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#1
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I was looking at the 68404-16 - Crower Valve Springs. Is the seat pressure of 113lbs going to be sufficient or is there a better choice.
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#2
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Good choice.
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#3
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thats fine for break in, but after 1000 to 1500 miles I would add atleast a .030" shim as that 113 lbs will drop off to around 106 and you really want to see 120 to 125, so at that point a .060" shim would do the trick.
I would try both size shims now and note how much pressure they add so 1000 miles from now you know what shim to stick in. |
#4
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Why would you need that much spring pressure for a hydraulic cam that won't see 6000 RPM? I'm just curious.
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#5
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Seems like 110# @ 1.59" would be plenty...after break-in
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63 Catalina coupe 467 cid budget drag car 11's 1/4 , 7.20 1/8th pump gas n/a 66 Star Chief Executive 57k mile 69 Le Mans 2 dr HT 350 85k mile 15 sec 1/4 69 Firebird 400 Burgandy/Black 70 Olds Rallye 350 F85 4 speed 3.91's 70 Olds Cutlass Cruiser Red Wagon 350 101k miles 15 sec 1/4 12 sec w 455 74 Cheyenne Super C10 LWB Gen 6 454 w ZZ502 cam 3.07gear 13.1 1/4, 8.3 1/8 2020 RAM 1500 SLT 4x4 5.7 A8 Hemi 2007 Hummer H3 3.7 liter turd 2019 Chevy Spark petrol car 38 mpg |
#6
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steve25 is on the money.
Pontiac used 125lb@1.586" installed height on the #744 for a reason, valvefloat. I tried the "std" valvesprings of my lowmiles 1971 #96 heads with the #744 and the engine refused to rev above 4500rpmīs, i switched over to the valvesprings (used) from a set of #48 heads with the correct strength and the engine now revīs until the TH400 shifts at 5400rpmīs. Also, a quick look at the lobes of a #744 will give you an idea why the somewhat high valvespring pressure is required? I think most people trying the #744 and dislikes it used too weak valvesprings for it. 1973-74 455SD uses the same grind as the #744 with 110lb@1.800" installed height springs. |
#7
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I used stock springs and did not have an issue with this cam. I missed a shift and the engine saw somewhere around 7000rpm and did not float the valves. I probably was lucky (well, maybe not, it would have been nice if the valves had floated at 6200rpm
![]() Track73, In a 400 it will pull to 6000rpm easily. I ran it with a T1 and it felt like there was more left after 6000rpm but I didn't dare go higher with stock rods/bolts. I think an unmodified stock intake will have best shift point at 5700rpm or so. |
#8
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[QUOTE=Kenth;3556477]steve25 is on the money.
Pontiac used 125lb@1.586" installed height on the #744 for a reason, valvefloat. I tried the "std" valvesprings of my lowmiles 1971 #96 heads with the #744 and the engine refused to rev above 4500rpmīs, i switched over to the valvesprings (used) from a set of #48 heads with the correct strength and the engine now revīs until the TH400 shifts at 5400rpmīs. QUOTE] Kenth, Using 35+ year old stock springs on a build is never a good idea.. I doubt they had over 75# on the seat. I used to use the Erson springs all the time and also had good results, I have swapped aftermarket used springs from one set of heads to another but only if I new the history/age of it.. worked good.. 125# on the seat is on the high end most hi-perf cams and with a low-lift cam with gentle ramping I don't see the need. I have yet to try a 744 would like too..
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63 Catalina coupe 467 cid budget drag car 11's 1/4 , 7.20 1/8th pump gas n/a 66 Star Chief Executive 57k mile 69 Le Mans 2 dr HT 350 85k mile 15 sec 1/4 69 Firebird 400 Burgandy/Black 70 Olds Rallye 350 F85 4 speed 3.91's 70 Olds Cutlass Cruiser Red Wagon 350 101k miles 15 sec 1/4 12 sec w 455 74 Cheyenne Super C10 LWB Gen 6 454 w ZZ502 cam 3.07gear 13.1 1/4, 8.3 1/8 2020 RAM 1500 SLT 4x4 5.7 A8 Hemi 2007 Hummer H3 3.7 liter turd 2019 Chevy Spark petrol car 38 mpg |
#9
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I am using the HO VS-11 springs. They are stock dimensions and give around 120# seat pressure @ 1.59. They list that they are good up to 0.517 lift but Ken at HO says they will handle much more than that without a problems. Great spring and they are very reasonable pricewise.
http://www.hoenterprises.com/WSFF/ho...?vCompID=27383
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1968 Firebird 400HO convertible 1971 Trans Am 4-speed, white/blue |
#10
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Springs I have tested usually loose about 10% after run a while.
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