1.5 vs 1.6 RR
 

I am doing a 355 build and I have most of it together, I have a set of AI 200cc CNC heads and one of their custom cams, the Cam numbers are 228/234 @.050, .612/.612 111LSA (lift with 1.6 RR).

The springs on the heads are rated to handle .600 lift so the heads were run with 1.5's before to make the lift lower. I have all the parts to run it with my 1.5 rockers.

So my question is am I hurting my engine by just using 1.5 vs 1.6. Am I losing something other lift on the cam?

I know the best answer is to go buy 1.6 RR and new springs. But I'd like to use what I have if it makes sense. Thanks for your time and answers!

Along with about .040" lift that you are losing by using the 1.5s, you are also losing a tiny bit of duration if you were to measure it at the valve. The 1.6s also help the valve open and close at a higher rate but the 1.5s will be fine.

As soon as you can afford springs though, buy them. That cam was spec'd for 1.6s.

I would call A I. Their 200 head says it comes with .650 lift springs. I'd want the most I could get out of that set up.

It's not the big deal some want to think it is. Make sure you have plenty of valve-to-piston clearance when you test assemble it (especially the intake) for higher ratio rockers later. If you don't have money for 1.6 right now just put it together with what you have. Buy them when you can, but don't expect to be blown out of the water when you do put them on. LOL

Another part I didn't want to add in is the fact that I'm using dome pistons and would like the added room on my pistons. I just didn't want to say that and complicate things, but thank you for the advice!

Yeah, the heads are pretty old (still in great shape though!) but the springs have obviously been replaced with PAC 1220's and I could replace them, but at the same time there are other things I need to use the money for. Ed said it wouldn't be a HUGE difference so I'm probably going to use what I have over getting new springs and rockers for now.

like ed said don't expect ground breaking power with the swap but im sure it would pick up some......you're not hurting anything with the 1.5's if anything theres less pressure on the PR side of the rocker from the reduced leverage........like ed also said make sure you have good PTV clearance , with a HR cam you want .100/.080 MINIMUM I/E

Okay, thank you for all the information, (if I'm not expecting huge gains from it then I'm not expecting huge losses :jest:)

Did you say CNC heads, as in CNC Cylinder Heads, from Florida? If so, great heads! My old 383" has their heads. Those are keepers for damn sure. I never had anything come across my dyno that made more power than their heads. OL' Pete Incaudo forgot more about cylinder heads than most of these guys will ever know. Don't let the corner machine shop screw up the valve job.

I think the OP mentioned they are AI cylinder heads

Sorry. Guess I missed that. Those are OK too.

Yeah, they're AI heads, I wish they were the CNC heads but I got a good deal on these and the cam was specially made for a 355 that was built like mine.

Question for y'all, is there and reason that I shouldn't use self aligning rockers? I don't know if there's a certain point in which you need guide plates? Thanks again guys.

pretty good info!

I don't run self-aligning rockers on anything that will turn over 5500-6000 RPM.

At that point I switch to NSA because guide plates are just cheap insurance and piece of mind.

Just keep in mind when you run guide plates, hardened pushrods are a must.

But you can't run guide plates with SA rockers can you? :bang:

No absolutely not. So to reword this.

Less than 6000 RPM = stock 3/8" studs, stock pushrods, SA 1.6 RR

More than 6000 RPM = ARP 7/16" studs, hardened pushrods, guide plates, NSA 1.6 RR