Mark IV 454 block
6223 crankshaft, 3.76 stroke
781 heads, Stainless valve 2.12-1.81 or 2.19-1.72, mild bowl blend and smoothing around the guides.
Holley750 DP
Edelbrock Air Gap intake
Comp stainless pro magnum roller rockers
JE/SRP pistons with -30.00 dome ( could use an ICON piston with -28.20 to drop compression a little if needed )
Howard's GEN 6 roller cam 120326-10
Not sure i understand the reasoning for the 3.76 stroke but using a hydraulic cam.....it's a 427 baby, feed it some RPM and rev it up!
I'd got to 850-950 carb too, especially on a divided plenum intake where each cylinder can only pull off 1/2 of the carb. Dual planes need a bigger carb for a given power range than a single plane does for that reason..
The 781 heads really need a full-on bowl blend on the intake side, with larger valves and the short side turn laid back to correct how bad it is in stock form.
Why limit yourself to 427 Cubic Inch Displacement (Howard's Gen 6 is a 454 - 502 stick. there's no replacement for displacement)?
What Transmission and rear axel ratio (Holley recommends a Vacuum Secondary with an Automatic. A DP will work with a fairly high stall speed and rear gears)?
It is very tempting to build a 454; but I have always wanted an iron headed 427. When the day comes to go bigger, I will most likely buy aluminum heads. Goin for that old school look this go around.
I have a TH400 transmission and Dana 60 with 3.54 gears. I have considered a vacuum secondary carb, could happen.
Judging by your compression, gear ratio and cam choice, I take it that this is intended to be a driver? Usage makes a big difference in parts. As a driver, I would expect it to have a rowdy idle, and pretty good pull to 5500-6000 or so.
If you haven't bought your parts yet, I would suggest stepping up to a 4.25 crank..More of everything you want and no visible difference.
I'm just about finished on a similar build myself. 4.310x3.76, mild hydraulic roller cam, 990 heads only because I had them, factory dual plane intake, 10.0:1 compression. I am just after a driver, and would have gone either 396 or 427 depending on which block I could find that was in best condition. I actually wanted the smaller engine for better fuel mileage if you can imagine that. I'll run a 750 vacuum secondary carb, and spend a bit of time getting it just right for my combination.
454, only comment is that with any hydraulic roller that you'd like to RPM a bit, valve spring choice is critical. and 427 do prefer to RPM a bit to make power. My new 454 runs something like 170/420 and its good for 6200-6500. I think I;d put more like 200/500 on a 427, or whatever would give me 65--6800 reliabily w.o any hint of float. Ti retainers can also help here.
I went with a Scat forged 4.25 crankshaft because I didn't have any crank but he has a 6223? crankshaft, I'd probably would've used that too if I already had it and it was good to go, no machining needed
750 dp sound like a good choice for that engine; larger is not needed for the rpm you are gonna turn..
i also think the cam choice will be nice.
should be quite nice for cruising and running hard, lots of mid-range...
You only said a dozen times that you really, really really wanted to stay with the 427.
Go for it.
The only thing I would advise you on would be to not scrimp on the head flow and valve train. A 427 makes power with RPM.
Remember that since this is a street car, everything attached to the crank will be spinning fast when that tach hits 7000. Things like belt alignment become super critical.
To the op, combo looks good to me. Lots of 427 threads lately.
It's weird, last week I was very surprised to see the "go bigger" people didn't PILE ON in the 307 engine thread and insist that person "go bigger". Instead, it was a very supportive and lengthy thread which appeared to really help the op. Most other times when someone mentions a 307 on here they get flamed. The nature of forums, I guess.
that cam is close to the one in the Chev crate 427 should run good, I would miss the old school clatter of mech lifters
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