Carb adapters, missed bOres and proper air flow

[Guest tony78_280z]

What I got is a Holley equal bore carb on top of a (stock) spread bore manifold. This set up, of course, uses an adapter that adds about 1/2 an inch to the height. If one were to look down through the carb you would see that the spread bores of the manfold do not line up (very well at all) with the equal bores of the carb. And this HAS GOT TO interfere with easy fuel flow. Particularly with the accelerator pumped gas (it hits and collects on these mis placed bores) and I know my accelerator pump is causing the engine to bog on sudden throttle.

 

What I'm thinking about doing to solve this problem... No, not replace the intake manifold as I do not intend to change the motor specs any more. I instead am thinking about grinding off the spread bores from the manifold so they are no longer in the way. The Carb adapter would still bolt to the manifold and the carb to it's adapter but without the bores getting in the way.

 

Does anyone for see any problems with this? Has this ever been done before? How much of an improvement in proper air/fuel flow should I expect to see?

 

Thanks

[datsunlover]

My engine builder friend is going to do something similar (ford engine, but basicaly the same issue) and he's thinking about just hoging some material out of there, and basicaly 'port matching' the intake to the carb. IMO it would work..

[jbk240z]

Yo,

A friend of mine has done this in the past. He had a cast-iron spreadbore manifold and a Holley 600 square-bore. He simply ground out the offending pieces and it seemed to work much better. Good luck

[Guest tony78_280z]

Thanks for the replies.

 

"ground out the offending pieces and it seemed to work much better"

 

This is encouraging. Talking off all the crap on the manifold and removing it just to put it all back on sounds like a chore, but in my opinion it has got to be done to improve performance.

 

Thanks again =)

[quicker240]

really,IMHO,for the price of a manifold these days,85-100 bucks,that actually is made for the carb you have,why not just get the right one?your gonna have to take everything apart anyway to do the job,and the right manifold will work better,probably substantially.And as a kicker,you would'nt have much trouble gettin 40 or 50 bucks for your used one,and the new one will be shiney and clean!I say get the right one,but hell,everybody has an opinion,right?

[Guest tony78_280z]

Update

 

Removed the intake, Ground out the offending parts, and was left perplexed about a new 5th hole in the intake, The EGR channel. I'm not using and EGR, and they aint got emisions test here so...

 

My cousin and I used to played around with a forge and pouring metals into sand molds. We used to make sand mold poured hilts around our leaf spring hammered sword blades. Conan would have been impressed. So we fired up the old forge and began to melt some alluminum. I made a sand mold inside the intake manifold so the alluminium wouldn't run everywhere except into the one hole I wanted filled, and a slight ridge there in the center of the (very large now) intake hole. After the alluminium cooled we blew the sand out and ground down the aluminum blob tho the desired ridge shape.

 

Reinstalled the manifold and fired it up. It runs better than it ever did. It was a MAJOR improvement.

 

Before you make a comment, yes I am sure all the sand was blown out before reassembly. And no the Aluminium didn't pour into or clog anything that I didn't want it too. I wonder if I'm the first person to fill my intake with sand and pour molten aluminium into a manifold.

 

The only problem I had was the gaskets didn't seem to match up exactly. Yes I had them right side up. I supose they are some kind of universal 350 gasket set. But I used forma gasket so hopefully it'll be alright. Only time will tell I supose.

[Pop N Wood]

Sounds like a pretty good way to block the EGR. Most people just bolt on a flat plate, but your way would have to look more factory.

[Guest tony78_280z]

I wouldn't say it looks factory =) But it is effective.

 

The block of plate only blocked it on the outside of the Intake Manifold. On the inside of the manifold, right under the carb, there is a hole that connects to the EGR. This I was afraid would fill full of gas from the Accelerator Pump and cause problems later (a backfire and BOOM!) So I had to plug this hole.

[BrandonsZ]

If it works it works. What was wrong with the spread bore? They tend to get better gas mileage, although they do have a reported problem with uneven charging for all the cylinders.

[Guest tony78_280z]

Well, my spread bore that came with the motor was shot... Lets just call it "fuel pressure problems". =) And I had the holley equal bore. I think I'd rather have the spread for gas millage purposes but I had the holley, modified the intake which cost me only the gasket, sealant & labor. I went the cheap route =) Besides I do like the customizable aspect of the holley. Now I need to add a 50cc pump and .... your right. Should'a got another Quadra.

[Guest rick458]

How well does an adapted 4BBl work on a 2BBl manifold?

I plan on opening it up as far as the bolt pattern will let me

[jbk240z]

Yo, This has been tried before and usually doesn't work to well. You would be much better off getting a Holley 2 barrel, they work really well. Good luck.