More Power!

Ian Deady · Post by **Ian Deady** » Wed Sep 07, 16 9:17 am

Hi,
My 73 Charger does not yet live up to its name, it should be called a 73 Sluggish. However, I'm not prepared to give up on her just yet. Currently it runs a 400ci with Edelbrock performer intake/Edelbrock 750 cfm (Ported) and makes 260bhp through a 727 Torqueflite and 2.71:1 diff.

I am getting a better ratio Suregrip this winter, and have long-tube headers to fit. I cannot afford a full stroker kit although I'd love to. Has anyone raised the compression with taller pistons and tried a better cam? With the Headers, do you think it'd make 400bhp?

I want to try Santa pod and maybe aim for mid to high 12's.

Any tips, recommendations, links or advice welcome.

Thanks

MilesnMiles · Post by **MilesnMiles** » Wed Sep 07, 16 9:39 am

They wont make power, but better gears will use what you have more effectively. Even 3.23 would be a major improvement.

I think Blue and Pete will be along with recipes, but usually I believe it does involve stroking the motor.

You'll be advised to do it once, as in build it once and do it right first time.
12s in one of those heavy cars will take some power

http://musclecarmastermind.blogspot.co. ... 2s11s.html

http://board.moparts.org/ubbthreads/ubb ... et-it.html

Pete · Post by **Pete** » Wed Sep 07, 16 9:47 am

400 bhp would just about get you into the high 12's if the car and you weigh around 3700lbs - personally I imagine a Gen III Charger is heavier than that.

The problem is that High compression pistons will not be that cheap (I would think at least Â£600) and then you have to re-balance the engine (Â£200 - Â£300) so you are a fair way cost-wise to a stroker kit already with no guarantee of hitting the 12's.

What heads are you running - this also play a very big part in the quest for speed.

We ran 9's on a 400 based motor but that was in a light car with a stroker and some deep breathing heads, a lot of compression, and a big roller cam. It made 697 bhp. Horrible on the street though.

As ever it is the combination of parts that are a success, and I'm afraid more money.

Pete · Post by **Pete** » Wed Sep 07, 16 9:51 am

...the only other option is Nitrous.
However, that will only get you so far on a stock engine - the pistons are the biggest issue, and the heads will still need to breathe well. It might get .75 second off your ET, but its like HP.....

My mate is running a 250 shot and he only gets 2 full runs out of that before he has to get the bottle filled to obtain the correct pressure. A full re-fill is around Â£80 a go....just like HP, you never finish paying for it....

MilesnMiles · Post by **MilesnMiles** » Wed Sep 07, 16 9:59 am

For some comparison.
My recently sold 340 1973 Roadrunner (so very similar to your Charger)
had a properly built 340 with high comp forged pistons, a cam and some of the best non race heads you could buy plus all the good induction and exhaust parts (TTI etc).

With a open diff and 3.23 gears I could only muster mid to lower 14s un an unprepped track.

The wheel spin was comical even with drag radials and lasted for 60 foot losing much time.
The new owner, Craig is dropping in a set of 3.73s with a suregrip. I would suggest the car will now run in the upper to mid 13s if he chooses to race it.
To understand the costs involved I spent Â£2400 just on the heads, intake, carb and a further Â£1500 on a very well built trans and convertor.

As Pete suggests, it aint cheap and my old car even in the mid 13s is a long way from 12s.

Ian Deady · Post by **Ian Deady** » Wed Sep 07, 16 10:05 am

Thanks, the replies have been very helpful, especially the links.

I should have mentioned my budget will be around Â£2k. I'll be pulling the motor myself with help from a Mopar mechanic. Price is to include parts and machining. I was guesstimating Â£500 for Pistons, Â£300 for cam with the rest on gaskets, bolts, machine work and paying my mechanic.

I understand that stroking would cost in the Â£3.5-4.5k and I can't justify that kind of outlay.

Perhaps high 12's are over ambitious, but I thought 400-450bhp would get me in that arena.

The question is, can I get that power with just cam, pistons, headers at around Â£2k?

MilesnMiles · Post by **MilesnMiles** » Wed Sep 07, 16 10:33 am

I guess if your stated HP of 260 is accurate you are asking for 140hp from just cam, pistons and headers. Maybe a tall order. Good heads make, or free up power.

For example, my Fox Mustang heads are such poor design, changing cam, inlet, throttle body etc is largely wasted as the heads still cant breathe.

Meantime, this looks interesting

http://www.hotrod.com/articles/mopp-000 ... ottom-end/

Bear in mind I'm just a small block guy, Ian. I'm sure the BB boys will be on this thread some more.

Ian Deady · Post by **Ian Deady** » Wed Sep 07, 16 10:47 am

That is a great article and written by Steve Dulcich. I need to find the final part now. Thanks.

Pete · Post by **Pete** » Wed Sep 07, 16 10:50 am

You keep skirting the "heads" issue.

If that is a stock 400 then my guess is the motor is running "452" heads which are Ok and are designed specifically for lead free use, which is nice.

However, they are small valve heads with single valve springs and are not great for making power.
I put a cut-out 400 in a car once and got valve bounce at 5300 rpm....ran 13.2 with 4.10 gears. About 500lbs lighter than your car too....

Also, I would guess your pistons are stock and will not have big valve reliefs cut into them, so you cannot run a big cam, but then again the heads will not flow the numbers.

I am not having a "dig" but I am trying to demonstrate that there is no "Silver Bullet" here and the sum of the parts must be considered.

I think you are sensible in setting your budget and expectations accordingly.
The biggest "feel" of more power is always the rear gear choice, it will make the car feel a lot more responsive, if a little "buzzy".

Maybe do them first and then make a plan on the engine...the next issue will be matching the Convertor (you will probably end up needing a higher stall one), if the Transmission, prop, and rear end can take any additional power.

Definitely slippery slope time!

But FUN!!!

Ian Deady · Post by **Ian Deady** » Wed Sep 07, 16 11:03 am

They are 452 heads. I asked for advise and therefore, happy to receive it. I don't even mind a dig if it's constructive. lol.

You make a good point about the heads being the limiting factor though. I'm looking at the best way to spend my Â£2k to get the best power. I will no doubt throw far to much cash at this over the long term and further work will probably follow. Is my plan fair, or should I do the heads first?

I thought raising the compression and matching the cam would be the best start.

Thanks

MilesnMiles · Post by **MilesnMiles** » Wed Sep 07, 16 11:10 am

Something else Ian. Do you have big tyres on the back (275s)?, borrow some wheels and tyres that are smaller, note the rpm difference at 70mpg and that will maybe just hint at what a rear gear change will do.

Also, something Alex Doig told me a long time ago. Do you want a race car or a street car? Anything in between is a compromise of some kind.
Be good if some of the guys with 12 second B bods on the street gave some input.
I once drove 500 mile round trip on 3.91 rear and small tyres on my Dart.
Never again

Dave999 · Post by **Dave999** » Wed Sep 07, 16 11:56 am

I'd decide what I was going to do with the heads and the CR
then choose a cam that fits with the work done

a cam that works well with 11:1 static CR doesn't necessarily work well with 8:1

I used the tool at the bottom of this page to work out my Dynamic CR
to check my selection of cam in respect to my static CR (i.e bore stroke and the space left at the top at TDC .

http://cochise.uia.net/pkelley2/DynamicCR.html

but then again I have built very few engines so took advice where I could get it.

Dave

Blue · Post by **Blue** » Wed Sep 07, 16 5:13 pm

I don't know if there are readily available high compression Pistons available for the 400 at a sensible price I'd be looking at 10.5 compression. A cam change will mean a converter change as well so factor that in. 3.55 is a sensible compromise as regards rear gears. IF you are handy with a die grinder you can pocket port your own heads, it's not hard but it is very time consuming. Set of ferrea 2.14" and 1.81" valves and a decent valve job and you'll have some reasonable head flow.
Gen 3 Chargers are heavy, I spent a fair amount of effort getting weight out of one to get it to 3800lb so a full weight one will be 4000+ if we're being honest.
I think your 2 grand spent wisely will really wake the car up, not sure about 12's though.
Consider this, losing 100lbs reduces your ET by about a tenth, you might want to consider losing a little inconspicuous lard, often it costs nothing and dosn't have to be obvious.

Ian Deady · Post by **Ian Deady** » Wed Sep 07, 16 8:15 pm

Ok, I guess I was being a tad optimistic asking for 12's. What I want is a fun car, that feels fast in a straight line. I'd like to 1/4 mile for fun and post respectable times. I'm sure I can throw some more cash into it later but Â£2k, a mechanic and a heated garage, is what I'll have this winter. Mopars are hard to buy for second hand but if anyone knows of some good useable parts for sale I'd be interested.
Thanks again for taking time to reply.

Pete · Post by **Pete** » Wed Sep 07, 16 8:24 pm

I know it can be tough, especially when you can buy Chubby stuff more cheaply.

You will get lots of advice and assistance on here who have done it and pretty mush written the book in some cases.

The GOOD news is that you have a really strong block which is ripe for a stroker.

The alternative is to find a 440 and swap that in for a relatively quick fix (bigger capacity, potentially better heads, etc).

You can either sell the 400 to finance the swap or hang on to it for a robust stroker later.

What rear axle do you have? Center section?

Prop UJ size?

Convertor stall speed?

We spent loads upgrading the transmissions to avoid wearing internal parts. That can also be very costly, but so too can be new legs and feet.