a roller cam - or I should say, a cam designed for use with roller lifters. Using hydraulic lifters when idling a big fat cam at low rpms is a sure way to kill it ... you don't have enough oil pressure to pump up the lifters or to lubricate the lobe/lifter interface. (BBCs and to some degree even Rover V8s are notorious for eating cams.) To my knowledge, there are no roller cams commonly available for the Rover V8.
This thread was discussed between 02/10/2002 and 07/10/2002
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