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Discussion Starter · #1 ·
I have been all over all the threads from many websites--can't find the actual mechanical differences listed.
I am restoring a '68 Malibu from the KC GM Manufacturer. It has (what I believe to be original) a 327 L30. If it is not, I'd like to convert it to a L79. What's the compression differences, piston size differences, header/manifold/carb differences (parts to replace)? I appreciate the help!
 

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1968 Malibu sport coupe, 489 ci. 590 hp 600 tq, RV T-400 Freakshow 3200 stall, 3.73 12 bolt posi
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Bill aka Billdini has a 68 L79 vert that he restored, he'll see this thread, also RichL79 has a 65 IIRC, EDIT just noticed what time it is lol
 

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Wlcome to Team Chevelle. I have an L79 in my wagon.

L79s have forged domed pop up pistons & 11:1 compression, where the L30 has cast flat tops & 10:1 compression. Piston diameters are all the same, the only difference is in the dome. L79s in 65 & 67 had an aluminum intake & a small Holley. L79 in '68 had a cast iron intake & a QJet. All L30s had a cast iron intake...not sure of carb specifics, but none came with Holleys.

The head casting numbers are the same, but the L79 had 2.02 intakes valves, 1.6 exhaust valves, where the L30 had 1.94 & 1.5 respectively. All 327s in Chevelles came with the same cast iron exhaust manifolds, no factory headers. I believe factory L79s had forged crank shafts, but I'm not 100% certain.

Billdini can tell you the correct part numbers for '68 intake, carb, exhaust manifolds, etc. It's a pretty easy conversion if you already have the L30 long block.
 

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Biggest difference is the camshaft. L30 had grocery getter .390/.410 lift 190/200 something degrees duration at .050 lift stick, while the L79 had .447/.447 lift and 222/222 degrees duration at .050 lift.

This cam is what breathed life into the L79.
 

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1968 Malibu sport coupe, 489 ci. 590 hp 600 tq, RV T-400 Freakshow 3200 stall, 3.73 12 bolt posi
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I remember when I was in my teens those heads with 2.02/1.6 valves and that cam were what we always looked for at the JY's to hop up our sbc's or grab the complete engine when possible Edit double hump heads and whatever cam was under them I guess is what I should say
 

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Yes everything above is accurate and I will just comment to firm up a couple statements. The L79 in 68 used the same cast intake and exhaust manifold as all SBC 4 bbl 327's in 68. However the head pipe was 2.5 inches in diameter with 2 inch tailpipes. The 68 carburetor and distributor had unique #'s for quicker timing and a richer mixture and was a 750 cfm Quadrajet versing earlier L79's were undersized Holley 585cfm's. The intake still used the front oil fill as did the L30. The L30 used a cast large journal crankshaft (same as the 307)where the L79 used a large journal forged crank. Prior to 68 all small journal 327s cranks were forged. Pistons were 11 to 1 forged. The cam was the famous 327/350hp cam with a duration of 222/222 and lift of .447/.447 with 1.50 rockers. The heads in 68 were one year only #291 castings with 64cc chambers and 2.02/1.60 valves and mostly differed with the inclusion of a temperature sending unit in the head unlike the previous year #462 casting. . It was rated at 325HP in 67 and 68 but many speculate that was purposely downgraded so it didn't compete with the 396. The 68 Vette was still rated at 350hp. The L79 had a chrome open element air cleaner and chrome flashed valve covers with one grommet for the air cleaner and PCV valve. Here is a picture of mine that is 100 correct and number matching minus the air pump which I have with correct brackets for AC. The L79 did not have HD cooling unless equipped with AC like mine. The rest of the package included a floor mounted manual HD 3 speed or a optional M20/M21 and a 12 bolt rear end. Standard was 3.31 ratio and posi was available as were other gear ratios.
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Discussion Starter · #7 ·
Ah! Weeks of questions have been answered!!! Thank you! The car arrives this weekend and the block is third on the list to start working on (behind brakes and fuel lines). Will keep you all posted.

Billdini: it sounds to me like this conversion is more parts replacement then modification? Is that right?
 

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Ah! Weeks of questions have been answered!!! Thank you! The car arrives this weekend and the block is third on the list to start working on (behind brakes and fuel lines). Will keep you all posted.

Billdini: it sounds to me like this conversion is more parts replacement then modification? Is that right?
All the parts are available, many like Howard make the cam, heads you can modify if they are 251's and most are 1.94's but try and find original 2.02 since many shops lack the expertise to unshroud the valves properly. It's just a matter of $. Finding a large journal forged crank might be more of a challenge although a lot of Vettes had L79's. Pistons are readily available. The L79 cams overlap does bleed off some compression so stay with dome pistons. I do not ping or knock on 93 octane.
 

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Biggest difference is the camshaft. L30 had grocery getter .390/.410 lift 190/200 something degrees duration at .050 lift stick, while the L79 had .447/.447 lift and 222/222 degrees duration at .050 lift.

This cam is what breathed life into the L79.
Was typing before I fell asleep last night, cannot believe I forgot to include the most obvious difference...the cam.
 

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The L79 cams overlap does bleed off some compression so stay with dome pistons. I do not ping or knock on 93 octane.
Two questions:
1.) What do you believe a roller valve train would do for/to this engine?
2.) Is there a way to bump the octane of 93 pump gas up a little?
 

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Two questions:
1.) What do you believe a roller valve train would do for/to this engine?
2.) Is there a way to bump the octane of 93 pump gas up a little?
Lou I would only be guessing but a good set of roller rockers like Pro Magnums are good for 20hp. I ran a 224/230 Comp roller cam in my 1974 L82 that made decent power over the stock GM 350/350 cam. However I was never a big fan of that cam when compared to the L79 cam. I have run that L79 in a lot of cars from 307, 327 and 350's and it always worked for me with good heads with small chambers. I would be willing to bet a L79 with full roller like I mentioned above would be close to 400 Gross Hp or a true 330-350hp net but that L79 exhaust note will be diminished.
 

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Thanks.
I don't want to mess with the way the engine sounds unless it sounds better. Roller rockers sounds like a plan as I have to put new ones in anyway and if I can cut some friction out, great!
 

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Thanks.
I don't want to mess with the way the engine sounds unless it sounds better. Roller rockers sounds like a plan as I have to put new ones in anyway and if I can cut some friction out, great!
It's not just friction. They are a accurate with 1.52 ratio. Unless you are running tall covers you will have to run dual gaskets at a minimum and one reason I do not have them on mine.. Headers would do a lot more IMO.
 

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Wlcome to Team Chevelle. I have an L79 in my wagon.

L79s have forged domed pop up pistons & 11:1 compression, where the L30 has cast flat tops & 10:1 compression. Piston diameters are all the same, the only difference is in the dome. L79s in 65 & 67 had an aluminum intake & a small Holley. L79 in '68 had a cast iron intake & a QJet. All L30s had a cast iron intake...not sure of carb specifics, but none came with Holleys.

The head casting numbers are the same, but the L79 had 2.02 intakes valves, 1.6 exhaust valves, where the L30 had 1.94 & 1.5 respectively. All 327s in Chevelles came with the same cast iron exhaust manifolds, no factory headers. I believe factory L79s had forged crank shafts, but I'm not 100% certain.

Billdini can tell you the correct part numbers for '68 intake, carb, exhaust manifolds, etc. It's a pretty easy conversion if you already have the L30 long block.
The distributor is 1111444 and the pics below.
Automotive tire Motor vehicle Light Hood Automotive lighting
Motor vehicle Gas Auto part Nut Machine
 

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The L79 is a magical engine whose performance is greater than the sum of its parts would indicate.
 

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Billdini, since your engine does not ping on 93 octane, is there anything that might help make this happen for him, so that the new guy can duplicate it such as say 3.73 rear, stick/auto, headers, cylinder head work, tuning etc. I could see a car would less likely ping with say 3.73 then 3.08 or a loose converter etc. The L79 is a nice engine for this car.

It's not just friction. They are a accurate with 1.52 ratio. Unless you are running tall covers you will have to run dual gaskets at a minimum and one reason I do not have them on mine.. Headers would do a lot more IMO.
I have been all over all the threads from many websites--can't find the actual mechanical differences listed.
I am restoring a '68 Malibu from the KC GM Manufacturer. It has (what I believe to be original) a 327 L30. If it is not, I'd like to convert it to a L79. What's the compression differences, piston size differences, header/manifold/carb differences (parts to replace)? I appreciate the help!
 

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In 1975, my 1967 Caprice NHRA stock class drag car (3713 pounds minimum) was running low 13's (13.15) at over 100 with a L30 327 and a stock bottom end, so a Chevelle should be able to do the same, if not better.
 
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In 1975, my 1967 Caprice NHRA stock class drag car (3713 pounds minimum) was running low 13's (13.15) at over 100 with a L30 327 and a stock bottom end, so a Chevelle should be able to do the same, if not better.
Although it would not be quite as fast a L30 with the L79 cam and 64cc 1.94 heads would wake it up for sure. 327 is a nicely balanced power plant that responds well to engine mods. With a better intake and headers with the car correctly tuned would probably stay up with my stock L79.
 
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