I was just shortening it, and typing fast, what I meant was you get about .400 or .0400 whatever it is, over 1.6s with 1.7s. 1.6s are $280 1.7s $340 =$80. I wasnt too clear, my bad.

 

All this and no talk of what his head flows at those lifts? Just a level1 P&P might not be that big of a difference at those lifts. What does your heads flow at the lifts for 1.5/6/7?

Hal

 

This wont be done anytime soon, this will all be next winters teardown project. The heads are just mildly ported and polished now maybe flowing 230 or 240 if im lucky. But next winter will bring stage 3 heads flowin above 280. If I find from the flow sheet that they dont flow crap above .500 then I wont bother with trying to get higher lift, but if they flow best at .600 I dont want to buy a new cam to get this increased lift. Just askin the question now to find out if it was even an option.

 

Don't see the relevence in the flow numbers. Guys who swap from 1.5 to 1.6 on stock heads will always see some gains..... I've yet to hear anything to the contrary. No consideration for the stock head's flow numbers there either.
Seen much of the same on modified heads.... again my concern would be in the acceleration rate of the lobe. Is it going to be harder on the valvetrain? Most likely yes... but what are the effects an stability? I don't know but I'd imagine it depends on the lobe design and I can't pretend to know anything there.

On the specs from that article, they were using a 242/248 @ .050 cam with .575/.585 lift and a 110 degree lsa. The valve to piston clearnace was tight at .07/.090 vs the "ideal" .100/.120. That cam is going to have a good deal more overlap than your Xtreme so that should give you some idea. Always check though.... rocker to retainer and retainer to valve-guide/seal.

-Mindgame

 

Im not being smart, but Im confused about what you are saying mindgame. Are you saying that the piston to valve clearance will be fine, but something else might not be. I dont understand the overlap part of it, so if you could please explain a little more indepth please. It sounds like you are saying it doesnt have anything to do with the amount of lift, but the amount of overlap between the intake and exhaust, but I dont understand how that can be dangerous. Thanks.

 

It's ok jon, I'll do the best I can here.

When the piston comes up the bore on the exhaust stroke, the exhaust valve is already open (been open since before bottom dead center). The piston pushes the exhaust out on it's way to tdc. Near tdc the intake valve opens and the pressure difference pulls the intake mixture in. Anyways... the two valves are open at or near tdc and that's where the minimum clearance thing comes into play. If the intake valve opens earlier then it will be farther on into it's lift and the clearance between piston and valve will be closer. If the exhaust valve is open longer then the same thing applies. See, the two valves have more overlap (period of time in crank degree that both are open at the same time). It's overlap that makes the difference, not the lift.

Does that help?

-Mindgame

 

A bunch, thanks. Now..how do you check this? I think theres a tool that Ive seen, but dont remember. So thats what the 224/230 means then. When the crank is at 224* the intake valve starts opening, and when its at 230 the exhaust opens, is that right, or even close?

 

jon,

For you're timing questions, I think you'll get more with illustrations and the like. Go here: http://www.compcams.com/information/tutorials/

On the checking thing.
You can use clay... just place a bit on each valve pocket and rotate the engine through a complete firing cycle. Use a compressed gasket or factor the difference into you measurement. The "measurement" is your thickness check on the clay after you've done this.
I prefer to use lightweight check springs (Comp and others sell them) and a dial indicator. You get the piston for the cylinder to be checked at tdc and push the rocker so the valve makes contact with the piston. You read the amount of travel at the retainer with the dial indicator. No clay and no chance of hydraulic error from the hydraulic lifter squishing out oil as the clay is smashed by the valve. Either that or you can use a solid lifter like alot of guys do. I prefer the spring method but that's just one of many ways.

-Mindgame

 

OK, I have to bring this back to the top for myself. I've been seriously contemplating putting 1.7 RR on my 1997 SS, but for a different reason. My car is essentially stock right now. I plan on doing a home port job on the heads, while installing some bigger valves. I don't want to replace the cam yet because I'll want to have a specific grind made when the car finally gets some forced induction. I know wjen I have the new cam ground that I can have them grind it around the fact the car has 1.7 RR on it.
Is this a good idea on a stock cam? It seems as though this would be a good situation to install some 1.7s. Comments, concerns?

 

I would think so, but the problem is nobody really knows, Ive only ever seen one car in a mag with them, and theyre the crane variable ratio. Its basically a trial and error thing right now I think. It sounds good on paper, with the extra airflow, but a lot think that it will hurt port velocity and cause turbulence. Id like to do a dyno test before and after, but dont see that happening, maybe youd wish to.

 

Mindgame and company, just adding a few thoughts, comments, and/or questions:
1) Would there be any chance of this causing the pushrod to contact the head?
2) I believe you would run into problems w/ hitting the valve seal unless you changed this.
3) FREEBIE!!! instead of using a solid lifter w/ the "clay method" you can take a lifter (old preferably) pop off the retainer ring and put the plunger in backwards. Its pretty much the same height and won't compress.
4) I have special valve clearance clay (Play-doh brand) on sale right now for only $69.99 per 12 ounce can!!!
5) For $400 exactly why wouldn't you just buy a different cam? Come one, the installation takes a day.
6) I do commend you for your adventurous curiosity
7) LS1s come w/ 1.7s stock and SLP makes up to 1.85s for it. I've heard that Jesel has 1.9s now???
The reason these work on an LS1 is the different geometry of them.

 

I have seen the 1.7s for sale in the PACE catolouge, and thiers are stud mount. They are 300.53 for 16, with use of 7/16 studs. The problem I would be worried about is if the rocker will stay on the valve through the entire rotation of the cam. I'm no valvetrain expert, but have done some reading, and if I remember right then the tip of the roller should stay on the stem of the valve trough the entire rotation of the cam, someone correct me if I'm wrong though. Putting 1.7s on a SBC though, would more than likey mess with the valvetrain geometry. This is probably why you hardly see anyone use them, otherwise I would think that everyone would be bolting them on.

As for p/v clearance, The only sure way is to do a clay check, but .6 lift is roughly the max, though if I were going with something with that much lift I would want to do a clay check anyway.