Author Topic: L78 vs W72  (Read 1327 times)

Bdaz78ta

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L78 vs W72
« on: November 12, 2018, 02:45:49 PM »
My 78 TA is equipped with the original L78 Pontiac 400 with 86k on the clock. I’m investigating a Butler performance rotating assembly kit & Kauffman aluminum heads with a goal of 300 to 350 HP. I’m not building a race car just a dependable safe street cruiser. With that being said I would love to keep the numbers matching block. Is there any concerns with the L78 vs the W72 Pontiac 400’s?
1978 Trans am, L78 400 auto, WS-6, Fisher T Tops.
2017 Challenger Hellcat.
2017 Ram Sport. (Daily)
1972 Dodge Charger Rallye. (SOLD)
1999 30TH Anniversary TA Convertible. #0625

Grand73Am

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Re: L78 vs W72
« Reply #1 on: November 12, 2018, 04:26:15 PM »
I believe the L78 engine in 1978 still used the weaker "557" block casting. So, I'd look at your casting number to see if your number ends in "557". Even if it is, it doesn't sound like you're going to use a stroker kit. So, I don't see a problem just replacing the stock rotating assembly with the same size assembly. And it's generally accepted than a 557 block can handle up to 400 hp. Here's a quote from somebody on a forum:  "A 500557 400 can handle around 400-450 hp, but only from a head/cam/exhaust upgrade- no forced induction, stroker kits, or nitrous."

It would be better if you had the W72's stronger "988" block, but not a necessity for what it seems you want to do.

So, that's the only concern I know of.
Steve F.

Bdaz78ta

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Re: L78 vs W72
« Reply #2 on: November 12, 2018, 05:18:12 PM »
Sounds great. Thanks for the info, my build sheet does indicate the L78 400. I'm probably going .30 over with a cam and a set of aluminum Kaufmann heads. I want to still use my shaker, i think Butler has a better flowing intake that supports the original shaker mounting on the new carb. Round it out with a set of headers and a new TCI tranny and I think I'll be good to go. I definitely want to ensure my new A.C. goes back on after the rebuild. Thanks for the reply, I'll keep you posted.
1978 Trans am, L78 400 auto, WS-6, Fisher T Tops.
2017 Challenger Hellcat.
2017 Ram Sport. (Daily)
1972 Dodge Charger Rallye. (SOLD)
1999 30TH Anniversary TA Convertible. #0625

Jack

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Re: L78 vs W72
« Reply #3 on: November 12, 2018, 07:10:38 PM »
That's a good set up but I don't know about 350 HP, more like 280 HP which is very respectful for a 40 year old car.




Regards, Jack

Bdaz78ta

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Re: L78 vs W72
« Reply #4 on: November 12, 2018, 07:38:44 PM »
Your probably right, definitely better then the original 180 HP. I’m hoping the parts I’ve chosen to use will fit the bill. I hear Butler has great tech advice and customer service. I hoping to get a improved reliable driver with their help on my OEM block.
1978 Trans am, L78 400 auto, WS-6, Fisher T Tops.
2017 Challenger Hellcat.
2017 Ram Sport. (Daily)
1972 Dodge Charger Rallye. (SOLD)
1999 30TH Anniversary TA Convertible. #0625

Re: L78 vs W72
« Reply #4 on: November 12, 2018, 07:38:44 PM »

roadking77

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Re: L78 vs W72
« Reply #5 on: November 13, 2018, 08:03:15 AM »
What kind of driving are you going to do? I think a lot of people get wrapped in Horse Power for the wrong reason. It sounds macho to say 'my car has x more horsepower than your hellcat' but is it really necessary? If you plan on putting together a good weekend cruiser than moderate is fine. If you are going to race/auto cross or something like that than yes, you need to put some serious attention and money into the car. When I had my motor rebuilt (557 block) I told the guy that I wanted more than stock, and be able to use pump gas. Honestly, I have no idea if its 150hp or 500hp. All I know is that it runs great, will get out of its own way, sounds great, and will get right along if I hammer it. I have driven probably less than 1000 miles in the last 2 summers and I couldn't be happier with the amount of power I have.
Finished!
77 T/A - I will Call this one DONE!
79 TATA 4sp-Next Project?
79 TATA - Lost to Fire!
86 Grand Prix - Sold
85 T/A - Sold
85 Fiero - Sold
82 Firebird - Sold
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Bdaz78ta

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Re: L78 vs W72
« Reply #6 on: November 13, 2018, 05:00:16 PM »
Your also right, my Hellcat is definitely more than enough to scratch the itch. I am just looking for a set up similar to yours. Dependable, street cruiser that sounds as good as it looks. I wasn’t sure what my block- L78 would support that’s why I wanted to go with a cam and a good set of heads. I’m going to be calling Butler next week and have them make some suggestions and depending on the dollars I’ll get the ball rolling. Thanks for your input. I appreciate all the feedback.
1978 Trans am, L78 400 auto, WS-6, Fisher T Tops.
2017 Challenger Hellcat.
2017 Ram Sport. (Daily)
1972 Dodge Charger Rallye. (SOLD)
1999 30TH Anniversary TA Convertible. #0625

Maxthe222

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Re: L78 vs W72
« Reply #7 on: November 13, 2018, 06:45:05 PM »
There is always the option of taking your original block out and buying another bare block and going up from there, right? You can tuck the original one safely away in the garage. But of course, I am very well aware of the costs in that regard, originally I wanted to have two 400 blocks for my '79, the original and just another identical one I could abuse, but that being said they both need parts, one will just sit there taking up space, and then it all just makes you question why you'd buy another block in the first place. In your case, the L78 isn't the best for big HP, I am no Pontiac block specialist but I've read posts and articles that also back up what others have said that 400 HP would likely be your max.

 However, you can likely find a early 70's 400 Pontiac block for very cheap, and if you're not concerned about having a "period correct" spare block then you'd have heaps of options to go by. Number's matching is more of a re-sale thing right? Imagine a guy wants to buy your car, and you say "I have the original block 100% complete and neatly packed away safely", i'm sure the buyer would be no less enthralled if not more.
1979 T/A Y84 WS6
1979 F/A W72 WS6
1971 Formula ???

Bdaz78ta

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Re: L78 vs W72
« Reply #8 on: November 13, 2018, 07:14:25 PM »
That is something to consider. I am pretty set on keeping the original block in the car though. However depending what Butler tells me I may have to reconsider my plan and go with one of theirs.
I’ll keep you posted.
1978 Trans am, L78 400 auto, WS-6, Fisher T Tops.
2017 Challenger Hellcat.
2017 Ram Sport. (Daily)
1972 Dodge Charger Rallye. (SOLD)
1999 30TH Anniversary TA Convertible. #0625

roadking77

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Re: L78 vs W72
« Reply #9 on: November 14, 2018, 08:00:50 AM »
LOL, I used the hellcat as an example because it seems that is the car that everyone compares to. I just saw in your sig that you have one. That must be one fun car to drive. Also see you have a vintage mopar as well. Would like to see some pics of that one.
Finished!
77 T/A - I will Call this one DONE!
79 TATA 4sp-Next Project?
79 TATA - Lost to Fire!
86 Grand Prix - Sold
85 T/A - Sold
85 Fiero - Sold
82 Firebird - Sold
'38-CZ 250
'39-BSA Gold Star
'49-Triumph 350
'52-Ariel Red Hunter
'66-BSA Lightning
'01-HD RoadKing

firebirdparts

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Re: L78 vs W72
« Reply #10 on: November 14, 2018, 09:02:22 AM »
If you want to run it I think yes, run it.  I don't know what really is the danger point, but personally I would still enjoy the car at that horsepower.  Everybody says the danger point is above that.  I guess it's all relative to how good the casting was to start with, and whether anything cracked in the last 40 years.
I want to be like Paul Kenny when I grow up
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1977 Y82 4-speed (red interior)
1978 Skybird 350
1978 Redbird 305
1979 Redbird 301 4-speed
1992 Lincoln Mark VII LSC/SE (red)
1970 Datsun Pickup
1953 Chevy pickup (converted 4x4)
1988 T-bird Turbo Coupe

oldskool

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Re: L78 vs W72
« Reply #11 on: November 14, 2018, 02:54:37 PM »
Here's my thoughts.

If you got plenty of money, then use the 557 block & don't give it another thought.

BUT, if budget & longevity is a concern, then why even take a chance on a weak block which has had many documented cases of failure, with the main webs cracking at the main cap dowel pin holes ?

Bdaz78ta

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Re: L78 vs W72
« Reply #12 on: November 14, 2018, 07:27:52 PM »
Definitely a lot of opinions to consider. Thanks for all the reply’s. I’m excited to get this project going. More to come...
1978 Trans am, L78 400 auto, WS-6, Fisher T Tops.
2017 Challenger Hellcat.
2017 Ram Sport. (Daily)
1972 Dodge Charger Rallye. (SOLD)
1999 30TH Anniversary TA Convertible. #0625

72blackbird

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Re: L78 vs W72
« Reply #13 on: November 23, 2018, 05:42:43 PM »
Bdaz,
Nice choice for a second gen TA- I just picked up a 78 Martinique blue W72 4-speed TA hurst t-top project car myself.Since these TAs are special, i would definitely keep the L78 400- stick it in storage since you only get one original engine. I've pulled apart more than one L78 that had cracked main webs or pieces falling out- not worth even pulling it apart as long as it runs.

There's more than a few W72 xx blocks out there- IMO it's an excellent choice for an upgrade. Put a decent rotating assembly with lightweight forged pistons,  4340 rods, 3.75" factory crank, add your KREs, and a good roller cam, and you'll make 500 hp like falling off a log. A forged 4.25" stroker crank, 310+ cfm port option from KRE, and a more aggressive roller profile will bump the hp to the 600 hp level.

Geno.
1977 SE T/A (sold :( )
1974 455 T/A (sold :( )
1972 Esprit restomod
1976 T/A restomod
1975 Formula 400 4-speed donor car
1978 Martinique blue W72 4-speed T/A, hurst tops

Aus78Formula

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Re: L78 vs W72
« Reply #14 on: November 24, 2018, 12:04:02 AM »
Build it and use it. You won't lug around an old block and it won't one day find its way back into the car with a future owner either.

Re: L78 vs W72
« Reply #14 on: November 24, 2018, 12:04:02 AM »



Bdaz78ta

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Re: L78 vs W72
« Reply #15 on: November 26, 2018, 09:12:05 AM »
Well I ordered a bunch of parts from Butler performance on Black Friday. They are running the same promotion today as Black Friday, 5% off and free shipping. I ordered parts to support as much HP as my #s matching 400 should handle safely. I’m hoping all goes as planned when we tear it down, if so then great.... if not I already spent some $$ so what’s a few more for a new block. Either way it’s going to happen, can’t wait and we’ll keep updates coming. If you need anything from Butler the 5% off runs all day today 11/26/18.
1978 Trans am, L78 400 auto, WS-6, Fisher T Tops.
2017 Challenger Hellcat.
2017 Ram Sport. (Daily)
1972 Dodge Charger Rallye. (SOLD)
1999 30TH Anniversary TA Convertible. #0625

Bdaz78ta

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Re: L78 vs W72
« Reply #16 on: November 29, 2018, 06:58:18 PM »
Update... building a Butler 461!!! They are legit and very customer service oriented. They made it easy to price building my 557... block and with my BF savings from the sale they suggested the option of a stroker engine kit. They priced it out both ways and for 2k more the 461 block kit will be by his best guess right around 500 horses. They even helped me source a new turbo 400 tranny. 6 to 8 weeks and I can’t wait. I’ll keep updates coming????
1978 Trans am, L78 400 auto, WS-6, Fisher T Tops.
2017 Challenger Hellcat.
2017 Ram Sport. (Daily)
1972 Dodge Charger Rallye. (SOLD)
1999 30TH Anniversary TA Convertible. #0625

Aus78Formula

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Re: L78 vs W72
« Reply #17 on: November 29, 2018, 09:39:26 PM »
Sounds Bdaz...see what I did, huh huh? Never mind...

Wouldn't mind a Butler in my car..."your horsepower, Sir..."  why, thankyou, Bernard.
« Last Edit: November 29, 2018, 09:41:58 PM by Aus78Formula »

72blackbird

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Re: L78 vs W72
« Reply #18 on: November 29, 2018, 10:21:10 PM »
Update... building a Butler 461!!! They are legit and very customer service oriented. They made it easy to price building my 557... block and with my BF savings from the sale they suggested the option of a stroker engine kit. They priced it out both ways and for 2k more the 461 block kit will be by his best guess right around 500 horses. They even helped me source a new turbo 400 tranny. 6 to 8 weeks and I can’t wait. I’ll keep updates coming????

Good luck.
1977 SE T/A (sold :( )
1974 455 T/A (sold :( )
1972 Esprit restomod
1976 T/A restomod
1975 Formula 400 4-speed donor car
1978 Martinique blue W72 4-speed T/A, hurst tops

Bdaz78ta

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Re: L78 vs W72
« Reply #19 on: December 02, 2018, 06:01:59 PM »
My TA has a g80 10 bolt 8.5 differential with 256 gears. I was looking into an upgraded nitro posi carrier from East Coast Gear. I’m considering a gear swap to something like a 308, however the 256 is awesome on the highway. Anyone have any suggestions keeping in mind the swap to the 461 and Turbo 400 tranny.
1978 Trans am, L78 400 auto, WS-6, Fisher T Tops.
2017 Challenger Hellcat.
2017 Ram Sport. (Daily)
1972 Dodge Charger Rallye. (SOLD)
1999 30TH Anniversary TA Convertible. #0625

Bdaz78ta

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Re: L78 vs W72
« Reply #20 on: December 02, 2018, 06:09:11 PM »
Probably should mention this is not going to be on a drag strip or racing. It is to be a fun streetable cruiser. TY!
1978 Trans am, L78 400 auto, WS-6, Fisher T Tops.
2017 Challenger Hellcat.
2017 Ram Sport. (Daily)
1972 Dodge Charger Rallye. (SOLD)
1999 30TH Anniversary TA Convertible. #0625

oldskool

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Re: L78 vs W72
« Reply #21 on: December 02, 2018, 08:36:00 PM »
Probably should mention this is not going to be on a drag strip or racing. It is to be a fun streetable cruiser. TY!

Don't see any reason to change gears. At least try it with the new engine. Then, if you want more acceleration, change gears.

72blackbird

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Re: L78 vs W72
« Reply #22 on: December 03, 2018, 03:00:23 AM »
I think with a 461 you'll find the 2.56 posi ok. But with the 3.08 gears you'll really like it- great acceleration, decent top end without excessive revs. I've had a 3.08 posi in my 72 Esprit with a built 400 for over 20 years- if it works, you leave it and enjoy it.

Geno
1977 SE T/A (sold :( )
1974 455 T/A (sold :( )
1972 Esprit restomod
1976 T/A restomod
1975 Formula 400 4-speed donor car
1978 Martinique blue W72 4-speed T/A, hurst tops

Bdaz78ta

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Re: L78 vs W72
« Reply #23 on: December 04, 2018, 05:01:40 PM »
Going with a 342 and upgrading to a HD posi and 30 spline axels. Sourced the parts from East Coast Gear Supply in North Carolina. Very helpful and great customer Svs.
More to come...
1978 Trans am, L78 400 auto, WS-6, Fisher T Tops.
2017 Challenger Hellcat.
2017 Ram Sport. (Daily)
1972 Dodge Charger Rallye. (SOLD)
1999 30TH Anniversary TA Convertible. #0625

Aus78Formula

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Re: L78 vs W72
« Reply #24 on: December 05, 2018, 01:49:27 AM »
wow, that's a big step in a direction I wouldn't have gone

sCI

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Re: L78 vs W72
« Reply #25 on: December 05, 2018, 07:41:35 PM »
I think what Aus is implying is that 3.42:1 is the ragged edge of "hiwayable" gears without an overdrive. The main purpose of a built engine that has that many cubes--which means macho torque--is to avoid needing lower gears.

Now that you'll have killer torque AND lower gears, you're gonna have a brutal lower end, but have given up any reasonable cruising speed above 70mph... :?
However this car doesn't sound like a car you're going to drive very often, so it should be a real killer.

Aus78Formula

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Re: L78 vs W72
« Reply #26 on: December 05, 2018, 08:11:20 PM »
Exactly, it'll be a blast around town if you want the attention.

Bdaz78ta

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Re: L78 vs W72
« Reply #27 on: December 06, 2018, 07:03:50 PM »
Yeah I know what your saying. This process has been a roller coaster as you can tell if you followed the post from my original inquiry. My problem is that number one I didn’t think it was in my reach.. ie the 461, now I want the best result for the cash spent. You guys have given me some valuable feedback and helped my make some of the decisions that I have made to this point. As far as hiway speeds I will do the majority of my cruising around town thus the more bang for my buck. The other thought is I have purchased the TCI turbo 400 3 speed tranny. I’m thinking if the highway becomes  a concern in the future I could swap for an over drive tranny and accomplish both goals with the 342’s. I think I’m just happy to have this experience and the current plan will be a thousand times better than the stock L78. I’ll keep you guys posted and finally hope to attach some pics along the way. Waiting on the diff parts to arrive and I’ll install them at the same time I install the Hotchkis subframe connectors. Can’t wait!
1978 Trans am, L78 400 auto, WS-6, Fisher T Tops.
2017 Challenger Hellcat.
2017 Ram Sport. (Daily)
1972 Dodge Charger Rallye. (SOLD)
1999 30TH Anniversary TA Convertible. #0625

Bdaz78ta

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Re: L78 vs W72
« Reply #28 on: April 19, 2019, 05:56:46 PM »
Well last post since 12/06 and can say it’s finally done!???  Update. 461 short block kit from Butler, port matched Edlebrock aluminum heads, port matched Tomahawk intake, edelbrock carb. RAR Ram air manifolds, forged crank, h beam rods, roller rockers. New 200R4 OD tranny from Art Carr California Performance Tranny. New 30 spline posi 342 with axels, Sub frame connectors. Cold case aluminum radiator with duel electric cooling fans. Completed last week and in the break in process. Sounds RAW and runs awesome. Question, is it done?.. I say.... can you ever really be done?..
Thank you to all who gave advice and ultimately helped me make the right decision! 8-)
1978 Trans am, L78 400 auto, WS-6, Fisher T Tops.
2017 Challenger Hellcat.
2017 Ram Sport. (Daily)
1972 Dodge Charger Rallye. (SOLD)
1999 30TH Anniversary TA Convertible. #0625

Aus78Formula

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Re: L78 vs W72
« Reply #29 on: April 19, 2019, 07:33:14 PM »
Done? But that didn't take years, must be something wrong!

sCI

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Re: L78 vs W72
« Reply #30 on: April 20, 2019, 01:19:26 AM »
Please post a video of the engine running, idle too.

Re: L78 vs W72
« Reply #30 on: April 20, 2019, 01:19:26 AM »
You can help support TAC!