The Dodge Challenger Message Board

I've read a few of the threds and comments made in regard to the 318 that came as standard equipement on most challengers and appreciate the suggestions about going down the 340, 360 or even big block road. For those of us who are happy with the 318 set-up for the time being, I wonder if anyone (more mechanically inclined than me) can make a few suggestions in regard to getting more ooomph from it.
I borrowed a Holley performance catalogue from a mechanic friend of mine yesterday with the objective of installing a four barrel carb/inlet manifold to suit. Mine is an original 2 barrel carb set-up with all factory equipment. The motor has had the heads "done-up" (whatever that means) according to the previous owner, at the same time as having the timing chain replaced with a double-row one and a mild "waggot-grind police cam" installed (Waggot was a highly regarded engineer here in Oz). The tone of the exhaust sounds good through the aftermarket twin system (slight burble and mildly lumpy) and the motor seems relatively tight and responsive, although I feel that performance could be enhanced by improving the fuel delivery system.
In the catalogue, the suggested improvements include the installation of a 600 CFM vac secondary carb with electric choke (clear air carb item # 80454) and a single plane manifold to suit 'stock heads' (part # 300-7). Both of these are Holley part numbers.
Someone also mentioned to me that the vac secondary carbs can, under hard driving conditions, "wash" the oil from the bore and cause excessive ring wear, so suggested to install the non vac secondary type 4 barrel carb. What do the experts have to say or suggest?

It is the non-vac type that tends to wash the bores because these "double pumpers" have accelerator pumps on the secondaries which squirt fuel in every time you move the throttle.

I don't like Holleys much. I do like the Carter/Edelbrock carbs. Whichever you prefere a 4bbl will have much better top end power with a good cam than your 2bbl. However throttle response will suffer unless you pick a carb with a primary pair about the same size or smaller than your existing 2bbl. The vacuum secondaries will help with throttle response too although there may be a slight delay in the secondaries when you floor it.

I would use something like an Carter/Edelbrock carb with adjustable secondary opening rates and the Edelbrock air gap intake.

Thanks for the advice Dave. I believe the factory carb I have is a 'Holley economaster' or something like that and is about 350-380 CFM. I'll take on board your advice about the primaries.
Carters were also standard equipment right? What of the kick-down linkages if I change my set-up? Are they easy to get an adapter for, or can you buy them already to bolt on?
Do you have a link to a Carter/Edelbrock site that I can look at to do some research? Thanks mate...

Here's something I did to my first challenger conv living with a 318. If your 318 has factory fly-cut piston tops, such as 68-69 blocks do. I would bolt on a factory set of 273 closed chambered heads, cast 318 spread bore intake, and a carter thermoquad (exhaust manifolds were stock) and oh boy when you dump those 2 1/4 secondaries open I'd have one howling experience. Those drof and chivie boys would hang their heads in disbelief.

Tony - about the only thing I understood was "one howling experience......boys would hang their heads in disbelief" - I enjoyed that bit, but the rest went straight over the top of me.
I assume mine to be all original - 318 built in either 70 or 71, stock inlet manifold and carb. The only changes to the motor are as previously mentioned.
One howling experience is what I want, but accept that it's only a 318 and can only get out of it what I can. Having said this, I have great faith in this motor, as I've owned several before and found them to be reliable and trustworthy. Since many Aussie Mopars came with them too, I can source parts here readily, thus my intention to keep it for a while, but make it more "streetable".

Roger, I'll try to elaborate... fly cut, if i'm using the right terminoligy, is two half moon reliefs in the top of each piston allowing for valve clearance. 273 closed chambered heads are off of a 67 273 hp block, being closed chambered, dramatically increases compression to not sure what. And the intake came off a mid to late 70's police car with a 318 4 bbl. Spread bore is two small holes to the front and two gargantious holes to the rear of the intake. The carb was off a.....I think a 69 or 70 big block, possibly a carter 850 thermoquad. Remember back in the early 80's this stuff was all over in yards and cheep. Have fun making your challenger howl!

I was running a Holly Street Dominator for small block Chryslers, with a Holley 600cfm vac secondaries 4bbl carb with Blackjack headers and dual exhaust, running the timing in the 7 degrees in advance sweet spot. It gave the Mustang 5.0 more than they could handle.

That was a Holley Street Dominator INTAKE manifold, by the way.

Did I forget to mention that 318 had a spun main bearing? We didn't know it at the time, becuase it gave no indications of there ever being a problem, funny huh. You would think that an engine would be doing funny things with a spun main bearing, but it ran as strong as ever. You were right on the money, Roger, when you said the 318's were reliable engines, worthy of putting your trust in.

I thought I posted a reply, but it hasn't appreared so here goes again.
According to this Holley catalogue, an ordinary low perfomance motor has a "volumetric efficiency of only 80%", a high performance 85% and "all-out race" motor 95%. In the example shown on thier scale, a 300cid engine with a max rpm of 8000, volumetric efficiency of 85% would require a 595 CFM so they suggest a 600. It's obviously all relative to the breathing efficiency of the motor, (heads, compression, exhaust manifolds/headers etc). Given that my motor is probably an "ordinaly low-performance" one, and I have no idea what the max rpm would be, I assume that anything greater than 600 CFM would be a waste? I'm not a mechanic's "ar*e" and don't pretend to be anything other than this, so all advice is readily accepted and much appreciated. If this was your car and you wanted to achieve more from the small block that seems to run pretty well, what would you personally do, with modest financial resources?

Generally you only need to worry about the linkage when you go to a much different intake manifold.

The bigger the carb the less restrictive it is at max rpm - up to a point and then making it bigger is a waste of time.

The smaller the carb the higher the speed of the air/fuel going into the engine. This is better for throttle response and the air/fuel mixture is much better with the fuel dropping out of suspension less.

So you see it is better to have a carb that is not too big or too small. A 600cfm 4bbl is plenty for a 318.

When comparing 2bbl carbs with 4bbl carbs remember that they are NOT rated the same way. I have a conversion tool on my Maths Spreadsheet available from my web site.

I have some old MP and Hot Rod Magazine articles on hopping up the 318 Roger. I will scan them and send them to you.

Hey Roger, would you mind if you forward them on to me at iolite01@msn.com? I would ask Dave, but he seems to be a busy guy and I don't want to have to bother him with trifling requests.

It will be easy enough to cc them to you too Joel. No problem.

Dave you're a champion and I look forward to getting this info. I'm not into making a drag racing power house, but a more streetable car and one that I can have more confidence in with acceleration against the local "Holden" (GM) and For* brigade, as any Chrysler product in Aus, is generally jeered at (my car is often called a "Valiant"). The good ol' Aussie Valiant was a favourite car with migrant Italians in Aus and was often referred to as a "Wog car" which is a very insulting term for a migrant of Mediterranean background. There's a popular aussie movie called Wog Boy and the main character drives a V8 powered Valiant of 1970 vintage. Given my surname, I'm an easy target for the ignorant 'ocker aussie', so would like to show him/her a thing or two when put to task.
Incidentally, Chrysler were the first manufaturer to market the V8 in Australia when they introduced the first Valiant with the popular 273 in the early 1960's. GMH and FixOrRepairDaily took another 3 years or so, before they offered anything close to the power available in the Valiant.

Joel, nothing seems to be too much for Dave if your request is compassionate and objective. I'm more than happy to forward any info on to you when I get it.

To be honest I don't think the 318 is worth spending much money on. A pair of 340 or 360 heads with bigger valves would be a good swap. A Huges Engines cam with just a bit more than the stock duration I would fit. I already suggested a 600cfm 4bbl and the air gap manifold. A set of headers and a good free-lowing exhaust will be all you need finish the job. Expect around or just over 300hp.

As I'm a man of limited resources at the moment, I'm quite happy to live with the 318/904 combo. I'm not sure what I have in the way of heads, as they have already been "addressed" at some earlier stage, so I'll leave them for the time being until an opportunity arrises that I cannot refuse. The cam installed is quite good from my research, so that will stay too. The inlet manifold and carb I'll follow-up on and probably get what you've suggested Dave. Headers and exhaust system are also on the list, as well as a mini-starter to accommodate ease of fitting the system too.
Once I manage to source the suppliers (here hopefully), I'll engage myself in the project, as I WANT MORE GRUNT.
Thanks once again to all who have helped.
I can't begin to tell you all just how much I appreciate the wonderful resource this group is to me and the hours of enjoyment I get from reading the posts and hopefully I'm contributing in some small measure too (he bows with cap in hand) - Thanks again

Roger, I have headers on my 440, they were cheap, good side is they have great flanges, bad side is, they are quite thin. But as Dave says "you get what you pay for" Mine cost £98 the pair from USAutomotive. I am happy with them, but would probably TTI next time, as I am now doing it right! Mini Starter from Mr Hauser, if he has any left, one of the better buys for me! And I seen that Dave looking at it! Unless he has one now?

As Roger lives 'down under' Jeff he will not know of US Automotive or Hausers.

The next time I have to put these or any future headers on the Challenger I will be getting a mini starter for sure. The TTI headers are dreamy and are on my wish list for the future. After making my own 3-inch exhaust system I never want to do that again so a TTI full system is also on the dream list.

UH OH. Sorry Roger, I think Joe is hoping to hop up his 273ci a little this summer. Probably intake, carb and headers. I think a local guy is going to donate a 318ci free as well! I know it's not the ideal, but hey at 18 I think its cool. He has put 4500 miles on it in 3 months now! Puts me to shame.

I can't wait to see Joe's Barracuda Jeff. Obviously he does not follow in his fathers shoes as his car seems to work!

Well Dave, funny you should say that. He started a new job today. A van drove into the Barracuda while it was parked in his car park!

Dave - thanks for the info. Made interesting reading. The 'new' 318 heart-shaped combustion chamber heads seemed to make the biggest difference in output performance according to the article. When I rip into my engine, I'll have a look at my heads to see what gives. In the mean time, I'll address the inlet and carb and possibly diff ratio too, once I determine what's in there (still haven't figured it out).
Cheers...

Oh NO! Jeff! Tell me the car is going to be OK?

ar is OK Dave. Needs front bumper, headlight surround and maybe a new fender, depends if the body man can loose nasty crease or not. some work needed to the front top panel too. He said the van was a mess.

What kind of delivery can was it, *ord, Chuvy, or was it one of those import Mitsubishi, UD, or Isuzu things?

I don't know about the rest of you, but getting my hands on any kind of parts from a 318 police engine is kinda of a challenge to say the least. I think I would have a better chance finding a 413 or 426 Maxwedge than a police 318 from 1986.