GT40X Heads: Rocker Size and Rod Length?

One Bad Sixxx · October 28th, 2010, 09:20 PM

Just bought GT40X aluminum heads for the 306 I am building. With it I am throwing in a TFS1 cam, and upper and lower Cobra intakes. I know I can use the stock lifters, but with a TFS1, would it be bad news bears to go with 1.6 rockers? Or should I go 1.7? And what would the rod length be? Would it stay stock length? Or is it going to change?

69fastback · October 28th, 2010, 09:31 PM

1.6 rockers are fine. Anytime you change heads, cam, ect.....you have to measure for the correct pushrod length. There can be 20-30 hp loss with the incorrect pushrods.

One Bad Sixxx · October 29th, 2010, 11:19 AM

Would the extra port jobs on the heads, upper and lower intakes make a difference into what size rockers I should get for how much valve lift?

StangBanger302 · October 29th, 2010, 05:35 PM

Originally Posted by 69fastback

1.6 rockers are fine. Anytime you change heads, cam, ect.....you have to measure for the correct pushrod length. There can be 20-30 hp loss with the incorrect pushrods.

Really?? Damn...That's a decent amount on the table just from valvetrain geometry...So do you think I should tear my car apart, measure for pushrods and then order the better size? Cause my heads utilize stock pushrods. My local mustang shop suggested them for that reason: I was on a dirt low budget.

fogged306 · October 29th, 2010, 06:03 PM

Anytime you change valvetrain parts or heads or even have the block decked, valvetrain geometry needs to be checked, otherwise you could be leaving power on the table.

69fastback · October 30th, 2010, 01:23 AM

Originally Posted by StangBanger302

Really?? Damn...That's a decent amount on the table just from valvetrain geometry...So do you think I should tear my car apart, measure for pushrods and then order the better size? Cause my heads utilize stock pushrods. My local mustang shop suggested them for that reason: I was on a dirt low budget.

Yes, if you changed something. You're engine has to work a lot harder if the geometry is wrong, not to mention it can cause premature wear.

marshall88lx · October 30th, 2010, 09:56 AM

I have 1.7 rr on my gt40X's, but yeah def ought to get my valvetrain geometry checked also!

69fastback · October 30th, 2010, 09:59 AM

You can run 1.6s, or 1.7s. Whatever you want.

rauscher89lx · October 31st, 2010, 11:43 PM

this kind of helped me. hahaa thanks! i just scooped up a cobra intake, tfs1 cam, and trying to decide which heads, and then this was the next step. ha

October 28th, 2010, 09:20 PM	#1
One Bad Sixxx Enthusiast '02 4.3L V6 / '95 GT 5.0L Join Date: Apr 2007 Location: Nellis AFB, Las Vegas, Nevada Posts: 515 iTrader: 0 reviews	GT40X Heads: Rocker Size and Rod Length? Just bought GT40X aluminum heads for the 306 I am building. With it I am throwing in a TFS1 cam, and upper and lower Cobra intakes. I know I can use the stock lifters, but with a TFS1, would it be bad news bears to go with 1.6 rockers? Or should I go 1.7? And what would the rod length be? Would it stay stock length? Or is it going to change? __________________

October 28th, 2010, 09:31 PM	#2
69fastback Premium Member 1969 Mustang Mach 1 6.824@101.61 Join Date: Aug 2006 Location: Oklahoma jackass, get to driving Posts: 5,565 iTrader: 0 reviews	1.6 rockers are fine. Anytime you change heads, cam, ect.....you have to measure for the correct pushrod length. There can be 20-30 hp loss with the incorrect pushrods. __________________ ./___ _ ____ ___ \. ( ]]] _ _ O _ _ [[[ ) \_ o _ _____ _ o _/ \|___\| ......... \|___\| http://www.youtube.com/watch?v=HyYU3...e_gdata_player

October 29th, 2010, 11:19 AM	#3
One Bad Sixxx Enthusiast '02 4.3L V6 / '95 GT 5.0L Join Date: Apr 2007 Location: Nellis AFB, Las Vegas, Nevada Posts: 515 iTrader: 0 reviews	Would the extra port jobs on the heads, upper and lower intakes make a difference into what size rockers I should get for how much valve lift? __________________

October 30th, 2010, 09:59 AM	#8
69fastback Premium Member 1969 Mustang Mach 1 6.824@101.61 Join Date: Aug 2006 Location: Oklahoma jackass, get to driving Posts: 5,565 iTrader: 0 reviews	You can run 1.6s, or 1.7s. Whatever you want. __________________ ./___ _ ____ ___ \. ( ]]] _ _ O _ _ [[[ ) \_ o _ _____ _ o _/ \|___\| ......... \|___\| http://www.youtube.com/watch?v=HyYU3...e_gdata_player

October 31st, 2010, 11:43 PM	#9
rauscher89lx Regular 1989 Mustang LX 5.0 slow..help Join Date: Sep 2010 Location: Ocean County, NJ Posts: 113 iTrader: 0 reviews	this kind of helped me. hahaa thanks! i just scooped up a cobra intake, tfs1 cam, and trying to decide which heads, and then this was the next step. ha __________________

October 29th, 2010, 06:03 PM	#5
fogged306 MM Fanatic 89 GT Join Date: Apr 2007 Location: NY Posts: 4,875 iTrader: 2 reviews	Anytime you change valvetrain parts or heads or even have the block decked, valvetrain geometry needs to be checked, otherwise you could be leaving power on the table.

October 30th, 2010, 09:56 AM	#7
marshall88lx Newbie 88 Mustang lx Join Date: Apr 2010 Location: Millbrook,al Posts: 43 iTrader: 0 reviews	I have 1.7 rr on my gt40X's, but yeah def ought to get my valvetrain geometry checked also!

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