How much power do engine mods yield?

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Lahti35

Lahti35

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I pulled this posting from the forum and was wondering how much extra power you're going to get with mods like this...


See if he will recurve the distributor for you too. That is a low cost high gain improvement.
I would do this in this order:
Cam and head work (dutra cam/shaved head)
Distributor recurve

2 bbl Supersix with the next $200-$300 you can invest.
Better throttle response and better pull up through the rpm's

Dual exhaust with the next $500-$600
Better mid to high rpm power

Is it a noticeable difference or just a slight bump up. My car is going to be a '65 Valiant 2 door and I'm wondering how much of a difference these mods would make along with adding a manual trans and better rear end gears...

I don't want to swap the engine, I really dig the slant 6!
 
Done correctly, that group of mods, along with the rear end gears could make a night & day difference. Still wont set the world on fire, but it will definately be a lot more fun to drive.
 
Even with the puny single exhaust you can really feel the carb upgrade. Getting that timing right with the curve job will hit you in the buns too.
 
First, try the free things like advancing the spark as much as you can without pinging up hills, and adjusting the carburetor idle mixture screw. Also, insure the choke pull-off works or you will stumble around when engine is cold.

If you ever take the exhaust off, weld an O2 bung in and plug it until you get an O2 monitor. Pulling spark plugs to judge O/F is tedious and inexact.
 
I paid $250 shipped for a 3 inch dual (maybe it was 2.5, I cant remember) for my V8

I don't see how a dual exhaust in a smaller diameter would be twice as expensive
 
Does dual exhaust really make enough of a difference to offset the time and money it takes to do it? I've heard it does and I've heard it doesn't.
 
diymirage said:
got a point there


then again, the ones krazykuda posted look rather "affordable"
Click to expand...


Those are custom made by our member Waggin. :cheers:

He's made three sets that I know of. :glasses7:

Look him up and pm him if you want him to fab a set up for you... :D
 
GEARZZZZZ
Bestest bang for the buck!
3.55s over 2.76s is a 28% improvement in torque.
To get that in the engine will cost many times more than gears.
It does make the hiway ride a little buzzy tho.
City driving will be a blast!

Stock /6 cams are lo-perf. Very lo-perf. But if you upgrade them, without in increase in compression, the Dcr goes away, making take-off with the same gears, even more sluggish.So then the gears are mandatory.
Might as well start with gearz and a sharp tune-up. Maybe that will be all you want. If its a city-only car, you could consider even more gear. But if you are sticking to low diameter tires, dont go too far, as first gear rapidly becomes useless. I don't know whats available for 7.25ers. I think 3.55s will put your small-tired Valiant at a tic over 3000rpm at 60mph,depending on TC slip.
I would forget the M/T swap, as you will lose the off-the-line snap, that a T/C offers. A slightly looser T/C might be nice, but do the gears first and see if thats enough of an improvement for you.A looser T/C will mostly be felt just in the first car-length,or so.

Do not be misled into chasing horsepower. Horsepower requires rpm. Rpm has all kinds of requirements.Mostly expensive, and all destroy low-rpm torque, requiring even more bandaids on a DD or cruiser. Torque is what you are after for that slanty. And thats exactly what the factory built. You just need to bias the output to the chassis to satisfy your personal performance need. Gears will do that. Effectively,Quickly and Cheapy. Good luck what ever you decide.
 
ArizonaKid said:
Does dual exhaust really make enough of a difference to offset the time and money it takes to do it? I've heard it does and I've heard it doesn't.
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Yes, it helps.

I have 2" all the way from the exhaust manifolds to the tail through 2" dynomax super turbo mufflers.

When I replaced the old mufflers with new and got new rear pipes, it even helped improve some...
 
When I was a youngster "my mods" got better and better and more effective depending on how much beer was being consumed LMAO

You think the www is sometimes wrong? Back then we had mags like Car Craft and Hot Rod, and everybody knows "they would never lie" yeh. righeeett
 
krazykuda said:
Those are custom made by our member Waggin. :cheers:

He's made three sets that I know of. :glasses7:

Look him up and pm him if you want him to fab a set up for you... :D
Click to expand...

shoot, and I just dropped 500 on a set of dougs headers :banghead:

AJ/FormS said:
GEARZZZZZ
Bestest bang for the buck!
3.55s over 2.76s is a 28% improvement in torque.
To get that in the engine will cost many times more than gears.
It does make the hiway ride a little buzzy tho.
City driving will be a blast!


Do not be misled into chasing horsepower. Horsepower requires rpm. Rpm has all kinds of requirements.Mostly expensive, and all destroy low-rpm torque, requiring even more bandaids on a DD or cruiser. Torque is what you are after for that slanty. And thats exactly what the factory built. You just need to bias the output to the chassis to satisfy your personal performance need. Gears will do that. Effectively,Quickly and Cheapy. Good luck what ever you decide.
Click to expand...



according to Carol Shelby; "horsepower sell cars, but torque wins races"


and in case you don't know the difference, here is a good definition

"horsepower determines with what speed you will hit the brick wall,
torque determines how far the brick wall moves after you hit it"
 
Thanks for all the info guys! Torque is indeed what I am after...

The car will be used mostly as a commuter on 55mph roads with city driving making up 50% of the trip. Previously I used a 1961 Falcon as my commuter but that 144 inline was a dog... really got tired of people thinking I was an old fart poking along and cutting me off!

Interesting comment on keeping the auto tranny... would not have guessed that.
 
Brandon Weaver said:
Hey, how does the super turbos sound on a slant? I've wondered about them and the ultraflows.
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They sound pretty good. Not too loud, but not too soft. They rumble when you rev it up.

I'm not a fan of the flowmaster sound. I prefer quiet at idle and a little loud when you rev it up...
 
Turbo mufflers sound nice, but turbo-chargers sound better... much better piece to put in the exhaust line IMO...
[ame="https://www.youtube.com/watch?v=QTutTfYHVI8"]Turbo 225 Sound Bite Engine bay and Exhaust - YouTube[/ame]

[ame="https://www.youtube.com/watch?v=HElZ4DB49k0"]Turbo Slant Six Dyno Pull HybridWorks - YouTube[/ame]
 
Ben Drinkin said:
Done correctly, that group of mods, along with the rear end gears could make a night & day difference. Still wont set the world on fire, but it will definately be a lot more fun to drive.
Click to expand...

Thats about it in a nutshell.

No need for dual exhaust on a slant. Just run a single 2.25-2.50 exhaust through a free flowing muffler.
 
250 HP "or so" is about all you will get out of a N/A slant without serious head work.

That said, that IS a night and day difference from a stock one. It will certainly be a peppy little beast.

But, if your basis of comparison is a V8, then you will always be down 2 cylinders.
 
Serj22 said:
Turbo mufflers sound nice, but turbo-chargers sound better... much better piece to put in the exhaust line IMO...
Click to expand...

Guess that's your perogative, sounds like a diesel and a leafblower had a baby to me. Plus it don't have a cool lumpy idle. If I wanted something that whined all the time I'd get a wife, but to each their own I s'pose! :D
 
Johnny Dart said:
... No need for dual exhaust on a slant. Just run a single 2.25-2.50 exhaust through a free flowing muffler.
Click to expand...
A supporting "data point". I read that for the early 273 V-8, the engineers test both dual and single exhausts and found the single exhaust gave more horsepower, so that was used even in the High Performance "Commando" option. Early-A small block owners go to extremes to convert to dual exhaust (cut-out in tranny x-member) apparently for no gain.

Another. In the 1970's, I had a Honda 4 cyl motorcycle w/ 4 separate exhausts. The magazines were filled with ads for 4-into-1 exhausts, claiming "30% more power". Honda finally put 4 into 1 exhausts on their production bikes and there were then ads (from same companies) for single exhausts, claiming "30% more power". One way to honestly make such claims is to first run an engine cold on a dyno, quickly make the part swap and then run it again warmed up. Do you think Split-Fire did that?
 
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