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New member - new acquisition - opinions wanted
https://www.slantsix.org/forum/viewtopic.php?t=51590		 Page 1 of 1
Author:  dpstark2 [ Mon Apr 01, 2013 12:45 pm ]
Post subject:  New member - new acquisition - opinions wanted
Hello all,

I recently added a 1972 Dart Swinger to my arsenal. My other Mopar is a '67 Charger with a 440 and 727 that gets me around town quite nicely, but it's a bear to drive for any distance. That's where the Dart's 225 comes in. However, the Dart's motor is beat. #1 has almost no compression and tremendous exhaust blow by. The exhaust manifold is cracked. The carburetor is toast. My plan was to rebuild the motor eventually, but "eventually" has become "now." My goal for this car is to make it a daily driver and replace my (also beat) commuter. I just can't see sinking another $15-20k into a plastic box. I'd rather put half that into a car I can be proud of.

I know this has probably been covered, but I'm looking for suggestions on cam, compression, carb, and manifolds for building a reliable, efficient daily driver. My Dart currently has a 904 and 8.75" axle (factory installed, unknown ratio, but probably steep), and I am also considering swapping in an aluminum manual OD.

Another board member and friend of mine, Pierre, has a Megasquirted 225 that was just rebuilt by Doc at 9:1 with the RV10 cam- I'm quite impressed with this motor. With the manual OD, I'm looking for a broad, flat torque curve. With the traffic I drive in and a manual (if I go that way), I need to be able be able to pull from a pretty low RPM. Not overheating is definitely a bonus- and it gets hot in the summer in the CA central valley.

Thanks for any advice.
Author:  Aggressive Ted [ Mon Apr 01, 2013 1:00 pm ]
Post subject: 
Check out the engine build matrix's in the Engine FAQ
Lots of good info there to compare.
Author:  DusterIdiot [ Mon Apr 01, 2013 2:02 pm ]
Post subject:  X2
I would encourage looking at the engine build matrix and see what is in there. If going with the wide ratio A-833OD box, it would be good to find a kinder ratio for the rear end, the 2.76 coupled with the OD is kind of clutch burner to get it motivated even with a 9:1 build, and the final ratio in OD would be great if you were cruising at 90mph to keep the carb in the mains.
I have found that 3.55, is a good all around ratio with this box, 'fun' to drive, but gives you a nice 2.59 final ratio in OD which is great for longer commutes and the rpm drop from the widegear ratio isn't as noticed.
(I had built a 9.6:1 mill with short cam for my '67, coupled with a 2.94:1 rear and an A-230 3speed- got good mileage, still could smoke the tires, and was fun in the 'lighter' A-body like your dart.) I would also look at upgrading the stock points ignition to mopar EI (if you have spare parts laying around), or the HEI conversion if you haven't done so.

If you did your own engine assembly, and buying the manual transmission and associated parts, and an open 3.55 pumpkin for the 8 3/4", I don't see how you could spend more than $3k at the worst and have a really nice running mileage getting machine.

Oh and welcome to the board, hope you know what Pierre has gotten you into! :wink:


-D.Idiot
Author:  dpstark2 [ Mon Apr 01, 2013 2:46 pm ]
Post subject: 
Thanks! I have looked at the build matrix, but at this point, it's a little daunting to sort through. There's so much information it's hard to make sense of it all. I know a lot about B/RB motors, but the slant and its seemingly strange cam needs are a bit of a mystery to me. Hopefully in the near future I can add my own entry.

The car already has an orange box, but it's old and really corroded. It was also added relatively poorly. HEI or and MSD is definitely in the plan. I can do top end engine assembly myself (I've been through a couple 440's and a hemi), but I don't trust myself to do the bottom end. I'd rather leave that to a pro. Or semi-pro, at least.

I was a bit worried about the <3:1 gears and the OD. I have a set of 3.23's I could swap in if necessary, and I figured that would work well with the final drive ratio and low first gear. The transmission I would be using is an aluminum case, so I assume it has the low, low first gear but I'm not totally sure. 3.23's should put me at about 2200-2300 rpm at 75 mph, which is a pretty normal speed for me- any comments on the ability of the /6 to push the Dart at that speed at that RPM?
Author:  DusterIdiot [ Mon Apr 01, 2013 5:32 pm ]
Post subject:  Hmmm..
Quote:
I know a lot about B/RB motors, but the slant and its seemingly strange cam needs are a bit of a mystery to me.
Actually the slant is in some ways similar in logic to the B/RB field. I know one early racer that commented that he had his cam ground to the specs of the chrysler 300 cam at that time (about 284/284 advertised duration). Because we are more stroke and less bore than the B engine (lots or bore and stroke), and with the restrictive head the engine on the top end builds prefers a bit more intake duration and less exhaust. All of your engine building and modifying skills will come to bear here, but on the milder build not so much extra is needed.
Quote:
I was a bit worried about the <3:1 gears and the OD. I have a set of 3.23's I could swap in if necessary, and I figured that would work well with the final drive ratio and low first gear. The transmission I would be using is an aluminum case, so I assume it has the low, low first gear but I'm not totally sure. 3.23's should put me at about 2200-2300 rpm at 75 mph, which is a pretty normal speed for me- any comments on the ability of the /6 to push the Dart at that speed at that RPM?
I actually used to daily drive my duster on the stock 2.94's and the OD tranny and it was doggy in OD with the 2 barrel due to the low rpm in that gear on the highway, switched to the 3.55's and things were much better...eventually changed to a 4 barrel on the mild engine and got more out of it, still kept good mileage with 4 barrel, 10:1 compression and switching to 4.56's out back. If you are running a mid 9:1 SCR build like Ted or a RV10 cam with same compression, or even a comp cam 252S in that realm the engine will have a nice flat torque band from idle to 5500 rpm. It mostly will run out of top end if you keep the 1 barrel carb, and don't clean up the ports in the head (that usually occurs about 4000 rpm, but need a lot of road to get there)

FYI, on the A-833OD aluminum case version from 1976-1980 A/F-body is OK, things to check are the countershaft holes in the case, if they were behind a V-8 or hard driving the pressure on the countershaft gears when not in 3rd gear can wallow out the holes it sets in. Also pull the bearing retainer and check to make sure that the surface the bearing sits against is smooth, if there is a ridge in there the bearing may need replacing and the retainer spot faced.

-D.Idiot
Author:  Pierre [ Mon Apr 01, 2013 10:03 pm ]
Post subject: 
I think the lust for the megasquirted slant is what convinced him to squirt the 440, that's going to be a fun project. That motor is nuts, it can spin a tire that's like twenty feet wide in second gear.

How set are you on the manual part? An auto will make the commute a bit more enjoyable. If you want OD, how about a 200r4? There was a group buy some time back for the adapter plates - someone may be willing to sell their unused one otherwise you can get one directly from Wilcap. The lockup version even better for gas... I think only minor tunnel surgery was required to get it in.
Author:  zorg [ Tue Apr 02, 2013 9:45 am ]
Post subject: 
Quote:
3.23's should put me at about 2200-2300 rpm at 75 mph, which is a pretty normal speed for me- any comments on the ability of the /6 to push the Dart at that speed at that RPM?
Your estimate is quite accurate = 2350RPM at 75mph, on a 25" tall tire. I did that for 3 hours straight yesterday, the slant does just fine. I'm over cammed, so mine is a bit doggy at that speed/RPM. I'm hoping to go to a RV10 or RV15 cam soon to bring the powerband down to something usable.

('76 Dart Swinger, mild 225, 833od, 3.23sg)
Author:  dpstark2 [ Tue Apr 02, 2013 10:01 am ]
Post subject: 
Thank to everyone for the replies. It definitely seems like my plans are taking shape. I do intend to use the manual OD, though it may be done after the motor is built, installed, and broken in.

Can anyone comment on the power band and relative qualities of the RV10 and RV15 cams? I definitely plan on some minor head work, but I wasn't really planning on going to a 4BBL. I guess I need to plan on a 2BBL at least. But, if the MPG issue can be sorted with a 4BBL, I guess that's fine too.

After talking to another B/RB guy, it seems the cam issue isn't really that different. The larger intake duration than exhaust was confusing, but I see how that can work with lower compression and power band requirements in a low-flowing head. It all makes enough sense for me to work with at this point.

Yeah, the 440 is super fun- but I'm looking forward to being able to drive the Dart regularly and fit it in most parking places. Dang ol' Charger is LONG.
Author:  Doc [ Tue Apr 02, 2013 11:08 am ]
Post subject: 
Quote:
.... Can anyone comment on the power band and relative qualities of the RV10 and RV15 cams? ...
The RV10/295 RDP is designed for a 1bbl engine with factory compression ratios (8.4 to 9.0) and to have smooth idle with strong off idle and mid-range power.

The RV15/295 RDP needs a little more compression (9.0 to 9.5) and just moves the power a little higher up the rpm range. This cam should run a 2bbl carb minimum.
DD
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