390 w/open chamber heads

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Thanks Moper,

I've heard of Bullet Racing Cams but not Dwayne Porter at Porter Racing Heads in VT. The Hughes website talks as if they are Mopar experts??? Since I haven't ever had a custom cam made I don't have an opinion.

Treblig
 
They are experts first and foremost in self promotion. They have some good ideas but bullet has got them beat by light years as far as I'm concerned. You're asking for a unique part - Dwayne works a lot with the FAST guys and is not only very good but much more experienced with your kind of situation.
 
I bought an RPM airgap as recommended, and yes I agree that the RPM should help more than the performer. My TCI adapter came in yesterday. I've been wondering...will the 390 require a bigger carburetor, I'm running and Edelbrock 600 on my 318. I want good, strong low end response and just remember....nothing over 5800 RPM.

Treblig
 
Some will argue this but I like the 870 Street Avengers for a street 4" arm engine. Decent price, great response, good mileage, and plenty of capacity. It's almost impossible to overcarburate these things.
 
I was thinking 750 edelbrock??? I already have the jet/rod kit to make mods to edelbrocks. But I'm open to suggestions for the torque monster.

Treblig
 
If you want to stay Edelbrock then I'd recommend the biggest Thunder AVS: the 800. But - the carb when compared apples to apples to the Avenger is closer to 700cfm and is $420 plus the strip kit for $60. The 870 Avenger is bigger and is $410. Jets and a power valve if needed might be another $20.
 
Moper,

Would I need that much carb if I'm not going to any high RPMs...just wondering?? I always was told that you get a lot better low end response if you don't over carburate (sp). I'm not saying that the carb(s) you recommend won't work on the engine, but do I need that much CFM to run at 5800 RPM max? Or is it that the 390 will need that much carb to function well at any RPM??

Thanks,
Treblig
 
Would I need that much carb if I'm not going to any high RPMs
High rpm is a simplified way to say "higher airflow demand by the engine". You increased the stroke by 20%. That's the single largest component to affect the airflow any engine needs. So yes - you have an engine with a need for 20% more airflow at every rpm, and that's assuming no other improvements in power or efficiency over the orginal stroke engine.

I always was told that you get a lot better low end response if you don't over carburate (sp).
That is true - but it's relative to the stroke, displacement, other components, and the carb type itself. In my opinion that statement is so overly general that it's not relevant unless it's accompanied by the complete engine specs.

do I need that much CFM to run at 5800 RPM max?
At wide open throttle that engine can use all the carb you can afford. At part throttle it comes down to the calibrations and sizing and a 2bbl would work. The trick is to balance the size and shape of the carb's venturis to best meter and mix the fuel at all throttle openings. A smaller carb will not be calibrated as well for mid throttle or have the capacity for best power at wide open throttle.
 
Moper,

I like the way you explain things!!!! To the point and one item at a time.
Does the AVS also use the same metering rods like my 600 edelbrock?? I got a whole box of them and they worked great getting my Cuda to have excellent throttle response at all speeds. I found a brand new edelbrock 750 for $200 haven't bought it yet.


Treblig
 
I think the AFB metering rods will physically fit the AVS, but if memory serves, the graduations of sizes required are different from the AFB to the AVS...

I'm sure moper is correct in asserting the Edelbrock will work and may be easier for you to deal with personally, but the Holley would likely be better suited for the application...your call
 
Thanks STANG!!

I'll check into it. If I can't find a AVS for a good price I'll go with the 750 AFB. Either way I think my engine will do OK!!

treblig
 

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I'm pretty sure the original AVS and AFB rods are not interchangable. I am not sure if Edelbrocks are the same deal. I think they are - meaning seperate strip kits for each. It's the steps in the rods and how each design's rod hangers operate. AFBs had less movement and one step plus the power step. IIRC AVS had two steps and power, just lik the Thermoquad successor.
 
On the secondary side all the jets interchange between Carter AVS, Carter AFB, Edelbrock AVS, and standard Edelbrock. On the primary side the rod caps, rods, and jets need to be matched set. So if you find a Carter AVS you will need to run the flat rod caps from a standard Edelbrock or Carter AFB carb. An Edelbrock AVS already has the flat rod caps so what you have will work. Do not buy an Edelbrock 750 those carbs are known to be problem prone hence the low price. Get an 800 AVS or better yet sell that jet kit and get the Holley.
 
340sfastback,

damn bro....you know you carbs:prayer:!!!!!

You know I think I have an 850 Holley sitting on a shelf in the garage??? I also have a box of Holley jets (or whatever they're called), like the edelbrock box.

treblig
 
At least I think it's a 850. But it is a Spread bore for sure.

Treblig
 

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According to Holley's PDF listing, it's an 800cfm, jetted 62/85, 0.025"/0.037" squirters...
 
I haven't received the RPM airgap I ordered. Will the spread bore fit on the RPM?

Treblig
 
I guess I have to worry about the air cleaner hitting the hood?? Or get a square bore carb.

treblig
 
Just my opinion here - I disagree with the choice to not bother addressing the deck issue "because this is just a torque engine". There are two things that need to be "right" in my mind: crank centerline, and deck height. The factory machining sucked. All of it. so if technology exists to correct the result of the scuking, then I'm all for using it. The end goal is higher performance than a factory engine. Whether performance be horsepower, torque, emissions, economy, or a combination of some or all. So with that in mind - The crank centerline (or main bearing bore centerline) is one two bores that modern machining equipment uses to index itself. Every engine I do gets the mains honed and the decks square decked. Because everything is related to those being a given spec. "Zero deocking" is BS in terms of a description because it can be any height that leaves the piston flush with the deck surface. It's a minor misuse of a word but you can have a small block deck "zero decked" and that deck hieght could be 9.590, 9.600, 9.550 all depending on the accuracy of the main bearing bores, the crank, rods, and pistons used. Decking is the action of milling the gasket surfaces of the block. Depending on the block, the machinist, and the milling equipment used this could be a good or bad thing as there is no reference to setting a deck hieght or correcting any relationship of the deck to anything else. Square decking is machining the head gasket sirfaces in order to make them parallel with the crank centerline, perpendicular to the bores, and set at a known height. Because the deck surface placement and accuracy affects individual cylinder compression ratios (static and dynamic), gasket sealing, valvetrain stability, and individual pushrod lengths it IS that important to get as perfect as possible.

I understand what your saying about "zero decked" but then again, that's what it refers to, Zero decked for that particular application.
As for your underlined statement above, I'm a bit baffled. Its a simple fixture for older machines to set deck heights, and correct the 90° deck angles and crank/cam 45° to decks.
Treblig, I have yet to see a block not out at least .003", of all brands. Running an indicator from the cutter head along the deck will show more than laying any straight edge across it.
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CPMotorworks,

I am a machinist so when I talked about the .003 I meant out of parallel with the crank centerline. If you've never seen a block less than .003 out of parallel then I most likely will have to "square" my block (get the deck parallel to the crank). Wasn't even planning on putting a straight edge on the block. My plan was to take it to the machine shop and let them tell me what I have then go from there.

Thanks,
Treblig
 
CPMotorworks,

I am a machinist so when I talked about the .003 I meant out of parallel with the crank centerline. If you've never seen a block less than .003 out of parallel then I most likely will have to "square" my block (get the deck parallel to the crank). Wasn't even planning on putting a straight edge on the block. My plan was to take it to the machine shop and let them tell me what I have then go from there.

Thanks,
Treblig

I noticed that, Journeyman Machinist/CNC programmer myself. So you understand castings move around with heat cycles and have to be checked all over. What I see is some blocks will be less than .002" front to rear along an outer edge or centerline of the cylinders, but check an outer edge and it will be off. Just did a SBC that was pretty square to the crank CL thru the middle of the cylinders but kicked up .007" at the corner above #7 cylinder.
Also, a word of advice. Ask your machinist how they check things and what they do to setup parts. Too many think a machine level is acceptable practice for setting up blocks and heads for decking. Ask them what part of the warped deck is their reference point? Just like doing anything precise, tools and procedure matter.
 
Not to sound like a big dummy but aren't there any datum point on the block?? And also I thought the flycuttter was set parallel to the fixture that holds the crank (crank Center Line) or were talking about being out of square radially along a circle concentric with the crank center line??

treblig
 
I guess I have to worry about the air cleaner hitting the hood?? Or get a square bore carb. treblig

Get a square bore or try and find a used LD340 intake they will accept a spread bore or square bore carb.
 
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