Welcome to the Corvette Forums at the Corvette Action Center!

Where did the cubes go?

Dad

Well-known member
Joined
Nov 18, 2001
Messages
611
Location
West Unity OH
Corvette
15Gray/8sp 72Blk/Blk4Spd 64Red/Red/Wht4spd
I’m in the engine rebuild mood and have some questions of the learned folks out there.

First off it’s a 350, 1978 vintage, big valves and 4 bolt mains. With the bore of 4.00 and stroke of 3.48 to get the 350 C.I.D., the question comes to mind that with the new pistons with the offset pins it would seem like the displacement would increase by the distance the pins move up. As an example, if it were .50 longer stroke (throw of the crank would have to change) the C.I.D. would increase about 50 C.I.D. or 400 C.I.D. total. I would also think that the lower drag pistons and rings plus the lighter powdered metal rods hooked up with the better bearing they are using today would give you more and quicker RPMs.

Here is my problem, the ZZ4 has the offset pins and the latest pistons and should have the latest in bearings, rods and rings. The data I have still lists the bore and stroke as 4.00 X 3.48. What am I missing here? With a price of $4500 for the ZZ4 you would think they would take advantage of the extra cubes unless they can’t swing the crank. If nothing else they can swing a 3.75 stroke that was used in the old 400 which would add at least another 27 cubic inches. The mains would have to be bored .200 oversized and that may be the draw back.

I haven’t built an engine for 14 years and the task of getting the extra cubes is looking like more than I want to tackle.

Lay it on me, what has been going on out there in the engine rebuild world and is this doable?
;help
 

Ken

Gone but not forgotten
Joined
Jan 30, 2001
Messages
8,236
Location
Hermosa Beach, CA
Corvette
1987 Z51 Silver Coupe
:L Sorry Dad, I had mine built. I'm one of those guys! :L

_ken :w
 
K

KenSny

Guest
Have you looked at the PACE performance site for GM crate engines? All sizes and cubes galore...... Get what you want. However, cubes alone is not always the solution, depends on what you want to do with the engine, and car. You could certainly take a 327 motor and make it a high rpm, or take a 502 motor and make a real stump puller.
 

Dad

Well-known member
Joined
Nov 18, 2001
Messages
611
Location
West Unity OH
Corvette
15Gray/8sp 72Blk/Blk4Spd 64Red/Red/Wht4spd
Size isn't the question.

I fully understand what cubes do and what can be done with RPM, my question is, WHY, why are the cubes ignored with the new technology (bearings, low friction rings, lighter pistons, lighter rods), are those cubes too hard (expensive) to get in the older blocks?
 
C

Colorado

Guest
Dad - I have a question:

All numbers totally imaginary and for this question only.

For a given length rod and a given length stroke, full compression is attained when the piston pin centerline is set at 1.25" below the top of the piston dome.

If the pin is now set at .75" below the top of the piston dome (the effect of raising the pin centerline .5"), a longer rod is needed to reach full compression, or a longer stroke is needed, or maybe a combination of the two.

During crankshaft rotation, what happens to the rod/piston sidewall and rod/cylinder wall relationship when a longer rod or longer stroke is used? Is there enough clearance within the piston and the block casting to accomodate the rod angle change?
 

Dad

Well-known member
Joined
Nov 18, 2001
Messages
611
Location
West Unity OH
Corvette
15Gray/8sp 72Blk/Blk4Spd 64Red/Red/Wht4spd
That's what I'm trying to find out, some of the time we did bob some material out of the block to clear for the swing of the longer stroke and the bob weights. I've been away from major rebuilds for 25 years, just head work and then not much of that for the last 14 years. With the advent of the new equipment it looks like some easy cubes are being missed. I relize it will take all new lower rotating componets and some major head work to do this but that's a given when you go up in HP either by cubes or RPM. RPM was the choice when I was drag racing but not my bag today. Ever see a flywheel come through a bell housing and a scatter shield at 9 grand? I also see a few 383 stroker kits and wonder if that's whats going on with the new pistons, rods, and rings.
 

Ken

Gone but not forgotten
Joined
Jan 30, 2001
Messages
8,236
Location
Hermosa Beach, CA
Corvette
1987 Z51 Silver Coupe
:L Dad, I wish I could get my builder to participate here; he talks this stuff to me, but half the time it's in-one-ear and out-the-other before I realize it. :eek:

_ken :w
 
C

Colorado

Guest
Originally posted by Dad:
Ever see a flywheel come through a bell housing and a scatter shield at 9 grand?
Not through a scattershield, no. The most spectacular show that I saw was when a guy missed a speed shift, at night, on a four-laner, and blew out his bottom end. It was like fourth of July! It took about 250 feet for the array of fire and sparks and ricocheting pieces to subside. I never even saw a show like that at the figure-eight races.

Back to the strokers. Even though they can forge custom rods and pistons, they still have to do SOMETHING with the block.

Here is what's in one of the kits: http://www.strokerkits.com/383.htm. One line in that list sticks out: Please let us suggest block clearance on this one. This one is $999, and you still need to work the camshaft, carb, etc to max the results.

Here is a 383 stroker motor: http://www.built4speed.com/html_docs/350_stroked_to_383.htm. Read this one. Noticed they use a "seasoned" block...ha. How they can make the HP/Torque claim is beyond me, since it's not a complete engine. You'll see some words about that, too. And somebody is paying $3400 for this!

On the other hand ...

The way the ZZ4 develops max torque at such a low RPM, 405@3500, makes it such a streetable, forgiving engine. The GM 502HO comes in with 550@3500. The LS1 has that good characteristic, too, but at a little lower volume (360@4000 for my automatic). My LS1 wishes I hadn't looked :L. For a little less money than the ZZ4 ($4000), you can get a complete GM 350 HO Deluxe that will give you 350 ft-lb @ 3800, and 330 HP @ 5000.

Our background is similar...I quit building in '72, took an eleven year break, built one for a friend in '83 and haven't done it since. Actually, the one I did in '83 was fun. It was a '78 Triumph TR7, we were stationed in Italy, and getting the parts was one huge adventure :Silly.

You want my 2 cents worth? Personally, I would go with one of the GM engines and call it good. That's just my 2 cents :).

By the way, what's this going in?

:w

- Colorado
 

69MyWay

Well-known member
Joined
Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
Hey Dad,

I think it is just a package deal. The 350 is a great combo of bore and stroke, and for middle of the road street applications it is near perfect. I think it is just easier for them to assemble, sell, package, and deliver apples to apples cubes. Most popular V8 Chevrolet and pontiac cars came with 350 engines, so it is a natural to put another one in.

Some stroker motors require special balance items, larger dampners, etc. By going straight up 350, the installer can reuse many of the original parts from the tired old 350 being replaced.

Just my .02 as well.
 

Dad

Well-known member
Joined
Nov 18, 2001
Messages
611
Location
West Unity OH
Corvette
15Gray/8sp 72Blk/Blk4Spd 64Red/Red/Wht4spd
I started out trying to find out what was happing in the engine building community and as I read these the old saying comes back to haunt me. "How fa$t do you want to go, and how much money do you have?"

Most of you may have already figured this out but if I do the old 350 I might just as well stay with the stock configuration. If I want the added power, buy the crate engine, not only the new technology of the rotating lower but also, the new heads, intake, cam, roller tappets, and valves are matched to the assembly.

What am I putting it in? My travel van, pulling a car trailer. I want something that will wake the camp grounds when I stop for the night. :eyerole My problem in the past was keeping the SB cool pulling all day long, tried fans without much good results. Didn’t want the big block that do run cooler/easier and thought I could pick up the extra cubes to pull easier. What I will do is go back to the old misting systems on the radiator and the transmission cooler. I tend to keep my vans a long, long, long, time and this one has 150K on it now.

Thanks for the much needed imput.
 

Dad

Well-known member
Joined
Nov 18, 2001
Messages
611
Location
West Unity OH
Corvette
15Gray/8sp 72Blk/Blk4Spd 64Red/Red/Wht4spd
Pace Performance

KENSNY,

Great site Pace Performance, they beat the price I had on a crate motor by nearly $1000, and they're right here in Ohio.

Thanks again.
 
K

KenSny

Guest
Yep, in Niles, Ohio. Now, if you can get a couple buddies and a pickup truck, think of all the shipping $$ you can save......Good luck.
 

Ken

Gone but not forgotten
Joined
Jan 30, 2001
Messages
8,236
Location
Hermosa Beach, CA
Corvette
1987 Z51 Silver Coupe
Dad said:
"How fa$t do you want to go, and how much money do you have?"

It's actually "Speed costs money, how fast do you want to go?", but the thing that most people forget, or don't understand in the first place, is that the costs grow exponentially. The first hundred horsepower will cost you so much, but for every ten after that, the costs escalate quickly. The things people do for a tenth-of-a-second. :L

_ken :w
 
Joined
Jan 1, 2002
Messages
7,246
Location
Washington, Michigan
Corvette
'67 Marina Blue Convertible
Pin location/rod length doesn't affect displacement - only bore diameter and crank throw - nothing else matters. I've been building 383's from 350's with 400 cranks for years - just have to turn down the main journals for the 350 saddles/caps, notch the pan rails for rod clearance, use stock 5.7" rods and custom pistons (I use KB hypers), and use external-balance dampers and flywheels.

GM has just released a 383 crate engine made specifically for towing and RV-type use; might meet your needs - all the latest factory parts, warranty, etc.
 

JCL

Well-known member
Joined
Feb 23, 2001
Messages
56
Location
SEVILLE,OHIO
Corvette
1979 "383" TORCH RED- 2000 Torch Red "FRC."
"383"

You mean GM FINALLY figured out have to keep that new crank in one piece. They started advertising it well over a year ago and had nothing available but the PRICE. Sounded like a super motor, but I got tired of waiting and had one built. JCL "Sidepipes are the way"
 

Dad

Well-known member
Joined
Nov 18, 2001
Messages
611
Location
West Unity OH
Corvette
15Gray/8sp 72Blk/Blk4Spd 64Red/Red/Wht4spd
Johnz,

Pin location/rod length doesn't affect displacement - only bore diameter and crank throw - nothing else matters.

Yep, you're right about that. If you read the post my question was not how to figure displacement, more as to how the added displacement could be obtained with the advantage of the shorter (lighter) pistons and the low drag rings. Also what advantage it would have as far as a more responsive, higher revving engine. As the rotating mass gets lighter wouldn't this be a power output increase?

My quote

As an example, if it were .50 longer stroke (throw of the crank would have to change) the C.I.D. would increase about 50 C.I.D. or 400 C.I.D. total. I would also think that the lower drag pistons and rings plus the lighter powdered metal rods hooked up with the better bearing they are using today would give you more and quicker RPMs.

My reason for asking was not knowing how long the present piston is, and how much stroke is available in the standard cylinder of a stock 350. Does the cylinder and rod interfere if the stroke is to long? I'm well aware that there is need to add some clearances for some of the new parts but I'm not aware of all that needs to be changed.

I threw out a .50 move in the pin location; do you know what it really is?

Thanks for the impute.
 

Jack

Well-known member
Joined
Dec 27, 2000
Messages
1,825
Location
Florence, SC (Timmonsville SC)
Corvette
71 War Bonnet Yellow VERT 71 BH Blue CPE (SOLD)
compare & contrast 400 & 350

Yes, the rod-cylinder and rod-cam can (& probably will) interfere when stroke is increased ... I increased stroke less than 1/3" and it interfered ... saga follows:

400 crank in a 400 block doesn't interfere/bang cuz the 400 block is factory clearanced and the factory 400 used a short 5.565" long connecting rod ... the resultant rod angle is different than what most stroker builders get when they use the longer, more desirable rod lengths (i.e. 5.7", 6.0", 6.125" etc). The 400 rod also has a profile at top of big end that's different than 350 profile and uses a different rod bolt than does a 350. The dimension from centerline of crank to centerline of cam is same in both 400 and 350 ... hence they both use same timing chain & gears. Both 350 & 400 also share same block height 9.025" (centerline of crank to top of cylinder deck), average compression distance 1.560" (centerline of pin to top of piston) and average deck clearance 0.025" (top of piston at TDC to top of cylinder deck). The factory 400 is an Externally balanced motor while the factory 350 is Internally balanced ... they do NOT share harmonic balancers-dampers and flywheels/flexplates.

The newer GM 383 mentioned has a different crank ... stroke is also different from 400. 400 cranks had 3.750" ... new GM 383 has 4.000" bore and 3.800" stroke (shoves piston both up & down 0.025" more than a 400 crank) .

Stock 350 block height is 9.025", stock rod length is 5.7", stock piston pin compression height is about 1.560", stock-everyday 350's pistons are "down in the hole" and have about 0.025" deck clearance. I'm using Scat's 3.8" cast stroker crank in 4.030" bore 388 ci buildup of my 71's tired 350. With 5.7" "pink" rods (std 350 profile) and 1.425" compression distance "made for 383 stroker" pistons ... this puts my piston-deck clearance at Zero on a block that has NOT been decked/surfaced. Even with Dished pistons and 76cc UNcut iron heads, my 388's compression ratio will be at about 9.2:1 with the nominal 0.038" head gasket thickness. As for 3.8" crank's fitment, block's required minor grinding at block's oil pan rails and at cylinder bases where rods' beams approach bottom edge of cylinder walls. More careful & aggressive (& more precise) grinding required on connecting rods. The rods required clearancing to prevent them from contacting the relatively small lobes of my mild (.460"/ 224º@0.050") hydraulic flat tappet camshaft (essentially an L82's cam spec). I inserted modeling clay between the installed rods-cam ... then measured the thinkness of flattened clay ...then ground-fitted-ground-fitted-etc until I got a minimum of 0.050" clearance ... then ground-matched all rods to the one requiring most grinding. Aftermarket rods having cap screws (as opposed to rod bolts & nuts) are available as "H-beam" at about $300 & up. H-beams' profiles and some high-dollar I-beam profiles typically do not require grinding; they have cam-clearance built into their design. Roller cams (even more big$) or other "small base circle" cams MAY clear stock rods without grinding rods. Although many Forged stroker cranks and Scat's Cast stroker crank for 6" rods'll work w/ 350 dampers and flywheels ... MOST sbc 3.75/3.8 Cast cranks for 5.7" rods require both harmonic balancer-damper and flywheel/flexplate designed for a 400 crank. MOST combo's based on a 400 or 400-TYPE crank are Externally balanced ... while factory 350 motors are Internally balanced. Although the 350 stuff'll fit right up to a 400 crank ... 350 stuff usually won't balance ... results disasterous. After all this stuff is clearanced, assembled & double-checked ... then the rotating assembly must be balanced by a machine shop (about $100-$150 more) ... then re-assembled into block. Given other circumstances, I'd suggest the stroker builder might begin with a good 400 block & crank ... maybe even an aftermarket 4.00" stroker crank in a 400 block. Sorry for the book; maybe this'll help point up/clarify some issues.
JACK:gap
 

Ken

Gone but not forgotten
Joined
Jan 30, 2001
Messages
8,236
Location
Hermosa Beach, CA
Corvette
1987 Z51 Silver Coupe
Re: compare & contrast 400 & 350

Jack said:
I'd suggest the stroker builder might begin with a good 400 block & crank ... maybe even an aftermarket 4.00" stroker crank in a 400 block.

That's what my builder did guys. :cool

_ken :w
 
C

Colorado

Guest
There's probably at least one CACer squishing clay in his or her Visible V8 right now to figure out why it doesn't rotate.

- Colorado
 

Corvette Forums

Not a member of the Corvette Action Center?  Join now!  It's free!

Help support the Corvette Action Center!

Supporting Vendors

Dealers:

MacMulkin Chevrolet - The Second Largest Corvette Dealer in the Country!

Parts/Accessories:

Vetteskins

Advertise with the Corvette Action Center!

Double Your Chances!

Partners

Top Bottom