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Discussion Starter #1
A few of you may remember my post about helping a friend with his carbed 306 combo. He's now decided to go with a carbed 347 and we've managed to put together a possible combo and would like some opinions. So far the plan is: CHP street fighter kit, AFR 185 58cc, FMS 1.6 RR, polished performer RPM, Holley street avenger 770, BBK 1 3/4" longtubes. Anyone have any opinions on this combo and mainly advice on a good cam to use. Also, is the Tremec 3550 a good transmission to go behind this engine? Any help will be appreciated.:)
 

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Discussion Starter #2
C'mon, I know someone has something to say. BTW, does anyone know how much lift you can have with box stock AFR 185's?
 

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From what I have read, they are good to .60, AFR recommends upgraded springs for over .55. I have read guys running over .55 with no valve float on the stock AFR springs.
 

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Cam recommendation??? hydraulic or solid??? Your carb motor will like a big cam!!! I don't know what compression you are going to run but if over 10:1, I like the TFS stage 3 for your setup if you want a off the shelf cam. Just my .02
 

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Discussion Starter #5
The TFS stage 3 is one I've been thinking about, looks like a real monster:lol: :evil: !! So you think it'll be okay w/ the stock springs? BTW, how much are the upgraded springs?
Oh, and it is gonna be hydrolic.
 

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The AFR upgrade spring kit part number is 8032 and the cost is $175.00
I've already purchased my cam for my 331ci. I am strongly considering the TFS stage 3 cam for the 393ci SC motor. If you go to Trick Flow's site, you can click on specifications for what they recommend with use of their cam. I remember that the stage 3 cam liked over 10:1 compression. My 393 will be 9:1 but I don't think it will matter much with a SC.
 

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Additional info on AFR's, they say valve float is possible at 5800-6000 rpms and recommends the upgrade. People running stock springs to 6250 rpms, haven't had any problems that I have heard of. I will be running my motor to 6000-6250 with my cam using the stock AFR 185, 61cc springs.
 

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What size carb are you going with this is the same setup the crawford strawberry car had in it. A 347 with a carb and it flew.:joy:
 

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You may want to consider using the 61cc AFR head with this 347 instead of the 58cc if you are going to run on pump gas. With a typical .039" thick compressed graphite gasket, 4.030" bore, typical 5cc valve reliefs in a flat top piston, and the pistons .005" in the hole, you'll have 10.84 to 1 compression. Pretty high with pump gas and a .044" quench area.

Substituting the 61cc heads would give you a more 92 octane friendly 10.45 to 1.

Even if I did want the higher compression, I would still go with the 61cc heads and tighten up the quench area to discourage detonation. With the combo above and zero decked pistons, you'd be at 10.58 to 1. With the pistons .005" proud (out of the hole), you'd have 10.72 to one. I've found that running a tight quench clearance, around .030" - .035", will allow the extra quarter point compression that is created by bringing the pistons closer to the heads. Just pay attention to tuning; timing and air/fuel must be right. Cooling system must be right also.

The #8032 option on the AFR heads is a steal at $175. It gets you longer stem, higher quality, upgraded Ferrea valves, and taller, larger diameter springs/retainers designed to handle healthy hydraulic roller cams. This combo is designed to handle the stress of the aggressive ramps used in contemporary hydraulic street rollers.

The AFR heads flow exceptionally well on the exhaust side, so don't go too extreme in split duration, i.e., keep the exhaust duration fairly close to the intake. This is especially true with your 1-3/4 long tube headers, and if you put a very low restriction exhaust behind them.

All the aftermarket stroker pistons have deep valve reliefs; with the #8032 AFR option you will be free to use a cam with mid-.500's lift. You might consider using the Comp XE276HR that is designed for 1.7 roller rockers. It gives 224/230 duration, mid-.500 lift and 112 lobe centers. If you choose something else, I'd suggest not going below 224 degrees intake duration nor above 112 lobe centers unless you reduce your compression some for street use. Your cylinder pressures at lower rpms would be too high and invite detonation.

You could step up to a similar cam with 230/236 duration and probably run a tenth quicker at the strip, but you'll like it a lot less for everyday driving, and will provide less "real-world" performance on the street. Would handle the compression well, though.

The Tremec 3550 is an excellent transmission. If buying new, shop around and get the TKO instead for as little as $150 more. It will be the last transmission you'll buy for your small block. The TKO is identical to the 3550 except for stronger input/output shafts with more splines that handle even more torque. Yoke included; different clutch disk required.

Steve A.
 

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Discussion Starter #10
So the compression would be about 10.45:1 with the flat-tops and 61cc heads? The carb is probably going to be the Holley Street Avenger 770, does this seem like a good choice? Also, does anyone think the TFS stage 3 is actually too much for this motor?
 

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Yes, the compression would be as stated in my previous post...IF...that is the correct gasket thickness actually used, the piston relief volumes, and, importantly, the deck height of the pistons. You must tell the machinist what you want when the block is decked.

I haven't used the 770 Avenger. Talk to a good carb shop guy about the best choice for your combo.

What is the weight, rear gearing, and intended use of this vehicle? If it's a street or street/strip machine, that stage 3 cam is too much, IMHO. You'll like a Stage 2 or similar grind much better. For racing, the Stage 3 would work fine.

The long crank arm of the stroker motor wants to boost up the torque in the lower rpm range. Unless this is a race-only car, let it. Give it components that match its ability to pull very hard in the 2500-6250 range, and you'll love it. If you want a high rpm screamer, a 331 would be a better choice.

Steve A.
 
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