Will runnin boost with 500cfm hurt anything?

[Anonymous]

Actually.....the model 1946 Holley 1 bbl is very easy to "Change things"

And if you are scared of drilling a carb, then FORGET turbos. Even Holleys need to be drilled to be "right on". The nice thing is, drilling power valve channels is very easy, and NOTHING to be scared of!!!

ESPECIALLY on a motorcraft, they are super easy to reach because the PVCR (power valve channel restrictors) are on the bottom of the carb, under the power valve. WAY easier to get at than on a holley!! You don't even have to take the carb apart, just four screws! (pics to follow soon)

The only time the PVCR flows fuel is when you have your foot into it.

If you try to make the car run rich enough under booost by just changing jets, you will be WAY too rich under cruise conditions. You don't want that. You only want to be rich when making power.

1.21" carbs can be found on most all V8 from the 70's. I usually buy them for $1-2 a piece at the scrap yard, so I can have extra jets to drill out. If you ever have questions tuning them let me know.

 

[Anonymous]

Here is where you find carb size, on the side of the float bowl. this one is 1.08"

Here are the power valve channel restrictors. If you drill these, you will have enough fuel under boost, without having to put in such large jets you only get 10 MPG!!

 

[Nathan289]

Linc,
Thank You for the info.

I'd rather swap stuff out to tune a carb because its a little more accurate than drilling things. If I drill too much I have to scrap the carb and start all over.

I was kinda of hoping to be able to run a 350 like Does10s is.

I ordered 3 books today. The Ford Falcon 6 or "The Bible"
Maximum boost and Turbo Chargers.
Who ever posted the link to the book store in the other post got a bad deal if they bought books from that place.

How are you able to drill at that angle and be accurate or is it just look like a funny angle because of the picture?

I think I have an old Motorcraft Carb or an autolite from a 66 mustang I owned that had a funny six cylinder with extra cylinders.

Carburators I can tune and rebuild. modifying is alittle different for me though.

I'm sure I'll have many questions. if you dont mind me asking everynow and then.

Thanks,
Nathan

 

[Anonymous]

Linc,
1) Thank You for the info.
2) I'd rather swap stuff out to tune a carb because its a little more accurate than drilling things.
3) If I drill too much I have to scrap the carb and start all over.
4) I was kinda of hoping to be able to run a 350 like Does10s is.
5) How are you able to drill at that angle and be accurate or is it just look like a funny angle because of the picture?
6) modifying is alittle different for me though.
7) I'm sure I'll have many questions. if you dont mind me asking everynow and then.

1) You are welcome, any time.

2) Go back and read again, YOU STILL HAVE TO DRILL A HOLLEY's PVCRs ALSO! Or with changing jets only you WILL be too rich at cruise, period. This is something you just need to accept.

3) Who told you that???? There are always ways to fix stuff like that. I have soldered brass jets shut and redrilled them, and also used epoxy, too.
If you ever get to the point like I have, where you have mofified so many carbs you don't remember them all, your fears will be gone. If you do somehow think you screwed something up, I'll tell you how to fix it. You need to get over your fears.
AND running a Holley 350 DOES NOT necessarily get you off the hook from drilling! (if you want it to be RIGHT, or not a drag car only)

4) I like to not only try new things, but there are features about the Motorcraft carb that make it a better candidate for blow through than the Holley. I think it is the "Best Kept Secret".
(Shhhhh.....just you and me keep it to ourselves, let everybody else waste their money on Holleys!)

5) The angle just looks funny because of the way I am holding it.
It is a pretty clear shot to drill.

6) You are not afraid to try to make a turbo set-up by yourself,
but you are scared to drill two holes a little bigger?? :roll:
The Folger's is brewing.

&) Good questions so far. I always welcome good questions. You are a little scared to get your feet wet, but I guarantee that once you start trying to get you feet wet you will get over it. Everybody starts somewhere, right??

 

[Anonymous]

YOU STILL HAVE TO DRILL A HOLLEY's PVCRs ALSO! Or with changing jets only you WILL be too rich at cruise, period. This is something you just need to accept.

 

[Anonymous]

A numbered drill bit set is needed to do any drilling. This one from harbor freight has bits from 1 through 60 and sells for $20

http://www.harborfreight.com/cpi/ctaf/D ... mber=34627

You will only be needing drill sizes from 60 (smallest) to about 40 something, but most numbered sets have all 60 bits.

This particular 1.08" motorcraft carb came from an auto parts store, and was listed as for a 1968 or 69 F-100 with a 302. I didn't pay anything for it since it was a warranty exchange. The one that got traded in was for a 1970 F-100 and was 1.21" venturis, go figure.

These PVCRs are #56 drill bit. To go larger needs a smaller number, like a #55 or a #54, #53, etc.

 

[Anonymous]

OK, here is another motorcraft, this is a 1.21 off of a mid 70's something or another..... I bought it off ebay for $6



It has TINY PVCRs, at only .0292" (that's a #69 drill bit)

(What do you think of that #80 bit, at only .0135" !!!)


Now, there is a reason why they are so small..........
This carb has TWO enrichment circuits!! The power valve circuit, and some weird spray jets in the top of the carb.

They are in the choke horn itself (red arrows).....and are fed from the brass tube that drops down into the float bowl (green arrow)

I would reeally like to speak to the Ford engineer who came up with that idea. I really can't come up with any good reasons for it (why there? Why not add fuel at the venturi like all other carbs? Why so crude?).

I have watched fuel pour out of these things (fuel jets in the air horn) on the dyno, and they look like two big accelerator pump jets, - - - - just two big streams of fuel. It seems so crude and primative, in an era when everyone was so concerned about emission (But I guess not gas milaege).

As as far as adding fuel under full throttle goes, I guess it does work, but there has to be a better way, I would think.

It doesn't matter, when the choke horn gets milled off, that feature will disappear along with the rest of the metal shavings and fuel enrichment will come from the drilled out power valve CRs only.

(Oh, and if anyone needs carb mods done, I can help.)

 

[Nathan289]

Linc,
Thank you very much.
I'll be reading lots of books when they arrive so I wont have any dumb questions.

I'll have to pick up the numbered drill set as mine dont go that small.

Do you have any recommendations for a book that would help assist in rebuilding the 250 I6? Other than the "Bible"?

I wanted to run forged pistons or atleast something better than Cast pistons without ordering special pistons.
I havent spent alot of time looking yet, but was wondering if one could bore a 250 .032 over to get a 4.00 bore and order some stock 302 pistons?

Just wondering. i need to start researching I'm sure this has been covered before.

Nathan

 

[Stubby]

Linc

The tube on the Motorcraft carb reminds me of the tubes on the secondaries of a Quadrojet. Do they pick up fuel only or a fuel and air mix? I would ask if it is an emulsified mix but I would probably mispell it
I have never played with a Motorcraft.

 

[Anonymous]

Nathan,

You will have to bore a 250 MUCH LARGER than .032"
Check your decimals.... .320" is over 5/16" (.3125") overbore!!
It'll never happen.

A seller on eBay named j*s*s* has forged 200/250 pistons. I bought one set at STD from him and another set at .020" from another seller.


Stubby,
The brass pickup tube shoots straight gas, no emulsion, Two solid streams.

It only happens at very high throttle openings.

After looking at the carb again, I might be able to keep them If I don't mill too far down. They might come in handy when on boost, you gotta have a whole lotta fuel flow when on boost.

 

[Anonymous]

Do you have any recommendations for a book that would help assist in rebuilding the 250 I6??

I'll scan the pages from chiltons manuals I have.
PM me with an email address that can handle large .jpgs

 

[Nathan289]

Linc,
I can get the Chiltons dont need to scan them.
i was wondering if you knew of any other books.
There are tons of them for the bent 8s just thought I'd ask if there were any for the sixs.

Thanks again,
Nathan

 

[Nathan289]

Linc,
Went to the wrecking yard today.
Picked up a motorcraft 1.21 today. Damn this is the same carb that was on my mustang. I have a modified one at my parents house in the garage somewhere.
The wrecking yard wanted $15 a carb otherwise I would have bought a 1.08 just to play with. I also saw a weber 5200?? progressive 2 brl too.
I grabbed the 1.21 motorcraft off an 83 f-150 with a 351W. Suprisingly there isnt a bunch of smog crap on this carb. Just what looks like an idle control solenoid. It still has the build tag on it, though its been rebuilt once.

Nathan

 

[Anonymous]

Sounds like you scored!