Plastic Fantastic 2

Looks like a great motor - but probably the wrong choice for a road racer. Too long a stroke - slow winding (relative) and too much torque down low (corner exit). Pretty heavy too. You are better off with a shorter stroke, higher winding motor with really good, forged internals, light weight pistons, good heads, and a robust valve train that will live. My personal choice was an aluminum, big bore (4.6"), short stroke (3.875") and high compression. It's only 515 CI, but it makes 850 hp at less than 7000 rpm, and it was built to be an 8-grand + motor.
 
mfain said:
Looks like a great motor - but probably the wrong choice for a road racer. Too long a stroke - slow winding (relative) and too much torque down low (corner exit). Pretty heavy too. You are better off with a shorter stroke, higher winding motor with really good, forged internals, light weight pistons, good heads, and a robust valve train that will live. My personal choice was an aluminum, big bore (4.6"), short stroke (3.875") and high compression. It's only 515 CI, but it makes 850 hp at less than 7000 rpm, and it was built to be an 8-grand + motor.
Click to expand...

I agree with you and in full disclosure - I've been watching your motor build with a look to copying it (sorry, not sorry).

I also asked several questions in that vein at SEMA. Those heads bolt onto older blocks - granted, you have to use GM's intake as well (though if there's ever an opportunity to build a stack/flat EFI intake - this would be the perfect time).

Some considerations:
- I still don't know how the oil drive works, the 632 is coil-on-plug but there's not the normal 'stub' oil pump drive in the intake - it's has as close to a valley pan as I've ever seen on a BBC.
- those heads are TALL, without measuring, I'd say 1/3rd taller then a stock head. C3s are already hood-height-limiting so the motor must move down to accommodate them. With that said, in this game of fractions of an inch, being able to run a shallower dry sump pan could be the difference between it working and not....
- those heads are, basically, a LS head for the BBC but with a much straighter path - which means normal headers won't work
- in that same vein, I think there's a learning curve to make power with those heads.
- it has its own unique rocker system
- I have no idea its weight and no one knew there.... because the distributor is gone, I'd certainly move the engine back

I'm still on the fence on this, this would be a lot of fun to have, but I also think this would be a challenge to race in any venue - especially if it was done without traction control. One of the challenges with my current car is this - I can't count the times I've rolled into it and thought the clutch was slipping when it was, in fact, simply losing traction... add twice the hp and I can only imagine how much more of a problem that would be. Nice thing about NA, though, no peaky power.

and in really thinking out of the box - wonder what a flat plane crank would do here.... 632 ci at 10000 rpm would be an amazing sound but if the flat plane design netted GM 1/3 more NA hp then before.... probably dumb but it's what's rattling around in my head
 
Last edited:
Apparently there are big vibration issues with a flat plane crank in big inch motors. I have read that is why Ford stayed with such small motors, and GM more or less followed suit. Look at the C8R motor. I doubt you will find anyone offering a flat plane crank for a BBC. Another issue I am running across is parts availability to build a good motor - backorders on all kinds of stuff like cranks, rods, heads. I think the problem is centered around metals and forgings.

BTW, you mentioned moving the motor back. That is how I solved some of my height problem with the fabricated intake. The further back you shove the motor, the taller the available space becomes. Lowering the motor in the chassis needs to take into account how low the centerline of the crank is with respect to the above ground height of the pinion. As your driveshaft gets short, there isn't much tolerance for differences in heights due to driveshaft angle problems.
 
mfain said:
Apparently there are big vibration issues with a flat plane crank in big inch motors. I have read that is why Ford stayed with such small motors, and GM more or less followed suit. Look at the C8R motor. I doubt you will find anyone offering a flat plane crank for a BBC. Another issue I am running across is parts availability to build a good motor - backorders on all kinds of stuff like cranks, rods, heads. I think the problem is centered around metals and forgings.

BTW, you mentioned moving the motor back. That is how I solved some of my height problem with the fabricated intake. The further back you shove the motor, the taller the available space becomes. Lowering the motor in the chassis needs to take into account how low the centerline of the crank is with respect to the above ground height of the pinion. As your driveshaft gets short, there isn't much tolerance for differences in heights due to driveshaft angle problems.
Click to expand...

the problem I had was I changed how I was doing the car mid-stream. My initial 'build' was a BBC in a slightly modified (read, bolt on) chassis. No EFI, no transmission change, no C5/Gen 5 clips. If I had started with the C5 front suspension, I could have easily lowered the motor (and moved it back) by using a dry sump system... but who knows, maybe I simply change the motor in this car - then move it back and down....

At this point, it'd make more fiscal sense to sell then build again. That said, supply issues are likely going to last for another year - but I have tons of work I can accomplish first... and with that said, I'm looking for a 73 or older shell. No frame, just the shell and good title... maybe even a convertible.... but first, a CTS is coming on Sunday, then the Buick wagon. I'll do the CTS motor swap and FJ40 trans swap simultaneously.

The thing about getting a shell, the expensive parts don't have to come until the end (and yes, tube chassis this time)...
 
Intake stuff.... One of the worries about the current set up is it could take water in - this should solve it, might even help since there is more space for the air to turn into the motor
3ZFp0Gjh.jpg
RXIQoxmh.jpg
 
SBG-

I've been away a bit - so will back up to the new tank.

Looks like you have an opportunity to use the spare time at Thanksgiving to fab a nice diffuser to add to that space beneath the tank. Maybe an easy Remove & Replace style. Won't be full on race - but favorable with low- very low drag for the downforce it could provide. Something that has a slight roll to it and a few fins - you might consider the idea.

I am enroute to home and could share an idea or two. Let me know - you have my addy.

Seems the dimensions are pretty well know with your "blue tape tools!"

Cheers Jim
 
that tank was a 'simple' solution that simply doesn't work... it's not big enough...

but you bring up a question - is carbon fiber flammable?


One thing I don't like about my color combo of Dakota Digital dash is it's nearly impossible to read at speed... to time for a linear display with warning light
sOAuAwrh.jpg
2RuXWvTh.jpg
it's a good spot, no water gets there, it's in line of sight, and it's really easy to wire.
ZuuLqCVh.jpg
time to construct the cold air intake
r4Y1FbCh.jpg
things are so screwy, it's cheaper to use 304 4" stainless tube, mirror finish then it is to use aluminum
Gr6i5c4h.jpg
lay out
pJpsdrgh.jpg
finished
T4MedAxh.jpg
and check for clearance
​​​​​​​uxsFLtKh.jpg
another issue - I need to seal the radiator to the core support... done
qXH0L2Bh.jpg

in other news, I fixed the e-brake and I correctly wired the speedo.edited Tomorrow (hopefully) I can go do a loop with it and my '40 to set the speedometer.... it's funny, it's the little things that are most useful...
 
Last edited:
I answered my own question... 400c = 752f.... it will oxidize but stop if the fuel source is removed.... I think I need to learn how to lay carbon fiber... a splitter, defuser, skirts....
 
it annoys me when I put the dash all back together then need to pull it apart again... the brown wire that needs to go to the blue wire is inside...edited
​​​​​​​V1Xy0cv.jpg
 
Soooooo

I'm considering PF3. Still in planning stages but here's some general outlines (oh, and it's getting built on here and Bangshift.... no 'other' corvette site)

Full custom chassis using the c5/6 front and ZL1 Camaro rear.
68 Convertible body. 3"/4" flares (probably my own design - one that actually considers aero and integrated brake ducts for the rear)
Also, we know that the convertibles with a hard top were the race cars - so it'll have a hardtop but no soft top (saves weight).
632 ci motor (and this is a big maybe because that's one, tall beast)
6 speed

With that said, using the 632 heads on a standard height block then a shorter stroke.... the GM motor retails for 37k and is 30k out the door.... that's a lot of money.

and PF2 is going nowhere but quickly around local (and national) racetracks.
 
Not familiar with this product but seems like a good method to "tune" sound levels on the fly.

varitune_muffler_marken_performance.jpg


[ame="https://www.youtube.com/watch?v=0HXheCxzyFY"]https://www.youtube.com/watch?v=0HXheCxzyFY[/ame]
 
bobs77vet said:
i like the sounds of a pf3 build! and the sedanette gets sidelined for a while?
Click to expand...

nope.. wagon is back in the shop soon, then we'll see... the wagon needs to be self-powered. Body work is going to take awhile, but it needs to run. Once that's done... I dunno, I'm not sure I'm ready (skill-wise) to start the Sedanette....
 
I've complained before that people take my ideas without even a thank you.edited That's fine, I like they did, now I can take their updates to my design and help a few around here save some dollars
RMvSxv1h.jpg
C5 motors and controllers
they put the motor on the opposite side - which created its own issue of having to build back the part I cut out
K8PhlEKh.jpg
tomorrow, wiring - my car's alternator is on the opposite side as stock - but even so the wiring needs quite a bit of mods.edited Shop was 26* tonight so I figure I can get more proactive heating tomorrow and perhaps have feeling in my fingers while I wire.
 
You must log in or register to reply here.

Latest posts

Back
Top