69 289 heads,520 lift cam with 1.7 rockers?????

[jaradt2006]

got a non roller 302 block has a 5420 lift cam with 69 model 289 heads been shaved 14 ive got 1.6 roller rockers on it right now wanting to put my 1.7's on that i took of my other car will it work or will i have problems

 

[jaradt2006]

520 lift cam that is

 

[85_SS_302_Coupe]

Well, for starters, pistons to valve clearance has more to do with lift duration than lift itself, so you need to post up the rest of the cam specs. Second, you didn't mention anything about notched pistons...are we dealing with stock pistons or aftermarket? Third, if the heads haven't been ported you most likely don't need any more lift than you already have since they're not flowing much more than a stock E7 head.

The main reason to use 289 heads would be because they have small combustion chambers, and yours are shaved even more. If i had to guess i'd say you're somewhere close to about a 50-52cc chamber which is pretty tiny. Shaving them also takes away piston to valve clearance. If i had to guess, i'd say no the 1.7s aren't a good idea. Either way you really should get a pushrod tool and measure them regardless of what anyone here tells you.

 

[jaradt2006]

yeah itsall stock bottom end so stock pistons the heads have been shaved and they have been ported they are port matched to my torker 289 intake

deg. dur. @0.50 deg. advance lobe center line gross lift
cam lift duration
int. exh.
224 234 300 309 110deg. .496 .520

 

[85_SS_302_Coupe]

The way you figure out lift with different rockers is...

.520 (since that's the highest of the 2) / 1.6 = .325

.325 x 1.7 = .5525

So that'll bring your highest lift to about .552 lift, which is probably pushing it. Personally i wouldn't even bother, but if you do then definitely check piston to valve clearance before you run the engine.