68 L79 refresh.
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Le Mans Master
Joined: Jun 2019
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From: Loveland
68 L79 refresh.
I have a numbers matching L79 HT code engine. It has a Holley 4175 that works well, I don't really want to change it. 60,000 miles,,,,,,I think. I would like to get it refreshed/overhauled. I don't want different exhaust manifolds, heads, intake ETC. A bit more power wouldn't hurt. It's supposed to have 11:1 compression and 350 hp already. I know the old engines have issues with the unleaded fuels today that could be upgraded. What needs to be done to the engine and what would be good to do? Just for the engine. I know there are millions of thing I can do to other systems while it is out. Could this be done and not remove the entire engine from the car? About how much should it cost?
Team Owner
Joined: Oct 2004
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From: altered state
St. Jude Donor '05
First you need to tear it down and measure the bore see what kind of wear/taper it has.
That will dictate if you can ring/hone which Im not convinced lasts long or rebore.
Probably doesnt have an honest 11-1. Id so a nice valve job, portwork and a roller cam for power increase you can actually feel. It will still appear stock outside 100%
Mark ie Vortecpro is out by you, he is expert with builds like this and iron heads
PS easier to pull the whole engine doenst take long and makes it so much easier to work on. You should be putting freeze plugs and more, cant do it in the car
That will dictate if you can ring/hone which Im not convinced lasts long or rebore.
Probably doesnt have an honest 11-1. Id so a nice valve job, portwork and a roller cam for power increase you can actually feel. It will still appear stock outside 100%
Mark ie Vortecpro is out by you, he is expert with builds like this and iron heads
PS easier to pull the whole engine doenst take long and makes it so much easier to work on. You should be putting freeze plugs and more, cant do it in the car
Last edited by cv67; May 30, 2021 at 11:30 AM.
Burning Brakes
Joined: Sep 2019
Posts: 923
Likes: 155
From: North Port, FL
You can easily do that at home and you dont have to pull the motor. 60K miles is nothing if it was taken care of. Mine has exactly twice as yours 120K and it runs like a swiss watch. I'm just gonna pull it clean it up and put it aside for the next owner. No reason to open a perfectly good #'s matching motor.
Last edited by 0311 jarhead; May 30, 2021 at 04:44 PM.
Drifting
Joined: Mar 2009
Posts: 1,461
Likes: 361
From: Monson MA
I have the same L79 in my 68. I used new 11:1 pistons, Comb roller cam, roller lifters, comp magnum roller tip rockers, port pocket the original heads, new valves. Reconditioned the rods and crank. I have the original Quadrajet rebuilt. It dyno'd at 383 hp and 423 tq. Plenty of fun for me.
PS. The CR is closer to 10.5:1 with the Felpro head gaskets i used.
PS. The CR is closer to 10.5:1 with the Felpro head gaskets i used.
Last edited by twinpack; May 30, 2021 at 07:10 PM.
Le Mans Master
Joined: Oct 2010
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From: melbourne florida
2023 C3 of the Year Finalist - Modified
I'd be checking your distributor advance and the general operation of it confirm your timing. Make sure your carb opens fully when you push the gas pedal to the floor. The L-79 was a strong running engine I'd make sure everything is fine before you tear into it.
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Le Mans Master
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From: Loveland
Yep,,,, Done that.
Thread Starter
Le Mans Master
Joined: Jun 2019
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From: Loveland
I dont think youre gonna get all that for $230, good roller tappets cost that much. Pull the heads, check the bore, if its good get some good alum heads (trick flow. AFR) intake and a matching Carb. Best bang for the buck.
You can easily do that at home and you dont have to pull the motor. 60K miles is nothing if it was taken care of. Mine has exactly twice as yours 120K and it runs like a swiss watch. I'm just gonna pull it clean it up and put it aside for the next owner. No reason to open a perfectly good #'s matching motor.
You can easily do that at home and you dont have to pull the motor. 60K miles is nothing if it was taken care of. Mine has exactly twice as yours 120K and it runs like a swiss watch. I'm just gonna pull it clean it up and put it aside for the next owner. No reason to open a perfectly good #'s matching motor.
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Race Director
Joined: Jul 2015
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From: SW Florida.
i would leave the bottom end alone if compression is good. that steel crank and forged pistons are very nice pieces-and collector's items. pull the heads and get a good valve job and do some bowl area clean up. this is one of the few where "numbers matching" actually means something.
my 75 L48 is numbers-matching. because no prev owner was willing to spend the money to put a real engine in it. at least they did L82 valve covers!
my 75 L48 is numbers-matching. because no prev owner was willing to spend the money to put a real engine in it. at least they did L82 valve covers!
Last edited by derekderek; May 31, 2021 at 09:52 AM.
Le Mans Master
Joined: Oct 2010
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From: melbourne florida
2023 C3 of the Year Finalist - Modified
Pull the valve covers and see if the cam is going flat. A stock replacement cam and a set of heads would probably work well. You might also check your timing chain that's a likely suspect too.
Thread Starter
Le Mans Master
Joined: Jun 2019
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From: Loveland
Redoing the heads is a good idea. So if I redo the heads, I wouldn't have to worry about using zinc additive in the oil? How much should this cost? I have done a compression test. I am at 5000 ft so the numbers are very different than sea level.
Burning Brakes
Joined: Sep 2019
Posts: 923
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From: North Port, FL
You can buy aftermarket heads cheaper then doing yours. Check Summit online. Intake, carb and a disto if needed and youre done. Right around a grand ? if you do it yourself.
Race Director
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From: Golden Colorado
ZDDP (zinc in the oil) has nothing to do with the heads. It is an additive for flat tappet cams and not required if you go to roller cam. 
I see you are in Colorado also, so don't overdo the duration on the cam. High altitude likes less duration on a street car. Just my .02
I see you are in Colorado also, so don't overdo the duration on the cam. High altitude likes less duration on a street car. Just my .02
Last edited by Vette5311; May 31, 2021 at 12:56 PM.
Burning Brakes
Joined: Sep 2019
Posts: 923
Likes: 155
From: North Port, FL
ZDDP (zinc in the oil) has nothing to do with the heads. It is an additive for flat tappet cams and not required if you go to roller cam.
I see you are in Colorado also, so don't overdo the duration on the cam. High altitude likes less duration on a street car. Just my .02
I see you are in Colorado also, so don't overdo the duration on the cam. High altitude likes less duration on a street car. Just my .02
Its the gas that eats up old soft iron valve seats
Burning Brakes
Joined: Aug 2007
Posts: 897
Likes: 246
From: Green Valley Ca
ZDDP (zinc in the oil) has nothing to do with the heads. It is an additive for flat tappet cams and not required if you go to roller cam.
I see you are in Colorado also, so don't overdo the duration on the cam. High altitude likes less duration on a street car. Just my .02
I see you are in Colorado also, so don't overdo the duration on the cam. High altitude likes less duration on a street car. Just my .02
Thread Starter
Le Mans Master
Joined: Jun 2019
Posts: 5,503
Likes: 2,202
From: Loveland