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So my 92 LT1 6 speed feels like a turbo vette. It feels nice off the line, but at 3500 RPM it gets an extra boost. It is stock. It is not a Turbo vette, but feels like it. The boost isn't as drastic as a turbo, but it is a boost. I changed the plugs, wires and power brake booster along with the clutch master. It felt the same before and after doing the plugs. Its not slow below 3500 and doesn't feel like anything is wrong, but I am curious if others have the same thing. She does have 184k on her. I also replaced the thermo sensor. The plug housing broke so the connector kept coming off that triggered the check engine light code 15. It is fixed now and still feels the same. The air filter is new too. I have a new fuel filter, but haven't yet installed it. The previous owner changed the water pump and opti.
So I'm curious if this is the way the LT1 with a 6 speed feels, or if I should have a little more power down low.
I have a 93 6 spd, I do not notice any dramatic change and it seems to pull smooth/strong through the entire power band. Not sure how accurate it is but I googled the torque curve and it appears to peak around 2300 RPM... The only other thing to note is the gears are fairly tall, and 6th gear is a cruise only gear (do not accelerate in 6th or really 5th for that matter unless you are really moving). So perhaps this is a gearing thing more than anything/getting used to it? When I am not accelerating hard I generally shift around 3500 (at least as far as I can remember, I'll pay attention the next time I'm out)...perhaps you are shifting a bit early or not downshifting when you want to accelerate?
As far as possibilities *if* something is wrong: Maybe take a look at your knock sensors? Perhaps they are pulling timing/incorrectly detecting knock? Also, if your 02 sensors have not been replaced in a long time something to look at...
Is the flywheel single mass, if so what weight? Any codes? Any other odd driving behviors? Stock Dana 44 gearing? Stockish wheel diameter?
As a WAG .. I'd assume that with the high mileage what you're experiencing is retarded cam timing from excessive timing chain slop. If the timing set is still original you'd best change it out asap..before it jumps teeth and bends valves !!
She has stock 275/40/17s and came with those per her RPO codes. She has the 3.45 rear end. I notice this from first through 4th under heavy acceleration. Not cruising and then accelerating in too high of a gear. I haven't really pushed the RPMs in 5th and 6th. Those RPMs in 5th and 6th she'd be doing over 100 and I need new tires before I'll do that. Her tires look ok, but fronts are from 2006 and rears are 2011. I have noticed how 6th really is just a cruising gear. She doesn't hold 65 in 6th when I go up a steep hill on the freeway.
I think I'll do knock sensors and o2 sensors just to have them done. Then do the timing chain, cover and oil pan gasket. I'm not happy with the plug wires I got. They are all too long. I am going to buy wire and ends and make my own, so that will be the perfect time to do that.
Thank you for the replies.
Last edited by topfuel67; Nov 22, 2021 at 12:31 PM.
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Sounds like you have a good plan, hopefully you get it sorted! It would be ideal to datalog to see what the ECM believes is happening, but not sure how comfortable you are with that/if you have the equipment...if these maintenance items don't resolve it though, rather than chase parts it would be by far the best thing to do.
On the tires, I really like the riken raptors on mine (michelin off-brand) based on other's recommendations. They are about the best bang for buck you can get (I got them around 100/tire they have crept up a little bit)...and it will make a huge difference to your ride (and safety!). It was the first thing I did!
I need to figure out how to datalog. I am willing to invest in the equipment. I got into that for my 2006 SRT8 as it was a bit easier with a laptop/diablo tuner and had great results. I already did the o2 sensors and replaced with Delphi. The old ones were actually in very poor shape, but still made no difference. I'm surprised I didn't have a check engine light for those. I did notice an extra o2 bung welded into my exhaust. She has flowmaster cat back exhaust with only the front 2 cats.
I plan on getting tires at the end of the week. I am going with the Mickey Thompson Street Comps. I'm not sure if their performance is any better or worse than the Michellins, but to me nothing looks cooler than having "Mickey Thompson" on the side of my tire. I'm never going to track this car and dragstips in So Cal are a thing of the past. She'll never see the rain either. I got a sub for those 2 days out of the year when it rains here.
You need either a USB or Bluetooth ALDL adapter and then software such as TunerPro or aldldroid (if you have android and the Bluetooth adapter). There are also options like tech2 or similar. I am planning on getting a USB adapter at some point...just looking for an excuse.
The previous owner changed the water pump and opti.
When you do get to the timing chain , and if you find it was replaced by the previous owner, it could be new but installed with some degrees of retard from a poorly manufactured gearset and/or just installed incorrectly. This you must check - IF the timing set is new. Degree the cam, and/or use a better brand of timing set - but check your cam timing regardless.
I have always been plagued by POs that didn't know what they're doing. I don't think this timing chain has been done though as the front cover is very grimey and leaking. She also leaks from the rear of the pan. Hopefully the oil pan gasket and timing cover fix the leaks. Doesn't the chain/sproket line up dead center, retarded or advanced? Usually you can't degree the basic ones unless you get a racing balancer and timing set with multiple options.
This sounds very typical to me. If you are lugging around in a taller gear and you lay into it without downshifting, you will feel a switch like effect when the engine gets into the power band. My cammed 6.0 LS swapped '84 gets the party starting around 3800-4000 rpm and it is a night and day difference. Literally like a switch.
This isn't happening in too tall of a gear, well it may be also. When I start off in first and lay into it there is a boost above 3500 RPM. Same in second, same in third etc all under heavy acceleration. She feels fine in all gears under normal acceleration. If you just drive her like a normal person you wouldn't even notice. She's not slow, doesn't hesitate and sounds great. There's just a slight boost above 3500 while accelerating hard off the line. Makes me feel that she should be even quicker if she had the power from the extra boost down lower. I raced a newer Mustang 5.0 and beat it by over a car length so she's not slow by any means.
I am going to do the timing chain and I'll report back once that's done. I probably won't get to it until January though. I'll try replacing the knock sensors and maybe even the injectors. I started looking at newer 4 hole injectors with the same flow rate and plugs as these stock single hole injectors. I've done that on my 93 jeep that had the single hole injectors and it is a noticeable improvement.
Plus the PO advised this car sat for a while and that's never good on injectors. His uncle passed away and didn't drive it for the last several years. He got it and then did a few basic things, like the opti, water pump and new battery, but really wasn't into it. He did work at a shop that repaired all sorts of off road toys so his work wasn't too bad. He installed a new top, but lost several trim pieces and didn't glue it. So I'm guessing the injectors are due. They look original. The o2 sensors were original and in really poor shape. The knock sensor from looking under there is really old. I'm sure she needs lots of little parts replaced.
I'm thinking of doing the oil pump while I have the oil pan off too.
I started my vette today and heard a loud shearing sound from under the hood like the serpentine belt shredded. Shut her off and popped the hood. Sure enough the serpentine belt was shredded. The tensioner pulley looks like it melted and a big part broke off. In ordering a new one I came across symptoms of a going bad belt tensioner are erratic timing, noise etc. I didn't really hear anything until the failure, but definitely have erratic timing. I also looked at the harmonic dampener and it looks pretty bad. There are gaps in the rubber ring. Another thing that can cause erratic timing. So for the time being I am going to replace the belt, tensioner, idler pullies and the balancer and hope that solves the "turbo" issue.
As a WAG .. I'd assume that with the high mileage what you're experiencing is retarded cam timing from excessive timing chain slop. If the timing set is still original you'd best change it out asap..before it jumps teeth and bends valves !!
I doubt it. Mine has 203k and experiences no such "boost". The LT1's tq curve is very flat and linear....even at 203k.
IDK, but the outer ring on the damper could slip/rotate 180* and the engine would still run the same. Damper has nothing to do with cam or ignition timing; the engine has "no idea" nor does it car where the outer ring of the damper is.
I haven't really stayed on the throttle or really pushed her to her limits yet. With 184k on the clock and new to me, I am still going through the easing into her process. Plus the tires are risky. I just got my Mickey Thompson 275/40 17s and was taking her to my shop to install them when the tensioner pulley gave out. Figures. As far as what I have experienced with her, when I accelerate onto the freeway she does the boost thing right at 3500 rpm. I usually shift no later than 4500, max 5000 rpm. The power feels constant at that level. I'm sure I could push her harder, but haven't due to tires and just not being confident in her yet.
At this point, I'll do the idler, tensioner and dampener then see how she feels. I do plan on doing the timing chain and oil pan gaskets, but would like to wait until it warms up. The weather has dropped into the upper 60s. At night it gets into the low 50s.
Thought I'd throw this up...this was my dyno results when I put my car on the rollers. IIRC, it had about 170k on it at the time. Look at the shape of the tq curve. That's how an LT1 should look (and thus, feel)....
Turbo Vette
