I've had an idea bouncing around in my head for the last few days. I've got an opportunity to purchase a 327 crank and block i great condition for ~$200. Would it be worthwhile to put the 327 crank into a 400 block, making a 352, I think? I read one post about someone else doing it and they achived impressive results. You would get a strong bottom end by getting rid of the cast crank without spending all the money on a new forged crank, and your not losing any displacment. Good/bad idea?? Your thoughts and input would be appreciated :cheers:
I have done this exactly, although I have not had a chance to install the engine in the car yet...
The advantages are low rotational inertia so you can rev the sucker as much as you want with a stout bottom end, more displacement than a 327, and still pretty nice torque potential.
The main disadvantage is that you give up lots of cubic inches to a 350 crank (377), stock 400 crank (406), stroker crank (415 or 421). You can build amazing torque from the 406 or bigger motor (at the expense of high RPM characteristics), and the 377 is an interesting compromise.
I guess before you do this, will a high revving engine be what you want? What transmission do you have? How will you be driving it? I went from a 327 to this, so I really expect the engine to behave very much like my old 327, just with a ton more power...
The Crank block journal sizes are different. Modern metals make destroking a thing of the past unless your in c.i. displacement class racing. People with 4 & 4.250 stoke motors are doing over 7000 rpm in high end street cars.
I wouldn't even rebuild my 355 with a 3.48 stroke again. It will be some kind of stroker between 3.600 and 3.875
I though it would be a cool idea because it would be a cheap way to get a steel crank into a 350/352. I wouldn't be losing any displacement over my 350 right now, would be gaining a stronger bottom end, and the motor porbably would perform a little better with the valves unshrouded a little more because of the larger bore. I don't want to sping the motor to the moon if I don't have to, but with a stronger crank and new rods I probably would get an increase in safe useable RPM.
While I will not disagree that you can run 7000 RPM with a 4 inch (or bigger) stroke in a small block, and that metals are better, no matter what you have, the stresses will be larger with a longer stroke. An equal strength rotating assembly will have a higher RPM limit with a shorter stroke than with a longer one. The corrolary is that to have the same RPM limit, you will need stronger parts for a longer stroke assembly.
Here are some numbers for 7,000 RPM:
stroke:....................3.25.....3.87 5...4.00.....4.25...Inches
Rod:........................6.30.....6.0 0.....6.00.....5.70...Inches
Max Piston Speed...6155....7472....7738....8328...F eet Per Minute
TDC Piston Accel.....1707....1961....2014....2107.. .g
BDC Piston Accel.....2847....3570....3714....4063.. .g
So, to run at 7,000 RPM the 4 inch stroke motor has 18% more stress on the crank and rod stretch at TDC, and 30% more stress and rod complression at BDC.
My next build might just add to the stroke of my engine, but for my driving style and budget, a 7,000 RPM 434 stoker small block is not in teh cards.
Chief - Is it a later 327? 67 or later? GM changed the rod journal size that year to match the 350 larger size. I don't think that valve shrouding is a consideration until larger than 2.10 intakes.
I was thinking of doing the same thing a few years ago. It is basically the same as a Winston Cup 358 (the 358 has a slightly longer stroke.)
These are great for stock cars and boats that see constant sustained rpm.
I am not sure how it would work in a street car.
Here are some things to take into consideration. The crank must be large journal, you must use main bearing spacers, you will have to use custom made pistons, and you should use at least 6" rods to take advantage of the high rod/stroke ratio afforded by the short stroke. You will need all of the parts needed to turn high rpm. Roller valvetrain, large fuel system, hot ignition, etc. :chevy
Chief - Is it a later 327? 67 or later? GM changed the rod journal size that year to match the 350 larger size. I don't think that valve shrouding is a consideration until larger than 2.10 intakes.
Don't know on this, I will give the guy a call and find out
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