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I have a 72 LS-5 4 speed car numbers matching. It has headers but is otherwise stock. Engine rebuild to stock configuration has 800 miles on it. Just bought it 2 months ago. Almost finished with brakes, rotors, rear suspension replacement, shocks and exhaust. Going to drive it this summer. I had a 1970 LS-5 4 speed car that I ordered from Vietnam that only got 13500 miles on it then, the new wife convinced me it had to go. She just convinced me we needed to replace it. This is as close *** I could find to it. What do you recommend for simple horsepower upgrades? I don't want to get into the block or heads. and would like to at least get to the 400hp mark and still burn 93 octane with some 100LL adder. Or run 90 non ethanol with the 100LL adder. Better if I don't need the adder but....
I am thinking of some cam change, electronic ignition and the Holley sniper. I will save all the original parts in case of a sell in the future after I am gone? Open to suggestions and thanks for the help in advance.
Welcome to the forum. 400hp should not be too hard for that engine. I had one in my 71. if you already have good header then a decent 2.5- 3.0 inch exhaust and low restriction mufflers will help. the biggest issue is hood clearance if you want to put a better intake on it. the only intake that will work that I know of is the Edelbrock torker II but for 400hp you probably do not even need it. get a good cam with intake duration at .050" lift in the 220's and you should be good if you can afford a roller set up that would be even better. electronic ignition and fuel injection are nice but totally unnecessary. if it was me I would put the money for them into other addons like a roller cam or intake or heads. this is all assuming your bottom end has good compression. otherS with more experience than me will be chiming in with more suggestions for you.
Pat
'72 has low compression and hardened valve seats. No need for any lead additive. E10 pump gas can be a problem if you let the car sit for long periods but as long as you drive it occasionally it is fine.
A cam change will make the biggest difference for the $$$. Since you said you didn't want to go into heads/shortblock...the heads you have flow plenty even though you have low compression.
But of course a nice set of aluminum heads with smaller chambers would help.
CK into Straub Technologies (ask for Chris). He's put together some proven cams for low compression engines like this.
If you can squeeze an intake in there it will really help too.
if you did not purchase the mufflers yet I would recommend checking out other brands. Flowmaster makes several models and I am not familiar with them but there are dyno comparisons where they lose to other mufflers like dynomax ultraflo's which are a straight thru design. I run the Ultraflo's and they sound great and on 2 different dyno tests on a 496 they beat out the Flowmaster by 50hp. Maybe it won't make any difference for what you want to do but I would do a little research on mufflers before you buy, they are not all the same. Pypes race pro's are another straight thru design worth considering.
I run the Pypes Race Pro's on my C2. 1240 RWHP and it doesn't pick up any power when I uncap it. Now I have 3.5" exhaust...but you get the idea. They are good sounding and only get really loud when you stuff your foot in it.
Way back when in it's first 540" iteration, it was N/A and I chassis dyno'd it with a set of 2 chamber Flowmasters on 3" pipes. It literally picked up 50 RWHP when it was making "only" 615 RWHP uncapped.
BUT....I'll say Flowmasters are some of the best sounding ones out there and under 500 HP they do pretty darn well overall. My buddy has a set on his 525HP 388" C2 and it sounds wicked...and runs deep 11's on street tires.
Beautiful car!
The C.R. is the main difference between that and your old 70, it is only 8.5 advertised, and usually around 8.2 actual.
The gross HP is around 360-365 already.
400 is easy because the cam is so mild. It is 214/218* @ .050"
I would not push it past 220 or so with that low CR.
You want to use a modern faster ramp cam to keep up the low rpm TQ with that low CR.
Something around 270 adv / 220 @ .050" should work.
A single pattern grind will also help with the TQ., and no tight LCs, keep it wider, 110-112, for less overlap and more TQ.
So would going to a hydr roller.
That low CR needs all the help it can get.
Talk to a good cam grinder.
Get a good carb and distributor tune, and good exhaust and you are there, plus more.
More CR would add a bunch more. And you'll need more CR if you want more duration.
A Comp 268H hydraulic fits the bill, so does a 270HR Roller.
As does a Howards 120991 hydraulic, you could widen the LC some.
Thanks Pat. Should have asked before ordering but based on your info I should be ok. Was happy with my 390hp 70 in 1970. Don’t need anything more. Bet every time I go start it my wife will come running to the garage to get in. She doesn’t like fast.
Leigh1322. Thanks. I am not much of a technical guy so your info on a specific cam is great help. Might need your advice more over the winter as I do the hp work. Going to drive her as is this year. I just wanted to be sure that there were some simple things I could. I don’t need a beast, just something that will kick you back a bit like my 70 did
I have a 72 LS-5 4 speed car numbers matching. It has headers but is otherwise stock. Engine rebuild to stock configuration has 800 miles on it. Just bought it 2 months ago. Almost finished with brakes, rotors, rear suspension replacement, shocks and exhaust. Going to drive it this summer. I had a 1970 LS-5 4 speed car that I ordered from Vietnam that only got 13500 miles on it then, the new wife convinced me it had to go. She just convinced me we needed to replace it. This is as close *** I could find to it. What do you recommend for simple horsepower upgrades? I don't want to get into the block or heads. and would like to at least get to the 400hp mark and still burn 93 octane with some 100LL adder. Or run 90 non ethanol with the 100LL adder. Better if I don't need the adder but....
I am thinking of some cam change, electronic ignition and the Holley sniper. I will save all the original parts in case of a sell in the future after I am gone? Open to suggestions and thanks for the help in advance.
You didn’t mention if the hp target was at the crank or rear wheels. Regardless, I got to 398hp and 465 ft lbs of torque (dyno) with all stock components besides the roller cam. These numbers were with the cast manifolds but NOT the mufflers. The builder did do a bit of gasket matching, etc. if your interested I can get you the build specs, but compression was around 9.5 to 1.
I’d like bigger numbers but enjoy the drivability of this set up.
KC
You should do the distributor curve now.
It is amazing how much that helps.
Uses LARS's procedure. He has this down to a science.
Email him, and he will send you instructions.
Duntov himself said the stock mufflers choke 50HP out of a BB. The straight thru Dynomax or Magnaflow style seems to work the best. A lot of guys here swear by the Magnaflows.
2025 c3 ('74-'82) of the Year Finalist - Unmodified
1971 engine specs 1972 engine specs
This is a comparison between basically the same engine, rated in gross…1971 and net…1972.
Hope this helps.
Prior to 1972, American carmakers used the SAE (Society of Automotive Engineers) “gross” measurement of horsepower. Gross meant the figure was taken from an engine running on a test stand, with no air cleaner assembly, accessories or exhaust system connected.
By 1971, carmakers began reducing compression in many engines in order to meet upcoming emissions requirements and to use unleaded fuel. General Motors and Chrysler began advertising both gross and SAE net figures in 1971, derived from an engine tested with air cleaner assembly, accessories or exhaust system connected.
72 LS-5 upgrade
