rcknrolfender79

Hey guys I finally found a hemi to drop in a my chally! Its a 392, I know it wouldnt be correct but I dont really care. Only thing I really wanted to know is right now my chally has a 318 with a 600 cfm 4 barrel. I drive it every day when the weather isnt crappy. Anyone know what kind of gas mileage a 392 would get with 1 4 barrel? It is kind of a built motor, it has been bored 30 over, and from what the guy said it has a pretty hefty cam in it. BTW anyone know what cubic inches a 392 bored 30 over is?

I know it seems like a dumb question to ask about gas mileage. But I dont want to make her to where she isnt my daily driver, I mean if the difference is really severe. But I also hate just having that weak 318 in it. And I can finally answer that question EVERYBODY asks: "thats nice man, does it got a hemi?" lol Hell yeah it does!

And one more question for the road, anyone know how much horsepower is to be gained from balancing the rotating mass (crank rods pistons). And how much gas can be saved from doing so? And possibly how much a machine shop generally charges for that.

deadkelly

over here in oz a balance is around $350-450 I'd say it's a bit cheaper over there I'm guessing $300 - 350 ?? .
balancing won't really give you any horse power gains ( maybe a tiny bit , under 10 hp ) it's more to keep your vibration down to a bare minimal , it would help a tiny wee bit with fuel consumption . so little you wouldn't notice though .
but a balance will help your engine rev out quicker & smoother & last a lot longer in the long run , it's more for durability & to keep your rotating Assembly spinning in sink .
well a pretty hefty cam , 750 cfm carb or bigger & top end type inlet manifold will guzzle the fuel .
I'd say keep your cam in the 474 - 484 lift range with 280* duration ( 245ish @ .050 ) or smaller & 600 - 650 cfm spread bore carb ( carter or eddlebrock are good ) if fuel is a real concern & a dual plane 1500-5500 rpm range manifold . thats if you still want some good hemi power . I'm sure some will say that cam lift & duration is still to much .... mmmm i suppose you could even run a std hemi or 440 6 pack cam around the 450-460 lift range for every day driving . sorry I'm a bit on the race side of things .
can you get anymore specs from the engine . ie carb size , headers or exhaust manifold . inlet manifold . compression ratio , cam lift , ported / unported heads ?? ect ect manual or auto , exhaust size & diff ratio . thanks have fun .

johnthegoalie

don't take offense - if all you care about is a hemi and mileage is important, why not drop a late model 5.7 or 6.1 in the car. computer controlled, parts easy to come by and not as expensive and you can add modern features like a/c, etc. correct me if i'm wrong, but doing up a 392 in a later muscle car is like putting an 8-track in a 08 charger.

67 GTX

30 over on a 392 would make it a 396 or 397 i believe
gas mileage will be poor
8-10 in the city
11-13 on the highway
if it is somewhat built up

BuckNeccid

GTX is telling you right, especially if they didn't raise compression. We have a 354 in a '56 F*** PU, and it runs great, but mileage is something right around 14 or so with 3.30 or so gears in it. Great looks, lots of wow factor, and plenty of power, but don't expect gas mileage.

BuckNeccid

Don't see an edit button, but I forgot to add (and this is important) parts ain't cheap for them, and you're gonna need some sort of tranny adaptor most likely, and hop up parts are either mega bucks or hard hard hard to find

deadkelly

if you want a hemi thats good on fuel & still goes ok but still a hemi it says so on the block . a lil aussie hemi 6 cylinder . still makes 260 - 300 hp quite easy .

MReeves

X2.... Normally a Hemi and gas mileage don't go together.. The hemi may be albe to get good milage but the right foot has to be put under control and that is impossible!!!!!!!

rcknrolfender79

I believe he said the compression is going to be right around 10.5:1. Is that gonna help or hurt? And someone asked what intake and carb. I'm not sure yet, cause it doesnt have either. But I do have a 700 holley in my shed. I would probably give that a try on it. It is also missing the oil pan but is a complete engine other wise. He is asking 1,500.00 for the hemi. He also has a 340 with X heads but it is missing the pistons it is also .030 over he said he would sell for 800. I know you can get some power out of a 340 also, I know the 340 would probably be quite a bit better on gas, but I don't want to have to run a 6 pack set up (although it would be way cool) to get any real power out of it. Any idea how much it takes to get a 340 running around 350 to 400 HP? Actually the 340 would save me alot of money cause I already have the small block 318 in it, the mounts trann and headers should bolt right up I believe (correct me if I'm wrong).

Also you mentioned a '56 f**D PU, you wanting to sell that? I know it sounds terrible but there is just something about those old '56 f100 that I love. And they are pretty scarce anymore.

deadkelly

10.5:1 is a very good power making compression . oil pan & pick up isn't a issue . 440 source sump & pick up quite cheap . you could get a windage tray while your there . you would gain more power & fuel mileage from a windage tray than a balance .
a 2nd hand dual plane manifold & your 700 Holley would be fine . it's all about the right foot . with that compression the hemi would make more low end power that the 340 & fuel consumption would be similar to a extent . depending on what was done to the 340 of course . will 10.5:1 compression give you guy's trouble over there with pump gas ??? i know you can buy in-line fuel catalyst that will up your octane about 3 points but they do cost around $1 per hp but they last for ever .
I'd say the 340 would work out cheaper depending on how much of a rebuild it needs & weather the hemi is in running order ? .
but the hemi is a hemi & thats priceless .
you could run thicker head gaskets to lower compression a little bit in the hemi .

rcknrolfender79

I agree with you that the 340 would be cheaper, but like you said the hemi is a hemi and that is priceless. And I believe 10.5:1 is the highest you can go on pump gas around here. And yeah we have octane boosters too. The same guy has both of these engines, he owns a machine shop and said he could do a magnaflux so we could make sure they arent cracked anywhere. I am having a really hard time deciding, cause I dont want to leave either behind, cause both of those engines are a really good deal. As I will probably never see a 392 hemi for 1500 again, and probably never a 340 with X heads again for 800.00. I am taking these factors into consideration: Gas, Power, and the money that it is going to cost me to drop that motor in the car and get it running. And so far the 340 is winning but the want for the hemi is really causing me hell lol. And I also vowed myself that I am not swapping motors without changing her out to a 4 speed car. Cause I honestly cannot stand driving such a nice car and not being able push in the clutch switch the gears and feel all of that power transfer as I let out on the clutch. So that is another pricey little factor I gotta add in.