Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
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Yes, they are center bolt version of the 416. I don't think that a .6 lift on those heads is going to help you. First, there is no way those heads will take that kind of lift without machine work, 2nd .6 lift I think is well beyond the lift at which these heads have maximum flow. I think they peter out around 0.5" lift.
__________________ 91 Formula WS6 305TPI
Transmission: WC T5
diff: limited slip 3.42:1
exhaust:dual cat with 3" magnaflow cat back
mods: fully rebuilt 305 bored .020 over and decked 0.020, comp cams xr258hr12, 22lbs bosch design 3 injectors, full wide band tune, eibach lowering springs - 1.5" drop, spring tech shocks and struts, slotted brake rotors, underdrive pulleys, MSD ignition, K&N air filter with air foil.
Yes, they are center bolt version of the 416. I don't think that a .6 lift on those heads is going to help you. First, there is no way those heads will take that kind of lift without machine work, 2nd .6 lift I think is well beyond the lift at which these heads have maximum flow. I think they peter out around 0.5" lift.
so a .500 lift is pretty much the limit with out mods?
Yes, they are center bolt version of the 416. I don't think that a .6 lift on those heads is going to help you. First, there is no way those heads will take that kind of lift without machine work, 2nd .6 lift I think is well beyond the lift at which these heads have maximum flow. I think they peter out around 0.5" lift.
do you have any mods on your head with the xr258hr12cam your running?do you have any sound clips?
so a .500 lift is pretty much the limit with out mods?
What do you mean by "without mods"? Any aftermarket cam you put in there is going to require something better than the existing stock valve springs. Also, once you start exceeding let's say .47 lift, you may end up running into clearance issues which may require grinding down the valve guide bosses. But I would say that with the stock port size and valves on those heads, you don't want to go any bigger than 0.5". Beyond that you will likely start losing power. Also, when you start approaching lift near the .5" mark, you may want to also consider machining the heads for screw in studs. Probably the biggest you may want to go as far as lift is concerned would be a cam like the comp xr264hr12 without major head work, but with some head work.
What do you mean by "without mods"? Any aftermarket cam you put in there is going to require something better than the existing stock valve springs. Also, once you start exceeding let's say .47 lift, you may end up running into clearance issues which may require grinding down the valve guide bosses. But I would say that with the stock port size and valves on those heads, you don't want to go any bigger than 0.5". Beyond that you will likely start losing power. Also, when you start approaching lift near the .5" mark, you may want to also consider machining the heads for screw in studs. Probably the biggest you may want to go as far as lift is concerned would be a cam like the comp xr264hr12 without major head work, but with some head work.
well the springs I am going to be running have a max .6 lift,have a set that comes will the keepers,seals and all thats needed for a new spring install
do you have any mods on your head with the xr258hr12cam your running?do you have any sound clips?
I went with better springs (don't remember what the comp part number for them was). My heads were fully rebuilt (same heads as you have). Also things were measured to make sure that all clearances were met. I had a reputable machine shop do all of this. Also as I recall I don't think it was necessary to get screw in studs for that cam.
As far as the sound is concerned, it is definitely more aggressive than stock. Try this link, it may give you an idea of what the car sounds like: http://www.youtube.com/watch?v=P3dpbnLcP4Y. This was taken about 1200 miles after the rebuild, with the sock computer tune, stock catalytic converters, and no muffler, just a muffler eliminator and tail pipes. The car sounds much better now after the tune and with the 3" magnaflow exhaust. The link however should give you somewhat of an idea of how choppy the idle is, but is not as refined as it is now.
I went with better springs (don't remember what the comp part number for them was). My heads were fully rebuilt (same heads as you have). Also things were measured to make sure that all clearances were met. I had a reputable machine shop do all of this. Also as I recall I don't think it was necessary to get screw in studs for that cam.
As far as the sound is concerned, it is definitely more aggressive than stock. Try this link, it may give you an idea of what the car sounds like: http://www.youtube.com/watch?v=P3dpbnLcP4Y. This was taken about 1200 miles after the rebuild, with the sock computer tune, stock catalytic converters, and no muffler, just a muffler eliminator and tail pipes. The car sounds much better now after the tune and with the 3" magnaflow exhaust. The link however should give you somewhat of an idea of how choppy the idle is, but is not as refined as it is now.
okay cause the cam I want is either the XR264HR-12 or XR258HR-12.
okay cause the cam I want is either the XR264HR-12 or XR258HR-12.
I went with the 258 instead of the 264 because wasn't sure how well the speed density computer would like the bigger cam, thus I desided to err on the side of the smaller cam. Some people have had no problems with the 264 and perhaps with a MAF car you would not have as much of an issue. But I must say, that even with the 258 my car was badly out of tune. Fuel economy was horible, and the power was not what I expected to get. There were numerous flat spots in the power curve. It ran too rich at some spots and too lean at others. Tunning it made a tremendous amount of difference in performance. I don't think that I can over emphasise that. A computer compatible cam does not mean that will not require tuning. I ran my car for 12000 mile with the stock tune before I got a full wide band tune and a set of new injectors. Needles to say, my brand new park plugs were shot by then and so were my stock catalytic converters. Just my .