Cranking Compression
Thread Starter
Drifting
Joined: Jan 2018
Posts: 1,255
Likes: 316
From: Western NY
Compression
Use a set of NGK XR4 spark plugs, WIRE THE HEAT RISER WIDE OPEN, check your float bowls and metering blocks for warping before re-assembling using BLUE gaskets. A slight amount of smoke on startup is normal for an older engine due to weak valve seals. The smoke should clear after about 30 seconds. Once you wire the heat riser open, the vapor burnoff and/or slight valve seal related oil smoke will emanate equally from both sides and should stop evenly across both sides.
AC 44 or NGK XR4 plugs
Heat riser to be wired wide open
Check Meter blocks/float bowl's for warpage
Blue and black gaskets on the carb rebuild
No Hardened Valve Seats if it comes to head work
Re-run Vacuum test with engine warm and idle adjusted to spec.
Just got the assembly manual in the mail today, have the 66-82 Vette shop manual and the Chassis manual is on the way.
Will not have results to post until later Friday.
Race Director
Joined: Apr 2005
Posts: 11,265
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From: Bowling Green, Kentucky
Not to start a argument, but I would run AC 45 plugs in a street driven small block car today. Not AC 44.
We (I) learned this lesson back in 1966 and no reason to repeat it today. However, the fact that today's gas is unleaded should help the AC 44 to live on the street better.
Still, I run AC 45 today in my car and have for 52 years.
FWIW.
Larry
We (I) learned this lesson back in 1966 and no reason to repeat it today. However, the fact that today's gas is unleaded should help the AC 44 to live on the street better.
Still, I run AC 45 today in my car and have for 52 years.
FWIW.
Larry
Safety Car
Joined: May 2003
Posts: 4,797
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From: Ocean Township NJ
Got it:
AC 44 or NGK XR4 plugs
Heat riser to be wired wide open
Check Meter blocks/float bowl's for warpage
Blue and black gaskets on the carb rebuild
No Hardened Valve Seats if it comes to head work
Re-run Vacuum test with engine warm and idle adjusted to spec.
Just got the assembly manual in the mail today, have the 66-82 Vette shop manual and the Chassis manual is on the way.
Will not have results to post until later Friday.
AC 44 or NGK XR4 plugs
Heat riser to be wired wide open
Check Meter blocks/float bowl's for warpage
Blue and black gaskets on the carb rebuild
No Hardened Valve Seats if it comes to head work
Re-run Vacuum test with engine warm and idle adjusted to spec.
Just got the assembly manual in the mail today, have the 66-82 Vette shop manual and the Chassis manual is on the way.
Will not have results to post until later Friday.
Last edited by 65tripleblack; Apr 11, 2018 at 07:31 PM.
Race Director
Joined: Apr 2005
Posts: 11,265
Likes: 2,131
From: Bowling Green, Kentucky
But AC 45, R45 or R45S will serve you best if you have a relatively stock and street driven small block car. And the R plugs are available and cheap.
FWIW.
(Maybe nothing). 
Larry
Thread Starter
Drifting
Joined: Jan 2018
Posts: 1,255
Likes: 316
From: Western NY
Compression
Just as a point of clarification, reproduction AC 44 plugs are currently being manufactured and sold. Cost is about $60/set. I have not tried them, but I believe they are likely equal to AC NOS originals. So they are available..............as are the originals if you shop Ebay and have plenty $$$ to spend.
But AC 45, R45 or R45S will serve you best if you have a relatively stock and street driven small block car. And the R plugs are available and cheap.
FWIW. (Maybe nothing).
Larry
But AC 45, R45 or R45S will serve you best if you have a relatively stock and street driven small block car. And the R plugs are available and cheap.
FWIW.
(Maybe nothing). Larry
Now plan to do the vacuum, compression and leak down tomorrow. Have only a half day today so I am working on installing the new directional switch in the column.
Team Owner
Joined: Aug 2007
Posts: 58,061
Likes: 7,145
Army
You will NOT have to swap out the NGK-XR4 plugs unless your car is being judged.
After years of using them in a C1 and C2 I find them superior to any other plug I've used including the much-touted AC/Delco series and the Autolite 86 replacements...
After years of using them in a C1 and C2 I find them superior to any other plug I've used including the much-touted AC/Delco series and the Autolite 86 replacements...
Team Owner
Joined: Mar 2003
Posts: 26,118
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From: Greenville, Indiana
With the lead out of gasoline, I quickly found out my points fired ignitions and a carburetor would allow plugs to run at least 40K miles.
Race Director
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The NGK XR4 is a "V-power" plug with the notched center electrode, but it's also a resistor type.
I recommend the B4, which is not resistor, plain center electrode plug that is essentially identical to the old out-of-production AC 45.
Another good plug is the Denso W14-U... same heat range, non-resistor and it has the Denso "U-groove" ground electrode.
The NGK V-power notched center electrode and Denso U-groove are good features because the spark likes to initiate and propagate from sharp edges. That's why old plain electrode plugs show a rounded center electrode after several tens of thousands of miles of service.
If you insist on "AC" plugs then the R45 is best for normal driving (small blocks) and R45XLS for big blocks.
Duke
I recommend the B4, which is not resistor, plain center electrode plug that is essentially identical to the old out-of-production AC 45.
Another good plug is the Denso W14-U... same heat range, non-resistor and it has the Denso "U-groove" ground electrode.
The NGK V-power notched center electrode and Denso U-groove are good features because the spark likes to initiate and propagate from sharp edges. That's why old plain electrode plugs show a rounded center electrode after several tens of thousands of miles of service.
If you insist on "AC" plugs then the R45 is best for normal driving (small blocks) and R45XLS for big blocks.
Duke
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Safety Car
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From: Olive branch Ms
Can't help it! LOL. If you take your heads to be rebuilt and they don't strongly suggest installing hardened exhaust seats I would immediately leave and go to another shop. You may make the decision not to install them but then any warranty issues would fall on you. Oh and one more time every single head both factory and aftermarket produced since 1973 has hardened exhaust seats. If there's an exception to this I've never seen it.
Last edited by Robert61; Apr 12, 2018 at 09:14 AM.
Melting Slicks
Joined: Jan 2007
Posts: 2,842
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From: Pasco Florida
It was true back when gasoline contained lead and new plugs didn't stay clean for very long. But that was decades ago.
I've had the same set of correct AC 43N plugs in my 66 425 HP 427 car for about 15 years now and they don't miss a beat. Same for one of my FI 63's with AC 44's.
If spark plugs don't survive for more than a few hundred miles using lead free fuel, the engine is either huffing oil or running too rich.
Old myths never die.
Race Director
Joined: May 2000
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Spark plug tip temperature should achieve at least about 750F to burn off deposits, but exceeding about 1600F can lead to preignition.
This is a fairly wide range, and I prefer to use the hottest plug that doesn't get into the preignition range since they tend to burn off deposits faster and don't build up permanent deposits as fast, which means longer service life.
If the plug does get hot enough to get into the preignition region deposits will melt and form a glaze on the insulator, which is nearly impossible to remove and is visually obvious.
TI/HEI systems can get away with colder plugs because they have about double the per spark ignition energy of the single point system, so they will fire a plug that has wider gaps and more shunt resistance deposit buildup.
Duke
This is a fairly wide range, and I prefer to use the hottest plug that doesn't get into the preignition range since they tend to burn off deposits faster and don't build up permanent deposits as fast, which means longer service life.
If the plug does get hot enough to get into the preignition region deposits will melt and form a glaze on the insulator, which is nearly impossible to remove and is visually obvious.
TI/HEI systems can get away with colder plugs because they have about double the per spark ignition energy of the single point system, so they will fire a plug that has wider gaps and more shunt resistance deposit buildup.
Duke
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Posts: 11,265
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From: Bowling Green, Kentucky
Critter and Mike:
You guys are probably right and the colder plugs will last. But so will the the hotter 45 series and I can't see a downside at this point for street driven cars.
I currently run a 50/50 mix of non-ethanol and leaded 110 octane race gas in my 1967..............and the 45 plugs work very very well. I still have about a dozen boxes of AC 44 on the shelf along with the same amount of AC 45. Although I tried, I went thru two sets of 44 when I used them from awhile back (in the early 1990's). The 45 plugs are still in since that time. I should be ashamed, right.......not changing these in all that time
Now we can also debate my expensive taste of using non-ethanol/leaded race gas in the car, but it really does run better with that mix. And for the miles I put on it each year, the cost to me is nil. It's just a hobby.
I enjoy and learn from your experience with these cars, but some of us have also spent time with these cars since new.
Larry
You guys are probably right and the colder plugs will last. But so will the the hotter 45 series and I can't see a downside at this point for street driven cars.
I currently run a 50/50 mix of non-ethanol and leaded 110 octane race gas in my 1967..............and the 45 plugs work very very well. I still have about a dozen boxes of AC 44 on the shelf along with the same amount of AC 45. Although I tried, I went thru two sets of 44 when I used them from awhile back (in the early 1990's). The 45 plugs are still in since that time.
I should be ashamed, right.......not changing these in all that timeNow we can also debate my expensive taste of using non-ethanol/leaded race gas in the car, but it really does run better with that mix. And for the miles I put on it each year, the cost to me is nil. It's just a hobby.
I enjoy and learn from your experience with these cars, but some of us have also spent time with these cars since new.
Larry
Last edited by Powershift; Apr 12, 2018 at 11:47 AM.
Safety Car
Joined: May 2003
Posts: 4,797
Likes: 239
From: Ocean Township NJ
Yup, I agree. But we probably won't be able to convince most of the folks here though. Everyone still thinks they need HOTTER plugs to survive. Not true.
It was true back when gasoline contained lead and new plugs didn't stay clean for very long. But that was decades ago.
I've had the same set of correct AC 43N plugs in my 66 425 HP 427 car for about 15 years now and they don't miss a beat. Same for one of my FI 63's with AC 44's.
If spark plugs don't survive for more than a few hundred miles using lead free fuel, the engine is either huffing oil or running too rich.
Old myths never die.
It was true back when gasoline contained lead and new plugs didn't stay clean for very long. But that was decades ago.
I've had the same set of correct AC 43N plugs in my 66 425 HP 427 car for about 15 years now and they don't miss a beat. Same for one of my FI 63's with AC 44's.
If spark plugs don't survive for more than a few hundred miles using lead free fuel, the engine is either huffing oil or running too rich.
Old myths never die.
But, tell me, back in the "good old days" did a hotter heat range burn off lead deposits?
I always thought that a hotter plug would burn off carbon faster than a colder plug would. But, then again, I'm not a Corvette Historian, just a simple Engineer/Mechanic who has been fixing cars for the last 55 years, so, WTF do I know.
Last edited by 65tripleblack; Apr 12, 2018 at 11:39 AM.
Race Director
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Can't help it! LOL. If you take your heads to be rebuilt and they don't strongly suggest installing hardened exhaust seats I would immediately leave and go to another shop. You may make the decision not to install them but then any warranty issues would fall on you. Oh and one more time every single head both factory and aftermarket produced since 1973 has hardened exhaust seats. If there's an exception to this I've never seen it.
GM did find that seat recession could be an issue with unleaded fuel back in the seventies, but only in truck engines that operate at high sustained load. In normal road driving Corvette engine loads are much lower, so seats and valve run much cooler.
GM did start induction hardening exhaust valve seats and installing rotators in the seventies, but I don't recall ever hearing of excessive valve seat recession on an old Corvette, whether a fairly recent rebuild or an old original never rebuilt engine.
It's a tradeoff, and there's a vast amount of anecdotal evidence that indicate the risk of seat inserts outweighs any possible benefits.
The lead oxide coating that forms on the valve seats does appear to provide seat protection, though I don't think the mechanism if fully understood. This coating is very long lived once it reaches a steady state, so my advice to those who are concerned is to run some leaded fuel in the first couple of tanks after an engine rebuild, and if it continues to be a concern, repeat it every few thousand miles.
Duke
Safety Car
Joined: May 2003
Posts: 4,797
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From: Ocean Township NJ
Going back nearly 20 years the archives have many tales of field-installed valve seat horror stories... turning OE heads into scrap due to cutting in too far, coolant leaks, and seats popping out that did a lot of internal damage.
GM did find that seat recession could be an issue with unleaded fuel back in the seventies, but only in truck engines that operate at high sustained load. In normal road driving Corvette engine loads are much lower, so seats and valve run much cooler.
GM did start induction hardening exhaust valve seats and installing rotators in the seventies, but I don't recall ever hearing of excessive valve seat recession on an old Corvette, whether a fairly recent rebuild or an old original never rebuilt engine.
It's a tradeoff, and there's a vast amount of anecdotal evidence that indicate the risk of seat inserts outweighs any possible benefits.
The lead oxide coating that forms on the valve seats does appear to provide seat protection, though I don't think the mechanism if fully understood. This coating is very long lived once it reaches a steady state, so my advice to those who are concerned is to run some leaded fuel in the first couple of tanks after an engine rebuild, and if it continues to be a concern, repeat it every few thousand miles.
Duke
GM did find that seat recession could be an issue with unleaded fuel back in the seventies, but only in truck engines that operate at high sustained load. In normal road driving Corvette engine loads are much lower, so seats and valve run much cooler.
GM did start induction hardening exhaust valve seats and installing rotators in the seventies, but I don't recall ever hearing of excessive valve seat recession on an old Corvette, whether a fairly recent rebuild or an old original never rebuilt engine.
It's a tradeoff, and there's a vast amount of anecdotal evidence that indicate the risk of seat inserts outweighs any possible benefits.
The lead oxide coating that forms on the valve seats does appear to provide seat protection, though I don't think the mechanism if fully understood. This coating is very long lived once it reaches a steady state, so my advice to those who are concerned is to run some leaded fuel in the first couple of tanks after an engine rebuild, and if it continues to be a concern, repeat it every few thousand miles.
Duke
And, I can attest to having had to scrap a head because the seats were into the water jacket.
The culprit is known as "core shift", where olde fashionede manufacturing processes and fixturing led to wide variations in how a core pattern was suspended within the casting pattern as a whole. Short of it is...........some heads are safe to convert to hardened exhaust seats and some aren't.
In my case, two identical 461 castings: one head was OK and the other one had all 4 exhaust seats into water. The leak was very slow and finally caused the head to crack. Once the crack was fixed, I had that head pressure tested, and that revealed the underlying problem. I had the seats installed long before I became aware of the riskiness. I never would have had it done had I known.
Wasn't this thread about cranking compression?
Safety Car
Joined: Oct 2016
Posts: 4,617
Likes: 1,547
From: Olive branch Ms
And, I can attest to having had to scrap a head because the seats were into the water jacket.
The culprit is known as "core shift", where olde fashionede manufacturing processes and fixturing led to wide variations in how a core pattern was suspended within the casting pattern as a whole. Short of it is...........some heads are safe to convert to hardened exhaust seats and some aren't.
In my case, two identical 461 castings: one head was OK and the other one had all 4 exhaust seats into water. The leak was very slow and finally caused the head to crack. Once the crack was fixed, I had that head pressure tested, and that revealed the underlying problem. I had the seats installed long before I became aware of the riskiness. I never would have had it done had I known.
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From: About 1100 miles from where I call home.
Close for review of ongoing conflicts
——————
Reopen after review
Members:
For the second time today, I’ve had to close and clean a thread due to personal bickering among members, in some cases the same individuals. Unlike the last thread, I simply deleted full posts which included useful information because it’s not worth editing out all the personal namecalling, personal commentary about people and other BS.
I’m going to reopen this thread rather than close it, if people want to restore lost information or continue the technical discussion.
Multiple members had posts removed and were sanctioned at various levels. This is a reminder not to engage in personal hostility and conflict, no matter who starts it. If you cannot attack ideas rather than fellow members, try a different thread.
——————
Reopen after review
Members:
For the second time today, I’ve had to close and clean a thread due to personal bickering among members, in some cases the same individuals. Unlike the last thread, I simply deleted full posts which included useful information because it’s not worth editing out all the personal namecalling, personal commentary about people and other BS.
I’m going to reopen this thread rather than close it, if people want to restore lost information or continue the technical discussion.
Multiple members had posts removed and were sanctioned at various levels. This is a reminder not to engage in personal hostility and conflict, no matter who starts it. If you cannot attack ideas rather than fellow members, try a different thread.
Last edited by vettebuyer6369; Apr 12, 2018 at 04:50 PM. Reason: Re-open thread
Safety Car
Joined: May 2003
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From: Ocean Township NJ
Its not really that risky. Because someone tries to put too thick of a seat in does not make the operation a bad idea. It makes them a questionable machinist. I've never seen a 7/32 thick seat of the correct diameter go through. I wouldn't suggest trying to put seats in 461 type heads with 1.600 valves.
The seats that broke into water are 7/32" thick.