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| /6 rebuild https://slantsix.org/forum/viewtopic.php?t=60158 |
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| Author: | Docmcg [ Mon Sep 12, 2016 8:21 pm ] |
| Post subject: | /6 rebuild |
I've removed and disassembled the motor from my'65 Dodge A100 pickup. I've rebuilt a few small and big block V8's, but this will be a first /6 for me. I'd like to pump it up a little. Any recommendations/suggestions? I intend to put the Offy 2x1 bbl manifold on it. I'd like to bump up the cam, put in larger valves and of course hardened seats, and I'm swapping out the 3 speed stick for a 727 automatic which I got out of the same year A100 van. What other areas do I need to maybe pay particular attention to? How about the oiling system? I read some posts on here and recognize experience and knowledge when I see it. Anyone care to share? |
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| Author: | Badvert65 [ Tue Sep 13, 2016 4:45 am ] |
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Right off the bat, I'd tell you to swap the 727 for a 904 trans. The 904 is smaller and lighter , plus needs less horsepower to operate. 727 is a great trans but major overkill on a slant. Others will chime in, but basically ignition upgrades (HEI) and shave the head to bump the compression higher. |
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| Author: | Docmcg [ Tue Sep 13, 2016 7:47 am ] |
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Thanks Badvert, I have a 727, I'll check with the tranny shop and see if they have a 904 and maybe do a swap with them. I don't want to be scrounging around finding more stuff. I have everything I need except for the rebuild parts. Just gotta get after it and get it done. |
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| Author: | Reed [ Tue Sep 13, 2016 8:02 am ] |
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The problem with putting a 904 in an A100/A108 truck or van is the transmission mount. The A100s used a transmission mount that bolted to the top of the tailshaft housing, not the bottom like just about every other mopar. Unless you want to get into fabricating a mount you need to track down at least a tailshaft housing from an original A100 application. From 64-67(?) the A100 could only be had with a 727 transmission. That is why Chrysler made the engine adapter. The A100s powered by slants were mated to V-8 727s. Starting in 68 (or so), the 727 got a slant six case. I don't know offhand if the 904 was ever installed in the A series trucks/vans from the factory, but if it was, you would be looking for a 1968-1970 A series truck/van specific transmission or tailshaft housing. There won't be many out there. Unless you have an original A series vehicle transmisison (or tailshaft housing) you will be into fabricating a transmission mount anyway. I second the recommendation that you use a 904 instead of a 727. Unless you are building a heavy camper, will haul heavy loads, or will pull a heavy trauiler very often, the 727 just isn't necessary behind a slant six and has too much parasitic loss to justify installing one. I recommend a 1979-up 904 transmission, especially the 904T transmissions form the 1980s. These will already have less parasitic loss since they are a 904, but also will potentially get better fuel economy due to the lockup torque converter. If you get a 1980s era 904T transmission it will have the wide ratio gearset which can help the vehicle accelerate better, especiually if you run a higher rear gear ratio. If you are just building a daily driver or cruiser, I recommend 3.2:1 rear gears. As far as an engine build goes, the main modifications have already been mentioned. Update the ignition to HEI, recurve the dustributor, I would upgrade the cam to at least the 1972-1980 factory cam, or, if you are willing, jump to an Erson RV10 or RV15 reground cam from Oregon Cam grinders. Upgrade the exhaust to 2 1/4 to a free flowing muffler and then 2 inch after the muffler. Once you have your cam picked, have the head or block milled to put your DYNAMIC compression ratio (NOT STATIC) at around 8:1. The head is the main limitation point for the slant six. Porting the heads helps a lot, even on a street motor, and porting plus oversize valves is a good idea. Stepping up to a two barrel carb would be another great improvement, but you will have a few issues since you are working on an A series. The engine cover will interfere with a factory two barrel carb air cleaner. You will have to get creative. If you can find one, the factory air cleaners for B series vans powered by a slant six are offset. You may win the lottery and find a factory van specific two barrel air cleaner (not likely) but most likely you will need to get a single barrel air cleaner and weld in the opening for the carb from a two barrel air cleaner. You will also need to craft a throttle and kickdown linkage. Personally, I would skip the 2x1 Offy setup. The linkages are a nightmare to get set up right and I don't know if you wil have the clearance for the air cleaners. Plus, finding a matched pair of serviceable one-barrel carbs is going to be hard to do these days. Another thing to consider is the installation of a true cold air intake system. A100s vans are known to have probelms with heat soak in the engine compartment and pverheating. Sucking in all the hot engine bay air doesn't help your power or economy. I strnglyrecommend you use a closed air cleaner from a later modelvehicle and rig up a cold air duct to the end of the snorkel on the air cleaner. If possible, please post pictures of your project as you go! We all love to see them. |
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| Author: | Docmcg [ Tue Sep 13, 2016 5:43 pm ] |
| Post subject: | |
Awesome info Reed, thank you. As stated, I do have an A100 specific 727 tranny with the correct short tail shaft housing and the donut mount on top. I don't want to get all wild and crazy with this build, but being a former drag racer, I feel this need for power. Granted, I'm not going to race this truck, but I like the idea of surprising folks when they get inquisitive. When I picked up this 727 tranny, I got all the linkages (throttle and kick down) and will undoubtedly stay with it. I think I can build enough motor to overcome the parasitic loss, to a certain degree. I have found a machine shop in the area that has a guy that is really into the /6 and was real excited when I was inquiring about my motor. Seemed very knowledgeable and was truly anxious to get to work on this. I would also ask, are there any other areas in building this motor that I need to pay particular attention to? How about the oiling system, does it need any help like the BB Mopars? Thanks again everyone, I really appreciate this board and all it's friendly, knowledgeable people. |
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| Author: | Charrlie_S [ Tue Sep 13, 2016 5:59 pm ] |
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Quote: Awesome info Reed, thank you. As stated, I do have an A100 specific 727 tranny with the correct short tail shaft housing and the donut mount on top.
Do you have the adapter plate that goes with a 727 trans to slant six? Without the adapter the V-8 727 will not bolt up to the engine. Also, if the 727 trans is the later style slant six unit, it still will not work as the pilot nub on the converter will not fit into the hole in the end of the crank, if you have an engine with the 67 or older crank.
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| Author: | Docmcg [ Tue Sep 13, 2016 6:08 pm ] |
| Post subject: | |
Well now, I could be mistaken about the year of the van this tranny came out of! Opens up a whole new can of worms. Looks like I better get out the calipers and do some measuring. On a different note, can someone school me on how to post pictures here. I'm definitely not the most tech savvy guy and need some guidance, Thanks. |
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| Author: | Reed [ Tue Sep 13, 2016 6:49 pm ] |
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Yup, Charlie nailed it. Check the bellhousing bolt pattern and check the diameter of the torque converter snout. Honestly, you will go faster using a 904. It weighs less (plus number 1) and it takes less power to operate it (plus number two). Plenty of drag racers use 904s for precisely these reasons. Honestly, it will be cheaper and easier to switch to a later 904 (provided the torque converter hub matches the crank pocket) and build a trans mount. If I remember correctly, the trans mounts from the 71-93 Dodge B series vans can be adapted to the A series van fairly easily. The kickdown and throttle linkage from a V-8 A 100 will be very different form a slant six A100. The slant six is a pretty durable and well designed engine. You can radius the oil pasages in the block if you want (see HERE) and do the same with the oil pump, but the oiling system is pretty stout in stock form. The biggest performance limiter on the slant six is the cylinder head. The valves are really too small for a performance oriented 225 engine. You can greatly improve the performance and economy of the engine by porting/bowl hogging the head and installing oversize valves. A warmed up head with an increased compression ratio will really wake up the slant six, even with the stock cam. |
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| Author: | Docmcg [ Tue Sep 13, 2016 7:28 pm ] |
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I know this tranny came straight off the back of the /6. Just to clear things up, how can a tell if the motor in my A100 pickup is original to the truck. I still intend to do some measuring and checking the size of the converter snout. I have a slight suspicion the motor in the truck could possibly not be the original. |
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| Author: | Docmcg [ Tue Sep 13, 2016 8:23 pm ] |
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Well now the plot thickens. I just checked the measurements and it's not good. Obviously the tranny is from a later /6 and indeed the converter snout is larger than the crank hub. Also the flex plate bolt pattern has the odd bolt pattern. Way I see it, I could get a crank from a later /6 and all might fit. Hope so. Will the converter snout from a later 904 fit the older ('65) crank? What will I do, what will I do? |
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| Author: | Charrlie_S [ Wed Sep 14, 2016 6:04 am ] |
| Post subject: | |
Quote: Well now the plot thickens. I just checked the measurements and it's not good. Obviously the tranny is from a later /6 and indeed the converter snout is larger than the crank hub. Also the flex plate bolt pattern has the odd bolt pattern. Way I see it, I could get a crank from a later /6 and all might fit. Hope so. Will the converter snout from a later 904 fit the older ('65) crank? What will I do, what will I do?
You really need to determine, if the 727 trans is a V-8 (requires the adapter) or a Slant six (bolts directly to the engine) unit. Neither will fit the early (67 or older small pilot) crank, directly. All 727 trans have the big converter nub.A late (68 newer) 904 trans has the same problem, the big converter nub. |
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| Author: | Docmcg [ Wed Sep 14, 2016 12:56 pm ] |
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Did some measuring and checking this morning. The tranny is definitely a /6 727. It does bolt up to my motor (actually did it today to check). The convertor hub is too big, so now I will have the crank machined to fit the snout. All is well now with fitting the pieces back together. I won't swap for a 904 because one with a short output housing will be very hard to find. I won't worry myself about the 727 being heavier (how much could that be?), and not going to get all caught up with potential parasitic losses. This is not going to be a race vehicle, hell I probably won't be driving it a lot anyways. Certainly won't be working it like a real truck either. It's just for the fun of it and I think it's a cool truck! If I could figure out how to post pictures here, I'd show some of the truck. |
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| Author: | Reed [ Wed Sep 14, 2016 1:10 pm ] |
| Post subject: | |
OK. My 76 D100 shortbed pickup was factory built with a 225 and 727 and even with 3.91 gear in the back it will do 80 on the highway and still gets 12-13 MPG. I plan on switching to a 904, but it will be much simpler for me to do that than for you to do a swap. I throw those numbers out just to give you an idea of what to expect. For a fun cruising vehicle you will be fine. |
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| Author: | Docmcg [ Wed Sep 14, 2016 5:05 pm ] |
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Checked the numbers on the tranny pan rail and it turns out this tranny is from a '70 vehicle. I'm going to have it serviced and freshened up, and put it in the truck. I plan on taking the block and head to the machine shop on Friday and get started on that. I'll have them machine the crank to fit the converter when it's there. I'll keep you all posted on my progress. I'm sure I'll be asking for some more help along the way. Thanks everyone. |
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| Author: | a100gary [ Mon Jun 22, 2020 11:37 pm ] |
| Post subject: | Re: /6 rebuild |
Doc, it's been almost four years since your last post on this thread. What did you do with your /6 A100. I specifically want to know if you were able to modify the crank of the early /6 to the 727. I am currently in your that situation. I have a 1965 A100 with a 225 /6 and a 727 tranny. The head in the truck has drool tubes, so I thought the engine was an early version and I bought another early engine with drool tubes to build up and plug in. Checked the dates. Engine in the truck is April 1976, engine on the stand is Sept 1964, won't mate with the 727 trans in the truck. What is the answer? Can you modify the crank? Or can a 904 fit in the shortened space? What are the options? Anyone?? |
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