1. By adding 1.7RR's to a stock internaled LT1 you would increase the lift from .450 .460 (Stock) to .510 .521 (1.7RR's) right?

2. Would this allow the engine to rev higher, allowing higher shift points?

3. Would I benefit from a custom tune for the increased lift?

Thanks!

JW

 

Good question, I'm also very interested in this.. How much more power would you make using the stock cam?

 

It will simply increase the valve lift, no more and no less.

This may allow more air into the combustion chamber, limited of course by cylinder head flow. Since the stock LT1 cylinder heads typically has max flow around 0.500" lift (exact point hard to determine), it may be of some use.

Higher RPM? No. More power, maybe. Measurable? On LT1 stock casting, doubt it.

You will have to change stock valvesprings to use 1.7 rockers because it's past coil bind.

 

Why would you say measurable? Of course it is measurebale. If people are gaining 10rwhp from 1.6 RR's, then 1.7 RR's will gain atleast that. I would call that measurable.

 

Just because someone "might" see as much as 10 hp from 1.6s doesn't necessarily mean that they would see another 10 from 1.7s. As mentioned, it is just more lift. The duration stays the same.

If anyone can prove that just adding 1.7RRS to a stock cam will provide a good 15RWHP, I will go out and get one at lunch.

 

1.7rr on stock heads. Uh oh!! I would strongly recommend NOT doing that. You will creat alot of turbulence which will end up robbing you of alot of power and second to that you'll need some strong valve springs to support that kind of lift.. RR shouldn’t even touch stock heads unless they are being accompanied by a cam swap or a blower/turbo/NOS.

 

MattysTA just did the 1.7 install on his car and i believe he has stock heads. He said it was a big gain on his car.

 

Perhaps you would lose power up top when the RPM get's higher. It's like your tap, open it up and it flows after a while the more you open the less gain in the water pressure.

 

Niterider buddy how will adding lift creat turbulence... stress on the valvetrain i'll go along with, but not turbulence. if you lifted past the point where the lt head (unported) goes turbulent ~600... maybe then. otherwise it'll be the same as it always was. and frictional losses in a stamped rocker being eliminated will lessen the heat in the top end and the stresses on some of those parts. as for it adding more power. well when a stock cam with 1.5 rockers on it is at x amount of lift vs. a stock cam with 1.7's the one with 1.7's has more lift at any given point along the curve something like 1.118 x nomral (note: this is an aproximation). which will get more air in the engine which makes more power. its sort of a trade off though in that you get rid of frictional losses but it takes slightly more power to push open the valves now with heavier springs... i say in the end you still come out ahead. lt1 heads tend to stall around .450 or .500 in stock form... but they dont fall off until about .600 so if you can get to where the peak is longer and stay there longer you make more power. on another note with 1.7's i recommend installing larger studs like has been mentioned before. i now own a set of 1.7's but its because i wanted something odd when i order my cam .
the amount of power gained well thats a crap shoot just like with any engine production motors like different things because they're all just a little different. get good pushrods if you do this though. and dont skimp on any parts the valvetrain ain't the place to cheap

 

Your right, I forgot the heads will handle up .600 lift. But it simply is not worth it going 1.7.

 

When it comes right down to it, we can speculate all we want to, but proof is in the experience.

Just like cam profiles, you need to look first at what kind of driving you expect to do and then put together the package that will best support that decision.

If you just put 1.7 RRS on with stock cam and heads, you will probably notice a signifcant gain. Or maybe even adding the higher ratio to an RV cam which tends to preserve lower-end torque and maybe the the higher lift will really wake it up. I just don't know.

I do know that if I want more power, that going with good heads and cam is the way. And if you go that route, you probably don't need to concern yourself with going with 1.7RRs.

Save your money for real performance. JMHO

 

even in some cammed applications you cant achieve the lift you'd like to out of the lobes available with 1.6's so stepping to a 1.7 is a very easy solution. thats why i have them. for the general public though i would still recommend 1.6's. as for worth it going to 1.7's from flatlanderracing you can buy a set of 1.7 scorpion rockers for about 200. so if you're talking about it not being worth it.. i suppose they could wiegh more than the steel rr's offered from comp. but yeah most of this stuff is speculation. except for more lift makes more power look at the solid rollers granted they have more aggressive ramps but they all blow hydrolics out of the water if you look at the right catalog for lift vs. duration. thats a small part of why they make more power.

 

I installed 1.7's last year on my TA with EXCELLENT results. There is NO turbulance issue created with 1.7's and stock heads. The lift produced just is nowhere near high enough for that to happen. Yes it will increase the power band, my bolt-on combo pulled to 6300 after the rockers.
Hell 11.94 out of a Bolt-On LT1 ain't bad.
The only issue you will have is valvetrain geometery. You must use GM Bow Tie guide plates for a good set up. I can't remember the PN for these guide plates, but Matt might. Also I'd reccommend the Isky stock replacement springs as they are good to .550 lift.
I understand that Comp Cams now has a 1.7 rocker. I had dinner a few weeks back with Chris from Comp Cams and he was giving me a hard time for using Crane rockers on my car and told me about the Comp rockers, LOL... all in fun.
Anyway go with the 1.7's you wil not be disapointed.
Give the folks at Thunder a call as I believe they can set you up with the Comp 1.7's and all required components.
Good luck guys!
Steve...

 

Nice. What was the mph?

 

11.94 @ 111.50, 1.53 60'