Howdy everyone,

I'm building a '72 Demon street machine which right now is just a body shell on a rotisserie. The car was originally a low-optioned /6 automatic and it spent all of its life in Texas.

What I want is a fun street/strip car and I plan on installing a T56 Tremec 6-speed manual transmission, a Strange S-60 rear end, Cragar wheels, disc brakes all around and I anticipate keeping the interior pretty much stock (including a bench seat) except for a Peak Dashes gauge cluster. I'll likely use both manual steering and brakes and an aftermarket A/C. I also want the car to have a slight sleeper look so I may keep the stock flat hood for now.

I don't have any of the drivetrain or suspension parts so I'm building it completely from the shell.

I am, however, having a hard time deciding what engine to put in the car. I'm looking for good power which also doesn't have fuel economy constantly in the single digits, which the overdrive in the Tremec will help prevent. To put it in perspective, my daily driver is a TJ Jeep Wrangler which, at its worst, will give me 12 mpg in the city and I'm okay with that. I want to drive the Demon semi-regularly, i.e. a couple of times during the week and on weekends, so I don't want a radical engine that gives five mpg even on the highway.

Here's what engines I've been contemplating so far:

1) Mild 440 - I already have a complete '75 440 I pulled out of a junk yard this summer for around $300. It will need a complete rebuild including a forged crank. If I rebuild it for the Demon, I'd probably keep it slightly hotter than the stock 440 Magnum, for example with a Lunati 60302 or 60303 cam, Stealth Heads, good compression, etc. Combined with the T56, I figured it'd be a good balance between low-end torque and decent gas mileage when cruising.

My major concern, however, is the fitment of a RB block in the A-body, mainly with spark plug access and general maintenance. Like I said, I'm going with manual steering and brakes so I'm not concerned with that and I'll also use Schumacher or TTi headers, but I am worried about if I'll have room for an A/C compressor, which is a necessity here in Texas.

I am drawn to using a big block because I like having the distributor in the front.

If I use the 440, I'll use aluminum parts where I can to save weight.

2) 400 Big Block, stock stroke - This is an interesting combo because most people just build a 451, but I think a 400 would be capable of good power plus a B block would give slightly more room under the hood. Is spark plug access and what not a notable difference between the B block and the RB block in an A-body? Also, even with the stock short stroke, can I get plenty of torque out of it? On another forum I saw a '72 Dart with a 400 which was running high 11s. I'm pretty sure I can get off-the-shelf pistons for it that give a good compression ratio.

3) 408 - If I build a 408 stroker, I'd build it to about the same power level as a mild 440, but will it have enough torque at a lower RPM comparatively? I would have more room in the engine bay but I prefer having the distributor in the front of the car plus simply the look of a big block when you open the hood.

4) 383 - Same advantages as the 400, but I'm wondering if I can build it for plenty of torque. I am running an A-body, however, which helps. A 383 would seem like a great balance between power, fuel efficiency (especially with two overdrive gears in the T56) and the look of a big block under the hood.

5) 451 - Also considered a 451 stroker, but it may lean more towards performance over everything else plus I already have a 440. Would the extra room in the engine bay a B block provides be worth the added expense of building a stroker motor over a 440? I know the 451 revs faster but I'm not building a drag car so a lot of its advantages are moot for my goals.

I also toyed around with the idea of a 360 or a carbed 5.9, but I do lean towards a big block.

What do you all think? I'd like to hear your comments and suggestions. Thanks!

not to sway you away from a big block (i'm a big block guy myself) but if and when I do an A-body i'm sticking with a small block and stroking it. way too many headaches cramming in a BB. now if someone already did it and I found one ....

Do you think some of these headaches could be alleviated by installing the engine and transmission from the bottom?

Patients is the key here. Both have pros and cons.

I have a 470"/400 in my 69 B'cuda with CPPA headers(much like the TTI) It's a tight fit but not all that bad. I run a 4 spd with the stock clutch linkage..again tight but can be done. The low deck choices will give you a little more room to work. The only plug that's a real challenge is #6(Eddy heads)Valve covers come right off for valve adjustments,etc. The blower motor is a tight fit but there are some work arounds for it.

I put Hellwig sway bars(frt and rear) and homemade frame connectors on mine so it drives just fine. Also did the disc brake/big bolt pattern conversion. Don't let guys scare you with the nose heavy talk...they handle just fine!

Obviously I'm a little biased but IMO BB A-bodies are a little less common a WHOLE lotta fun to drive!! Good luck with your project and post some pics as you go!!

440 in a '72 Dart. Fenderwell headers make starter and plugs an easy change.

If I ever did an a body, and the wife has said she'd like a Demon one day, then I would go small block stroker. They can have very similar power to a healthy big block, 450hp/500+tq. You can use a magnum core to get all of the benefits of a roller setup at no extra cost. It would keep the nose lighter which makes it easier to make it a handling car, and you would have plenty of room under hood for a/c, plug access, etc...The power you can get out of them would move an A body nicely IMO.

It sounds like you want a big block for the wow factor more than anything else.

With headers, the low deck versus tall deck will not make much difference. Number 6 is a pain. The low deck does fit slightly better, but it is not like having a small block in there.

If I were to do it again, I probably would do a small block stroker OR gen 2 or gen 3 hemi instead of a BB wedge. I'm not upset that I did the wedge but at the end of the day it was probably more trouble than it was worth considering my car was setup for a SB and at this point it will likely never be anything else than a street car.

If you want to do a BB make it worthwhile and get the extra cubes if you can. If you are not planning on anything more than 430 cubes or so I say to the SB stroker (i.e. 408).

IF you go BB, you can get 383s pretty easily. Get one, stroke it, and even with stock heads or Eddy RPMs, or Stealths, with a mild cam, it will be a blast to drive.

"Street/Strip" covers a lot of territory. With the 6 speed I'm guessing you want to have fun driving it on the road. Weight distribution and balance is a lot better in an A body with a small block... preferably lightened. Lighter front=more fun to drive. An aluminum headed SB stroker would really work well in an A.

Of all the combos you are considering, one to avoid would be a stock stroke 400. It is hard to build compression and power with this setup. Worst of all worlds... heavy and lower power than a SB stroker plus poor parts support. If you do go BB, suggest 3.75" stroke minimum and lowdeck for fit.

Slight sleeper to me means sb, I would build a 426" or so sb, use tti headers RHS X heads nice big solid ft or roller use a port matched and worked ld340, 950 carb under a stock air cleaner with stock valve covers paint it and dress it to look stock. I think an easy 500 hp can be had if the comp ratio is up at around 10.5 to one

I'll guarantee you a 408 stroker will put a smile on your face. It is an easy install and relatively less expensive to build compared to building and fitting a big block in an A body. It can have good street manners and handle well. I had a 408 a518 3.55 combo in a D100 short bed. it was nice daily driver and would surprise the crap out of the mustang and camaro crowd.

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Slight sleeper to me means sb, I would build a 426" or so sb, use tti headers RHS X heads nice big solid ft or roller use a port matched and worked ld340, 950 carb under a stock air cleaner with stock valve covers paint it and dress it to look stock. I think an easy 500 hp can be had if the comp ratio is up at around 10.5 to one

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This!

Internally this engine is nearly identical to the one in the Valiant above, (different heads but similar flow #'s) with a stock carb, intake, ignition, and exhaust manifolds, it's only down about 70HP but makes the same 500lbs of torque.

Find a good 360 block go with a 4.125 crank and a set of Airwolf heads.

As a owner, builder and racer of many different Mopars, 318, 340, 360, 383, 426M.W.,426 Street Hemis, 440 and so on the most fun street car, and fastest was a 400 block pump gas stroker motor, 512 C.I. and then 518 C.I. in a 1971 Duster With your goals I would put a 512 stroker, 400 block with a 4.250 stroke crank with after market forged steel H beam 6.700 BB Chevy type rods Put a 3.54 gear in the Dana and go have some fun with good mileage, if you can control the right foot to get good mileage My 512 pump gas stroker, which became a 518 C.I. later with a crank swap to increase the stroke to 4.300 to get some more compression after changing the iron 906 heads for a set of Eddy RPM heads was a blast to drive and way faster and more powerful than I had hope for With the Eddy RPM heads and a low deck sixpack intake and carbs. with 10.29 to 1 compression ratio with the 4.300 stroke that motor made over 700 HP at 5600 RPM and similar ft. lbs of torque at 4500 RPM on Oregon pump gas With the big C.I. stroker mtors you can run the RPM a lot lower and still have way to much torque and HP for most street tires

You can make power with factory iron heads. The Dart pictured in my first post runs 10.04/131mph in a 3,000 lb. car with 1967 915 heads. NO NITROUS.

With the t56 the sb will be cheaper. You can use a stock t56 bellhousing instead of aftermarket. Also the t56 will need less in upgrades to handle the power if you build for 450 torq instead of 550.

We run a stock stroke 400 in my sons 72 Dart. He uses Eddy RPM heads and the MP .557 cam and a 750 DP. With 3.91's and at 3550 lbs it has run 11.40's on good days. Ron