The Dodge Challenger Message Board

I've got a 318 with 904 LA and a 7 1/4 inch axle with a 2,74 reduction. Now I want to increase the engine power, by changing the cam and putting on a four barrel inlet and a 650 cfm carburator. The compression ratio is going up to 9,3. Has anybody got an idea about how much the power will increase. Will my transmission and axle survive these modifications? Are there ways to make the transmission and axle stronger or should I get a 727 and a 8 3/4 icnh axle?

Stock heads? Mild cam? Headers? I would say about 250hp at best. You are not going to start breaking things at this level. So drive and enjoy!

thanks a lot dave. Indeed a mild cam the original heads and not even headers.
Are you sure about the 250 hp. Originally a 318 has 230 hp. It would mean the power increases with 20 hp. Going from a 2 barrel to a 4 barrel I thought that would be a lot more, say around 280 or 290?

It depends on the cam you use but you are limited with the stock heads. Things like carb swaps never make much power. The heads, valves and capacity of the engine determin the power level.

Even with very good heads (bigger valves, ported runners etc), headers, and a street/strip cam I doubt a 318 could make more than 340hp.

I can sort you out some recommendations for parts for 318s if you want.

I've always thought the 318 was way overated anyway. 230hp was always very optimistic. I believe a figure closer to 150hp was always more realistic.

In those days it was not unusual for the car companies to overate some of their more mundane motors,- Chrysler would sell less 318 cars if they were honest about the hp figures.

Frod, GM and Chrysler, they all did it. Some engines were overated to help sell the grocery getter engines, while performance engines were often more realistically rated due to balancing the desire to claim high hp to appeal to the musclecar buyer, and claim lower hp to appease the insurance companies (and also factor the car to better advantage for NHRA class racing).

For any sort of performance purposes I have always rated the 318 as a waste of time. As Dave says, you are always limited by the cylinder heads, low compression, mild cam, 2 barrel carb, and not enough cubes.

By the time you've spent money to make dramatic improvements to a 318 you could have bought a 360. 360's are cheap, available, better heads, and more cubic inches. A much better starting point all round!

I found this in the sep 2000 Mopar Muscle for you Antonio:
A 318 in a Dart was seriously modified. These are the specs:
comp cam 268/280
High flow Edelbrock heads (2.02" in/1.60" out, these beautys costed $1200 back then!)
Port Job
Edelbrock Performer RPM dual plane
Carter 750 cfm comp series
headers of unknown origin

The compression was kept low, at only 8.88:1.
This configuration brought 273 horses, 340 at the crank. Varicom Performance Analyzer predicted 14.36 ET @ 104 mph. Rear axle was a 2.71:1

Unless you are realy exited with the challenge of bringing a 318 to the max (which is a respectable sport in itself I think), I agree with the previous writers that it is more economical to start with a 360, or a 340 if you can find one).
Results of a bigger inlet and carb only would be restricted by the heads indeed.
Good luck!

340hp was a pretty good guess from me then! I even amaze myself sometimes!

My mate Kev ran mid 14s last year in his Valiant with a stock 318. He used VERY low rear gears though. About 4.5:1 or thereabouts. That is still a bloody fast car by any 'normal' standards. I only did a 14.8 when my 440 was stock!

On the other hand Andy Neal's Barracuda has a small block that makes about 600hp before the Nitrous! however this is a serious bit of kit.

http://www.moparts.com/moparts/picture/oldweb/Andy.html

thanks a lot guys.
That's the kind of information I'm looking for. I think I'll put on the four barrel and the carburator, instead of searching for another engine. I allready did some checking, and a edelbrock four barrel inlet + a four barrel carb. costs about 700 euro. I allready put a lot of work in the engine, and it's the original one so I'll just stick with my good old 318.