Anyone using 1.7 rr on intake and 1.6 on exhaust with gt-40 heads?

bjl95mustang · Sep 26, 2004

I got 2 sets of rockers for my setup and I am trying to deciede if I should use the 1.6, 1.7, or 1.7 intake and 1.6 exhaust. I'm building up a budget 306 with home ported gt-40 heads between 62-58cc(not milled yet) with a tfs-1 cam and a home ported performer intake, shortie headers, off-road h-pipe and 24lb injectors. I have read about people doing half and half but i wanted to see if anyone here has done it.

Thanks,
Brandon

RIO5.0 · Sep 26, 2004

I wanted to try that myself....If there 1.7 peds, I'll buy the other 1/2 from ya...

It may not add alot. hp wise...but every little bit adds up....I posted it some time ago after reading and article in 5.0

bjl95mustang · Sep 26, 2004

Do you still have the post from 5.0?

wytstang · Sep 26, 2004

I thought it was 1.6 intake and 1.7 exhaust if your N/A and 1.7 intake and 1.6 exhaust for power adder.

Joes95GT · Sep 26, 2004

I'd do the 1.7/1.6 I/E combo. If you're using a standard split pattern camshaft or even a single pattern camshaft, use the 1.7's on the intake side. The exhaust will find it's way out.

You may pick up a few...

Joe

wytstang · Sep 26, 2004

I thought that ford's needed help on the exhaust side so using the 1.7 on the exhaust side would benifit them more. :dunno:

bjl95mustang · Sep 26, 2004

I have also been thinking about using 1.7E and 1.6I. Damn, I don't know.

Joes95GT · Sep 26, 2004

The TFS cam has a split in it, so a 1.6 on the exhaust is fine.

A 1.7 on the intake side will give you a little more top-end by making the cam act bigger than it really is. And no, there won't be any side-effects of running 1.7's on the intake side.

Joe

bjl95mustang · Sep 26, 2004

Cool, I guess i will do 1/2 & 1/2 and see how it is.

cmozez · Sep 27, 2004

In 5.0, thier best results came from 1.7 exhaust and 1.6 intake.

bjl95mustang · Sep 27, 2004

Does anyone have the 5.0 mag online so i can read it?

krahkin · Sep 27, 2004

I do, but I will have to dig through the pile to locate which issue

Joes95GT · Sep 27, 2004

cmozez said:
In 5.0, thier best results came from 1.7 exhaust and 1.6 intake.

And it was probably with the stock cam, which favors the intake side. So 1.6's on the exhaust "evened" things out. I'm not saying I'm right, but I wouldn't believe everything in magazines.

Joe

wytstang · Sep 27, 2004

But wouldn't having a larger lift on a N/A engine even with a cam help evacuate the cylinders better. Thus allowing the cylinders to fill back up with a more pure combustion able mixture.
EDIT: I’m not arguing with you just having a discussion.

bjl95mustang · Sep 27, 2004

Well, I wonder what I should do. If i do 1.6 on the intake will be at just around .499 and I think .512 exhaust. I believe my springs are good to .550-600. These are home ported gt-40 with stock sized valves.

1105 · Sep 27, 2004

I'd do 1.7 I 1.6 E. If you feel like it, do it both ways and see which one gives you the most power.

RIO5.0 · Sep 27, 2004

Info from the article....

1105 said:
I'd do 1.7 I 1.6 E. If you feel like it, do it both ways and see which one gives you the most power.

The 347 they tested in 5.0 mag with the 4 combos around 1.6/1.7. The motor had Z304 heads and an XE282HR comp cam...not exactly a stocker...They only got like 4 HP top with all the combos, 1.7s on the Ex side 1.6 Int was the best....Its kinda one of those "inching" things...theres not alot to be had, but some nonetheless...it also stated its one of those, why one combo will just pull a tad on another thats matched with the same stuff..all the gain was in the high RPM area...its not gonna be a seat of the pants thing...

GT40s are set-up for 1.7s anyway?? No?? Running 1,7 on a 1.6 can lead to valve guide wear some, due to the geometry being off some..Theres more cons than pros to doing it...rather than chg a cam for more lift, this swap can do it easier..

The article was in the Aug 2004 issue..." Lift and Invigorate" was the name..Whether its on line ???? Was a cool article on just 1.6/1.7 workings though...

bjl95mustang · Sep 27, 2004

The gt-40's on cobras come with 1.7rr. But i'm going to be using a tfs-1 cam.

bjl95mustang · Sep 27, 2004

The manufacture only has the specs with the rockers but no recomendations!!

bjl95mustang · Sep 27, 2004

Damn server.

Anyone using 1.7 rr on intake and 1.6 on exhaust with gt-40 heads?

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