L46 question
Thread Starter
Pro
Joined: Feb 2002
Posts: 730
Likes: 51
From: ATLANTIC HIGHLANDS NJ
L46 question
Hello all. Have not posted in some time.
Thinking of looking to buy a 69 or 70 4 speed small block. Mostly as a cruiser and most practical to me would be a L48 for today's pump gas. I had a 70 LT1 about 15 years ago and it did not run well on pump gas. A few years ago had a 69 427 400 which ran fine. Obviously a iron head 10.25 CR runs well at around 36 all in around 2,800 RPM.
So, does an iron head L46 @ 11.00 CR get by on today's gas or would it need an aluminum head upgrade to handle today's gas, or just back down on timing, etc.?
Thanks. Doug
Thinking of looking to buy a 69 or 70 4 speed small block. Mostly as a cruiser and most practical to me would be a L48 for today's pump gas. I had a 70 LT1 about 15 years ago and it did not run well on pump gas. A few years ago had a 69 427 400 which ran fine. Obviously a iron head 10.25 CR runs well at around 36 all in around 2,800 RPM.
So, does an iron head L46 @ 11.00 CR get by on today's gas or would it need an aluminum head upgrade to handle today's gas, or just back down on timing, etc.?
Thanks. Doug
Melting Slicks
Joined: Feb 2017
Posts: 3,235
Likes: 1,232
From: PHX AZ
Dear Doug;
I have my L-46 for 44 years.
Here are some statements;
Yes the L-46 struggles on pump gas.
Whenever possible I use 'some' AVGAS and premium.
I use lead additive because lack of lead can cause valve seat recession.
High compression ratios can cause pinging, which is temporary and detonation which can be very 'permanent'.
Some of this can be managed by timing retardation, but that's not why we have an L-46 in the first place!
Attending to cooling is key...I live in AZ... I use a 160° thermos and my cooling system has been optimized 'to the max'.
Frankly I have attended to this with 'applied chemistry' cooling and making sure the carb is not running lean, and leaving the timing optimized.
I'm at about $6.00 a gallon....but I feel this is a small price to pay.
Go after all the things that cause detonation....for me, the last thing I want to do is get rid of my 'camels humps'.
Best of luck.
Unkahal
I have my L-46 for 44 years.
Here are some statements;
Yes the L-46 struggles on pump gas.
Whenever possible I use 'some' AVGAS and premium.
I use lead additive because lack of lead can cause valve seat recession.
High compression ratios can cause pinging, which is temporary and detonation which can be very 'permanent'.
Some of this can be managed by timing retardation, but that's not why we have an L-46 in the first place!
Attending to cooling is key...I live in AZ... I use a 160° thermos and my cooling system has been optimized 'to the max'.
Frankly I have attended to this with 'applied chemistry' cooling and making sure the carb is not running lean, and leaving the timing optimized.
I'm at about $6.00 a gallon....but I feel this is a small price to pay.
Go after all the things that cause detonation....for me, the last thing I want to do is get rid of my 'camels humps'.
Best of luck.
Unkahal
Thread Starter
Pro
Joined: Feb 2002
Posts: 730
Likes: 51
From: ATLANTIC HIGHLANDS NJ
Dear Doug;
I have my L-46 for 44 years.
Here are some statements;
Yes the L-46 struggles on pump gas.
Whenever possible I use 'some' AVGAS and premium.
I use lead additive because lack of lead can cause valve seat recession.
High compression ratios can cause pinging, which is temporary and detonation which can be very 'permanent'.
Some of this can be managed by timing retardation, but that's not why we have an L-46 in the first place!
Attending to cooling is key...I live in AZ... I use a 160° thermos and my cooling system has been optimized 'to the max'.
Frankly I have attended to this with 'applied chemistry' cooling and making sure the carb is not running lean, and leaving the timing optimized.
I'm at about $6.00 a gallon....but I feel this is a small price to pay.
Go after all the things that cause detonation....for me, the last thing I want to do is get rid of my 'camels humps'.
Best of luck.
Unkahal
I have my L-46 for 44 years.
Here are some statements;
Yes the L-46 struggles on pump gas.
Whenever possible I use 'some' AVGAS and premium.
I use lead additive because lack of lead can cause valve seat recession.
High compression ratios can cause pinging, which is temporary and detonation which can be very 'permanent'.
Some of this can be managed by timing retardation, but that's not why we have an L-46 in the first place!
Attending to cooling is key...I live in AZ... I use a 160° thermos and my cooling system has been optimized 'to the max'.
Frankly I have attended to this with 'applied chemistry' cooling and making sure the carb is not running lean, and leaving the timing optimized.
I'm at about $6.00 a gallon....but I feel this is a small price to pay.
Go after all the things that cause detonation....for me, the last thing I want to do is get rid of my 'camels humps'.
Best of luck.
Unkahal
Doug
Melting Slicks
Joined: Feb 2017
Posts: 3,235
Likes: 1,232
From: PHX AZ
Doug, tell me the miles on the car....building up carbonaceous deposits in the cyls and the tops of pistons is a prime cause.
Well maybe we're both old school...Do you remember the procedure for GENTLY dribbling water into the carb for 'flash steaming' out the deposits?
Unkahal
Well maybe we're both old school...Do you remember the procedure for GENTLY dribbling water into the carb for 'flash steaming' out the deposits?
Unkahal
Thread Starter
Pro
Joined: Feb 2002
Posts: 730
Likes: 51
From: ATLANTIC HIGHLANDS NJ
Doug, tell me the miles on the car....building up carbonaceous deposits in the cyls and the tops of pistons is a prime cause.
Well maybe we're both old school...Do you remember the procedure for GENTLY dribbling water into the carb for 'flash steaming' out the deposits?
Unkahal
Well maybe we're both old school...Do you remember the procedure for GENTLY dribbling water into the carb for 'flash steaming' out the deposits?
Unkahal
Instructor
Joined: Dec 2017
Posts: 169
Likes: 29
I think if you planned to keep the original heads on, you'd want to have the heads worked on, I'm sure that the valve seats will be an issue. I did put aluminum heads on mine, and I've had no issues whatsoever on 91 octane.
Burning Brakes
Joined: Oct 2012
Posts: 1,152
Likes: 252
I have C4 58cc aluminum heads on my '69 ZQ3 (same cam as L48) and have no detonation/ping issues at just under 10:75CR using 93 pump gas. IMO, If you are keeping the stock heads then when you get hardened valve seats then polish the chamber to remove any hot spots then use a thicker head gasket to slightly lower compression. Not optimal but will work.
Last edited by Dynra Rockets; Mar 30, 2021 at 07:41 AM.
Racer
Joined: Mar 2021
Posts: 278
Likes: 43
From: Kansas
My father has a L46, original owner and runs a lead additive and 93 octane and does good in weather below 90 degrees outside. Anything hotter outside and run into spark knock. He has run some higher octane fuel and runs great on it.
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Dr. Detroit
Joined: Mar 2012
Posts: 10,090
Likes: 4,015
From: New Braunfels Texas
Me being me, if I were considering buying this L-46.....the dealbreaker for me would be that it is not converted to lower compression for pump gas......I simply would pass. I could never see paying that kind of money for a car and have to dick with expensive fuel or additives to run it.......takes the joy out of it and limits how much one will drive it. I want to fill up at the corner and go.......
As far as originality is concerned, there is no way you could tell if it was done right.......a killer valve job and blending will more than make back the 15-20 horsepower loss from a point of compression....and could actually run better.
Jebby
As far as originality is concerned, there is no way you could tell if it was done right.......a killer valve job and blending will more than make back the 15-20 horsepower loss from a point of compression....and could actually run better.
Jebby
Le Mans Master
Joined: Oct 2010
Posts: 6,900
Likes: 833
From: melbourne florida
2023 C3 of the Year Finalist - Modified
I saw 72 Lt-1 vettes beat 70 versions I'm certain they were just tuned better but like Jebby said a point in compression usually isn't much.
Trick flow has those double jump aluminum.hrads that probably aren't a bunch more than seats a.valve job and some bowl work
Trick flow has those double jump aluminum.hrads that probably aren't a bunch more than seats a.valve job and some bowl work
Last edited by 7t9l82; Mar 30, 2021 at 10:46 AM.
Thread Starter
Pro
Joined: Feb 2002
Posts: 730
Likes: 51
From: ATLANTIC HIGHLANDS NJ
Me being me, if I were considering buying this L-46.....the dealbreaker for me would be that it is not converted to lower compression for pump gas......I simply would pass. I could never see paying that kind of money for a car and have to dick with expensive fuel or additives to run it.......takes the joy out of it and limits how much one will drive it. I want to fill up at the corner and go.......
As far as originality is concerned, there is no way you could tell if it was done right.......a killer valve job and blending will more than make back the 15-20 horsepower loss from a point of compression....and could actually run better.
Jebby
As far as originality is concerned, there is no way you could tell if it was done right.......a killer valve job and blending will more than make back the 15-20 horsepower loss from a point of compression....and could actually run better.
Jebby
If I found a great deal on a L46 I certainly could back down original heads to around 10.25 CR. So, your point well taken.
Doug