Hello All, I am a new user here on the SS forum and enjoy reading all the posts. I am in the process of building my 64 Dart 4 speed. I have been at it for 10 years now, on and off. I am putting a Paxton blower w ~ 8lbs. on with a draw-through setup. I am using a Paxton carb adapter that bolts to the intake and then the carb bolts to the top (pretty cool piece of hardware). The engine has a stock but balanced bottom end, Offy intake, Clifford dual exh., 1.75" - 1.5" valves and 9:1 comp ratio. I also have an MSD BTM. Also an 8.75" posi with 3.55:1 gears. I would like any input anyone has. Specifically carb size, vacuum or mech secondaries, cam and anything else. This will be a weekend cruiser that I want as fast but not a pain to drive. I hope to have it ready for Reading in August?
Thanks everyone!

With the blower setup I would use a 600 Holley, but that is just me.

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Official Cookie and Mater Tormentor.

Are you doing a blow thru, or a draw thru setup? All Paxton/McCullough that I have seen, are blow thru. I am not sure if that blower likes fuel going through it. Draw thru is when the carb is on the inlet of the blower. Blow thru, is when the carb is between the blower and the engine manifold.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

This is a draw-through setup. The part that I am using to make it a draw-through is made by Paton and is made specifically for their blowers. The reason I didn't want to use a blow -through was because I will have to use a mechanical seconary carb and I was afraid that would be too much carb before the boost came on. I am not absolutely set into using a draw-through if I can get a blow-carburetor to work at all RPM ranges. I appreciate your interest and help. AZ

If the parts are made by Paxton, then I say, "go for it". They know more about their equipment then I do. I was just trying to point out a possible problem. I don't know enough about those blowers to give much advice.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Ok, I will try it out and write a tech article. I may end up going to a blow-through setup but I will try a draw though first.
Andy

For information about blow through carbs check out Here

OK, After reading up a bit on blow through vs draw through it seems that a blow through is the preferred method for a lot of different reasons. Pooling of fuel in the compressor side is one major consideration. Ease of install is another. My only main concern on a blow through setup is carburetion. With a draw through I can use a vac secondary carb without all the upgrades that a blow through would need. A blow through set up would require a mech. secondary carb which may not be tunable for low RPM use.
Two questions:
1) Has anyone had luck with a mech seconary carb on a slant with a blower/turbo?
2) Can a vacuum secondary carb be converted to a "boost secondary" if a carb enclosure is used? It seems that if the vac. diaphragm is blocked internally and a hole is drilled to the outside (on the actuating side of the diaphragm) that boost in the carb enclosure would open the secondaries. Let me know if this has been done. AZ

Hi Andy: We have several slant6 cars that are going to try to make it to Redding in August. Mike Williams from Orland is working on a turbo slant6 and Doug had his Buick turbo on his Lancer for testntune this past weekend. If you want lots of runs and lots of time for testntune, be at Redding in August. Redding is a small track and you can literally finish your run and go around and get in line for another pass. We got 15 runs this past weekend. It was great for testing the new motor in our car. Also on my virtually stock 65 Signet, I was playing with the throttle pressure and different shift points..I tried shifting it manually and then just putting it in Drive..I was trying to get consistancy. After the 8th run, I have it down "pat". Now just have to eliminate the dreaded Red Light...Redding was great...Mark is on your calendars...AUGUST 26-27 and remember, only $10.00 to race...Wayne in Chico

AZ,I have some friends with a turboed falcon that is a blow thru set up.They are only running a Holley 350 2bl with extensions and a circle track float because of the carb orientation on the motor.They have driven it on the street with 13-15lbs of boost.Motor is very responsive.

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not just another 5oh

Sorry about being so late to the discussion, I don't usually surf this section. I will have to make sure I pay closer attention next time.

I have read about a couple of people making a vacuum secondary 4bbl work with boost. From what I understand, you reverse the arm on the throttle blades so the canister pushes the blades open (instead of pulling them), and swap the canister spring so it is under the diaphragm instead of on top. I don't think it takes much more than that (see below).

WARNING: You have to make sure the throttle blades close when you let off or boost will hold them open. I know of one guy that made this modification and said it worked fine, until he got boost greedy and up it to 12 or 13 psi. At that point the boost pressure was stronger than the spring and he went for a ride.

So, this seems to work up to 8 psi (?), but above that you need to find some way to either force the blades closed or cut boost to the canister.

Be aware that I am just reflecting other peoples experiences, and I have not done this myself. I may in the future (which is why I have researched this and read other people's input), but haven't yet. If you do this wrong, people could be hurt, and I except no responsibility. This is a proceed at your own risk kind of deal.

If it matters, there was a turbo /6 at the Seattle Mopar show two years ago with a blowthru 390 vacuum secondary holley, so he must have made it work.

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'15 Chrysler 200S V6
'74 Duster 360, factory 4 speed car

Another thought would be a carter AFB (?) off a 273. I know people have used them on /6's with success, and I know they can be made to work with boost, and they have mechanical secondaries.

They're hard to find, though.

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'15 Chrysler 200S V6
'74 Duster 360, factory 4 speed car

If you're going AFB just use a 500 Carter or Edelbrock. For blow through use get the marine AFB accelerator pump seal, rejet and run it. This assumes you have fuel pressure rising in proportion to boost. I have an EFI pump and a Mallory bypass regulator for this very purpose.

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Joshua

Does the Carter deal with boost leaks at the throttle shafts better than a Holley?

I know that a Holley needs to be modified when the boost gets higher (15 psi?) by supplying boost from the top of the carb to the throttle shafts. Because of the pressure drop through the carb, the shafts see a slightly higher pressure and any boost leaks don't include fuel. I've heard of people fogging their engine compartments with fuel because of boost leaks at the throttle shafts.

The Studebaker in Hot Rod this month uses two 600 cfm Carters on his twin turbo setup, and the info says they are stock. I've read that the marine accelerator pump is the only modification needed, but I am doubtful that the throttle shafts don't need something.

I guess nothing says you couldn't mod the shafts, but it would be nice if you didn't have to.

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'15 Chrysler 200S V6
'74 Duster 360, factory 4 speed car

Although I have no direct experience (yet) leakage around throttle shafts that are in good condition is quite small. Also, AFB types have a lot more length of throttle shaft in the carb body so the leakage path is longer than with a Holley. I think fuel leakage from other sources is a much greater concern, but if you're worried you could use a marine AFB with grooved throttle shafts.

The Studebaker Chicken Hawk uses Studebaker R2 carbs that are meant for blow through use from the factory. The R2 engine was a Paxton supercharged Studebaker 289. The blown Studebaker Golden Hawk (first blown production Studebaker) used a Stromberg 2bbl inside a box and the very rare supercharged R3 Studebaker 304 put the AFB in a box.

Once the horespower level gets high enough the stock AFB needle and seat becomes a restriction. This likely won't be a problem for most slants, but many V8s have to upgrade. I have a pair of large needle/seat assemblies on hand in case I get to that point.

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Joshua