Also, which:
Springs?
Valve?

And hows it run?
Valve-train noise?
Spring durability/life/breakage?

My scenario is 2.08 intake + 1.7 Scorpions + Howards beehives 130/320 1.8/1.2 + Hylift-Johnson Lifters + All the other good stuff.

Its what I got, gona run it. Need to pick a cam which wont break springs so wanting to know what others are running and their experiences.

Thanks in advance

 

.get a custom one made you are wasting time with a shelf cam

 

well thats as useful as **** on a bull!

Actually I am getting a custom cam ground but wanted to hear peoples experiences with different cams.

Unless you get something special they use the same lobe groups for shelf and custom cams you know.

So any one with real experience running 1.7 RR?

 

Been running shaft mounted 1.7's for awhile.

That having been said.....NO ONE.....can give you decent cam advice based simply off of rocker ratios.

In order, you should be able to supply:

engine size
compression ratio
head specs
vehicle weight
rear gear ratio
projected usage of the car
and the quality of street drivibility you require



All that having been said, the lobes themselves won't be much of an issue unless they are a particularly aggressive lobe set.. Otherwise.....with mild/medium lobes, you simply have a bit more lift.

KW

 

I'm fine spec'ing my cam when I order it. I have it narrowed down to a couple of options which are really just a couple degrees either way - splitting hairs really. Its going to be a sleeperish short duration high lift cam. But as I said I'm good with the actual spec'ing and ordering the cam, which is why I didn't ask for any help with this.

Before I pulled the trigger what I was hoping for was feedback from some other people who had put a few thousand miles on their own combos with aftermarket cam and 1.7 RR's. Hence the questions in my original post. I did provide details of my valve-train as reference.

I was hoping for replies along the line of say: I have a similar combo with brand x cam series y for the last 20,000 miles on Q springs and its been fine but there is a little valvetrain noise, etc.

I can take a punt just as easy as anyone else but if I can get actual experience straight from the horses mouth its money in the bank. So to speak anyway.

With shaft mount I'm assuming your setup is pretty radical and a lot different to mine and your experiences may not be relevant, but if so would you mind trying to answer my questions from my OP?

 

Quoting myself...

Thanks again

 

OP

the list of people running 1:7 RR is pretty short, and I am not on it.

With that said if someone does respond with "I use x cam.."...That in itself would be valid "if" their block and head deck height were the same as your motor and they were running the same thickness head gasket as you...and same piston valve relief, etc, etc.....Sooooo whatever kind of motor you have and what has been done to it, if it has been machined for rebuild (decked) what max lift your selected spring will handle...all are variables compared to just the ? of "what cam for a 1.7 RR motor".

If you are getting a custom grind and we are talking about a LT1 (gen 3) motor you might want to have this discussion with Lloyd Elliott at Elliott Portworks

 

Its just a zero decked 638 350 block with felpro gaskets, 2vr forged pistons and +0.1 valves. So of course I will need to check pushrod length and order the correct length. I will also check p to v clearance also, these are standard engine building practices I just assumed most people knew, and again is why I never actually asked for any help with this.

Assuming correct pushrod geometry and p to v clearance (honestly are there people running around with pushrods rattling around and valves hitting pistons - not for long anyway) these factors have no bearing on my question.

A 1.7 RR over say a 1.5 or 1.6 RR will have greater acceleration and velocity at the valve. So then the question of valve control, durability and noise comes up. Which is why I asked for peoples experiences.

Even though I don't have a gen 2 LT1 I asked in this forum because when searching google a lot of old posts came up on this forum with people running 1.7 RR's so that's why I posted my question: 'Scorpion 1.7 RR owners - which cam you running?' - which I thought was self explanatory.

I'm not knocking what advice has been offered, its all very sound and good and my thanks for posting your responses. But not what I was asking for. Thanks but never mind now.

 

There is nothing 'special' to note in going with the 1.7 rockers vs 1.6 rockers.........vs 1.5 rockers.

About the only thing I can tell you is that the higher rocker ratio allows for more valve lift vs the lift with the lower ratio rockers.

This allows you to use milder cam lobes (good for durability) to get the lift you'd have with using smaller ratio rockers and steeper/harsher lobes.....but I suspect you already know this. As stated.....going with the milder lobes pretty much compensates for all the issues you seem to be concerned with.

BTW......yes.....my shaft mounted rockers are on a solid roller set-up. I've driven about 20K miles with the setup, and maybe 25 1/4 mile passes. No issues so far.

BTW.....I have 1.8 ratio rockers in my stock displacement LS3 in my daily driver.....different engine, but no problems there, either.

KW

 

There's some good info right there. Yes I don't need to be told it but its good to be written down for anyone else reading.

 

I think your nearly there. For a given lobe an increase in rocker ratio will result in increased valve lift (displacement) in the same duration (time) period. Of course the first and second derivatives for velocity and acceleration will increase to achieve the increased displacement in the same time period.

The resulting increased first and second derivative values at the valve 'may' be too much for the valve/spring/retainer package resulting in instability.

If you do use a 'softer' lobe together with increased rocker ratio then yes the intensity of the first and second derivatives at the valve can be brought back into line with values which can be controlled by whatever valve/spring/retainer package is being run. Which I think is what you were getting at later on in your post.

Your combo with 1.7 RR on a solid roller with 20,000 miles I think is a good example of this.

The thing is, I'm pretty sure all the lobe profiles I'm looking at are 'soft' enough to be controlled by my valve/spring/retainer package with 1.7 ratio. But a valve can be controlled and still have a noisy valvetrain, there is one line of hydraulic cams from a certain manufacturer known for valvetrain noise - even though the valvetrain is stable. AFAIK its the exhaust valves landing on the seats hard, something I personally want to avoid.

So then I go and ask for other peoples experiences.

I think this thread has run its course now. Thanks again for your responses.