351C carb choice

[Odmark]

Hello, separate thread again

I need some advice on carburator choice on my 351c.

This is the setup:

2v block bored 0.30

Stock crank and rods, pioneer rod nuts

Flat top pistons

Mildly ported 2V heads

Elgin street cam 512"/538"

Edelbrock performer intake

Thunder HEI dist with 8mm cables

Stock manifolds with dual 2 1/2" pipes

The carb that came with the car is an edelbrock 600cfm, will this carb be enough?

Or should i go for an edel pr holley 650? 650DP?

 

[Odmark]

Also, headers are going on the engine this summer. Worth mentioning.

 

[Manu Mach1]

I guess you have a 4V intake?

600 cfm is good enough. It's what I have on my 351C 2V heads.

 

[Canted 393]

Quick fuel streetslayers are really nice carbs for the street , nice bang for your buck. They come in 600 cfm or 750, you would fine with a 600.


http://www.summitracing.com/parts/qft-sl-600-vs/overview/

Here is a link for one, holley street avengers are really nice too.

In higher horsepower motors guys have seen a 25 hp drop on eddy carbs compared to holley based carbs.

 

[mrmach1]

600 cfm should be fine. I have a 715 cfm Holley and to be honest I think it's a little too much for my stock Q code.

 

[turtle5353]

Quick Fuel all the way.

 

[barnett468]

The carb that came with the car is an edelbrock 600cfm, will this carb be enough?

Or should i go for an edel pr holley 650? 650DP?

As mentioned, the existing 600 will be ok, however, they can be hard for a non experienced person to tune . If it was mine, i would sell the eddy and buy this exact carb below . I would then buy the optional secondary spring kit and try lighter springs until it ran the way I wanted it to . 99$ of the people just toss these carbs n but never set them up and 9 times ot of 10, they could increase their performance by changing to a lighter secondary spring providing the carb was not way to big too start with.

http://www.summitracing.com/parts/hly-0-80783c/overview/

and

http://www.summitracing.com/parts/hly-20-13

or

http://www.summitracing.com/parts/cmb-03-0100

You will also likely increase perf by curving the distributor timing so it s optimal for your particular combo.

.

 

[Mister 4x4]

Stick with the Edelbrock. I have a very similar set-up in mine.

Ensure it's tuned right, and it'll be a monster. ::thumb::

 

[Odmark]

Thank you for all the inputs! I think ill stick with the edel for now, and see if i can tune it

I managed to tune the 750 edel in my 455 olds very nicely, but that was quite some time ago.

Another question, hopefully i can get an answer here so i dont need to start another thread.

This cam im running, i will need stiffer valve springs right? I have a problem in finding them.

I would prefer to find some in sweden, but i cant even find in the states.

What inner, outer diameter and height etc. springs to i need?

And do i need dual? Never replaced valve springs before, even on the 455 olds i ran a pretty big cam but used stock springs.

And ive said it before, this is the most helpful forum ever! Thank you all

 

[barnett468]

Ok, you should be able to tune the eddy them . there is nothing really wrong with an eddy and they work quite decent when properly tuned, i just dislike them for a few reasons including that i simply dont like the way they look and have actually given a few brand new ones away.

As far as the cam goes, i would definitely run stiffer springs but we need all the specs or the part number to determine which ones are best . if it is a flat tappet cam, you can definitely use singe springs with it and there are several that will work on your heads.

 

[Odmark]

It is and Elgin E-954-P

I attached a picture of the manufacturers specs. It is a hydraulic flat tappet.

It is and Elgin E-954-P

I attached a picture of the manufacturers specs. It is a hydraulic flat tappet.

Edit: I found springs on a swedish website, will these work?

Part no: CRA 99839-16

Single spring

Specs:

Inner diameter: 1.086

Outer diameter: 1.500

Seat pressure: 90 pounds

Height closed: 1.875

Open pressure: 280 pound

Height open: 1.300

Coil bind: 1.130

 

[mustang7173]

Odmark,

Accord to Hot Rod Magazine, here is the classic equation for determining an engine’s airflow needs based on engine cubic-inch displacement (cid), max engine speed (rpm), and volumetric efficiency (VE) at peak engine rpm:

First equation:

CFM = 351 x 5500 x 0.85 / 3456 = 474.804 -

Second equation:

Accordingly, then divide 0.9 in. Hg / 1.5 in. Hg and apply the the square root to get 0.77459666. Take the 474.804 divided by 0.7745966 and you get 612.969 CFM. According to HRM, this would help to determine the real world recommended Carburetor CFM.

Since you plan on adding headers, this will increase the performance or air flow, so , maybe going to a 650 cfm may be prudent.

Here is the article for further review.

http://www.hotrod.com/how-to/engine/1408-how-big-a-carb-do-you-need/

Cheers,

mustang7173

 

[Odmark]

Thank you mustang7173, that is an interesting read

I got a tip on springs from mercurycougar.net, the comp cams 924-16 dual with damper.

And reading on the subject, i have learned that many that run close specs to my cam run these springs on their 351c.

So those should be ok right?

I have read that i should break in the new cam with the old springs and then swap, is this true?

 

[barnett468]

ok, xlnt.

i would run around 110 thru 125 closed and 270 thru 290 open with those springs . 90 closed is way too light.


you don't need to break it in with lighter springs at those rates, but if they were any higher i would consider it.

 

[c9zx]

Odmark, There are a lot of variables here, valve overall length (intake and exhaust are not the same), tip length, retainer height, keeper offset, and depth of the seat cut, spring shims/cups, and all will affect installed spring height. Installed spring height and the spring specs will determine seat and over the nose spring (open) pressures. I would wait to order springs until your machinist can tell you what the installed height is. The machinist, if they are familiar with performance engines, should be able to help you select the proper spring. Once you know the height you can contact the manufacturer of your choice for a spring recommendation. Valve weight and max RPM play a large role in spring selection. At moderate to high RPM, too low spring pressure has the potential to damage the engine more than a spring that is slightly too high pressure. Determine proper rocker arm geometry when selecting pushrod lengths.

If you use a proper break-in oil for flat tappet cams and follow proper break-in procedures, you can use the new springs to break-in the engine.

Chuck

 

[barnett468]

oops, post correction.

"i would run around 110 thru 125 closed and 270 thru 290 open with those springs."

it should be

"i would run around 110 thru 125 closed and 270 thru 290 open with that cam."