yedister

What do you think?

My concerns (stroker small block Chevy, 4.125" bore X 4.000" stroke with 5.850" rods) are mostly related to rod angularity and cylinder sideloading with this combo. And of course, ring seal, piston and cylinder wear over time (mostly street driven with minimal track time on a road course to sort things out from time to time).

Crazy idea, but if a 4.000" stroke in a standard deck height block is likely to cause reliability problems over time...... Rather than destroke...... What about a tall deck block and longer rods? No, not one of the big buck store bought 9.325" raised deck blocks. Something homebrewed and taller.

With my present 4" stroke crank and 1.170" comp. height pistons, but with a taller deck and longer rods......

7.5" rod = 1.875:1 rod/stroke ratio...... Need additional 1.65" deck height (10.675")
7.0" rod = 1.75:1 rod/stroke ratio...... Need additional 1.15" deck height (10.175")

If I scrounged up a set of identical blanchard ground 1-3/4" thick cast iron honing plates for SBC, machined the water passages into them, brazed them to the decks of my block with yellow brass rod and then bored out all 8 cylinders and cold sleeved it with taller sleeves down through the honing plates before milling the new, higher deck to allow the pistons to be at zero deck...... Would that destroy the rigidity of the block?

Instead of brazing the deck plates to the block, could the deck plates be installed permanently using dead soft copper head gaskets between the plates and original block deck surface along with long studs passing through them (for the heads) that thread into the original block?

In theory, it would allow me to run rods around 7.5" long and get a rod/stroke ratio of 1.875:1 . But with a taller deck block without a raised cam as well, would cam lobe to rod clearance be worsened over what it is now? Or clearance at the bottom of the bores?

I have found a source for 4340 H-beam rods 7" long (170 cu. in. MOPAR slant 6 application) which might be adapted with a little work. Custom rods 7.5" long and having the big end sized for a 2.1" 350 sized rod journal might be insanely expensive, though?

Yes I know...... Will need to make spacer plates for the intake, longer pushrods, deal with distributor length,etc. But is this homebrewed tall deck, long rod 427 Chevy small block idea feasible or worth doing?

I already have my block, crankshaft, 5.80" rods and pistons. Am waiting on pushrods until I have the engine together to measure and see what I need. So the pushrods are a wash pricewise, but would need spacer plates for the intake, longer rods and the machine work to install deck plates and sleeve the block to do this.

leesvet

Its definately a machinist challenge type of fun project....BUT,

I've learned over the years that there is usually a reason why someone else has not done something that I've come up with. Usually because its not practicle or it simply does not work.

With all that very precise building up of deck, heads, intake angles....theres a ton of places to have a problem. Then the concerns at the bottom are still a guess as to whats gonna get nailed by the crank or rods.

I saw someone do something similar and had clearance issues at the bottom where the rod hit the bottom edge of the cylinder. 2nd rate machine shops answer was to grind on the new, very very expensive, balanced, titanium rods....instead of a non-moving part like the bottom edge of the cyl. Total fiasco.

If its just for fun...sure, why not. But if its to build a motor to count on, there are many other things that can be done with existing bore/stroke kits with known info on rods, deck heights etc..

C409

............ Super glue ?? ....................... lol ...

cv67

The Dart Little M walls are pretty thick betting they wouldnt move aroudn on you if the std deck deal appealed to you.

See what tpi421Vette has to say hes built a few of these.

Caboboy

I think this is a pretty intriguing idea, I'm a big fan of longer rod/stroke ratios in a street car.

I'm glad it's your wallet though

danno85

FWIW, I'm running a 4.00" stroke crank with 5.850" rods in my street machine without problems so far - have about 8000 miles on it to date. Good ring seal. Factory 509 casting block bored to 4.185" for 440 cubic inches . There are advantages to long rods, but there are advantages to short rods as well...

Sounds like an interesting project though. Have fun!

Dan

tpi 421 vette

I have built the motor you are talking about. It's in my car. Mines a 4.165" bore and 4.125" stroke, 450 CI. Standard deck height. Small journal 5.85 rod, 1.0625 compression height. I used the Crower billet maxilite stroker rods. I wanted a top shelf rod to help withstand the rod angularity and general stress a motor with a bad rod ratio has. Even with a high end small journal stroker rod, the rods still need a little massaging. It definately isn't a 100,000 mile engine. And it isn't for everybody. I did it because very few people have done it. The crank counterweights will also need to be cut down because the cranks are usually intended for a 6.0" rod. A 5.85" rod will make the piston hit the counterweight on the crank if it's not clearanced. And a .900" or .880" base circle cam is a must. This motor makes some torque. Mine makes over 400 rwtq from 1800rpm to 5500rpm. Peak rwtq was 508. And that is with a 252/260 solid roller and AFR 235 heads. You also have to plan on a low fill on the block. I am using a Bowtie block, and the notching on the pan rail is just about to the rod bolts. And a oil pan rated for a 4.0" rod is also a must. You will still have to notch the crank scraper. It's more work and money than smaller stroke engines, and you will have to decide if you feel like it's worth the extra money. Balancing it was a little hard, but do-able. Mine is almost internal balance. I have a very small counterweight on the flywheel. It's also a motor that isn't going to spin over 6000 rpm with 23 degree heads. But with that much stroke, you can make alot of power without reving it to the moon.

cv67

on a factory block you are a brave man
More on this

88BlackZ-51

It seems like its not a build for the novice.

Good read Jim.

87 vette 81 big girl

Its not a crazy idea what you are trying to do.

It was done on early Harley Davidson Shovelheads & Early Evolution engines raising the decks of the crankcases for a 4-3/4" inch & 5.0 " crankshaft stroke to build 110ci to 113ci using home made stroker plates or eventually S&S stroker plates.
The days before aftermarket Sifton crankcases.

And those 110- 113 ci stroker Harley's ran hard.
Blow away most any crotch rocket or 1,000cc Kawasaki strip srceamer running deep 10's or high 9's.

I know because my late bud had built several in the past in the 1970's - 1990's.

His old 113ci was sold & made its way to Daytona bike week & it blew away every single rice rocket & race modded 4cylinder Kawasaki there.

The guy that bought that 113 ci Harley was 100 times crazier than me.
He used to race for factory Harley Davidson AMA circuits for over 15 years.
Race prepped 4-cam Sportsters.

I like your idea of "Stroker Plates" on a production SBC.
It could be done.
Machine work must be very precise.
Down to the .0001" or tighter tolerance in all planes.

If it works on a Harley Davidson,
Why not a SBC.

You can only try & succeed or fail.
A person never knows till they try 1st.

If you are able to do most of the machine work yourself,
It makes the project entirely feesable for you then.

If you are going to braze,
I would make it a Furnace brazing operation.
Much more reliable results.

You think outside the box too like me.
That is admirable.

Do it your way & by no one Else's standards.

I do the same here.

Good Luck with Your Build.

Brian R.

BadSS

Kaase Racing has used spacer plates for monster truck and tractor engines for years to get extra cubes. It's "doable",, but not very practical for a SBC,,, especially just to run a longer rod.

yedister

Thanks for all of the information. I was searching on several other forums for raising the deck with plates and I came across this post (#1). I contacted the originator; he never got any real answers to the post, so I posted it on this board and sent him the link. I was planning to build a twin turbo 454 but, after driving a friend’s 1100+ horsepower at the rear, it was way more power than I wanted to have to handle. So I changed my direction to making as much torque, I was successful with my 434 making the torque that I wanted.

Now I am after 750 ft lbs. that would require more cubic inches and more RPM’s. Since I also have a small block 4.250 billet crank, why not use it to make a 468 instead. The heads Brodix GB2200, 293 port flows 390 CFM with a CSA of 3.2 will not have a problem. The only cost of concern would be rod/stroke ratio 1:41 with a 6 inch rod, the pistons CH are 1.128 which works for a 4.125 stroke and 6.125 in a 9.325 deck height block but, does not work with a 4.250 stroke in the same block. So if I could raise the deck height of the block, then I could use a longer rod which would give me a better ratio.
Here is a list of the PRO/CON on rod length that I found:

Longer Rod Pros
Less rod angularity
Higher wrist pin location
Helps resist detonation
A lighter reciprocating assembly
Reduced piston rock
Better leverage on the crank for a longer time
Less ignition timing is required
Allow slightly more compression to be used before detonation is a problem
Less average and peak piston velocity
Peak piston velocity is later in the down stroke
Less intake runner volume is needed

Longer Rod Cons
Closer Piston-to-valve clearances
Makes the engine run a little more cam at low rpm
Reduces scavenging at low rpm

Shorter Rod Pros
Increased scavenging effect at low rpm
Helps flow at low valve lifts (a benefit if the heads are ported with this in mind)
Slower piston speeds near BDC
Allows the intake valve to be open longer with less reversion
More piston-to-valve clearance
Can allow for a shorter deck height

Shorter Rod Cons
More rod angularity
Lower piston pin height (if the deck is not shorter)
Taller and heavier pistons are required (again, if the deck height is not reduced)
More ignition timing is required for peak power

Caboboy

I'm pretty sure you get more dwell at the point of ignition with a long rod motor as well. This is an advantage similar to crank leverage.