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Drove a 120 mile shakedown today after getting my 70 roadworthy after it was in storage for 20+ years. Much was done by my shop to get to this point. I've got several issues to follow up on:
1) Door Ajar warning light flashes on/off. Door switches appear to work properly for interior lighting, but this warning light is annoyingly lit (intermittently).
2) Vacuum troubles. My LS5 has a performance camshaft, which is affecting idle, timing and vacuum. The wiper door opens and closes at various RPM levels during highway driving. Low vacuum is definitely one issue. Possibly I have some leaks as well. Need to consider changing out the camshaft as this is not acceptable for several reasons.
3) Stopped for some parts: a new radiator cap which seems to have stopped discharge after stopping, PCV connected up to air filter.
4) I've got a high pitched squeal around 3000 RPM which I thought was a belt, but it may be the alternator. Still need to pinpoint the problem.
5) Timing/Carburetor is off. I get some slight lurching at constant highway speed. Seems like the distributor may be loose. Also I'm getting some backfiring if I open it up. So I took it rather easy accelerating smoothly. Vacuum problems may be affecting timing. Looking for advice on a new distributor.
6) valve cover gaskets leaking oil which should be simple enough to solve.
Car will be a long term project as I will be storing it at a seasonal family house. I'll get to it from time to time.
thats one beautiful looking car, whether they are running on point or not its such a buzz just to get them out on the road, im sure you will fix all the little issues as you go
enjoy
Last edited by raycam01_au; Nov 6, 2024 at 06:23 PM.
Reason: filter took a word meaning incorrectly
I’d start with the basics before jumping to a cam swap.
I’d address timing first, if you don’t know how to time the engine there are a thousand threads on this forum on how to.
If you are retarded timing then the engine will run poorly, make poor vac, etc.
once you know timing is good, address any vac leaks if you have them. Easy test is unplug everything from carb/manifold and measure vac. Then reconnect one at a time.
if your vac actually is too low, adding a vacuum pump is way easier than a cam swap. Just saying.
take the cap off the distributor and inspect if it needs replacing.
after the above, then it’ll be easier to determine if you actually have a carb issue, or a distributor issue.
I’d start with the basics before jumping to a cam swap.
I’d address timing first, if you don’t know how to time the engine there are a thousand threads on this forum on how to.
If you are retarded timing then the engine will run poorly, make poor vac, etc.
once you know timing is good, address any vac leaks if you have them. Easy test is unplug everything from carb/manifold and measure vac. Then reconnect one at a time.
if your vac actually is too low, adding a vacuum pump is way easier than a cam swap. Just saying.
take the cap off the distributor and inspect if it needs replacing.
after the above, then it’ll be easier to determine if you actually have a carb issue, or a distributor issue.
Thanks for the good advice. My shop, which is a long time Corvette specialist has spent a lot of time trying to get the timing in balance, where it runs decent and idles somewhat successfully. The advice was to look into a variable timing vacuum advance which I haven't had a chance to get after just yet. So there has been a fair attempt at making it work by some guys that know better than me. But, there is of course something to be said for persistence. The one thing that really has me thinking the disty is bad is the fluctuation while cruising at steady speed. The engine will very slightly advance and retract (terminology?) which I have experienced once before with a Mustang that had a bad disty. That's what has me thinking I need a replacement.
The weird part is vacuum changing at RPM. For example, at 2500 the wiper door is down. When I accelerate up to 3000 RPM it opens, and stays open until RPM reduce to 2500 again. At idle, it opens. I'm thinking I have multiple vacuum issues, but this one here has me a little confused.
I had enough time with the car to change the valve cover screws to the originals with the unique spreader washers and hopeful this helps with the oil leaks. So far looking good.
I fixed the door ajar light. Found a post on here that helped with that. Also repaired my loose rear view mirror and wrestled in the plastic trim cover. You must heat this up if dealing with an original aged part!
This camshaft vacuum issue is going to drive me nuts. I’ve never changed a cam but thinking this is in my future. Car won’t consistently idle down without stalling. Will dig deeper into this before making this move but I really prefer a factory tamed engine.
I had enough time with the car to change the valve cover screws to the originals with the unique spreader washers and hopeful this helps with the oil leaks. So far looking good.
I fixed the door ajar light. Found a post on here that helped with that. Also repaired my loose rear view mirror and wrestled in the plastic trim cover. You must heat this up if dealing with an original aged part!
This camshaft vacuum issue is going to drive me nuts. I’ve never changed a cam but thinking this is in my future. Car won’t consistently idle down without stalling. Will dig deeper into this before making this move but I really prefer a factory tamed engine.
This camshaft vacuum issue is going to drive me nuts. I’ve never changed a cam but thinking this is in my future. Car won’t consistently idle down without stalling. Will dig deeper into this before making this move but I really prefer a factory tamed engine.
I recommend addressing the timing of the engine before going down the camshaft route. A lot of guys here run beefy camshafts and have zero issues. With larger cams you need to run a lot more timing down low, with a smaller advance, and generally have the advance come on earlier.
what is your idle timing?
I bet if you ran 20-25 degrees 800-1000rpm it would solve your issue. Make sure your vac advance is actually usable too. For instance,
if your motor only makes 8” vac, it would not be wise to run a vac advance can that’s operating range is 10-12”.
ill share my timing table, feel free to use it as a guide for your own timing.
I recommend addressing the timing of the engine before going down the camshaft route. A lot of guys here run beefy camshafts and have zero issues. With larger cams you need to run a lot more timing down low, with a smaller advance, and generally have the advance come on earlier.
what is your idle timing?
I bet if you ran 20-25 degrees 800-1000rpm it would solve your issue. Make sure your vac advance is actually usable too. For instance,
if your motor only makes 8” vac, it would not be wise to run a vac advance can that’s operating range is 10-12”.
ill share my timing table, feel free to use it as a guide for your own timing.
this is really helpful. The shop I used is highly experienced but I’m not sure their mechanical engine expertise is top notch. They are an excellent paint and restoration shop. So I need to study this and take the measurements. It will be a while since my car is remote from where I spend most of my time. I really appreciate the confidence in solving this without a cam swap!!!
I’d start with the basics before jumping to a cam swap.
I’d address timing first, if you don’t know how to time the engine there are a thousand threads on this forum on how to.
If you are retarded timing then the engine will run poorly, make poor vac, etc.
once you know timing is good, address any vac leaks if you have them. Easy test is unplug everything from carb/manifold and measure vac. Then reconnect one at a time.
if your vac actually is too low, adding a vacuum pump is way easier than a cam swap. Just saying.
take the cap off the distributor and inspect if it needs replacing.
after the above, then it’ll be easier to determine if you actually have a carb issue, or a distributor issue.
About the vacuum pump idea: are you talking about an electric pump or belt driven? I'm curious about this in the event I can fix the idling/timing issues but vacuum remains a problem.
It really sounds like a timing issue more than anything else, as far as the engine performance.
It could be just the settings, but it could also be the vacuum advance canister on the distributor or it could have the incorrect springs installed in the distributor itself.
Contact forum member Lars and get a copy of his timing papers.
Lars papers are the worlds best guide for setting your timing and solving distributor issues.
If your car has been sitting, you probably have some serious vacuum leaks, which as stated above are easy to track down.
The cam would not cause a vacuum issue that will open and close the wiper door at idle or cruising down the highway, but a vacuum leak or bad vacuum canister will.
I would install a vacuum pump as a last resort before I would replace the cam.
There is also the option to convert the headlights and the wiper door to electric actuators.
The biggest concern which a large racing cam can effect is the power brake booster.
If your power brakes are working then the cam is making enough vacuum and you need not worry about swapping cams.
It really sounds like a timing issue more than anything else, as far as the engine performance.
It could be just the settings, but it could also be the vacuum advance canister on the distributor or it could have the incorrect springs installed in the distributor itself.
Contact forum member Lars and get a copy of his timing papers.
Lars papers are the worlds best guide for setting your timing and solving distributor issues.
If your car has been sitting, you probably have some serious vacuum leaks, which as stated above are easy to track down.
The cam would not cause a vacuum issue that will open and close the wiper door at idle or cruising down the highway, but a vacuum leak or bad vacuum canister will.
I would install a vacuum pump as a last resort before I would replace the cam.
There is also the option to convert the headlights and the wiper door to electric actuators.
The biggest concern which a large racing cam can effect is the power brake booster.
If your power brakes are working then the cam is making enough vacuum and you need not worry about swapping cams.
Actually the brakes are a concern, as coming to a stop the low idle is giving poor vacuum to the booster. I was thinking if I solve the idle problem that should be resolved, but it is definitely an issue at this point. I'll focus on timing and see if I can figure this out or get a speed shop involved. My shop did what they could. Just not sure how much expertise they have on this.
I'm thinking a speed shop and a recurved distributor should solve 90 percent of your issues. No offence to your Chevrolet shop. But it sounds like they are trying to time an engine with performance parts using a stock distributor. This can only lead to failure. Which it has.
Many of us run a fair amount of cam, properly set-up we have no vacuum issues and no idle issues. And no compromise between a good idle and good high speed and cruise running. This requires a custom curved distributor. Simply can not be done with.a stock timing curve.
I personally run a fair bit of cam. I run 18 degrees of initial timing, 35 degrees total mechanical timing, all in by 2,900 RPM. with a custom vac advance can designed to run properly with my camed engine, (Read about the 2 inch rule). That puts in only 12 degrees of vacuum timing. And actually does follow the 2 inch rule.
My car runs amazing. Very smooth at all times with excellent manors. And it makes power!
Some of your vacuum issues are clearly a poor check valve and or leaks.
Best of luck sir, but before you pull that cam I would highly recommend a distributor specialist.
I'm thinking a speed shop and a recurved distributor should solve 90 percent of your issues. No offence to your Chevrolet shop. But it sounds like they are trying to time an engine with performance parts using a stock distributor. This can only lead to failure. Which it has.
Many of us run a fair amount of cam, properly set-up we have no vacuum issues and no idle issues. And no compromise between a good idle and good high speed and cruise running. This requires a custom curved distributor. Simply can not be done with.a stock timing curve.
I personally run a fair bit of cam. I run 18 degrees of initial timing, 35 degrees total mechanical timing, all in by 2,900 RPM. with a custom vac advance can designed to run properly with my camed engine, (Read about the 2 inch rule). That puts in only 12 degrees of vacuum timing. And actually does follow the 2 inch rule.
My car runs amazing. Very smooth at all times with excellent manors. And it makes power!
Some of your vacuum issues are clearly a poor check valve and or leaks.
Best of luck sir, but before you pull that cam I would highly recommend a distributor specialist.
Thank you! Great advice on the board here. I'll abandon the idea of changing the cam and figure out the right timing solution first. I agree I probably have some leaks in the vacuum system as it is all original. Very pleased to hear you say this is completely possible. I have no idea what cam is in this engine.
Edit: I've just received Lars' paper and studying up to get back on this sometime in the next few months. Wish I could do it now.
Here's an update after several months of sitting. I managed today to get the VAC from Lars installed on the distributor and followed his timing advice (albeit a little sloppily). Max timing is ~36 deg. and with the VAC it idles down so much better than before re-timing. I had some trouble rotating the distributor to where I wanted it due to the tach cable having a tight bend and interfering with vacuum lines. I have room for improvement. Tomorrow I will take a 2 hour highway cruise and see how that goes. Barring any new issues I'm hopeful. Vacuum was not enough to keep the wiper cover closed, but I suspect I have some other gremlins in that system.
I'll post some pics with the new to me hardtop installed which is a nice addition.
Took a 250 mile round trip to go see my first newborn granddaughter yesterday. The vette performed well with the new timing VAC and I got a few more bugs to work out of the car now. Hardtop fits great and looks great. Last time I had a hardtop on my old 70 I did not have the correct hardware and it wasn't right. This one is tight and gives a nice cabin experience compared to the soft top. I'm going to leave it on for a while.
I noticed something in the suspension, which I think may be U-joints in the half shafts where I get a thumping vibration when the suspension is moving over dips in the road or banking turns. Only one side seems to be complaining. I'm going to have to look to see if there is a lube fitting and start there. My brakes are pulling hard to the left, but after use it goes away which is weird. I think the pads on one side may be grabbing. Had this happen on and old truck recently where I finally figured it out to be the brake lining. So I may swap out the pads first this time and see what happens.
Shakedown cruise
