Peanut Gallery Survey for my /6 Build ...

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Mopar Virgin

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Back from winter in Tucson to see my sight-unseen purchase of a '68 Bcuda Convertible. After inquiring to Forum prior about engines, I'm opting to stick with the 225 /6 that came with the car. Now the question is what to machine and config it with. I know everyone is going to have opinions, which is what I'm seeking here. Please LMK "why" you recommend what you do for context. Will be pulling the engine out and getting it to the machine shop in the thriving metropolis of Herminston, OR in a couple weeks.

This will likely be a 904 automatic 3-speed, as we don't want to cut out the tunnel and be unable to place the center console. We are facing the age-old trade-off of performance versus convenience/mileage. Will drive this car a lot (i.e. quasi-daily driver and long trips to car events). So highway mileage is important, but would like to have some HP behind it on-demand to "fun around" once-in-awhile. Will be adding power steering and A/C to the build.

So at the moment the options under consideration (open to more) are the following, in no particular order:
  • Dual Exhaust
  • Enhanced Intake Manifold
  • Performance Natural Aspiration (Triple Webers ... )
  • Electronic Fuel Injection (Suggestions? ... machine shop and a friend like Holly Sniper)
  • Turbo Charging (told is cheaper than supercharging but more complicated plumbing)
  • Supercharging (machine shop suggesting TorqStorm)
 
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I would ditch the dual exhaust idea. It only adds weight and gives no performance improvement over a good 2.25-2.50" single exhaust. It sounds like you want a peppy driver with good mileage so one of the OD auto transmissions with some fun street gears would help a lot. Up the compression to somewhere around 8.5 static and 7.75 dynamic. That will let you run standard pump swill. Have the head and/or block shaved to reach your compression goals, then pocket port the head and install larger valves, 1.70/1.45 or so. Triple Webers are sexy as hell but complicated to tune and not likely to give a ton of real world improvement over a super six setup or a small 4-bbl intake unless you want to get real serious about the rest of the engine. Add a good free-flowing exhaust. @moparmarkk has a set of long tube headers for sale that should fit your car and would be an excellent choice. Depending on your goals I'd talk to Ken at Oregon Cam Grinding and see what he suggests for a regrind that would fit nicely with the rest of your parts. And hell yes, if you have the coin for it, a Torqstorm would be the bees knees but if you go that way make up your mind before you do the rest of the engine - a blown motor needs different parts and specs than a NA motor.
 
halfafish said:
I would ditch the dual exhaust idea. It only adds weight and gives no performance improvement over a good 2.25-2.50" single exhaust. It sounds like you want a peppy driver with good mileage so one of the OD auto transmissions with some fun street gears would help a lot. Up the compression to somewhere around 8.5 static and 7.75 dynamic. That will let you run standard pump swill. Have the head and/or block shaved to reach your compression goals, then pocket port the head and install larger valves, 1.70/1.45 or so. Triple Webers are sexy as hell but complicated to tune and not likely to give a ton of real world improvement over a super six setup or a small 4-bbl intake unless you want to get real serious about the rest of the engine. Add a good free-flowing exhaust. @moparmarkk has a set of long tube headers for sale that should fit your car and would be an excellent choice. Depending on your goals I'd talk to Ken at Oregon Cam Grinding and see what he suggests for a regrind that would fit nicely with the rest of your parts. And hell yes, if you have the coin for it, a Torqstorm would be the bees knees but if you go that way make up your mind before you do the rest of the engine - a blown motor needs different parts and specs than a NA motor.
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Really appreciate the inputs. Beyond the performance of a dual exhaust, I kinda like the potential visual symmetrics of them with chrome ends. Concerning your suggestion about an OD transmission, are you aware of any that will fit within an unmodified tunnel? I want to retain the center console and from what we've been able to research, there isn't one that fits within cutting-out and refabricating the tunnel.
 
Mopar Virgin said:
Really appreciate the inputs. Beyond the performance of a dual exhaust, I kinda like the potential visual symmetrics of them with chrome ends. Concerning your suggestion about an OD transmission, are you aware of any that will fit within an unmodified tunnel? I want to retain the center console and from what we've been able to research, there isn't one that fits within cutting-out and refabricating the tunnel.
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you will lose power with dual exhaust on a slant 6, but it's your car and your money. If that's what you want, go for it. It'll be cool at least.
 
Didn't think he'd lose power with duals, but knew it wouldn't gain any either.

I have a delta flow 50 "flowbastard" I'm thinking of trying on mine, single in/dual out, again just for "looks" /but have been on the fence about using it. I'm not a fan of the "standard go to" flow master most people use on their "hot rods" but I have heard that the higher number ones aren't as harsh.
It may go back into the attic for something else.
I was also thinking of using a regular "RV" muffler like we're popular in the 70s and 80s the big, fat round, and long ones... To match my 2-1/4 pipes.
 
Mopar Virgin said:
Concerning your suggestion about an OD transmission, are you aware of any that will fit within an unmodified tunnel? I want to retain the center console and from what we've been able to research, there isn't one that fits within cutting-out and refabricating the tunnel.
Click to expand...

Well, I'm a three-pedal guy, so I'm no guru on OD autos. I believe there are some 904 sized units (42RH or 42 RE ??) as well as some others that will fit. You might want to do a search for that, I know I've read a number of threads on this but I didn't stash the info in my memory because the whole business is missing the clutch.
 
There are no modern OD automatics that don't' require an adapter or floor pans mods. Some are just less intrusive.
 
Guess it’s to late for me concerning whether or not to go dual exhaust or not on a Slant6. My Slant6 70 Challenger does have real dual exhaust starting at the engine with Hooker headers 3 into1 with 2.25 aluminized pipes and “H” pipe all the way to the back into twin 26” glass pack mufflers then around tank on each side thru Cuda style exhaust tips. For a daily driver it runs and sounds pretty good.
 
/sixchall said:
Guess it’s to late for me concerning whether or not to go dual exhaust or not on a Slant6. My Slant6 70 Challenger does have real dual exhaust starting at the engine with Hooker headers 3 into1 with 2.25 aluminized pipes and “H” pipe all the way to the back into twin 26” glass pack mufflers then around tank on each side thru Cuda style exhaust tips. For a daily driver it runs and sounds pretty good.
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Based on the prior comments about MPG, howz' your MPG on that config?
 
Typically HP and mpg are not mutually exclusive. When you up the efficiency of the motor, you will get better mpg if you can keep your foot out of it. I'd mill the head about .060 if it has not been milled. Get a cam in the 268 degree duration and about .450 lift. Add a double roller timing chain, 340 valve springs, a windage tray, a high pressure oil pump spring from a big block, an electronic ignition from a 73-74 /6, a Super Six intake and carb, and the exhaust from a Feather Duster. Enjoy.
 
To Mopar Virgin and 66fs, the exhaust changes are as mentioned. The engine, a 225 is basically stock configuration but I did add the late 70’s Super Six mods with Carter BBD 2 bbl an open element K&N air filter. Mopar elect. ign. with orange box, high output Accel coil. No other major internal changes. MPG’s anywhere from 18-23 on 87 at pump.
 
/sixchall said:
To Mopar Virgin and 66fs, the exhaust changes are as mentioned. The engine, a 225 is basically stock configuration but I did add the late 70’s Super Six mods with Carter BBD 2 bbl an open element K&N air filter. Mopar elect. ign. with orange box, high output Accel coil. No other major internal changes. MPG’s anywhere from 18-23 on 87 at pump.
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The larger exhaust will be fine for him but you get extra credit for headers and true duals. I had a 170 with single exhaust and the larger pipe. It ran and sounded great with even higher mpg, but it had all the mods I posted plus more and a 4 speed. Nice mpg by the way.
 
Here are couple pics of the engine.
A8387229-37DC-4651-A7C1-93D41644D36D.png
CD285642-8D66-4573-8152-8CBE069FA73B.png
A8387229-37DC-4651-A7C1-93D41644D36D.png
CD285642-8D66-4573-8152-8CBE069FA73B.png
A8387229-37DC-4651-A7C1-93D41644D36D.png
CD285642-8D66-4573-8152-8CBE069FA73B.png
 
Get some compression. First and foremost. At a minimum open the exhaust to super-sized spec on the downpipe, 2.25 inch up from 1 3/8ish crimped stock crap.
 
halfafish said:
I would ditch the dual exhaust idea. It only adds weight and gives no performance improvement over a good 2.25-2.50" single exhaust. It sounds like you want a peppy driver with good mileage so one of the OD auto transmissions with some fun street gears would help a lot. Up the compression to somewhere around 8.5 static and 7.75 dynamic. That will let you run standard pump swill. Have the head and/or block shaved to reach your compression goals, then pocket port the head and install larger valves, 1.70/1.45 or so. Triple Webers are sexy as hell but complicated to tune and not likely to give a ton of real world improvement over a super six setup or a small 4-bbl intake unless you want to get real serious about the rest of the engine. Add a good free-flowing exhaust. @moparmarkk has a set of long tube headers for sale that should fit your car and would be an excellent choice. Depending on your goals I'd talk to Ken at Oregon Cam Grinding and see what he suggests for a regrind that would fit nicely with the rest of your parts. And hell yes, if you have the coin for it, a Torqstorm would be the bees knees but if you go that way make up your mind before you do the rest of the engine - a blown motor needs different parts and specs than a NA motor.
Click to expand...
Half I have to disagree. I have a clifford performance kit on my 225 with dual 2.5 its amazing!
 
Road/Rage said:
Half I have to disagree. I have a clifford performance kit on my 225 with dual 2.5 its amazing!
Click to expand...


Thanks for posting and replying ... That is EXACTLY the sound I'm aiming for. Can you tell me what your engine and drivetrain build spec is? That sounds like our friend's '69 Roadrunner and I didn't think I could attain that sound out of a /6 ... Very encouraging!!
 
There have been several useful recommendations offered that have the potential to do what you need. Given the criteria you mentioned, I'd like to offer my take. If I were in your position, here is what I would do.

I'd just clean up the block, give it a 0.030" over-bore, line hone the mains, tank it, etc. I'd clean up the crap in the ports and bowls, and give it a good 5 angle exhaust and 3 angle intake valve job. For the cam, I'd use Comp Cams 252 mechanical grind. Stuff like ARP fasteners, magnafluxing and so forth would help.

Next I'd get a Super Six 2-bbl intake manifold and 318 Carter carb. Refer to the Turbocharging articles I wrote for Allpar.com many years ago. I'd modify the exhaust manifold so the standard Dodge 2.2 Garret Turbo bolts right on. Plumb a 2.5" exhaust the entire path. Limit boost to around 8 psi or so. I started running into issues around 10 psi without more hardware (blow-off valve, intercooler, etc). This will give you excellent cruise MPG with Low-Comp 340 type power when you need it. This would be an excellent package for towing as well.
 
mpgmike said:
There have been several useful recommendations offered that have the potential to do what you need. Given the criteria you mentioned, I'd like to offer my take. If I were in your position, here is what I would do.

I'd just clean up the block, give it a 0.030" over-bore, line hone the mains, tank it, etc. I'd clean up the crap in the ports and bowls, and give it a good 5 angle exhaust and 3 angle intake valve job. For the cam, I'd use Comp Cams 252 mechanical grind. Stuff like ARP fasteners, magnafluxing and so forth would help.

Next I'd get a Super Six 2-bbl intake manifold and 318 Carter carb. Refer to the Turbocharging articles I wrote for Allpar.com many years ago. I'd modify the exhaust manifold so the standard Dodge 2.2 Garret Turbo bolts right on. Plumb a 2.5" exhaust the entire path. Limit boost to around 8 psi or so. I started running into issues around 10 psi without more hardware (blow-off valve, intercooler, etc). This will give you excellent cruise MPG with Low-Comp 340 type power when you need it. This would be an excellent package for towing as well.
Click to expand...

So much of this is way over my head but sincerely appreciate the input. I'm going to pin my neighbor down in the next 1-2 weeks and sort through yours and everyone's comments to get it in terms I can comprehend cause-and-effect. I am actually very technical in the high-tech sales word, but the combustion engine, transmission and electrical topics are not in my wheels-house, so I'm relying on the wisdom of others to help me through this all. In the end, I want something tasteful, highly unique and contains modern elements to bridge into an outcome in which I have a '60s car with some of the cosmetics and performance of the new MOPARs of the 2020s.

thanks again for your input !!!
 
Road/Rage said:
Half I have to disagree. I have a clifford performance kit on my 225 with dual 2.5 its amazing!
Click to expand...


@Road/Rage I post a thread-level reply to your comment, but didn't see a reply ... "Thanks for posting and replying ... That is EXACTLY the sound I'm aiming for. Can you tell me what your engine and drivetrain build spec is? That sounds like our friend's '69 Roadrunner and I didn't think I could attain that sound out of a /6 ... Very encouraging!!"

Hope I hear back from you about your build ... cheers!!!
 
So hermiston Oregon isn't what I would call flatlands lol there's lots of hills in Oregon to get anywhere or any surrounding areas around it. You're talking a little horsepower while running AC power steering and the likes... Unless you're hell-bent on a slant six doing all this and willing to spend more money than it would cost to do a V8 that would do this simply without breathing then that's the way you should go... I wouldn't go slant six for the purposes you're speaking of.... My-2...
 
Mopar Virgin said:
@Road/Rage I post a thread-level reply to your comment, but didn't see a reply ... "Thanks for posting and replying ... That is EXACTLY the sound I'm aiming for. Can you tell me what your engine and drivetrain build spec is? That sounds like our friend's '69 Roadrunner and I didn't think I could attain that sound out of a /6 ... Very encouraging!!"

Hope I hear back from you about your build ... cheers!!!
Click to expand...
Yes I will work up a detailed list and post it to you when I get it ready!
 
Yowee I have thought about a turbo but sure can't afford that, even though it does look nice and well thought out//// if I wind up getting a turbo in mine, it'll be a combo of home brew/junkyard sourced.
I've seen articles on that too.
 
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