Another L48 automatic saga
Thread Starter
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Joined: Jan 2011
Posts: 52
Likes: 7
From: Des Moines WA
Another L48 automatic saga
I'm about to buy a clean 1977 L48 automatic 3.08 (I guess) that appears to be stock. The car runs ok nothing obviously wrong other than when I depress the accelerator. The L48 was 180 hp from the factory.
I plan to keep this 77 make it safe reliable and comfortable to enjoy. I have a reasonable budget to make improvements.
The performance is not acceptable.
My thoughts are a quality true dual exhaust with H pipe and short headers. And a 700R4. Sort out anything else needing attention. $5,000 may (I hope) cover that.
Later I'll have the L48 pulled replaced with a mild crate engine.
I've done a lot of reading here and it seems to me this would be cost effective and simple.
On the other hand I'd love to drop a mild LS into it!!!!
Any suggestions?
I plan to keep this 77 make it safe reliable and comfortable to enjoy. I have a reasonable budget to make improvements.
The performance is not acceptable.
My thoughts are a quality true dual exhaust with H pipe and short headers. And a 700R4. Sort out anything else needing attention. $5,000 may (I hope) cover that.
Later I'll have the L48 pulled replaced with a mild crate engine.
I've done a lot of reading here and it seems to me this would be cost effective and simple.
On the other hand I'd love to drop a mild LS into it!!!!
Any suggestions?
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
I bought a stock L-48 77 years ago and it is pretty sorry on power. Getting a better exhaust is definitely a must, you'll notice the difference. I went with side pipes vs full exhaust. Headers for sure on that mod. The stock ram horns are quite restrictive.
I still have the TH350 but have changed the rear ratio to a 3.55 from the stock 3.08. That makes a big difference. If you put in a 700R4 you'll need to change the rear ratio as well, the 3.08 is gonna be really high gear for the OD on the 700.
I got rid of all the emissions garbage on the engine including the EGR valve. It runs much better without it.
The Q-jet carb needs lots of help too. Sending it to Lars here on the forum is a popular option. I opted to rebuild it with some performance mods via Cliff Ruggle's book on the Q-jet. It runs sooo much better now.
Getting the timing curved right via Lars' papers is a huge improvement for the stock motor as well.
I dumped the stock HD cooling fan for electric fans, another jump in performance for the stock motor. You're talking 10% of the existing power goes to the stock HD cooling fan.
$5000 is a good start. However I think you'll find it will be twice or better than that number before you're all said and done. Spread out over several years it doesn't hurt as much.
I still have the TH350 but have changed the rear ratio to a 3.55 from the stock 3.08. That makes a big difference. If you put in a 700R4 you'll need to change the rear ratio as well, the 3.08 is gonna be really high gear for the OD on the 700.
I got rid of all the emissions garbage on the engine including the EGR valve. It runs much better without it.
The Q-jet carb needs lots of help too. Sending it to Lars here on the forum is a popular option. I opted to rebuild it with some performance mods via Cliff Ruggle's book on the Q-jet. It runs sooo much better now.
Getting the timing curved right via Lars' papers is a huge improvement for the stock motor as well.
I dumped the stock HD cooling fan for electric fans, another jump in performance for the stock motor. You're talking 10% of the existing power goes to the stock HD cooling fan.
$5000 is a good start. However I think you'll find it will be twice or better than that number before you're all said and done. Spread out over several years it doesn't hurt as much.
Thread Starter
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Joined: Jan 2011
Posts: 52
Likes: 7
From: Des Moines WA
From what I have read and been told by C3 owners who have 3.03 gears and a 700R4 swap it works great.
lm reluctant to do a cam up replacement due to not knowing what condition the short block is in my guess its tired but it could be great just don't know. When I look at overall cost a crate engine makes sense. On the other hand before I decide no real loss to pull the heads have it looked at. I would need cam heads intake and more to do a top end correctly. Parts about $2500 for that. Crate engine starts about 3k.
Great point having the distributor and carb done by an expert very well worth while we have a local shop that can do it. They would do the transmission as well.
lm reluctant to do a cam up replacement due to not knowing what condition the short block is in my guess its tired but it could be great just don't know. When I look at overall cost a crate engine makes sense. On the other hand before I decide no real loss to pull the heads have it looked at. I would need cam heads intake and more to do a top end correctly. Parts about $2500 for that. Crate engine starts about 3k.
Great point having the distributor and carb done by an expert very well worth while we have a local shop that can do it. They would do the transmission as well.
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
not a fan of tall gears and 700r everyones different
if you are going crate motor and keep that tall gear do yourself a huge favor and buy a stroker motor dont go too crazy on the cam...get that Q jet redon, curve the dist youl lhave the best of both worlds.
havent had a Qjet in many yrs (love my holleys) but will say theres nothing like a well set up one response is every bit as good as EFI and super reliable. DD cars with them for many yrs never once popped the hood except to change oil.
if you are going crate motor and keep that tall gear do yourself a huge favor and buy a stroker motor dont go too crazy on the cam...get that Q jet redon, curve the dist youl lhave the best of both worlds.
havent had a Qjet in many yrs (love my holleys) but will say theres nothing like a well set up one response is every bit as good as EFI and super reliable. DD cars with them for many yrs never once popped the hood except to change oil.
Instructor
Joined: Oct 2002
Posts: 223
Likes: 20
From: jim thorpe pa
your going to need a stronger engine
77 i bought had same "low power" prob, LS trucks beat me
406 solved that, headers, dual exhaust, 700r4 with 2500 stall, 308 rear
I did get the 700r4 for a steal,otherwise it would be 5 speed manual
406 solved that, headers, dual exhaust, 700r4 with 2500 stall, 308 rear
I did get the 700r4 for a steal,otherwise it would be 5 speed manual
Last edited by george2066; Jun 29, 2017 at 09:37 PM. Reason: missed last sentence
Race Director
Joined: Mar 2016
Posts: 14,406
Likes: 8,212
From: Napa Valley California
You will get a hundred different opinions on which gear and trans combination is the best. What it comes down to is that they all work and it just depends on how and where you plan to drive your car. 3.08's with a 700r4 and a stock small block or mild LS motor ???? A 406 or 427 sbc in front of the 700r4 and the 3.08's would make a nice around town and freeway cruising car.
Thread Starter
Advanced
Joined: Jan 2011
Posts: 52
Likes: 7
From: Des Moines WA
You will get a hundred different opinions on which gear and trans combination is the best. What it comes down to is that they all work and it just depends on how and where you plan to drive your car. 3.08's with a 700r4 and a stock small block or mild LS motor ???? A 406 or 427 sbc in front of the 700r4 and the 3.08's would make a nice around town and freeway cruising car.
From what I read a 700R4 and my L48 + 3.08 is a fairly good match as is.
I'll be going down the rabbit hole soon and will share my experiences. Thanks all
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