1.7 rockers on gt40 heads?
10-25-2012, 02:40 AM
#1
Thread Starter
Join Date: Sep 2010
Location: WV
Posts: 44
1.7 rockers on gt40 heads?
I've googled an searched lookin for a direct answer, sorry I'm sure this has been posted before so hopefully it won't be a long thread.running a 93 mustang block, gt40 heads with new springs and a e303 cam.Can I uupgrade to the 1.7 roller rockers with no other modification? I've seen some say yes some say to close gaskets make the difference n diff stuff.also if I can is it a worth while almost "bolt on" upgrade? Valve covers aren't a issue either running proform tall carbon fiber covers.Thanks for any input
10-25-2012, 07:18 AM
#2
2nd Gear Member
Join Date: Sep 2011
Location: Ohio
Posts: 325
When I added 1.7 roller rockers to my 89 years ago, it definitely added a few hp (and cost me 1.5 mpg). Whether you can do it or not will come down to piston to valve clearance, and every engine is different.
10-26-2012, 12:44 AM
#3
5th Gear Member
Join Date: Aug 2004
Location: Arizona
Posts: 4,103
Not only is it about piston/valve clearance but it's also about the valve springs.
Do you have enough spring for the extra lift without 'stacking' the springs?
The only way to find out is to mock the engine up with the 1.7 rockers and turn it so that one valve is all the way open, use a piece of wire that about.060 in diameter to check between the coils of the spring, if it will pass thru all the coils except the top and bottom, you are good to go.
I assume you used new valve springs with the new cam, ya did didn't ya...........
Do you have enough spring for the extra lift without 'stacking' the springs?
The only way to find out is to mock the engine up with the 1.7 rockers and turn it so that one valve is all the way open, use a piece of wire that about.060 in diameter to check between the coils of the spring, if it will pass thru all the coils except the top and bottom, you are good to go.
I assume you used new valve springs with the new cam, ya did didn't ya...........
10-26-2012, 07:41 PM
#6
The 1.7 rockers have advantages and disadvantages. Obviously they make more power and add in a bit more lift to the cam.
The down sides are you have to be careful with valve clearance. Most 1.7 kits will come with shims to ensure that you maintain proper clearance but you still have to pay attention to that.
The other down side is they do reduce valve train life, from what I've seen you will need to rebuild the valve train around every 80,000-100,000 miles with the 1.7s to maintain power and prevent the valves from "floating". Again this isn't a definite range as every motor is different.
The down sides are you have to be careful with valve clearance. Most 1.7 kits will come with shims to ensure that you maintain proper clearance but you still have to pay attention to that.
The other down side is they do reduce valve train life, from what I've seen you will need to rebuild the valve train around every 80,000-100,000 miles with the 1.7s to maintain power and prevent the valves from "floating". Again this isn't a definite range as every motor is different.
10-26-2012, 09:53 PM
#7
5th Gear Member
Join Date: Aug 2004
Location: Arizona
Posts: 4,103
Valve train that lasts 80-100,000 with no ware is sort of a dream.
I've seen valve springs with less than 10,000 miles on them lose more than 20% from both seat and open specs.....
They were Ford motorsport BTW.......
I've seen valve springs with less than 10,000 miles on them lose more than 20% from both seat and open specs.....
They were Ford motorsport BTW.......
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