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Old 07-15-2009, 07:00 PM   #1
60ratrod
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stock 305 heads max lift

i was wondering what the max lift on a stock 305 head was?? cause i have already changed out the springs, locks and retainers to the ones listed as required/recommended for the comp cams xe268h. will i need to take them in to get machined for more lift or should i be fine?
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Old 07-16-2009, 06:20 PM   #2
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Re: stock 305 heads max lift

You need to measure this clearance. With valve springs off (exhaust and intake on #1) install the valves. Then install the valve seals. It helps to have a valve spring micrometer as it makes this alot easier. If you are carefull you can hold the valve tight on the seat while holding the retainer and the valve locks up in their groove. Now measure with a small rule the distance from the valve seat to the bottom of the retainer. Take the retainer off the valve and measure the how far the valve lock pocket projects below the bottom of the keeper. Measure the distance from the spring pocket to the top of the valve spring seal. Now add these last two measurements and then subtract this number from the distance from the valve spring pocket to the bottom of the retainer. This is your clearance from the valve seal at zero lift. Multply your rocker ratio times the gross lobe lift on your cam card. This your max valve lift. Subtract your max valve lift from your zero clearance. If you have atleast .070 left you are good. If not then you need to have your guides turned down until you achieve .070 clearance.
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Old 07-16-2009, 06:51 PM   #3
purewhitemp5
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Re: stock 305 heads max lift

The machine shop said with stock springs the max I could do was .480 with 305 heads.
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Old 07-16-2009, 07:42 PM   #4
60ratrod
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Re: stock 305 heads max lift

well if 100% stock lift is .480, then i should be sittin pretty since i have swapped out to comp 981 springs(recommended/required for the xe 268h), but since i still have yet to install the springs on the other head then i'll do the measurements just to be safe. i gotta go to the LPH anyway to get some other items so i'll see if they have a micrometer and all that. i gotta get some easy outs since i found a broken bolt in one of the end exhaust bolt holes
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ERROR 404....... SNAPPY COMEBACK NOT FOUND
_______________________________________________________________________________________________
MY GARAGE:
-72 GMC C15 LWB, soon to be tpi350/th350 combo "The Banana"
-72 4 door Malibu, 350/th350 combo, undergoing suspension overhaul/disc brake upgrade "Tranny" (transvestite), wife can't decide if its a he or she
-60 Chevy C10, dead 350/good th350 combo, sitting on a 76 c10 blazer frame, built from 11 different vehicles "The Abomintation"
-05 Chrysler Pacifica, its the mrs's DD "Its name isn't Metroman, It's Metrovan!!"
-01 Chevy Tahoe LS 4x4, my dd "The Inmate," 5.3 with ported and polished throttle body, k&n airfilter, with electric fan conversion and hardware store cai in the works
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Old 07-17-2009, 04:36 AM   #5
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Re: stock 305 heads max lift

The clearance of .070 is without the seal. With the seal I believe it is .040. Sorry about that... brain fart!
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