Datsun#1 Posted July 6, 2015 Share Posted July 6, 2015 Hey guys,im building another l28 this summer.I have a fully ported mn47 head shaved .10 thousandths. The block is balanced,and fully refreshed with stock bore flat tops.(no valve reliefs)...the cam I am wanting to run is 295durr/495 lift...will I have any clearance issues with this cam? Id like to run it degreed at 4-8 degrees advanced. Thanks for the input. Quote Link to comment Share on other sites More sharing options...
madkaw Posted July 6, 2015 Share Posted July 6, 2015 I have read about bigger cams being run on stock flat tops. You are going to get replies telling to check clearance and not rely on guess work. The duration will get you in trouble more than anything. Just make sure you get it timed in correctly. Quote Link to comment Share on other sites More sharing options...
1969honda Posted July 6, 2015 Share Posted July 6, 2015 Throw some modeling clay on top of a piston, assembly and turn it over by hand. After going thru a couple rotations of the crank if you havent had to stop due to interference, pull the head and measure the thickness of the clay where the valves indentations are and go from there. Quote Link to comment Share on other sites More sharing options...
madkaw Posted July 6, 2015 Share Posted July 6, 2015 Hey guys,im building another l28 this summer.I have a fully ported mn47 head shaved .10 thousandths. The block is balanced,and fully refreshed with stock bore flat tops.(no valve reliefs)...the cam I am wanting to run is 295durr/495 lift...will I have any clearance issues with this cam? Id like to run it degreed at 4-8 degrees advanced. Thanks for the input. Sounds like my next build. Some cam grinders already have advance built in so check your numbers. Quote Link to comment Share on other sites More sharing options...
Datsun#1 Posted July 6, 2015 Author Share Posted July 6, 2015 I used a dial indicator and my cam is actually 292 durr/495 lift @ 0.50.. 108 lobe separation. Ill try the clay idea.But with this information,do you think ill have issues? Im thinking of running in the #2 position Quote Link to comment Share on other sites More sharing options...
NewZed Posted July 6, 2015 Share Posted July 6, 2015 Since this is just an opinion poll, I'm going to say no you will not have any problems. Let us know who was right. Quote Link to comment Share on other sites More sharing options...
Datsun#1 Posted July 6, 2015 Author Share Posted July 6, 2015 Wosrt comes to worst,ill have to buy new valves. Quote Link to comment Share on other sites More sharing options...
NewZed Posted July 6, 2015 Share Posted July 6, 2015 Put it together, but only install two rocker arms. That way you'll only waste two valves, and dent one piston. Not positive but I think that valve guides can be damaged also. Clay is cheap. Worse comes to worst, it's hard to clean from the piston top. You know you should do this. Quote Link to comment Share on other sites More sharing options...
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