Hard starting and insufficient total timing

[Barry M.]

Over the last weekend, I decided to do something about the hard start when hot condition in my 71 base convertible. The starter struggles to crank the engine for the first rev and then it will start. My battery is good and it is being charged by the alternator. I have suspected it might be heat soaking but wanted to check the timing first. I have a Breakerless SE unit installed instead of points. With the vacuum advance plugged, the timing light indicated 8 deg advanced as it should. Next, out of curiosity, and referring to John Hinckley's article on mapping the advance curve, I decided to check the advance curve with my dial back timing light. I discovered the following: at 800 rpm I get 1 deg additional , 1000 rpm 2 deg, 1200 rpm 3 deg, 1300 rpm 9 deg, 1500 rpm 11 deg and that is it. 11 degrees mechanical and 8 degrees initial is 19 degrees total timing. I then checked the vacuum advance and it will give 18 degrees when reconnected to full time vacuum on the carburetor.
I think the hard starting is heat soak but I think I have another problem with the distributor. I reconditioned it several years ago with a new shaft, autocam and bushings from Paragon. The springs and weights are original to the car. The engine runs alright but seems to lack some punch in the 2 -3K rpm range.
I would appreciate some advice as to how to proceed as I am not a mechanic.
Thanks, Barry

[Gene M.]

Re: Hard starting and insufficient total timing

Over the last weekend, I decided to do something about the hard start when hot condition in my 71 base convertible. The starter struggles to crank the engine for the first rev and then it will start. My battery is good and it is being charged by the alternator. I have suspected it might be heat soaking but wanted to check the timing first. I have a Breakerless SE unit installed instead of points. With the vacuum advance plugged, the timing light indicated 8 deg advanced as it should. Next, out of curiosity, and referring to John Hinckley's article on mapping the advance curve, I decided to check the advance curve with my dial back timing light. I discovered the following: at 800 rpm I get 1 deg additional , 1000 rpm 2 deg, 1200 rpm 3 deg, 1300 rpm 9 deg, 1500 rpm 11 deg and that is it. 11 degrees mechanical and 8 degrees initial is 19 degrees total timing. I then checked the vacuum advance and it will give 18 degrees when reconnected to full time vacuum on the carburetor.
I think the hard starting is heat soak but I think I have another problem with the distributor. I reconditioned it several years ago with a new shaft, autocam and bushings from Paragon. The springs and weights are original to the car. The engine runs alright but seems to lack some punch in the 2 -3K rpm range.
I would appreciate some advice as to how to proceed as I am not a mechanic.
Thanks, Barry

Those parts you replaced in the distributor are suspect. You should compare the original parts (the football cam, weights & springs) to the replaced stuff. The set up would be best verified on an old Sun Machine.

[Patrick H.]

Re: Hard starting and insufficient total timing

Those parts you replaced in the distributor are suspect. You should compare the original parts (the football cam, weights & springs) to the replaced stuff. The set up would be best verified on an old Sun Machine.

I agree. I had the same thoughts reading through.
The replacement parts are entirely generic, so to speak, in their application. Once installed the distributor will have to be recurved.

Have your distributor checked out by a competent distributor guy and go from there.

[Mark E.]

Re: Hard starting and insufficient total timing

You may have more than one issue.

The centrifugal advance isn't working properly; 11 degrees total mechanical is not nearly enough. As suggested earlier, have the distributor checked and remapped with a distributor machine. I recommend Steve Newsom with Northwest Florida Distributor. 850-776-7334. d64sln@gmail.com . Quality workmanship, quick turnaround, personal service, and very reasonable pricing.

However, the timing curve isn't the cause of hard starting, and 8 degrees initial timing shouldn't cause a cranking problem.

Carefully check the starting system... battery, cables, connections, starter. An affordable and easy way to troubleshoot the battery and starter is to replace them. A new Walmart battery is about $40. And a rebuilt starter from Autozone, RockAuto, et al sells for less than $50 with a lifetime warranty. Get a rebuilt starter that uses a Delco casting; avoid new aftermarket units. If the current starter is "correct" for the car, save it for judging events and the next owner.

[Patrick H.]

Re: Hard starting and insufficient total timing

Also, check the condition of the battery ground strap under the battery where it attaches to the frame. Corrosion can get to this one, as can road damage.

I've had the ground strap from the engine block to the frame on the right side at the engine mount go loose, and also cause a problem.

[Edward J.]

Re: Hard starting and insufficient total timing

Barry, slow crank on start-up could be the starter bushings are worn, during heat soak the armature can swell and can sometimes contact the field windings. The only way is know is to remove the starter and dissy. for inspection.

[Duke W.]

Re: Hard starting and insufficient total timing

The fundamental cause of all your problems is that fact that the spark advance map was set up for emission control, not performance and fuel economy. In order to oxidize HC and CO the spark advance map is severely retarded for all operating conditions. This causes very high EGT, which helps the oxidation process, but the hot manifolds and head pipes radiate a huge amount of heat to surrounding components compared to non-emission-controlled engine.

If you have an IR gun measure exhaust manifold temperature with the car fully warmed up and idling and tell us your result.

You gave us the centrifugal curve data you measured, but how does that compare to OE specs in the CSM and AMA specs? Did you rev the engine high enough to achieve full centrifugal?

I am assuming you have a base 350/270HP engine, and the optimum centrifugal curve would be the same as the '66-'67 327/300 with lighter springs to bring all 30 degrees in at no more than 3500 rather than the OE 5000.

Exhaust manifold temperature should drop several hundred degrees if you convert from ported to full time vacuum advance, but the best functional VAC depends on transmission type - manual or TH400, which you haven't stated. What's the data stamped on the installed VAC?

Optimizing the spark advance map will go a long way in extending the life of electrical components like the starter by reducing their temperature environment. You first have to determine if the spark advance map meets OE spec, and if not find out the cause, which could possibly be a malfunctioning centrifugal advance mechanism. Find and correct the cause then think about optimization.

You said you're not a "mechanic", but it sounds like you removed the distributor to change the shaft, etc, and successfully reinstalled it, which means you have the skills to overhaul it and optimize the spark advance map.

The starter is very simple and the step-by-step overhaul procedure to is in the COM. The only procedure that is tough for the DIYer is replacing the armature bushings. Everything else is simple. I don't trust rebuilt starters because many I've seen were "rebuilt" with worn out parts that should have been replaced like the shift lever and solenoid contact stud. All of these parts are readily available, but you don't know what you need until you take it apart. A properly rebuilt starter should receive all the simple electrical checks to ensure that the field coil sand armature winding are in spec and it's normal to install a solenoid rebuild kit, new shift lever, and overrun clutch.

Search for a thread stated by me in December 2012 "L-79 distributor blueprint overhaul". Yours is essentially the same, except for the centrifugal curve and, maybe VAC.

Also do a web search - my name, San Diego, Corvette, and take a look at my tuning seminar.

Duke

[Barry M.]

Re: Hard starting and insufficient total timing

Thanks guys for the quick diagnosis. Gene, Patrick, Mark-I will contact Steve Newsom in Fl. My battery is 4 years old and the alternator is a new replacement. It puts out 14+ volts charge. The primary wires are new but good idea to check under car ground connection. The frame is clean.
Edward, the starter is an autozone remanufactured Delco. The car has less than 800 miles since it was started after restoration in 2012.
I think the correct approach at this point is to have the distributor re-curved. I will send a future follow-up.
Once again, Thanks-Barry

[Barry M.]

Re: Hard starting and insufficient total timing

Duke, our posts just crossed. Lot of insight for me to consider in your post. My car is a 4 spd. I have checked the exhaust manifold temp at idle after warm up and is just under 500 deg. One side being greater than the other. Heat riser on the passenger side has been removed by the way and the passage under the intake blocked. When I took the timing advance readings over the weekend, the most I could get was an 11 degree increase beyond initial. The mark was steady from 1400 rpm not moving as I went past 2500 rpm. The vacuum advance is B22 and I believe it gets full time vacuum as when connected to the carb at idle the engine speed increases by about 100 rpm but I must confess I am not sure right now. The vacuum can fully turns the distributor plate with about 18" of vacuum from my pump.
As far as the hard start is concerned, I have ordered a remote solenoid to see if that solves that separate problem.
I will review thread of 12/12 as well as your tuning seminar. Thanks for responding! Barry

[Duke W.]

Re: Hard starting and insufficient total timing

I believe the OE VAC is 201-15, 15 @ 15.5" and the B22 is essentially the same. It should only require about 15" to pull to the limit, so yours appears to be a bit out of spec. Check idle vacuum and if it's at least 19" the VAC is probably okay to use with full time vacuum advance.

I'm surprised your exhaust manifold temperature is that low, so maybe it is set up with full time vacuum advance. IR guns read about a 4:1 aspect ratio cone, so you have to hold it very close to the manifold. The farther away it is the more cooler background temperature it will see and basically come up with an average.

An important point in physically checking the centrifugal advance mechanism is to understand how far it retracts. Depending on the weight design, the weights my retract all the way to the center of the football, but some don't retract that far because the weights contact each other before they contact the football. In the latter case, more centrifugal can be easily had by grinding the weights so they retract more up to all the way to the football.

You can check whether the VAC is ported or full time by checking total idle advance with the VAC connected. It should be initial plus about 16, if full time, and no or maybe a little change if ported. Also tee your vacuum gage into the VAC signal line and then another full time vacuum source. If the readings are the same, then the VAC is full time.

I know your OE centrifugal curve is probably short and lazy, but you need to tell us what is OE from the CSM or AMA specs.

It wouldn't surprise me at all if you disassemble the starter and find that some parts have far more wear than they should for a rebuilt unit with so few miles. I think on some of those rebuilds about all they replace is the overrun clutch.

Duke

[Barry M.]

Re: Hard starting and insufficient total timing

Duke, I would think grinding the weights so they return fully to the football would affect the advance curve by removing mass from the weights. This may not be significant? I have teed the vacuum gauge to the vacuum line from carb to VAC and at idle it pulls about 18'-19" so I believe I have full time vacuum.
From CSM-OE centrifugal advance for my engine is 0@865rpm, 2@1335, 11@2400, 18@4200rpm-initial advance is 8deg. listed under tune-up section but 4 deg under distributor section? 8 deg is on the decal above the brake booster. Centrifugal advance seems stuck at 11deg
Considering your comments on GM retarding spark to deal with emissions in that era, any reason not to recurve the distributor to that of a sbc of the mid 60's? I would like a bit more performance. The car is a 4 spd. The engine currently has a 3.75" stroke and a Melling ltc cam (I don't have the specs on this right now). The rotating assembly is new with the rebuild of 5 years ago. Pistons are flat top as original .40 over. Can you suggest a better curve not necessarily pushing the limits on this 45 year old motor? Thanks, Barry

[Duke W.]

Re: Hard starting and insufficient total timing

With only 18 centrifugal and 4-8 initial total WOT advance is only 22-26, and the optimum range is 36-40. No wonder it's lacks performance, and fuel consumption is likely very high.

It appears from your report the engine is configured with full time vacuum advance, but you need to tell me the "idle speed" that you measured vacuum. Specifying idle vacuum without specifying the idle speed it was measured at is meaningless.

I recommended a max centrifugal curve in post #7, and it's best if it starts just above idle speed.

Grinding the weights will reduce mass and slow the curve slightly, but it depends on how much you have to grind off, and lighter springs will offset the reduced mass to one degree or another.

At this point I recommend you remove and disassemble the distributor for a "blueprint/overhaul" as described in the Dec. 2012 thread I previously referenced. It's quite simple ,and the detailed disassembly/assembly procedure is in the COM. Make a 15 degree template out of cardboard and figure out how you can achieve that amount of centrifugal advance mechanism rotation. That will yield 30 at the crank. Grinding the weights to allow greater retraction, grinding out the slot in the cam assembly, or removing a thick bushing that might be installed over the limit pin are the three methods that can be used singly or in combination.

Given the atrocious current centrifugal curve, if you are careful and take your time to get the distributor set up properly for performance and fuel economy, it will seem like a whole new engine.

It might help to get you started by posting a photo of the centrifugal mechanism, so I can see what limits weight retraction. Then when you get it disassembled post photos of the pin/bushing (if installed) and the slot in the cam assembly - exactly as you remove them before you start making changes.

Duke

[Barry M.]

Re: Hard starting and insufficient total timing

Duke, Once again thanks for your input. I have set the idle speed for the car at 600 rpm as is listed on the decal above the brake booster and in the engine section of the CSM. As I am still working full time, I will delve into this over the weekend. I need to read your article to determine if this is something I feel comfortable taking on myself. I like the idea of setting up this distributor similar to that of the late 60's base 300 hp motor to take advantage of the increase advance. One question comes to mind. I would guess that the GM listed CR on the 67 327/300 would have been in the 10:1 range. When my motor was rebuilt we decided to go with a static CR in the 8.5:1 range. My goal had never been street or drag racing. Does a lower CR necessarily make a difference in the decision to increase overall total timing?
Barry

[Duke W.]

Re: Hard starting and insufficient total timing

CR may limit aggressiveness of the centrifugal curve and/or total WOT advance if fuel octane is insufficient, but at only about 8.5 I think your engine will tolerate what I recommended earlier without detonation on 87 PON fuel.

Duke

[Barry M.]

Re: Hard starting and insufficient total timing

I thought I would post an update on my distributor timing and hard starting. I took Marks advice and sent the distributor to Steve Newsom in Florida. Total turnaround time was a week door to door and back and the car has more pep than before. Now total timing is all in by 3200 rpm rather than 4+k.
The hard starting proved to have been caused by something I had not suspected. I decided to check all the connections before committing to installing a remote starter. I have a knife style battery cut-off switch on my side mount battery. With lots of use, the connection to the battery had loosened but I paid little attention to this. I had bolted the switch to the negative terminal with a flat and lock washer and thought it tight. The lock washer was tight at first but I found out that the bolt actually had bottomed out in the treads and over time as the lock washer flattened, the connection loosened. An arc had been jumping from battery to switch and welded the lock washer to the flat washer. The constant arc had ruined the battery. Autozone replaced the battery for free even though it was just over its three year warrantee. With a new battery and tight connection, no more hard start and no "heat soak" condition.
Moral of the story is to check the battery connections. Even though the multi meter indicated 12 plus volts and the alternator was good, the Autozone battery tester showed actual battery condition was otherwise.
Barry