Reasonable HP Gains
Thread Starter
Intermediate
Joined: Jul 2007
Posts: 40
Likes: 0
From: Springfield MO
Reasonable HP Gains
Wanting to add some decent HP to a 77 L48 without getting into the big $s. Will be strictly a street driver and want to keep reliability as much as possible. What would the most likely and easiest way to accomplish this? Your help is much appreciated. Have to step out for a couple hours for work and will check back. Thanks again.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Welcome to the forum. Very nice looking '77 you have.
You're engine is not the best platform to start with considering the low compression, mild cam, and poorly flowing heads.
To get some good cheap HP you'll need to address those issues and what comes to mind first is heads and cam combo. To do this cheap, used heads. A good upgrade for little money is a set of Vortec heads and a Vortec carb manifold. Add to that a hotter cam and you'll have better compression too with the heads.
I have not done this but a simple search for Vortec swap will get you plenty of info.
Maybe look into some headers, and 2.5" dual cat-less exhaust.
I'm up in Columbia, if you're ever in the area let me know and we'll go get a brew.
You're engine is not the best platform to start with considering the low compression, mild cam, and poorly flowing heads.
To get some good cheap HP you'll need to address those issues and what comes to mind first is heads and cam combo. To do this cheap, used heads. A good upgrade for little money is a set of Vortec heads and a Vortec carb manifold. Add to that a hotter cam and you'll have better compression too with the heads.
I have not done this but a simple search for Vortec swap will get you plenty of info.
Maybe look into some headers, and 2.5" dual cat-less exhaust.
I'm up in Columbia, if you're ever in the area let me know and we'll go get a brew.
Drifting
Joined: Apr 2002
Posts: 1,716
Likes: 4
From: New Baden Illinois
Define "big $s". You can get away with doing a cam, aluminum intake and dual exhaust. However, if you have the extra $ for better heads, that will make the best improvement. Believe me, if you want some help spending some money (and getting the best bang for the buck), the forum can help.
Melting Slicks
Joined: Dec 1999
Posts: 2,116
Likes: 156
From: Mid West
Cruise-In III Veteran
I addition, if you have the original cat. convertor in the exhaust it needs to be changed. They are the old "bean" style convertor that is a huge source of backpressure. If you can go with 2 new style high flow cat's and dual exhaust thats even better.Another option to going the Vortec route (which is very good for mild HP gains), you could try finding some L98 aluminum corvette heads ... they are pretty cheap and you can retain your stock manifold and carb if you desire. I would do heads before a big cam, it makes for a more street friendly engine.
Drifting
Joined: Feb 2005
Posts: 1,738
Likes: 2
From: San diego ca
Yeah you could do allright with a cam, exhaust, intake more or less in that order...heads will cap that off nicely. But you can get modest results without a head swap if need be.
I would start with a set of 4-1 headers (Dynomax, summit or Hedman) a high flow catalytic convertor and good high flow mufflers - replace your pipes with those for an L-82 (that ups you from 2 1/4" to 2 1/2" pipes)
then I would replace your cam with a comp cams high energy grind. 268H (p/n 12-210-2) this is a CARB approved cam that makes decent power for a mild motor...better than L-82 power..
After that an intake - Edelbrock performer and a well tuned carb...preferably a q-jet or holley
all of that is fairly inexpensive, can be run with your factory heads, and will wake your motor up considerably from L-48 stats.
I would start with a set of 4-1 headers (Dynomax, summit or Hedman) a high flow catalytic convertor and good high flow mufflers - replace your pipes with those for an L-82 (that ups you from 2 1/4" to 2 1/2" pipes)
then I would replace your cam with a comp cams high energy grind. 268H (p/n 12-210-2) this is a CARB approved cam that makes decent power for a mild motor...better than L-82 power..
After that an intake - Edelbrock performer and a well tuned carb...preferably a q-jet or holley
all of that is fairly inexpensive, can be run with your factory heads, and will wake your motor up considerably from L-48 stats.
Thread Starter
Intermediate
Joined: Jul 2007
Posts: 40
Likes: 0
From: Springfield MO
Really appreciate the input. Most of what has been mentioned is what I had in mind for this engine. Within budget and really enjoy shade tree to a point. I will have a fire breathing dragon
at some point ,after I get rid of some other toys, but this one I just want some decent power. This is like a dream come true for me. I REALLY FEEL GOOD TODAY! Ain't it cool!
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Burning Brakes
Joined: Oct 2006
Posts: 1,006
Likes: 28
From: Lutz Florida
If you can switch to true duals (2.5") with no catalytic converters you will see a big improvement. Headers will add some HP too, but if you are on a budget, bolting up true duals to the stock manifolds will still give you a pretty hefty boost. Next do a major tuneup, make sure your timing is set correctly and that your carb is adjusted right. You might need to rebuild your distributor, or overhaul the carb, but just try adjusting everything first (if it needs it). If it ain't broke, don't go trying to fix it. After that you are limited only by how much you want to spend on the engine. 
Safety Car
Joined: Oct 2000
Posts: 3,593
Likes: 103
From: Southern Indiana
Exhaust is always good, but my favorite of late is a perfect tuned igntion.
Move the mark on the harmonic balencer up to 12 on the timing tab( if you have a dial back timing gun then it should be around 22/23 on the zero) and make your advance 36@2500/3000.
Really the first step to better running, is a dial back timing gun!!!!!!
Move the mark on the harmonic balencer up to 12 on the timing tab( if you have a dial back timing gun then it should be around 22/23 on the zero) and make your advance 36@2500/3000.
Really the first step to better running, is a dial back timing gun!!!!!!
Drifting
Joined: May 2006
Posts: 1,480
Likes: 2
From: Circleville Ohio
Had A white 77
welcome to the forum. Raced my 77 at Mid Ohio First year wrong tires and had a wipped lobe on my cam (did not know). the 77 year is supposed to be a bad year for wiping A lobe on the cam soft or something . Second year at Mid Ohio 3 seconds faster and quickest time for my class and they all had newer cars. so cam it dual it and Have fun.
Melting Slicks
Joined: Jul 2004
Posts: 2,577
Likes: 2
From: Long Island New York
Get your distributor, carburetor and timing set up according to Lars papers and throw on a set of headers and true duals with no cats. This will give a very noticeable seat of pants difference in performance right off the bat at a very modest cost. If your budget allows, the changes that the others have mentioned will certainly make a significant difference in performance no doubt. Changing the exhaust system over alone will wake up some sleeping ponies.
Burning Brakes
Joined: Jul 2006
Posts: 830
Likes: 1
1. Headers to true dual exhaust
2. Hi-rise Alum intake
3. New carb (edelbrock 600 or Holley) all you old Q-jet guys back off
4. Mild/street cam
More cash??? Like DB said, Vortec Heads
Oh yeah, after these things, find a good dyno tuner to tune the car on the dyno. HUGE improvements. At least it was in my case.
MOST IMPORTANTLY: Take your time! These things all took over 12 months to be completed and I am happy it took that long. Because your idea's and opinions/intentions will change over the next 12 months.
Believe me on that. Ask anyone who has recently bought their first C3 Vette, they may say the same thing.
Welcome to the site
2. Hi-rise Alum intake
3. New carb (edelbrock 600 or Holley) all you old Q-jet guys back off
4. Mild/street cam
More cash??? Like DB said, Vortec Heads
Oh yeah, after these things, find a good dyno tuner to tune the car on the dyno. HUGE improvements. At least it was in my case.
MOST IMPORTANTLY: Take your time! These things all took over 12 months to be completed and I am happy it took that long. Because your idea's and opinions/intentions will change over the next 12 months.
Believe me on that. Ask anyone who has recently bought their first C3 Vette, they may say the same thing.
Welcome to the site
Pro
Joined: Sep 2004
Posts: 595
Likes: 0
From: Boston MA
adjust the timing curve and qjet.
cost: 0 to $20.
time: 0 to 2 hours.
That is the cheapest HP you will get.
Set a baseline before you start and keep track of all the changes and affect is has on the car.
Thanks,
Joe
cost: 0 to $20.
time: 0 to 2 hours.
That is the cheapest HP you will get.
Set a baseline before you start and keep track of all the changes and affect is has on the car.
Thanks,
Joe
Drifting
Joined: Jun 2007
Posts: 1,404
Likes: 1
From: Ansonia/NYC CT
Exhaust. I know everyone has said it before, but I ma stressing it again. My dad used to let me drive the 76' in SC on sunbdays, during open track day, on the race tracks there. I have driven it with the factory Y pipes, and with a new strait pipe. I would say, based just on the butt dyno, that true duals, without cats, is worht at least a 30-40 hp gain. I have since bought a new carb for it, as well as new headers, and an aluminum intake. These few things make it feel a bit more spry than an LS1 camaro, which I have driven quite a few times as well.
I have yet to get it to a dyno, as it is still not registered (guilty me....), but the butt dyno registers about 280 hp, 330 lbs of torque, or so. Just a guess, though.
I have yet to get it to a dyno, as it is still not registered (guilty me....), but the butt dyno registers about 280 hp, 330 lbs of torque, or so. Just a guess, though.
Drifting
Joined: Jun 2007
Posts: 1,404
Likes: 1
From: Ansonia/NYC CT
Yeah, but then you go from regular to premium fuel. that adds up fast.