Guest zfan Posted May 27, 2001 Share Posted May 27, 2001 Ive currently got edlebrock rpm heads with 1.50 aluminum roller rockers. My question is how much difference is there between the 1.5's and the 1.6's. My friend told me Im loosing out big time by not running the 1.6's, but I really do not want to spend more money where it is not really needed. Know what I mean, to many other area's that need it. Mike Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted May 27, 2001 Share Posted May 27, 2001 Yeah, I think Jim's right, from what I've seen in the mags, they used 1.5's then to 1.6's and the difference was in the 5-10 hp range at most and that was probably because it was more optimised with the cam they were using. I thought about using the 1.6's on my stock 350, but for such meager gain's it didn't seem worth the money or hassle of replacing the 1.5's. FWIW. Regards, Lone Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted May 27, 2001 Share Posted May 27, 2001 Zfan: Not a bad idea, but be careful when changing to a higher ratio rocker arm. There are a lot of factor that come in to play like valve spring coil bind, push rod slot hole clearance,and possibly rocker arm contacting the springs or you could increasing the lift to where the cyl head is not moving air for example if you have a camshaft with .320 lift at the lobe with a 1.5 it would be 1.5x320=.480 of lift, now you change to 1.6 rocker,1.6x.320=512 of lift. If you head stop moving air at 400-500 lift range you are wasting motion and not making horsepower. So compare your cyl heads flow data match your camshaft. The rocker arms will affect only lift and not duration. Jack Quote Link to comment Share on other sites More sharing options...
pparaska Posted May 28, 2001 Share Posted May 28, 2001 quote: Originally posted by Michael Jackson: ...The rocker arms will affect only lift and not duration. Jack Not totally true. Look at it this way. The lobe on the cam is the same. With the 1.5 rockers, the cam has to move the lifter up 0.0333" to move the valve 0.0500". For that same cam with the 1.6 rockers, the lobe has to move the lifter only 0.03125" to move the valve 0.0500". Assume that all the "significant breathing" is done above 0.050" valve lift, you can see that the cam is moving the lifter a little bit less (and this occurs at an "earlier" angle) to get the valve 0.050" off the seat with the 1.6s vs. the 1.5s. It also turns farther to get the valve back to 0.050" off the seat near closing, with the 1.6s vs the 1.5s. This is why you get a bit more duration as well. Not to mention the area under the curve from the using the 1.6s, from 0.050" off the seat (opening) to 0.050" off the seat (closing). The cam has to turn throught more degrees to get these "opening" and "closing" lift points, and the max lift is larger as well. Personally, I think it's better to just get a cam that has the correct profile and max lift, and use the 1.5s. If anything, use 1.6s on the exhaust to experiment with "splitting" the cam more than it already is. Using 1.6s on the exhaust (and 1.5s on the intake) make the exhaust lift and duration increase over what's ground into the cam and may help fix a strangled exhaust port, etc. But I think the Edelbrock heads are pretty decent on the intake/exhaust port flow ratios anyway. I think if you want to spend some money, and think your vavle action isn't what you want, just buy a different cam. Oh yeah, another thng to watch for when putting larger ratio rockers on is valve to piston clearance, as well as that excellent list that Michael Jackson put up. [ May 27, 2001: Message edited by: pparaska ] Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted May 28, 2001 Share Posted May 28, 2001 I have those heads too - and 1.5 rockers. If you swap rockers you might also end up needing pushrods - maybe. It's a cheap way to bump lift and a slight duration bump too supposedly. But it's not much an dif money is tight I don't see a reason to do it. I bought into this with my Mustang but it didn't have roller rockers so it made more sense. If you needed rockers then buying bigger would be okay but why replace the good ones you've got now for bigger? On the Mustang I noticed NO difference with the butt-meter. Sure, maybe at the track I'd have seen a tenth but with my driving there wre plenty of other places to find a couple of tenths I'd say do it when you've got the money and some burning reason. This isn't a "big time" loss IMO. Ask your friend how much power you're giving up - if he says more than about 15HP I'd laugh. You can get that much tuning the carb up. Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted May 29, 2001 Share Posted May 29, 2001 Since we're mentioning possible issues with this swap... I believe it may also accelerate the valve faster. This can supposedly lead to an earlier valve float situation on a car with borderline springs. Quote Link to comment Share on other sites More sharing options...
pparaska Posted May 29, 2001 Share Posted May 29, 2001 Jim, I agree. Since the valve is going from 0 lift to full lift in the same amount of time (at a given rpm) and the lift is obviously more with the higher ratio rockers, the peak velocity and acceleration will increase. But the increased valve train flex may lesson that. Good point, hadn't thought of that before - thanks! Quote Link to comment Share on other sites More sharing options...
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