Stock manifold-carb question

[62 mark]

I have a stock Chevrolet cast iron 4 BBL. manifold that I want to run on my 283, bored .040 over, 305 heads,street cam. The manifold is a 327-300 hp version from the early 60's that accepted a Carter carb. That is what I want to run,however, the primaries on the manifold measure 1 9/16. None of the newer Edelbrock carbs seem to have that size primaries, only 1 7/16 . I would like to run a 500 - 600 CFM carb. My question is,can I bolt the smaller primary size carb onto my manifold with no flow problems ? Has anyone here run in to this?

[geezer#99]

That’s a non problem.
Bolt it on and go.
Maybe!
Are you sure you want an eddy carb?
You’ll likely need a heat spacer and a fuel regulator too.
Eddy carbs don’t like heat (boiling fuel) or fuel pressure over 5 psi (flooding).

[62 mark]

I am planning on using a phenolic spacer, and blocking off the heat exchange

[Dead Parrot]

As long as the carb holes are smaller then the manifold holes, good to go. If your manifold is a dual plane, make sure your spacer keeps the separation between sides.

I have a 1405 on mine, never used a regulator and never had an over pressure problem. I did verify the float levels before installation as they are commonly out of spec as shipped. Standard disclosures, sample size of 1, your results may vary, etc.

[geezer#99]

Originally Posted by Dead Parrot

As long as the carb holes are smaller then the manifold holes, good to go. If your manifold is a dual plane, make sure your spacer keeps the separation between sides.

I have a 1405 on mine, never used a regulator and never had an over pressure problem. I did verify the float levels before installation as they are commonly out of spec as shipped. Standard disclosures, sample size of 1, your results may vary, etc.

Some do, some don’t!
Just want him to be aware of a potential problem.

I ran a dual quad with two afb’s. Had pressure problems until I bent up some 5/16 inch fuel line for them. Smaller lines and multiple bends drop or control the pressure.

[crazy longhorn]

Set it & go....you could run a 1406 (600, elect choke) on that app.....the 500 cfm carb would be a better fit on the small mill . That said, I do agree with the other gezzer....Fuel pressure, is critical on these carbs.....shorthorn

[cadillac_al]

I have never got a mechanical pump that would out out more than 5 psi. I don't know where you guys get them.

[geezer#99]

I’ve run across 4 in my time,
Two made 7 psi, one 9 psi and of course the 11 psi 62 Pontiac superduty dual quad 421.

Think about this Al.
If fuel pumps never put out more than 5 psi, why would Edelbrock market one that’s set at 5.5 to control a pressure problem in their carbs.

[62 mark]

Thanks for all the helpful info!

[cadillac_al]

Originally Posted by geezer#99

Think about this Al.
If fuel pumps never put out more than 5 psi, why would Edelbrock market one that’s set at 5.5 to control a pressure problem in their carbs.

I think it's just business; an accessory to accompany your new Eddy carb. I have had a lot of fuel problems the last 10 years due to leaking sending units and a bad fuel pump cam lobe so I have done a LOT of fuel pressure testing in that time. It's always nice to test fuel pressure to rule out any pressure problems and verify that you aren't over 5.5. I just haven't found one yet. If you get a pump that puts out over 5 psi, I would just try another one and chances are it will be below 5 psi.

[geezer#99]

Or just use a better carb like a quadrajet (good for 7 psi) or a Holley.

The higher pressure, maybe it’s a Canadian thing eh!

[Dead Parrot]

I think some of the problems are due to the source of the fuel pumps. China can make some really good stuff if QC is high. But when your China made fuel pump costs $17 after shipping and store mark up, how good can you expect QC to be? I may have been lucky. But do check your float levels before you install your carb. Mine were off out of the box.

I suspect many of the fuel pressure problems were from folks who didn't check float levels first. If the fuel level in the carb is too high to start with, you have very little tolerance for over pressure from the pump.

In case you didn't know, most old school vacuum gauges have a 2nd scale for checking fuel pressure off an old style fuel pump for carbs. NOT for fuel injection.

[SunSoaked]

I just put my dependable Eddy 1406 back on my 350 to replace the horrible POS Holley Sniper that costs $1000. Couldn't be happier!

[geezer#99]

Originally Posted by Dead Parrot

I think some of the problems are due to the source of the fuel pumps. China can make some really good stuff if QC is high. But when your China made fuel pump costs $17 after shipping and store mark up, how good can you expect QC to be? I may have been lucky. But do check your float levels before you install your carb. Mine were off out of the box.

I suspect many of the fuel pressure problems were from folks who didn't check float levels first. If the fuel level in the carb is too high to start with, you have very little tolerance for over pressure from the pump.

In case you didn't know, most old school vacuum gauges have a 2nd scale for checking fuel pressure off an old style fuel pump for carbs. NOT for fuel injection.

Some of the problem of flooding comes from people setting the float level to spec. Some just assume the new carb is set good and bolt it on.
Setting the float to spec works good at sea level. When you start getting up over 1000 foot elevation you need to lower the float setting a bit.

[68Gold/white]

Originally Posted by 62 mark

I am planning on using a phenolic spacer, and blocking off the heat exchange

If your intake has 2 holes in the carb base gasket area, you need to block them off, You can tap them for a pipe plug or use a straight tap and cut the end off 4 bolts (grind a slot in the tops for installation...

Edelbrock carbs are widely used here, I do no recommend them. I would use a 500 if possible, although the 600 is cheaper (every autozone and HO'Reilly's has one in hand). There can be things that need to be done to an E-Carb to make it usable... many due to manufacturing abnormalities... If you use one, beware, hope you get a good one...

[AcampoDave]

500 cfm Eddys are only available jetted for perfomance. 600 cfm can be had with m.p.g jetting or perfomance. I know lots of folks around here are down on the Eddys, but my friends and I all have decent results with them. Sure better carbs are available but for the money I think they are a good value and they are easy to tune. The 500 on my 283 has been leaned out a bit and it sits on a 4 hole phenolic 1" spacer. Before I added the spacer it had a slight bog as the throttle just began to tip in. The spacer cured that. I also use no fancy pressure regulators and I run a mechanical pump. I've logged many a happy mile with mine from sea level to over 9000 feet.