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Old 05-23-2019, 09:27 AM
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is this symptom valve float?

So i have a 77 camaro, L31 vortec, gm hotcam 214/224, 3k stall, long tube headers, intake, HEI stock dizzy, 3.42 rears on a 200-4r -

When I mash it real hard, it sometimes feels like the car is in neutral for 2-3s at WOT.. like it just revs - when it settles down its back in power again.

Ive checked the trans fluid in N idling hot.. could the tranny be slipping at high rpms? Its quite a rocket, just wondering

Any ideas?

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Old 05-23-2019, 10:00 AM
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Could be a number of things. Do you have a tach? That trans is not the stoutest thing without some upgrades and depending on wear, previous use and the torque convertor clutch which is electronically controlled something could be going on there. I doubt seriously if the engine is climbing into valve float area but again depending on previous use and condition, the valve springs could be marginal as could the lifters. The stock HEI is a rev limiter in itself, typically not much good over 5000 rpm.



I tried looking up cams given the little information you provided but searches keep taking me to solid lifter hydraulic units and I think stock this engine was a hydraulic roller?
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Old 05-23-2019, 12:47 PM
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Is the TV cable set right? Any idea of line pressures? What has been done to the 200?

If this is a bone stock unit with an incorrectly set TV cable, then I'll predict it's time for a transmission rebuild.
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Old 05-23-2019, 01:09 PM
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3K stall converter? I'd be talking with the manufacturer.
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Old 05-23-2019, 03:42 PM
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You need to tell us when, and at what rpm this is happening.

If it is happening from a stop, as soon as you mash it to WOT, then it isn't valve float.

If this is happening at upper rpm, and goes away just as soon as the car settles into the next gear at the shift....then it could be float, but could also be ignition or fuel delivery, or even transmission related.

Does it feel like power is just going flat, at the top of the rpm scale, and then comes back after the shift is made.....or is it actually a free-rev rpm flare like it was placed in neutral??

What valvespring is being used??
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Old 05-23-2019, 09:01 PM
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Most likely the transmission isn't holding, probably the line pressure either isn't high enough or it doesn't come up fast enough.

Bogie
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Old 05-23-2019, 09:37 PM
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sorry guys - was super busy all day.

Cam: https://www.summitracing.com/parts/nal-24502586
LT4 Hot Cam
Lift: .525'' Int. / .525'' Exh.
Duration: 218 Int / 228 Exh. @ .050'' Lift
112 Lobe Centerline

I built this motor as my 1st and the 3k stall was ericnoavs continued convincing lol-

No tach - im seriously gonna get one.. but id have to say its when im at peak revs.. id take off from standstill and the car does pull pretty darn hard.. its when i hit maybe 60mph after its "bled out" it hits like a soft spot where very little happens, like its just revving but not much happening.

I have to say the headers to knock the shift linkage now and then, ive had it pop the tranny out of gear.. and wondering if thats whats happening - the tranny is getting thrown out of gear.. i usually play with the column shifter so cant say 100% its always out of gear.

I need to get underneath and sort the darn exhausts out! but i threw yet another rod bearing on this thing - so the motor is coming out and this time im not on some road 3k miles from home, im gonna mic and build this thing from head to toe, balancing rods, quench, checking springs and install height, the full whammy-

fyi what springs would be recommended? Iirc i used elgin matched springs after cutting the heads with the comp tool.. cant recall the model -

input welcome -
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Old 05-23-2019, 10:40 PM
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If the trans were really going into neutral, the rpms would free rev right out of site as soon as that happens 7500+ rpm just in the blink of an eye.

Sounds more like it is just going flat on power....which could be fuel delivery, ignition, valve float, cylinder head reaching airflow max(choke) or the same choke from the intake manifold, carb too small, exhaust a restriction.

If it doesn't do that in second gear at the same rpm, then you can eliminate valve float and ignition issues but could still be other things from that list.

This may also be something that you get from being in low gear, 3 and 4 speed automatics often run into the feeling like the car has "outran" the power of the engine in low gear, and they often respond to a 1st to 2nd gear shift 300-500 rpm sooner than the 2nd to 3rd gear shift.

With you having replaced the springs, I wouldn't expect valve float unless you are just flat over-running the rpm capability of the hydraulic roller lifters....and without a tach to verify rpms, we have no idea if that could be the case.
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Old 05-24-2019, 09:57 AM
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ok thanks eric - ill get a darn tach - even if i have to wrie in a temp junk chinese led one for now. Ill report back when I have sth..
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Old 05-24-2019, 08:06 PM
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You need to correct that transmission/shifter issue before spending much time and money on the engine. Most of the GM automatics do not take well to being "in-between" gears due to shifter linkage being out of whack. It's a quick way to burn up clutch discs and smoke drum assemblies.
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