Winter-storage of FI car - unit out of tune afterwards?

[Hank D.]

Re: Winter-storage of FI car - unit out of tune afterwards?

Betcha Jerry recommended .030-.030" for the valve lash. I definitely agree.

Yes, that made a huge difference in idle stability at 850 RPM.

[John D.]

Re: Winter-storage of FI car - unit out of tune afterwards?

I don't think that's a very good choice. GM 1960954 Distributor and Starter Motor Lubricant would be better, I you can find some. It's long discontinued.

I once took a dap of each between thumb and index finger and rubbed them together. The wheel bearing grease quicky became very gummy while the 1960954 remained very slippery.

Wheel bearing grease is designed for high load and heat. That's not the case with the FI drive cable application and wheel bearing grease may cause excess friction.

If you can't find 1960954 the next best alternative would be a NGLI #2 with a full synthetic base... what is commonly called "chassis grease".

Duke

Try my personal favorite. Dow corning #44 Not cheap and not readily available but good stuff.

[Duke W.]

Re: Winter-storage of FI car - unit out of tune afterwards?

Betcha Jerry recommended .030-.030" for the valve lash. I definitely agree.

Mechanical lifter cams have "contant veleocity" clearance ramps to allow for variation in running clearance, which may vary depending on engine operating conditions. At idle and low load there is little change from cold clearance on a cast iron pushrod engine, but sustained high load operation can close up the exhaust clearance a few thou due to valve stem expansion because the exhaust valve runs hotter at sustained high load. This is the reason mechanical lifter cams typically have taller clearance ramps on the exhaust side than on the inlet side.

The 30-30 cam lobe's constant velocity clearance ramps are .000360"/cam degree, which is somewhat less than the Duntov's .000440. The top of the 30-30's clearance ramp is .017" above the base circle. If you mulitply this by 1.5 you get .025", which is the clearance specified on the engineering drawing. However, actual rocker arm ratio is not constant, and according to measurements I took back in the seventies, it starts out about 1.37:1 and gradually increases to about 1.44:1 at max lift with a lobe height of about 0.3". My .023" cold clearance recommendation is based on the actual measured rocker ratio at the lash point, 1.37 times .017".

If clearance is set at .030", lash will be taken up at about .022" above the base circle at which point velocity has increased to about .009"/cam degree, which is nearly three times the velocity of the constant velocity clearance ramp. This will considerably increase the shock load on the valve train as the valve is jerked off the seat and slammed back down.

The tighter lash that I recommend effectively increases overlap and duration, which makes for a rougher idle and some loss of low end torque, but the top end is stronger.

The fundamental problem is that the 30-30 cam is just "too big" for a reasonable road engine, especially the easy way we drive these cars, today, and that's the reason why I recommend the LT-1 cam to replace the 30-30 when it comes time to rebuild. GM recommended the same thing as the 30-30 cam disappeared from GMPD not long after the LT-1 cam was released and was listed as replacement for all prior 30-30 cam applications.

I spent a little time "tweaking" John Seeley's newly acquried low mileage '65 FI Coupe last spring. He had set the cold clearance at .023", and it idled poorly. The vacuum advance did not work, but checking it out with a Mity Vac indicated it was functional. I then removed the vacuum advance signal hose and tried to blow through it. It was completely plugged. Probing with a piece of straigthened wire coat hanger revealed a steel ball bearing, which I removed.

With a functioning vacuum advance I tweaked the idle speed and mixture adjustments to 1000 revs were it idled stabily at about 9-10" Hg manifold vacuum and exhibited good low speed driveability and clutch take-up without stumbling.

John didn't rev it beyond 6000 on our trip south to a local chapter meet, but IMO it would have pulled useable power to 7000, even with the OE unmodified heads. The loss of low end torque was masked by the 4.11 axle.

Why do all the service publication list .030" instead of the .025" on the engineering drawing? Nobody really knows, but the larger lash reduces effective overlap and duration that allows lower idle speeds and a little more low end torque, which is definitely lacking. They apparently ignored the effect on valvetrain dynamics - maybe figuring that it wouldn't cause any issues at least within the two-year/24K mile warranty period.

Duke

[Michael H.]

Re: Winter-storage of FI car - unit out of tune afterwards?

Mechanical lifter cams have "contant veleocity" clearance ramps to allow for variation in running clearance, which may vary depending on engine operating conditions. At idle and low load there is little change from cold clearance on a cast iron pushrod engine, but sustained high load operation can close up the exhaust clearance a few thou due to valve stem expansion because the exhaust valve runs hotter at sustained high load. This is the reason mechanical lifter cams typically have taller clearance ramps on the exhaust side than on the inlet side.

The 30-30 cam lobe's constant velocity clearance ramps are .000360"/cam degree, which is somewhat less than the Duntov's .000440. The top of the 30-30's clearance ramp is .017" above the base circle. If you mulitply this by 1.5 you get .025", which is the clearance specified on the engineering drawing. However, actual rocker arm ratio is not constant, and according to measurements I took back in the seventies, it starts out about 1.37:1 and gradually increases to about 1.44:1 at max lift with a lobe height of about 0.3". My .023" cold clearance recommendation is based on the actual measured rocker ratio at the lash point, 1.37 times .017".

If clearance is set at .030", lash will be taken up at about .022" above the base circle at which point velocity has increased to about .009"/cam degree, which is nearly three times the velocity of the constant velocity clearance ramp. This will considerably increase the shock load on the valve train as the valve is jerked off the seat and slammed back down.

The tighter lash that I recommend effectively increases overlap and duration, which makes for a rougher idle and some loss of low end torque, but the top end is stronger.

The fundamental problem is that the 30-30 cam is just "too big" for a reasonable road engine, especially the easy way we drive these cars, today, and that's the reason why I recommend the LT-1 cam to replace the 30-30 when it comes time to rebuild. GM recommended the same thing as the 30-30 cam disappeared from GMPD not long after the LT-1 cam was released and was listed as replacement for all prior 30-30 cam applications.

I spent a little time "tweaking" John Seeley's newly acquried low mileage '65 FI Coupe last spring. He had set the cold clearance at .023", and it idled poorly. The vacuum advance did not work, but checking it out with a Mity Vac indicated it was functional. I then removed the vacuum advance signal hose and tried to blow through it. It was completely plugged. Probing with a piece of straigthened wire coat hanger revealed a steel ball bearing, which I removed.

With a functioning vacuum advance I tweaked the idle speed and mixture adjustments to 1000 revs were it idled stabily at about 9-10" Hg manifold vacuum and exhibited good low speed driveability and clutch take-up without stumbling.

John didn't rev it beyond 6000 on our trip south to a local chapter meet, but IMO it would have pulled useable power to 7000, even with the OE unmodified heads. The loss of low end torque was masked by the 4.11 axle.

Why do all the service publication list .030" instead of the .025" on the engineering drawing? Nobody really knows, but the larger lash reduces effective overlap and duration that allows lower idle speeds and a little more low end torque, which is definitely lacking. They apparently ignored the effect on valvetrain dynamics - maybe figuring that it wouldn't cause any issues at least within the two-year/24K mile warranty period.

Duke

Does this mean you are still recommending everyone ignore the engineering recommended lash of .030" for intake and exhaust?

Obviously, you have never owned a 64-65 FI car. (or a 67-69 Z28) Or any car/engine with a 30-30 cam. If you had, you would have learned that lash settings less than 30-30 just don't work on the street.

You can rattle off all the numbers and big words you want to but it isn't going to make that cam run any better by increasing the duration even more.

[Duke W.]

Re: Winter-storage of FI car - unit out of tune afterwards?

I've never seen an "engineering document" that recommended .030/.030" lash. The engineering drawing which is THE engineering source document for the part to this day still states .025/.025". I have no idea how all the service literature ended up with a different number. Maybe it was a misprint that was never fixed. Those things happen.

I think my clearance recommendations and the reasons why are clear in my previous post.

John Seeley's '65 FI runs fine at my recommendated lash. Most who use my recommended lash report a rougher idle even with a one or two hundred rev increase, less valve train noise, a little less low end torque, but a stronger/smoother top end, and certainly valve train shock loading is less severe at very high revs.

A small minority didn't like it and went back to .030/.030. Of course, they are the most vocal. Meanwhile those who found my recommendation okay just enjoy driving their cars and like the way the engine "sings" at high revs.

Duke

[Michael H.]

Re: Winter-storage of FI car - unit out of tune afterwards?

I've never seen an "engineering document" that recommended .030/.030" lash. The engineering drawing which is THE engineering source document for the part to this day still states .025/.025". I have no idea how all the service literature ended up with a different number. Maybe it was a misprint that was never fixed. Those things happen.

I think my clearance recommendations and the reasons why are clear in my previous post.

John Seeley's '65 FI runs fine at my recommendated lash. Most who use my recommended lash report a rougher idle even with a one or two hundred rev increase, less valve train noise, a little less low end torque, but a stronger/smoother top end, and certainly valve train shock loading is less severe at very high revs.

A small minority didn't like it and went back to .030/.030. Of course, they are the most vocal. Meanwhile those who found my recommendation okay just enjoy driving their cars and like the way the engine "sings" at high revs.

Duke

I know from a lot of experience (that you don't have because you never owned a car with a 346 cam) that a setting like you recommend will not make for a happy engine at idle or mid RPM range.

If you and some other owners are happy with the way their car runs (poorly) at that lash setting, then that's all that matters.

[John S.]

Re: Winter-storage of FI car - unit out of tune afterwards?

Michael,
I feel the need to chime in here. I have seen the "discussions" on this and other boards concerning the valve adjustment of these solid lifter cars. I was not able to drive these cars back in the day so can only relay my more current experiences. I looked for a real fuel car for 5-1/2 years before finding mine. I drove three cars. All 65 fuelies. All of them ran and idled good. I can tell you that the one car that had the motor rebuilt was a flat out dog! I firmly believe that it had lower compression pistons put in because it just did not pull like all these solid lifter motors do at 3000 rpm and above. Am I positive it had the 30-30 cam? Somewhat. Car definitely had a solid lifter cam and idled and sounded like the other cars including mine.

Now a little history on my car. Original 375 hp fuel car with original matching motor and fuel unit. Car had 35k original miles when I purchased last April. Also has what is believed to be the original vac advance can. The motor has never been apart. Engine has the original .018 thick head gaskets on both sides. More then one NCRS person with knowledge have also indicated that the intake gaskets are original. Fuel unit has been off the car and gone thru by Chris Wickersham. The car runs perfect on unleaded premium all day long. That is until the outside temps push into the 90s and above. At that point there are issues with percolation of fuel in the spider at idle. Very common as you know in fuelie cars. After discussing with Duke I adjusted the valves to the tighter tolerance. To be honest I fudged at .025 lash. That was last April and 3000 miles ago. After setting the proper timing the car runs outstanding. I currently have the idle set at about 950. Idles good there. I know that is higher then the factory setting an I am sure it has to do with the tighter lash.

I have since changed the rear end to a 3.36 unit for better more comfortable highway driving. I will tell you that the only reason I considered doing this is that the 4.11s were not original to the car. Believe it or not the car came with a 3.08 posi per the POP. Does it drive around town differently then when it had the 4.11s? Yes. Is it manageable? Yes. With either rear end this car plants your back in the seat anywhere above that magic 3000 rpm level.

Since that first month I have now taken the engine to redline on more then one occasion. Runs flawlessly up to there and I am sure would go past it. I am now going to be a little kinder to the engine after today's experience with my 300 hp 67 coupe. That car was a 33k mile duntove car when I purchased it 5 years ago. My first Corvette actually. I now have 44k miles on it. I drove it down to Pomona today to see good friends Charlie Bacon and Jim Gessner. On the way home I took the engine up to 5,200 rpm and experienced some vibration while getting on the freeway. Shifted and it went away. Drove the car 65 miles home with no issues. Took it back up to 5,000 rpm and it was still there. Now I am thinking what could it be. I have been playing with the fan clutch and the proper amount of viscous fluid for it to start to hook up at the right temp. When I pulled in the driveway I popped the hood to observe the fan and pullies at the higher rpm. Took it up to 5,000 one more time and vibration got much worse. Backed off and the blipped the throttle a time or two. Vibration and knocking now. I have had this happen one other time on a small block. It turned out to be a spun #8 rod bearing.

Sorry about being so long winded. Just thought I would set the record straight as I know it.

[Michael H.]

Re: Winter-storage of FI car - unit out of tune afterwards?

Michael,
I feel the need to chime in here. I have seen the "discussions" on this and other boards concerning the valve adjustment of these solid lifter cars. I was not able to drive these cars back in the day so can only relay my more current experiences. I looked for a real fuel car for 5-1/2 years before finding mine. I drove three cars. All 65 fuelies. All of them ran and idled good. I can tell you that the one car that had the motor rebuilt was a flat out dog! I firmly believe that it had lower compression pistons put in because it just did not pull like all these solid lifter motors do at 3000 rpm and above. Am I positive it had the 30-30 cam? Somewhat. Car definitely had a solid lifter cam and idled and sounded like the other cars including mine.

Now a little history on my car. Original 375 hp fuel car with original matching motor and fuel unit. Car had 35k original miles when I purchased last April. Also has what is believed to be the original vac advance can. The motor has never been apart. Engine has the original .018 thick head gaskets on both sides. More then one NCRS person with knowledge have also indicated that the intake gaskets are original. Fuel unit has been off the car and gone thru by Chris Wickersham. The car runs perfect on unleaded premium all day long. That is until the outside temps push into the 90s and above. At that point there are issues with percolation of fuel in the spider at idle. Very common as you know in fuelie cars. After discussing with Duke I adjusted the valves to the tighter tolerance. To be honest I fudged at .025 lash. That was last April and 3000 miles ago. After setting the proper timing the car runs outstanding. I currently have the idle set at about 950. Idles good there. I know that is higher then the factory setting an I am sure it has to do with the tighter lash.

I have since changed the rear end to a 3.36 unit for better more comfortable highway driving. I will tell you that the only reason I considered doing this is that the 4.11s were not original to the car. Believe it or not the car came with a 3.08 posi per the POP. Does it drive around town differently then when it had the 4.11s? Yes. Is it manageable? Yes. With either rear end this car plants your back in the seat anywhere above that magic 3000 rpm level.

Since that first month I have now taken the engine to redline on more then one occasion. Runs flawlessly up to there and I am sure would go past it. I am now going to be a little kinder to the engine after today's experience with my 300 hp 67 coupe. That car was a 33k mile duntove car when I purchased it 5 years ago. My first Corvette actually. I now have 44k miles on it. I drove it down to Pomona today to see good friends Charlie Bacon and Jim Gessner. On the way home I took the engine up to 5,200 rpm and experienced some vibration while getting on the freeway. Shifted and it went away. Drove the car 65 miles home with no issues. Took it back up to 5,000 rpm and it was still there. Now I am thinking what could it be. I have been playing with the fan clutch and the proper amount of viscous fluid for it to start to hook up at the right temp. When I pulled in the driveway I popped the hood to observe the fan and pullies at the higher rpm. Took it up to 5,000 one more time and vibration got much worse. Backed off and the blipped the throttle a time or two. Vibration and knocking now. I have had this happen one other time on a small block. It turned out to be a spun #8 rod bearing.

Sorry about being so long winded. Just thought I would set the record straight as I know it.

John

If you set your valve lash at .024" instead of the correct .030", because someone recommended it, and now the engine won't idle at less than 1000 RPM, then I don't know what to say. Probably best that I just leave it alone and go on.

Sorry to hear the bad news on the 67. I've been there a few times too, decades ago, and it's not an inexpensive repair. New/different crankshaft and connecting rod and rebalance the complete assembly.