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Old 07-13-2014, 09:35 PM   #1
rowen210
 
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Default GT40 heads w/ stock HO rockers?

Dont rost me about using the search function. I could not find what i was looking for!

I aquired some 93 GT40 heads off of craigslist today. Stock springs with no rockers. Can I use my 86 stock rockers on the cobra heads? I have a tfs stage 1 cam (510 intake lift) that recomends 1.6 rockers. I feel that 1.6 rollers would be a waste of cash on my slightly over stock powered build.

86 machined block, crank, and rods.
93 cobra heads and springs
Speed pro 4.030, 4 valve relief pistons
Tfs stage 1 cam
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Old 07-13-2014, 10:57 PM   #2
tinman
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The stock rockers are 1.6 ratio.
I would check valve to piston clearance before I ran engine however.
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Old 07-14-2014, 06:59 AM   #3
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those springs are not enough for a tfs 1 cam, you'd be wise to get the proper springs for that cam.............and search the classifieds for a decent set of roller rockers, but if you must use the stock rockers, retainer clearance should be checked and push rod length must be verified.
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Old 07-14-2014, 07:58 AM   #4
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Unconfirmed reports (people on the forums) say the cobra springs can handle 530 of lift and I'm a little below that at 510. I do not know what kind of life the springs have lived. Can my machine shop check the condition of the springs or do I REALLY need new springs.
Broke college guy trying to save money problems.
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Old 07-14-2014, 07:59 AM   #5
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Are the E6 rockers the same as the E7 rockers? How about the push rods?
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Old 07-14-2014, 08:51 AM   #6
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Originally Posted by rowen210 View Post
Unconfirmed reports (people on the forums) say the cobra springs can handle 530 of lift and I'm a little below that at 510. I do not know what kind of life the springs have lived. Can my machine shop check the condition of the springs or do I REALLY need new springs.
Broke college guy trying to save money problems.
Sure the cobra springs might handle a 510 lift of a letter cam , but the ramp rate is a little more aggressive with the tfs stage 1 . Your springs will not recover fast enough at high rpm and your going to start to see valve float up around 4500-5000 rpm.
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Old 07-14-2014, 09:17 AM   #7
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Quote:
Originally Posted by rowen210 View Post
Unconfirmed reports (people on the forums) say the cobra springs can handle 530 of lift and I'm a little below that at 510. I do not know what kind of life the springs have lived. Can my machine shop check the condition of the springs or do I REALLY need new springs.
Broke college guy trying to save money problems.
lift is not a criteria of what "those" springs can handle, there is way more to it that that,...such as lobe profile, ranp rates, lazy lobe vs semi vs aggressive lobe......you need to keep the roller on the lobe and those springs won't do it properly, unless the tfs 1 carries the same lobe profile as stock those springs will not work for that cam to perform optimally and risk valve float and destroy your hard work, (FYI TFS 1 DOES NOT CARRY SAME LOBE PROFILE) it won't pay to be cheap. Run those SPRINGS with that cam and do one dyno pull and watch the graph spit out valvetrain issues, that's of course saying you can interpret what you see on the graph and apply it to the running characteristics. I've been your route more than once. Broke college student or not, you'll be even more broke when you have to do the job twice, and measure for push rods!! all cams base circles are not created equal, which does change what length push rod needed.
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Old 07-14-2014, 11:08 AM   #8
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Ok. Enough said. I will replace the springs. While I have several members attention do I NEED to get new lifters to go with the new springs?
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Old 07-14-2014, 11:38 AM   #9
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Ok. Enough said. I will replace the springs. While I have several members attention do I NEED to get new lifters to go with the new springs?
Not a have to, but why not while you're already in there.
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Old 07-14-2014, 02:36 PM   #10
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Ok. Enough said. I will replace the springs. While I have several members attention do I NEED to get new lifters to go with the new springs?
no, lifters are fine, no need to replace
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Old 07-14-2014, 02:36 PM
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