Re: Edelbrock AFB blow thru modifications- pics - vid

I know.

 

Re: Edelbrock AFB blow thru modifications- pics - vid

what is your fuel system now?

 

Re: Edelbrock AFB blow thru modifications- pics - vid

Gapped the plugs from .040 to .030 and turned the boost back up to 11. Still went "lean" but not as bad.

Put the boost at 8 and its fine. Before anything north of 7psi gave me an issue. Ill inch up a little next time I get some gas money and see if 9 or 10psi is possible.

Otherwise the carb is set pretty damn on target.

 

Re: Edelbrock AFB blow thru modifications- pics - vid

Are you able to watch fuel pressure while driving?

 

Re: Edelbrock AFB blow thru modifications- pics - vid

No that's the big what if right now. Keep forgetting to grab some capillary tubing to hook up an old FP gauge to see for sure

 

Re: Edelbrock AFB blow thru modifications- pics - vid

You are shooting in the dark.

 

Re: Edelbrock AFB blow thru modifications- pics - vid

Quoted for Truth

 

Re: Edelbrock AFB blow thru modifications- pics - vid

haha. At least he's got a WB!

 

Re: Edelbrock AFB blow thru modifications- pics - vid

Cant argue that point. Lol

 

Re: Edelbrock AFB blow thru modifications- pics - vid

I have the solution to your Hi boost lean problem. Take your rear boosters out and open up the hole in the center of the large brass tube on the bottom side. I actually switched to an old booster out of a 4327 AFB that has no tubes. ALOT of the older afb's had none. Your current booster can't flow enough fuel through the small hole .Dave

 

Re: Edelbrock AFB blow thru modifications- pics - vid

Hmmm ill have to dig through my tote of carb parts and look for those

 

Re: Edelbrock AFB blow thru modifications- pics - vid

Ill take a look at that thanks

 

Re: Edelbrock AFB blow thru modifications- pics - vid

Where am I drilling exactly?


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Re: Edelbrock AFB blow thru modifications- pics - vid

usually the bottom of that large brass tube is rounded and has a restriction, I don't think that's it

 

Re: Edelbrock AFB blow thru modifications- pics - vid

Damnit.

 

Re: Edelbrock AFB blow thru modifications- pics - vid

Shouldn't the carb size still be chosen for the baseline engine without the turbo? I know a Carter 625 is adequate for my non-turbo 454, with mild porting in the exhaust ports and a Comp 270/276, 218/224, 112+2, 510/510 HR cam, at 4500' elevation, and a 750 carb isn't in the budget. Bad enough having to buy an electric 255 pump and a boost-referenced regulator for this newer block not accepting a mechanical pump. But better than buying a pre-roller block and buying retrofit roller lifters. You don't want non-rollers with boost.

 

Re: Edelbrock AFB blow thru modifications- pics - vid

The capacity of the fuel system is also needing consideration but yes, as far as air flow, it is the same size as what it would run NA. Also, I dont know why you dont want an elec pump, they are so much better than mechanical (cam pushrod style) and you dont have priming issues when it sits for awhile.

Last, a flat tappet cam is just fine with a turbo but a roller is always better. Has nothing to do with a turbo or not.

 

Re: Edelbrock AFB blow thru modifications- pics - vid

Yes and yes

I wanted to do it the hard to way to learn more about manipulating things to work outside their intend purposes

Btw no more blow thru carby for me. Yanking the whole bish out this week. And swapping in a toyota 4.0 v8

 

Re: Edelbrock AFB blow thru modifications- pics - vid

non-roller cams/lifters really hate lots of contact pressure, and the stiffer the springs, the more the contact pressure. But turbocharging requires higher-rate valvesprings if you want it to keep pulling to the same redline / WOT upshift RPM as non-turbo. For example, if you have a build that pulls 6000 RPM with a 2" intake valve and 100 pounds of seat pressure, and you add 15 psi of boost, and you still want it to pull 6000 RPM, you're going to need 130# of seat pressure. 30# on the seat isn't the big deal. It's the100# over the nose that ends up with wiped lobes and concaved lifters. With rollers, especially solids, you can run all the spring you want and never lose a lifter or a lobe. For the last 2weeks I've been thinking the 600 seems too small. Maybe put it on a 350?

 

Re: Edelbrock AFB blow thru modifications- pics - vid

Anyone still messing with these?

I've been prepping my Edelbrock 500 for boost, installed the marine accel pump seal and ordered the TQ floats, but I've been trying to get it tuned in N/A first BEFORE I put the turbo on, so I have a good starting point. I'm having trouble with it already.

The engine is a 300ci Ford six, Offy C single plane, Comp 268H and springs, dual exhaust manifolds, recurved distributor 32*@3000 all in. It makes 200whp/300wtq.

With the carb stock, the primaries were 12's in cruise and 11s WOT. 83 primary jet fixed that. Now 14.5 cruise and 12.5 WOT on the primaries only.

Stock secondaries would spike 18-20AFR around 2500 and maybe get to 15AFR by 5000. After upping the secondary jet to a crazy .125", adding lead to the air flap door, plugging the secondary early feed air bleed, removing the early feed tube swedge restriction, opening the main high speed air bleed slightly and even enlarging the emulsion tube high speed air holes, I finally got the AFR semi sane. 15s AFR around 2500-3k richening to 12.0-11.8 at 5000.

I just changed the secondary jets to .106" and raised the float fuel level to try to flatten it out more, but it's basically the same 15AFR to 11.8AFR

I'm looking for suggestions since this is the best Edelbrock tuning information I've ever found and I'm planning on adding a HE351CW as soon as I can figure the carb out.

Here's a dyno chart that shows the AFR problem. One pull is from 1700 and the other from around 1k. It's the same now. I log AFR vs RPM with a Zeitronix on the street.
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One thing I have noticed, but not sure what to do about is when on the dyno, I removed the air cleaner to see what it would do. It richened as expected, but over a full point by 5k.
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