85 corvette rev limit
Thread Starter
Intermediate
Joined: Apr 2014
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85 corvette rev limit
Where is the rev limiter on my 85 corvette?
I pulled out of a buddies house yesterday and got into it about half throttle, came out sideways and right around 5,000 ish it started cutting out during the spin. Like a rev limiter. So my question is, what is the actual rev limiter on it? It is all stock except a high output coil and opened air filter lid.
I just want to know if there is a miss or I'm hitting the limiter. I've searched but can't really come up with an actual answer.
I pulled out of a buddies house yesterday and got into it about half throttle, came out sideways and right around 5,000 ish it started cutting out during the spin. Like a rev limiter. So my question is, what is the actual rev limiter on it? It is all stock except a high output coil and opened air filter lid.
I just want to know if there is a miss or I'm hitting the limiter. I've searched but can't really come up with an actual answer.
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
There is none. People say that the Rev limiter is at 10000 RPMs, but that's probably because the computer has no more programming to go passed that. What's happening at 5000 RPMs to you is because of the long runner intake. It chokes the motor, so the motor can't breathe to go any higher than around 5000.
Thread Starter
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Had a full tank of gas. It just seemed like a rev limiter like it was cutting off right there around 5,000-5,500
Will searching I saw some people saying that the l98's are limited at 5200 where it cuts the fuel off. Others say the limiter on them is 6500. So many people saying so many different things. Almost seems like nobody actually knows.
Le Mans Master
Joined: Aug 2007
Posts: 8,735
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From: WV
When I was playing around in the tune for my 89 in TunerPro , I saw a slider/box for setting the rev limiter... I didn't touch it, but it was either turned off, or set very high ( I can't remember which), I believe my tuner set it for my new 383 engine when he was tuning..When I asked him about it, he said I didn't have any rev limit , so I should be careful not to over rev, I don't know if the 85 is the same or not....WW
Last edited by WW7; Jul 24, 2014 at 11:38 AM.
Melting Slicks
Joined: Nov 2010
Posts: 2,216
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From: Michigan
There are a lot of stock parts that don't like to rev air-intake, intake-manifold, ignition and valvetrain. Once you address those you should be able to rev, but then your limit is the rod bolts.
Safety Car
Joined: Aug 2009
Posts: 3,751
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From: Melbourne, Victoria, Australia
Definitly no rev limiter on the 85, the cam /TPI runners and valve springs will limit the rpm on a stock engine.
I have a supercharged 383 that easilly revs past 6,000 rpm, I accidently went over 6,000 rpm when running it in in the first hour of it's life.
I actually have no need to test the rpm limits as the h/p and torque is available from idle with the blower.
I have a supercharged 383 that easilly revs past 6,000 rpm, I accidently went over 6,000 rpm when running it in in the first hour of it's life.
I actually have no need to test the rpm limits as the h/p and torque is available from idle with the blower.
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Melting Slicks
Joined: Jun 2013
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The 870 ECU on the 1985 Corvette does not have any provisions in the tune for a rev limiter. Therefore, there is none. Plus, I know I can get to 6k without a rev limiter on an 85. I had to buy a MSD 6AL2 ignition box to prevent myself from going over 6k. Couple close calls. The rev limiter saved me a few times too.
Thread Starter
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Earlier it did it at 4,000 rpm. Based off what you all have said, I'm definitely having a problem. Can any of you point me in the right direction of things to check that could cause this. Have new coil, plug wires, cap and rotor.
Would an ignition control module under the cap and rotor cause this? Just shooting from the hip here. New to the car scene.
Would an ignition control module under the cap and rotor cause this? Just shooting from the hip here. New to the car scene.
Team Owner
Joined: Aug 2004
Posts: 21,543
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From: Park City Utah
First thing I'd check.
Team Owner
Joined: Sep 2003
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From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
For stock engine, the TPI is the rev limiter.
Unless your attempting to go outside box like down shifting into second at 75MPH.
Unless your attempting to go outside box like down shifting into second at 75MPH.
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Burning Brakes
Joined: Mar 2013
Posts: 1,131
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From: Illinois/Wisconsin Line
In my experience regulator's Dump fuel in the plenum and leak and pumps just go bad and don't work like turning off a light switch {but sometimes the damn sock collapses on the pump in the tank and wont do it all the time, it's a real pain to find that one} and Injectors leak down and stop working
Its up to u to figure if thats even whats going on and or which one.
Pulling the vacuum line on the reg should get ya 40psi and it will run rich and may make ur motor pull harder, if you don't mind cleaning plugs under anything but maybe full throttle.
I'd say u need to run a full can or 2 of Injector clean hooked up on the rails with the pump line pinched or shut off and put ur wires off of any head or manifolds or maybe move them around in the dark along with some fresh plugs and filters if u haven't done so lately
Also the firing order always needs to be straightened out on all 1975 to 1991 V-8's It's 1-8-4-3-5-6-7-2 Cly #'s 4,& 3 and really 5 & 6 need to never cross or touch from the dist to the spark plugs
It will/can cause a mid to upper rpm breakup,miss fire not really when the wires r new but when they get a little older and kinda dry out
So thats what I would be doing or have done
Its up to u to figure if thats even whats going on and or which one.
Pulling the vacuum line on the reg should get ya 40psi and it will run rich and may make ur motor pull harder, if you don't mind cleaning plugs under anything but maybe full throttle.
I'd say u need to run a full can or 2 of Injector clean hooked up on the rails with the pump line pinched or shut off and put ur wires off of any head or manifolds or maybe move them around in the dark along with some fresh plugs and filters if u haven't done so lately
Also the firing order always needs to be straightened out on all 1975 to 1991 V-8's It's 1-8-4-3-5-6-7-2 Cly #'s 4,& 3 and really 5 & 6 need to never cross or touch from the dist to the spark plugs
It will/can cause a mid to upper rpm breakup,miss fire not really when the wires r new but when they get a little older and kinda dry out
So thats what I would be doing or have done
Last edited by cudamax; Jul 24, 2014 at 11:52 PM.
Team Owner
Joined: Aug 2004
Posts: 21,543
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From: Park City Utah
Doesn't matter teh exact number though; that your car runs good up to high RPM/WOT indicates that you have good pressure in normal driving...when you have the gauge on it, it shouldn't drop or waver at all as you climb through the RPM range at WOT. If it does, you have a problem.
Pumps can and do fail in a wide variety of ways; like a "switch", losing pressure under heavy load, making a lot of noise, etc.
If your pressure is what it should be in normal driving or idle, then "fades" under high demand, that is pump, filter, sock etc. -The FPR would be working fine. if the FPR has gone bad, your pressure issue would be constant and present under most if not all operating conditions.
The problem you're describing only occurs under WOT/high RPM, so it's very unlikely that it's a regulator.
Last edited by Tom400CFI; Jul 25, 2014 at 11:41 AM.
Melting Slicks
Joined: Feb 2014
Posts: 2,409
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From: NC
32 to 39, is the pressure range you should be looking at.
personally I'd be a little concerned if my fuel pressure was sitting at 32, rather than the higher end of the spectrum.
Also I agree with Tom's analysis.
personally I'd be a little concerned if my fuel pressure was sitting at 32, rather than the higher end of the spectrum.
Also I agree with Tom's analysis.
Thread Starter
Intermediate
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Pulled the vacuum line off of the fuel regulator.
Took it for a drive and it still missed around 5,000 but it isn't missing as bad. It misses but I can still feel the power pulling though instead of just flatlining like before. At least that's what it feels like.
I pulled out the 2 and 4 spark plugs, easiest to get. And the tips are looking lean. These plus are the ones that were in it when I received the car. Haven't changed them yet. Car seems more sluggish since I've been driving it compared to what I remember when I used to drive it years ago before I bought it from my dad a few weeks ago. I took a picture of the plug.
The tip is white if you can't see it in the picture.
So it defiantly seems to be a fuel related problem. Now to find it.
Took it for a drive and it still missed around 5,000 but it isn't missing as bad. It misses but I can still feel the power pulling though instead of just flatlining like before. At least that's what it feels like.
I pulled out the 2 and 4 spark plugs, easiest to get. And the tips are looking lean. These plus are the ones that were in it when I received the car. Haven't changed them yet. Car seems more sluggish since I've been driving it compared to what I remember when I used to drive it years ago before I bought it from my dad a few weeks ago. I took a picture of the plug.
The tip is white if you can't see it in the picture.
So it defiantly seems to be a fuel related problem. Now to find it.
