Okay, I have a Pontiac 350 and I may think about some sort of blow through. I have a 750 DP which is too big for the engine. Engine mods are cam, 44bl stock iron intake with cutting work and an adapter. Fueling will either be an electric pump in a surge tank or a boost referenced mechanical pump TBD. I'm just wondering if I could make this carb work in such a combo or if I need to start downsizing. Obviously I'd rather have a 450ish carb but it may be making the most of what I have.

 

I'd give it a shot with some vent extensions.

 

what Mnlx said

 

super small main air bleeds help too depending on the overall combo and what it wants

 

drilling out the main wells and passages to the boosters was worth a full point richer in AFR with no other changes (for me at 10 lbs on E85, 650 CFM on a stock 305)

just nab a set of spare metering blocks from a buddies parts stash and start whittling

Im in the Oshkosh WI area north of Milwaukee aways....if I remember right you are in the Chicagoland area....if you ever get up this way I have some parts carbs you could nab some stuff off if you want.

 

My sister's in Wausau, I should make it a point to stop in next time I see her. Usually have the fam in tow so it kind of makes that fun harder.

Will VS metering blocks work? I probably have a set of those here. If not, I'm not too concerned about making permanent alterations to the carb. I got it in a steal of a deal with a 383, so it's not going to be the end of the world if I have to drop parts into it.

I was playing around with fitment, and decided that there's no way I'm getting a down pipe on the driver's side due to the steering shaft. Seems like a single will be the way to go. I have a T66 on center with a .69 turbine, and think that's probably going to be the best match I have. For an engine that will likely be lucky to make 200HP I think it will be plenty. If I can find a decent Pontiac 6 bolt exhaust manifold for the driver's side, I'll probably just run that there then a GN style log on the passenger side. Due to the way these are set up, the clearances are tight at best.

 

I have converted secondary VS blocks to double pumper with some careful drilling and using brass set screws as plugs (taping shallow so they seat like a pipe plug, accel pump channel)....ive also used primary metering blocks as secondaries on my 4 corner idle stuff....I just square all the metering restrictions up if the venturies are symmetric

Since you arent after big boost or E85 I dont think you will have much issue with a 750 CFM on a 350. Drop you MAB wayy down and plug most of the emulsion jets and I think you will be fine. I might even have a spare 650 main body laying around...I havent rustled through my parts stash for awhile since I havent had a new carb project for awhile.

 

So, I did a thing and yanked this carb apart. Probably against my better judgment, but we'll see. Right now my parts list consists of the below:

Holley rebuild kit
116-3 float nitrophyl
116-10 jet extension kit
Holley tuning kit (36-181?)
6-518-2 .120 needle/seats
50cc accelerator pump
JB weld
vent tube extension tubing

This is pretty strictly from the Hanger 18 stuff. Any other stuff I should be looking to toss in? I have a rear PV delete already in the carb, so that's good. My shooters are 29 primary 31 secondary while jetting is 71/80 P/S and a 6 PV. With Vent tube extensions, how much should I be looking to set this up initially for tune?

On another note, the main body seems to have all kinds of burrs and sharp edges on it like the finishing is pretty poor. I'm guessing that's pretty normal? Should I get some 1000 grit and knock the high spots down on a piece of glass?

 

I havent needed to do a 50cc accell pumps on a GAS carb...but your results may vary

Foam floats are required

I dont think you would need a jet extension kit if it isnt a drag car....just pay attention to the ID of them....they also mess with tuning a bit since you extended the main well.....think pipe flow pressure loss.

Im not familiar with the "tuning kit"

0.120" N/S will be fine since your power goals are low.....I typically go right for the 0.150" viton tipped stuff the BLP has

Make sure you have a numbered set of taps/drill bits / pin vise (harbor freight garbage works fine since the zinc alloy and brass is easy to drill, amazon has the 61-80 bits) on hand and some brass set screws...I use them for the PVCR's, air bleeds and emulsion jets.....mcmaster-carr has the brass set screws...I was never able to find some local to me.....IIRC i used 10-32, 8-32 and 6-32

Some other items I like are the nylon washers/seals for the N/S adjustments and float bowl screw washers since I always seem to tear the fiber ones.
Get some spare metering block and float bowl gaskets too (BLP again)

your main body surface sounds normal.....but knocking it down a bit wouldn't hurt



When making high load changes make sure you primary metering area equals you secondary metering area.....use the IFR and PMJ to get your cruise right and your PVCR and SMJ to get your high load settings right.....PMJ+PVCR~=SMJ on a symmetric venturi carb.....adjust corners as neccessary for distribution.......high end lean out or enrichment handled (hook correcting) by the emulsion bleeds and MAB.

Vent tube extension effect will depend on your bonnet and charge pipe configuration......I actually have a couple homebrew E85 carbs that do not use power valves...just jetting....only relying on vent tubes, MAB and emulsion tuning for boost enrichment.....~71 mains squared......15:1 cruise/11:1 (gas scale) at 12 lbs of boost....but this is due to the unusual bonnet configuration.

 

Cool, so I'll just rebuild with what's there. Some of the stuff indicated they had stiffer arms. Do you change the cams typically?

I'll probably get the kit anyways and set them aside, since the kit includes a solid float.

That's strictly a jet kit.

Buy once cry once, and it's not really any different in price. Thanks for the heads up.

Any pics of the set screws/where you're putting them? You've probably got a build thread somewhere I haven't seen.

Yeah, those seem like sundry items. Should I just be getting gaskets instead of a rebuild kit? Kind of the way I'm leaning.

I think I've got some reading ahead of me on this one. I'm gathering you're plugging and redrilling in a lot of cases to resize? My goal is to run the bonnet pretty well pointing to the front of the car. In the setup that's available to me I don't see this as being too much of a challenge. Also, I'm debating an intercooler initially but regardless chances are that the pipe's going to be straight for only a foot or so before hitting a 45 or 90. Not too big of a deal I hope?

 

I really havent had to mess with the accell pumps much on gas carbs....if it ran good N/A it will be ok blowthrough.....having said that I do have a pump cam kit.....nozzles I just drill out if I have to since I have parts carbs.


the ones that the needle is pointing to are the emulsion bleeds.....I usually end up having most of them plugged. I use brass set screws as plugs and for making my own metering restrictions...

PVCR's are in the power valve hole

IFR's are in the idle channel in the picture by the guys thumb.....they can also be down low below the emulsion channel or internal inside the idle well......depends on the carb

the air bleeds are in the main body near the accel pump discharge nozzles....again I just drill them out and tap for 8-32 set screws (drilled to what ever works best...somewhere in the low 0.020's should work for the MAB's on your mild set up, some work well plugged off too).

Really yours is mild enough....probably just a larger PVCR and larger SMJ (secondary main jet) with the lower emulusion holes plugged should get you there.


Kit vs. piece together is a personal preference .....really by the time you buy everything needed you replace everything in the kit except for the lower main body to throttle plate gasket, metering block/float bowl gaskets and accel pump gaskets

For your first shot at this it would probably be a good idea to mix in some race gas with your premium pump fuel for insurance.....that way if it goes lean under a bit of low boost you shouldnt hurt anything....double check the SG of the race fuel compared to pump because it will likely be higher causing it to run a fuzz richer than pump gas.

#ad

 

Two or three things, I'm far more ready on the carb probably than anything else like a turbo, headers or engine but here goes:
1-The 1/8 long screws are the ones to get right?
2-I enlarged the PVCR to .5905 (1.5mm) Not sure if this is enough, figure it's easier to make the hole smaller than bigger though.
3-I have 2 Emulsion holes, one that is between the bottom most and next one up roughly, and then the fourth one up as well. I have the option of using a block with no emulsion holes as well. It sounds like just plug the bottom one and good to try it.
4-lastly, what tap are you using for the plugs? Is it a bottoming tap, or a starting tap or the one that's in between? I still need to order from mcmaster and figure I'd hit it at the same time.
5-I got .15 Steel needle/seats. Did I screw this up badly? Guessing likely. Should I consider just getting the Viton ones, trying to lap these or running em and seeing what happens?

 

1. yes or the shortest ones you can get for the size.
2. You will likely have to go larger.....but I wouldnt until it is on the vehicle and you have some data to go by for making changes
3. Do not plug the kill bleeds (top of the "dog leg"). I would plug the bottom emulsion bleeds..these are small enough i believe 6-32 is required here.
4. Im just using a normal cheap tap (not a bottoming tap). You could use one if you wanted....I just continued tapping until I could tighten the set screw snugly and the top of the screw be flush or slightly below the gasket/channel surface.
5. One of the carbs I did is still running fine (3 years later) with the titanium N/S...however, I do prefer the viton units since they are much more tolerant of garbage in the fuel.

Here are the ones I like in the 0.150" size:
http://blp.com/cart/index.php?main_page=product_info&cPath=65_108_268&products_id=578

Id like to try these too (in the 0.164" size)..but I am afraid of them sticking:
http://blp.com/cart/index.php?main_page=product_info&cPath=65_108_267&products_id=577

 

Hey you still around Oshkosh? I'm moving to Nashotah.

 

I do still live near Oshkosh