348 engine to 380 in 55 Chevy

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Don Jacks

Well Seasoned Member
Supporting Member 3
You have 2 sensible options here.One is as Dave mentioned,THE 10.5 Icons on 409 rods which with the added stroke will put your compression at around 11-1.Option 2 is the Icon piston made for the 4 inch stroke,use them on the 409 crank with aftermarket 6.385 rods.Your compression ratio here will come in right at 10.25-1..The aftermarket rod will cost you around 350 a set,how much does the guy want for the "reconditioned" stock rods? Short of custom pistons there's no 9.5-1 option here.Cast piston are not advised at all.Either combo is a "drop in",no extra machine work required.
 
boxerdog

boxerdog

Well Known Member
Supporting Member 5
It sure does, and it's a lot easier if you aren't chasing every last HP. Most of us have no need for a max-effort build, regardless of budget, unless we really want to go fast. Many times, driveability or "cool factor" can trump that last few HP. A 409 based engine with a 3.5" crank has no need for a rod longer than 6" (look at your typical 350 sbc) except that the long rod forces you to use a much lighter/shorter piston, which is very important, and it also enables you to use a heavier, stronger rod if you feel the need or have them sitting around. Most street types could get by just fine with the 409 rods, a good inspection/prep and a good set of bolts. Like Don said (more or less) "what do you want it to do?" . If you are pulling the plug at 5500, no problem. If you watch Roadkill, better get some rods.

Same with the cam. There is always an optimum combination, but it doesn't have to be rocket science and it doesn't have to be the latest 4-pattern whatever to work for you. It usually boils down to how much driveability are you willing to sacrifice, what type of accessories you need to operate (PB, A/C etc), will it use EFI or power adders and how well it can be expected to "live" without excessive care and maintenance given the frequency of operation and mileage it will see? So there are many makes and grinds that will more or less work, and this group does a good job of offering up a ton of knowledge and experience. You are a lot better off here than on some of the other online boards, trust me. This is far and away the most reliable and reputable source of info that I have seen.
 
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GreenEyez93274

Well Known Member
OK here what i know at the moment with car and motor.

1. Motor - 348 motor that has standard pistons at 9.5 compression. Heads are off 409 motor (583). Planing to buy 409 crankshaft with recondition connecting rods. Rods are going to be $100 for the set. As far trying to get max HP I'm not looking for that. This is gonna be street vehicle with driving conditions from cruising to drive down the highway from town to town. I plan running AC later down the road but not at the moment. I do have coming disc brakes for all 4 corners. Comes with 8" brake booster. I would like to keep the compression around 10 but not deal breaker. All comes down to what my budget will allow. Camshaft i don't yet. Intake is 3814678. I up in the air about carb. I would like EFI but i think that not an option yet. Distributor is just stock but would like to upgrade to HEI or PerTronix. Fuel delivery is just electric pump from the tank.

2.Car - I do know that rear end is 3.55 posi. Still the original rearend. Plan on running 17/18 in rims. Transmission is 700r4. Currently updating front end with CPP 500 power steering box.
 
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427John

Well Known Member
With the big port heads and intake you should be able to make plenty of power for the street,if you can find some nice visible fenderwell headers for the 55 that would add some cool factor and make more power than the stock manifolds.Sounds like a great combination,with the W engine in a 55 there won't be any yawns when you open the hood.
 
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GreenEyez93274

Well Known Member
I've been going over Don two options he recommended. The 1st option seems more feasible at the moment but I like 2nd option better. Does that 11 to 1 take in fact of bigger heads? Someone stated that combustion chamber is bigger and actually loose compression.
What were the rods you looking at Don for $350? I've seen the 348 10.5 pistions with 4 inch stroke on show cars.
 
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Don Jacks

Well Seasoned Member
Supporting Member 3
Show Cars pn 7846 will get you done,339.00.This along with the 4 inch stroke piston and a 409 crank drops right in,balances easily and depending on the quench area that's built in it should put you in the 10-10.25 -1 range.As to a suitable cam,,for a flat tappet unit,go pn 0951 would be pretty close to perfect for over all performance.If the budget allows a hyd.roller set up,go with something in the 221-224 intake,227-230 exhaust duration at .050 range.
 
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Don Jacks

Well Seasoned Member
Supporting Member 3
Nice,now if you want to know what kind of power this combo to make on those very manifolds,look at Tim's 380 build as it's the same recipe.I hope they work.
 
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GreenEyez93274

Well Known Member
Finally got the engine, manifolds and 500 power steering box mounted. Everything fitted as it was close. Had to grind the left manifold up top because it was hitting the steering box. Next is to mount the brake booster with me valve covers to check for clearance issues. 20201207_143837.jpg20201207_143731.jpg20201207_143830.jpg20201207_143738.jpg20201207_143759.jpg20201207_143807.jpg20201207_143823.jpg20201207_144001.jpg20201207_144014.jpg20201213_172800.jpg
 
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Don Jacks

Well Seasoned Member
Supporting Member 3
I t would depending upon cam choice.An 0950 will clear and that's as high as you'd want to go with cast pistons anyway.
 
63impalass409

63impalass409

Well Known Member
Supporting Member 2
Oh man grinding on 65 only exhaust manifolds!! Gotta do what you gotta do. Looks like a fun project and I would love to have a 55 with a w in it.
 
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