Inliners International Forums General Discussion Hi Performance 4 barrel setup change

Well I thought I had my 228 running as good as I could get it for the last 3 years. Its was a 228 bored .040, mallory dual point, 390 holley, and fenton headers. But recently I had some problems with my holley and could not seem to get it tuned right. So I decided to try the edelbrock 500 cfm. I also went from the autolight plugs to the AC R45 plugs. I also put a heat plate under my intake. Fired it up and Man what a difference. It feels like I got 40 more horsepower. Now I'm not knocking holley i've used them for years but this setup works great on my 228. Just a little info maybe someone can use.

That is good to know. BUT you made many changes at one time so can you realy say it was the Holley all along??. One of the main things that Really Helped you was the Heat to the intake. But many have had problems getting the 390 to run right on just about any L6. for what i have seen over the past many years.

Wow! That's amazing that you got the 500 cfm Edelbrock 1403/1404 carb to run good on a 228!

I have one on a 292 that I'm running unmodified out of the box and it's too much carb for my engine. The 292 is built similarly to your 228 (4 bbl, tube headers, HEI, hi-lift cam, .060 overbore, water heated Offy intake). But with 60 less cubic inches, a smaller bore and smaller combustion chamber I would expect that carb to be waaaaaay too much for a 228. Maybe I'm doing something wrong.

-mnagic mike-

I would almost like to disconnect my heat just to see how much difference it makes. I have heard that it mostly helps for cold weather running. And have heard it helps all around performance by others. I do believe the heat helped but i think my biggest gain was from the carb switch.

yea, ill 2nd that... i have the same carb and i just disconnected the secondaries all together on my 250... all it did when i got into the secondaries, was bog... much better now with just the primaries.

Yea I thought it might be to much. I had my fingers crossed when I fired it up. I then drove it awhile checked for any smoke (black smoke of course)and checked my plugs. They looked great. What funny. With my 390 my plugs were always had a lot of carbon. Even when tuned well. And now very minimal carbon. Oh and my edelbrock is straight out of the box no mods. I don't know how much hotter the AC R45's are then the Autolite 303's But that could have made a difference too.

Without bashing Holley I can speak from experience and say that Holleys are better for racing and Edelbrocks are better street carbs. For whatever reason the 390 Holley is harder to deal with than any of the other Holley 4150 or 4160 series carbs.

A 500 Edelbrock is not too big unless you are in the habit of driving around all day with your foot to the floor. It is all in how you feed it to the engine. The primary side of these carbs flows around 175-180 cfm which is not far off what a good sized Roch monojet flows. When set up correctly the secondary side should not cause a bog.

If you are having problems with the 500 Edelbrock take the time to read and understand the manual that comes with the carb. They can be easily set up to run on anything from a stock 230 to a modified 292. I've even run one on a 200 inch V6 Chevy that was all stock and it worked well. I am in the process of putting together a tech article for the 12PN based on dozens of Edlebrock installations over many years.
It picks up where the booklet leaves off and is specific for our inlines.

Hey Mike, Thanks for the extra input. Glad to to see others are having the same success with their edelbrock 500 as I have.

The Edelbrock Performer has air valves above the secondary throttle butterflies. These air valves are supposed to open gradually as the air flow increases. There are counter balance weights on each end of the air valve shaft. It's a one-size-fits-all design and not adjustable.
The Edelbrock AVS is a copy of the Carter AVS that Mopar used on their 340, 383, 440 in the late '60s.
This carb has a air valve spring that is infinitly adjustable so that you don't get that bog from too low air flow as the secondaries open.
Short of buying a new carb, you might locate a spare air valve to experiment with. Increasing the counter balance weight would be the best option, if there is enough clearance in the cavities they are located in. You might also try drilling holes in the air valve butterflies. This would allow a little more air flow before the valves popped open and produced any bog. I've never tried either of these ideas, but given it a lot of thought after seeming countless other people struggle with this problem. So, so much easier with the AVS.
I'm using a Carter AVS from a '70 383 Mopar.
Holley uses the vacuum secondary to prevent this bog on their street carbs.
A 200 or 228 inch may not have as much air flow to slam the air valves open and cause as much bog. My thinking is that if you can control the bog with the air valves, the jetting may not be that far off.

The condition commonly referred to as BOG by just about everyone is caused by a quick loss of vacuum that results in too much air with no velocity. Until there is enough air velocity through the secondary boosters to draw fuel you have the bog. Given the same size carb a smaller engine will be quicker to bog because the smaller displacement cannot pump air as fast as a larger engine can.

This is one of the reasons Holley developed the double pumper carbs that have an accelerator pump for the secondaries. The shot from the secondary pump adds fuel to keep the mixture from being too lean until fuel is drawn through the secondary booster nozzles by vacuum / velocity when the secondaries are slammed open.

The vacuum diaphragm that Holley uses and the air valve that Edelbrock uses do essentially the same thing in holding back secondary action until air flow velocity is near correct. It probably isn't wise for the average person to attempt modifying the air valve in an Edelbrock Performer nor have I ever found it necessary on a street carb that has been set up correctly. Correcting it is not as easy as changing the secondary vacuum spring on a Holley.

The new AVS Edlebrock has a secondary valve like the old Carters adjustment and makes fine tuning the secondary opening much easier.