Staggered rockers.. mixing 1.7's & 1.6's

[Tubo(2-bo)]

I realize this is rather old school stuff, but all my experience is w/classic Mustangs & engine combos.
My 5.0 EFI(in 65 2+2) is dead stock, AOD w/3.25 T-loc. And will be till the body work is finished and a performance base with stock engine is established. The car will be a sometimes driver, weekend cruiser, occasional 1/4 mile trips & occasional 600 mile trips.
After the performance base is established, I'll add 70mm MAF, 65mm TB, port matched Exploder GT-40 intake, GT-40y heads(port matched-mild ported & 60cc chamber) JBA shorty's, BBK 2.5 X pipe-no cats, Dynomax 2.5 exhaust. All parts are already purchased & sitting on the shelf, so there are no "You should use" needed.
I have a set 1.7 rr's, but am interested in mixing 1.6 intake rr's with 1.7 exhaust rr's. A search has not revealed a lot. Apparently all 1.6's or all 1.7's dont really add all that much HP, but the mix will give an additional 10RWHP, and give a slight lope to the exhaust.
How well does this combo live on the street, and if this isn't done any more why?

 

[jackchan]

i thought about trying the same thing, but I just cant see buying two sets of rockers! The money would be better spent on a cam with exactly what you wanted for $50 more (custom cam ($250)! just my two cents!

as far as it living and giveing more power, lope, better sound.........it prolly will. NO reason will it not live on the street. The heads and rockers dont know anything but general work. They will live no problem IMHO!

let me know how that thing turns out, I'm just over the two bays (pensacola, mobile) from ya!
Jack

 

[Michael Yount]

It's not gonna make a big difference either way. The Y head is intake biased and could probably use the help on the exhaust side with the stock cam.

Perhaps you could dyno both ways and tell us what you find out. I'd be surprised if any combination makes more than 5 rwhp worth of difference. If I had both sets available and didn't need to sell a set intact, I'd do what you're doing -- I'd put the 1.7's on the exhaust side.

My combo is very similar to yours -- with a mild custom cam instead of the stocker.

 

[Michael Yount]

Just re-read -- if you have the 1.7's - put 'em on. As the other poster mentioned -- definitely not worth investing in a set of 1.6's. A different cam is a MUCH better approach than buying another set of rockers to mix/match. And long tubes would really help the exhaust side of things with those heads.

 

[Tubo(2-bo)]

I got the idea from a buddy who used to race his 93 Cobra. The rational is lift ='s duration. It essentialy makes the stock single pattern cam a dual pattern cam.
The searches I did here & at corral.net revealed dyno run not much gain, except friction reduction, w/all 1.6 or 1.7, but the mix gave a 10 RWHP gain.
The used Y heads(after porting & milling their closer to X's) came with a set of 1.7's, I'd been led understand that 1.7's arent the best street ratio, so I was looking for a set of 1.6's when my friend told me about mixing the ratios.
Thanks for the input.
Anyone interested in swaping 8 1.6's for 8 1.7's??

 

[Michael Yount]

I understand the rationale - but I don't think you can generalize that result to your set up. Too many differences it sounds like to me. Good luck with it.

 

[Speeds8erM-1]

Im curious also, would mixing the rocker ratios make more power than all 1.7's on a stock head and cam setup?

 

[Michael Yount]

With an all stock set up, I'm not sure which way the 'help' would be needed. Perhaps someone has modeled it. I doubt anyone has experimented on an all stock car though - so many other changes usually get made first. It's purely a guess - but if the car had the stock heads/cam/intake but a decent aftermarket exhaust system - it might benefit from some help on the intake side to overcome the stock lower intake's meager flow potential. Purely a guess.

 

[Tubo(2-bo)]

Here's an article, about using the mixed rockers. http://www.compcams.com/community/articles/details.asp?ID=-1449395609
There is a better article , I havent located it again yet.

 

[Michael Yount]

Neat article -- as I mentioned earlier though, it's only good for their set up. You can't do much generalizing of what occured there to other set ups.

 

[Tubo(2-bo)]

As I posted in the begining, this is still a bit into the future, just trying to stay informed.
As things sit right now, I have a set & 1/2 of 1.7's so anyone interested in swaping a set of 1.6's for a set of 1.7's??
Now, if we can figure a way of installing a 5.0 into my 850 wagon.....

That would be a Ford of Sweden.... Volvo 850 wagon

 

[Topdowncruise]

As you can see in my sig,my mods are similiar to yours. If you have 1.7's, I don't know why you wouldn't put them on both intake and exhaust.I was told the extra lift compared to the 1.6's with a stock cam was worth about 10 HP but i can't verify since I did all my engine mods at the same time.Valves are open 6.25% more so it should be worth something.My setup seems as streetable as before the mods just way more power.

 

[Michael Yount]

tubo3 - I'm one of the few on this board that knows what you mean when you say '850 Wagon'. A bit more work for you V8-ing that than it was my 242 -- you've got a fwd 'problem'.