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GT40X SPRINGS 

 

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 Post subject: GT40X SPRINGS
Posted: Tue Mar 20, 2007 8:46 am 
Stock as a Rock
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howdy,

i am buying a set of Gt40X heads and am thinking springs. are the Gt40X springs in the complete head OK. or would it be better to get a set of comp cams beehive type, remembering i may have to machine.

the cam is a CC XE270HR, and the car will be used for mainly street, so no competition. i guess springs are relativelt easy to replce if they are no good.

also the heads are the 58cc type, so do you think i will have valve-piston clearance issues? should i go 63cc.

cheers

 

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Posted: Tue Mar 20, 2007 11:20 am 
Tyre Shredder
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i dont know what springs gt40x comes with mate if not doubles id get the matching comp springs , i used them with mine and seem fine so far.....theyre quite high lift the comp cams, id ask the guys your gettin the heads from what sort of lift theyre ok for ....presuming your deck height is stock? i cc,d my gt40ps and took 20 thou off chamber size worked out at 61cc i had borderline clearance with 1.7 rockers
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Posted: Tue Mar 20, 2007 12:06 pm 
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I used an XR264 cam with stock GT40 springs with no probs and I used 1.7 rockers also. You really should check the springs in a tester first and see if they match what the cam sheet suggests.
The chamber is actually cast smaller in 40X head so the valves aren't any closer to the piston due to milling of the head hence chamber size does not affect clearance. However, once again you should dummy up the engine and use plasticine to determine piston to valve clearance.

Pete.
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Posted: Tue Mar 20, 2007 12:15 pm 
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On the topic of springs in GT40 family heads, Pete, whats your opinion of crow 7738s, with a TFS1?
Ever had problems with the crow product?
Specs on them are...
Installed Height - 1.800"
Installed Pressure - 115lb
Pressure @ .50" - 200lb
Max lift - .640"
Solid height = 1.140"

 

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Posted: Tue Mar 20, 2007 12:23 pm 
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thanks guys, good advice.

i think the springs that are used are FMS Single 3 1.006" 1.500" 110 lbs. @ 1.820" 240 lbs. @ 1.400" part # M-6513-A50. going by the comp cams spec sheet this should be OK. ford state these springs are compatible with all FMS roller cams.

XR9UTE, how did the 264 cam perform?

 

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Posted: Tue Mar 20, 2007 3:41 pm 
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Any performance roller cam should have 130Lb seat pressure / 350Lb open..
Roller cams require a firmer spring due to fast ramps & lift. Don't worry about wear, there's vertually no metal to metal contact to wear like flat tappet cams ..There is no way a Crane 2031 cam can run run with behive single springs long term, for example and they are quite a mild cam timing wise....

 

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Posted: Thu Mar 22, 2007 8:45 am 
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and if you already have the heads off ,doesent cost much to have them machined and spring heights set
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