Flat spot at 5000 RPM what can cause this?
03-12-2002, 09:46 PM
#1
Burning Brakes
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Flat spot at 5000 RPM what can cause this?
I have been trying to tune the car for runs on the dyno on the 23rd. I fixed my timing issues and trying to figure out why the car goes flat at around 5000 rpm.
First thought is fuel, maybe my vacuum secondaries are not opening.
Second thought, well I haven't got that far yet.
Any suggestions? I'll have to quick making hot run up and down my street tonight the neighbors are trying to sleep. But I will continue tommorrow.
First thought is fuel, maybe my vacuum secondaries are not opening.
Second thought, well I haven't got that far yet.
Any suggestions? I'll have to quick making hot run up and down my street tonight the neighbors are trying to sleep. But I will continue tommorrow.
03-12-2002, 09:52 PM
#2
Drifting
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Re: Flat spot at 5000 RPM what can cause this? (BLT-71)
Sure does sound like fuel. Have you removed the bronze filters from the
Holley. They have caused this problem many times.
You'll need an external filter.
Maybe fuel pump, however GM pumps usually develop a leak before they fail.
Barry
Holley. They have caused this problem many times.
You'll need an external filter.
Maybe fuel pump, however GM pumps usually develop a leak before they fail.
Barry
03-12-2002, 09:56 PM
#3
Le Mans Master
Re: Flat spot at 5000 RPM what can cause this? (Barry's70LT1)
did you change the valve springs when you installed the new solid lift cam? just a thought solid lift cams like fresh valve springs.
03-13-2002, 08:32 AM
#4
Burning Brakes
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Re: Flat spot at 5000 RPM what can cause this? (Barry's70LT1)
I already run an inline filter and it is brand new, bought 3 days ago.
When I had the engine rebuilt I had matched set of cam springs push rods etc.
Fuel pump is new also, lots of new stuff.
Fuel still may be it I am going to find if my secondaries are opening and how well.
When I had the engine rebuilt I had matched set of cam springs push rods etc.
Fuel pump is new also, lots of new stuff.
Fuel still may be it I am going to find if my secondaries are opening and how well.
03-13-2002, 08:41 AM
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Pro
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Re: Flat spot at 5000 RPM what can cause this? (BLT-71)
Wazzup! One good thing is that you have it running but going flat at 5k isn't going to cut it when you're up against those powerful Buicks :D It sure does sound like fuel though. Is it just going flat or floating out? Regardless of gear? Possibly in the carb? Maybe check the fuel line to see if its restricted anywhere (possibly kinked during install?). No real ideas here, just throwing thoughts out. Hope all is well.
I have been trying to tune the car for runs on the dyno on the 23rd. I fixed my timing issues and trying to figure out why the car goes flat at around 5000 rpm.
First thought is fuel, maybe my vacuum secondaries are not opening.
Second thought, well I haven't got that far yet.
Any suggestions? I'll have to quick making hot run up and down my street tonight the neighbors are trying to sleep. But I will continue tommorrow.
First thought is fuel, maybe my vacuum secondaries are not opening.
Second thought, well I haven't got that far yet.
Any suggestions? I'll have to quick making hot run up and down my street tonight the neighbors are trying to sleep. But I will continue tommorrow.
03-13-2002, 02:03 PM
#7
Burning Brakes
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Re: Flat spot at 5000 RPM what can cause this? (Tex71BB)
TEX! I couldn't handle all the spider webs. :lol:
Demar what are you doing on the 23rd. I'll be in Bloomington with other vettes running on a dyno. Drive over for the fun of it or to run. Check it out on the Great Lakes board.
FYI: Kristy and I found out that we will be having a boy. :cheers:
Demar what are you doing on the 23rd. I'll be in Bloomington with other vettes running on a dyno. Drive over for the fun of it or to run. Check it out on the Great Lakes board.
FYI: Kristy and I found out that we will be having a boy. :cheers:
03-13-2002, 02:56 PM
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Burning Brakes
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Re: Flat spot at 5000 RPM what can cause this? (BLT-71)
FYI: Kristy and I found out that we will be having a boy. :cheers:
03-13-2002, 04:07 PM
#9
Pro
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Re: Flat spot at 5000 RPM what can cause this? (BLT-71)
Brian - we're heading for Orlando on the 23rd - part business-part pleassure. We do need to get all together again, maybe Suds some Saturday? Let me know.
BTW - congrats on the baby boy! You'll need to get him one of those car seats with a steering wheel for when you take him crising with you! A little father/son bonding time - Kristy will understand.
BTW - congrats on the baby boy! You'll need to get him one of those car seats with a steering wheel for when you take him crising with you! A little father/son bonding time - Kristy will understand.
03-13-2002, 06:20 PM
#10
Platinum Supporting Dealership
Re: Flat spot at 5000 RPM what can cause this? (Demar)
Are you sure you just aren't feeling the point where the torque and hp curves cross? Is it really falling flat, or just a small letup in seat of the pants? Dyno or on the street?
03-13-2002, 08:48 PM
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Burning Brakes
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Re: Flat spot at 5000 RPM what can cause this? (Chris@VetteFinders)
Found the problem, but I am having problems resolving it.
The vacuum secondaries are not opening.
1) Put a paper clip on and it did not move after a few very hard pulls up and down the highwy.
2) pull the diaphram assembly off and tested it. The diaphram opens with very little vacuum from the vacuum pump and it holds. So it is good.
3) Sprayed carb cleaner through the venturi for the diaphram and it is clean and clear.
4) Put the lightest spring in the assembly.It barely opened an 1/8 inch or less or paper clip slid down.
5) I am waiting for devine guidance...........help..what should I try next?
The vacuum secondaries are not opening.
1) Put a paper clip on and it did not move after a few very hard pulls up and down the highwy.
2) pull the diaphram assembly off and tested it. The diaphram opens with very little vacuum from the vacuum pump and it holds. So it is good.
3) Sprayed carb cleaner through the venturi for the diaphram and it is clean and clear.
4) Put the lightest spring in the assembly.It barely opened an 1/8 inch or less or paper clip slid down.
5) I am waiting for devine guidance...........help..what should I try next?
03-13-2002, 09:19 PM
#12
Re: Flat spot at 5000 RPM what can cause this? (BLT-71)
Are you sure that your pedal and linkage are giving you WOT ? If I'm not mistaken, the Vac secondaries will not open fully until the primarys are wide open.
