twells, yeah it is just notched....cant even really tell since it is mostly covered by the alternator.

Thanks for the info Darren....i will call Cam Motions and see what they have to say. I was thinking of switching to shaftmounts anyway, that was the reason for the 1.7 though, although I then saw that Phil Tobin was running 1.7s on the intake side of his motor...then I started thinking about that, hence this post.

I may just re-cam then. I didnt really want to since I enjoy this cam/driveability so much.

Darren, do you still have your PS functional with the alt relocation?
I would relocate mine if I knew forsure a way to retain that.

Thanks, Jason

 

When George Baxter was running Jesel 1.7X shaft rockers on his LPE heads, he was still into making it look "stock". He took two pairs of stock LT1 centerbolt covers, cut the top off one (leaving a "tall" bottom") and the bottom off the other (leaving a "tall" top), then had the two halves welded together to make a very stock looking LT1 centerbolt cover that was at least 1" taller than the real stock covers. You had to know what you were looking at to know they were "different". I am pretty sure he still had the alternator in the stock position at that point. Just took a little extra shaping of the "siamesed" cover to clear it.

 

To me, using 1.7 ratio (w/oem physically dimensioned) arms defys logic.

When one understands that the 1.5 oem arm has such poor geometry, that was originally used/designed for use with app. .400" lift, it becomes easier to understand that by doing so, makes a poor situation worse. Ever wonder why some engine valve train designs are centered around very looong rocker arm assemblies? To accomodate such a ratio, should entail redesigning the physical dimensions of the arm, plus relocating the pivot point on the head.

This poor geometry was the core reason roller rockers came into being. Prety soon we'll need lash caps just to keep the rocker contact point anywhere on the valve stem.

 

What are the specific reasons why you say the 1.5 oem arm has poor geometry? Is the arm too short? Too long?

What gets done to modify it to a >1.5:1 ratio... is it simply a relocation of the pivot point, or do aftermarket companies play with the arm length a bit?

That leads me to another question: Assuming that what you say is true, why would GM put out the HOT cam based on 1.6:1 rockers, when they could have simply put the lift on the cam lobe and used 1.5:1 roller rockers?

Additionally, what changed with the LS1, with its 1.7:1 ratio?

 

When you have a pivot point or fulcrum, any dimentional point that you extend out from that pivotal point, is swung in an arc. It doesn't matter if it is a rocker arm or a see saw/teeder todder, or whatever they call them in your part of the country. On the see saw it is, aah was more difficult to see the arc, cuz you are sitting so far from the fulcrum.

Yes, the oem sbc rocker arm has a distance from the pivot to the valve stem contact point that is too short. The rocker arm does push down on the valve, but on an arc. IOW, it swipes across the end of the stem. Someone, some time ago, realized an engine builder could reduce the swiping action, (friction) by going with a roller tipped rocker arm. (I'm confident you already know most of this, but bear with me ) Now, the further you make this contact point from the fulcrum, the larger the arc, and the less the swiping action/friction. As you increase the rocker ratio, or the lobe lift, the more 'swiping' that is realized. (with the same pivot to v. stem distance of course) Pretty soon, you are starting your contact point on the valve stem at the very edge on one side, just to end up on the very edge on the other side. BTW, for those unsure, changing the distance of the push rod contact point to the fulcrum does not affect this arc on the valve end of the rocker arm. What it does change, is the ratio of input to output.

Years ago, it was popular in certain circles to relocate the stud location and install BB rocker arms. So, yes, on both counts. Actually, if you move/relocate one, you must alter the other to end up at the same location/point. Unless, you want to alter valve stem/guide locations. How much do you want to spend?

My guess? (hopefully educated) They decided to put up with the additional friction to have a less severe cam lobe ramp, and consequently, more durability.

Those arms are longer, aren't they? But, could they be longer as well?

 

Phil may be using Crowers now, but I thought that he had a mixed set of Harland Sharp rockers at one point. I may be wrong. At any rate, Harland Sharp has a 1.65:1 rocker available for small block Chevy with either 3/8" or 7/16" studs...

http://www.harlandsharp.com/Chevy.html

And as someone else already mentioned, Crane "Gold Race" rockers come in 1.7s.

http://www.cranecams.com/master/goldrace.htm

I think the money is well spent, personally. My engine has a set of Crower stainless shaft rockers to maintain valvetrain geometry and strength at extended rpm. Mark had the cam ground with all the necessary lift and we stayed with a 1.5 ratio, I believe. The set I originally bought from Crower were 1.6:1s, and Mark sent them back in exchange for a set with an offest on the intake rocker for the raised runner heads, so I'm not totally sure what I ended up with.

http://www.c-zone.net/markm/JimLaBre...d/P1190101.JPG

 

Thanks for all the info guys....it helps. I probably wont recam since I really like this grind, however I am going to do more headwork over the winter.

Jim, thanks. Have you talked to Mark lately? I hope everything is ok on his end...I have tried emailing and calling him for a month with no reply ???

Thanks, Jason

 

Crane cames has a set of ajustable ratio golds. One set is from 1.5 to 1.6 and the other set is from 1.6 to 1.7. The drawback to these is they are not a narow body rockers and they do not have a roller tip. But if you wnat the range of ajustment they are worth it. They cost about $390.00, I got mine from summit. And as for the tall valve covers they will fit but you will have to get creative to mount the alternator up top. I used a alternator from a 1990 chevy 1/2 ton truck it's a small case unit and it put's out 105amps.

 

Hey 1320.

Can you provide more information about what it took to use the small case alternator you used? What wiring was involved and what it took to mount the alternator?

Thanks, Dave.

 

Dave if you can give me your email i can send you the info. Because this this logon i have lost two mesages and four hours of typing

Chirs S
keith_weaver@msn.com
94 Z28 A4 13.96@98
72 MAVRICK GRABBER 12.53@104/1.67 60`

 

Comp Cams PN 1117-16 are 1.7:1 stud mount rockers. They are kick *** too

 

SStrokerAce...you live in the Elmira area right? I live in Bath.

Jason

 

No $hit, you gonna go test and tune tommorrow at NYIRP?

if it's nice i'm thinking about it.

Bret

 

Cant do it tomorrow unfortunatly....gotta fix a couple things on my car in the afternoon/evening.

We will be at the test and tune Oct 27 and Nov 3 if the weather is good though.

What all do you do at your shop (services)?
Thanks, Jason

 

Looks like it's gonna rain anyways.

We do some machining. I send most of the block stuff out. (bore/hone/line hone)

I do manifold work, port machng (the right way, and there is a right way) assembly and alot of engine design . I also sell lots of ported throttle bodies for LS1's.

High end engines, are usually what I build. 550+ N/A street small blocks. I'm working on a daily driver 500hp LS1 that is a complete sleeper. Stuff like that. I'm into the Popular Hot Rodding Engine Masters Challenge, working on a big block for next year.

Bret