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Finally spec'd my BBC 427 build, OPINIONS WANTED

4K views 23 replies 16 participants last post by  pbcbob 
#1 ·
Give me your thoughts on this.

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

https://www.howardscams.com/hydraul...54-502-gen-6-2000-5800-howards-cams-120326-10

Should have 9.8 static compression and 7.6 dynamic compression.
 
#2 ·
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.
 
#3 ·
:cool:

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)?

Don't know nothin' just askin'.
 
#5 ·
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.
 
#11 ·
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.

Devin
 
#16 ·
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.
 
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#20 ·
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...
 
#21 ·
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.
 
#23 ·
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.
 
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