Rod Journal Size?

[Anonymous]

What is the width of the 200-250 connecting rod journal?

Has anyone found a good data base for connecting rods on the web?
I found this one http://members.aol.com/FE3N/rods.html

John

 

[xctasy]

I have a vast repotare of rod dimensions too. I'll just have to go and look at them in my basement. These are only approx in the mean time.

I've never checked, but the GM Holden and Ford have the same 940 ish thou thick bearing. The SBF are about 832 thou, the SBC about 940 or so.

The VW Golf diesel (5.355", like the gas engine) has been used on the 188-200-221 short deck Ford I6'sand Holden sixes, and is 980 or so, and is similar.

Chevy 2.8/3.1/3.4 v6's were only 660 thou.

A 300 rod will fit a 250, with a low deck +20 or +40 thou Chrysler 3300 V6 pistons or expensive custom 305 size 1.26 deck pistons and a few little mods!

PS some of those rod dimensions are wrong. The 1275S is 5.75 inches long, (and it's only the rare 970S that is 6 inches). The Mitsubishi rods, the 2.6 Astron used in the US market Starion, are 6.500 inches.

But it sure is a great resource! Rod dimensions are a passion of mine

Note 1: Subaru 2.0 pistons have a low enough deck height to fit a 250 block. Then the use of 300 i6 rods would give you 1.59:1 L/r ratio..with a minor ream of the pin by 7 to 22 thou depending on the year of the 300 rod. Some RS Turbos could handle 12 psi of boost with the 93.5 mm (3.681 inch) pistons. Hmmmm

Note 2: The 2.5 HSC rod is the same length as the AU/BA Falcon SOHC/DOHC rod. With a 200 piston, this combo in a 250 would yield a perfect O deck, and give a better L/R ratio. The 2.5 is just a 221 to 250 type I6 cut down. Bearing sizes are the same, I think!

 

[Anonymous]

What I was looking for, when I found the spread sheet, was the compression hieght of Type 1 VW 94mm pistons. I think the CH is 1.377 or 35mm. If so then it looks like 6 inch Chevy V8 rods (bushed small end) would fit with the 94mm VW pistons.

Scat or Indy H-beam rods are cheap
94mm VW pistons, even forged, are cheap

If it makes a difference, I am looking at a USA 250 not the AU 250. I know there are differences in the short block but I don't know what they are.

John

 

[xctasy]

Note: The Aussies use letters for there cars, because they don't do yearly styling and engineering changes like Detriot. The AU is a 1998 to 2002 Falcon. The Aussie 250 is a cross flow or log/2v 250. The AU engine is a 243 or 3984 cc engine. Just had to muck up the English language for you


My Autoparts interchange is at work. 1.377 is correct, from memory. The great thing is those pistons are designed to cope with high revs, and big termal loads.

The Aussie 250 and US 250 have the same critical dimensions. I went to 305 forged pistons, decked to 1.475 inches and stock 3.3 6.275 inch post 1970 rods. The Chevy six-inch rods are the best idea, and the pistons will possibly be too shallow in the bore. If you used a 6 inch small journal rod (2 inches, rather than 2.1 inches), you could stroke it to 4.01 ", use 3.701 " pistons, and 259 cubes. If you could get 95 mm, thats 264 cubes. The piston would still be 98 thou down the bore, even then! Or use the 273-318-360 Chrysler rods, which are 6.126 inches, and have a similar pin size to the Type I. Then you'd just use undersize bearings, and end up with a 22 thou deck register. Perfect!


I've heard the Aussie block is very slightly shallower than the US Mother, but I think they are both 9.48 inches. Rods are 5.885, same on both sides of the Pacific. Pistons are similar. When Speed Pro and Federal Mogul made forged pistons, Aussies used the US spec 200 and 250 pistons on there short deck 200'S, medium deck 188/221's and the Aussie 250.

All the Oz cammers from 88 to date use the same 9.48 inch tall block and 4.045 bore spaces, same 3.91 crank throws, and pre 1998, they had the same rods as the 1969 250 US six.

But the pistons are 3.612 or 3.632 for the 240 cube SOHC and 243 SOHC/DOHC. Bad move, as it takes 68 or 48 thou to bore them out to stock bore 250 US/Aussie six sizes. Six inch rods were similar to the HSC 2.5 in size...I'll bet they are the same too!

 

[Anonymous]

That's even better

A Scat or Eagle 6.125 H-beam rod for a SBChevy and the 94 to 95mm VW type 1 pistons. Leaving enough room for a .023 deck cut.

I noticed that Keith Black sells a long rod 305 piston that has a CH of 1.261, Is that the one that you used?

I don't know how much abuse a 250 crank can take. Are the AU cranks the same as the USA cranks?
You guys run them pretty hard (turbos, high rpm) and they live.
I noticed that the newest Au engines are using a stud girdle on the crank, is anyone selling these? Are they needed in a high boost engine?

This is getting more interesting all the time. Now if I can just get my hands on an alloy EFI head.

John

 

[xctasy]

Not exactly, I used some old stock forged TRW pistons. I suspect they were 305, but they could have been 229 V6 numbers. The stock deck was 1.531, and they had 56 thou taken off them.

I got seven of them from a guy who used to work with a team that raced supercharged 229 V6 rails in NZ.

I'd love to get some 1.26 " deck pistons, but they'd be way out of my budget. And stock size? Don't think stock sized forgies for 305's would sell a lot of volume anymore!

The cranks on the post EA -ED-pre EF (I think) were not very different to the 250 cross flow, but I'd doubt they'd fit an OHV. EF's had the now you see it, now you don't distrubutor drive removed. Ford let it come back on the EL series.Crank weights would maybee hit the cam too. SOHC engines have no cam that close to the crank anymore. With the EL, they played around again with the counterweights, put the distributor drive back on. After the AU, the BA got a new oil pump drive. So each crank has had lots of work through the years to get to that 6000 rpm rev line.

The new 2003 BA engine is so much smoother, it's just hard to believe its related to the 250, but it is!

Getting back to rod journals, though, check the main journal to crank journal overlaps, calculated by:-

the result of [(rod journal diameter+main journal diameter)-Crank stroke]
all divided by 2

144 four bearing 963 thou overlap (8400 rpm reported)

170/188 four or seven bearing 743 thou overlap (never breaks)

200/3.3 x-flow/3.2ohc Aussie7Mains 700 thou overlap (never breaks)

200 four or seven bearing 650 thou overlap (never breaks)

221 Argentine/Aussie seven bearing 483 thou (never breaks)

215/245/265 Chrysler Hemi 6, 7- brg, 410 thou (breaks at 7000 rpm, but the bore sacing is wider than the small Ford I6's and GM Holden L6's, crank is almost 300 thou longer )

250/4.1 x-flow/3.9/4.0 pre AU (1998) seven bearing 308 thou overlap (doesn't break at 7500 rpm)

GM Holden 186 with stroked 202 7 bearing crank is 425 thou overlap. Unlikely to break

GM Holden 235 stroker, using 221 crank cut down to 1.9 inch crank pins, and stroked to 3.68, with mains ground down 100 thou to 2.2 inches is down to 210 thou from it original 483 thou. Breakage only happens with very high revs and abuse.

My custom 221 crank, welded to 2.4 inch main bearing size, is 533 thou. I hope the heating during welding didn't do something horible to the grain structure. Mechanical engineers reckon the strength is in the fillet radius and surface finish, not totally based on over lap.

A stroked 250 with Chevy size small 2" journals, 6.125" rods, would have around 258 thou of overlap. As long as you don't rev it over 6500 rpm, it should hang together.

Note that six cylinder cranks run into a torsional vibration period at various revs. When you stroke or chose a long stroke crank with less overlap, the torsional vibration zone comes down. An example is the old GM Holden 202, which vibrated like a beggar from 4400 on to 5500 rpm. The later 12 counter weght crank had no vibration period untill about 7500 rpm. A steel crank is often 3 to 5 pounds heavier than a cast iron crank, and the vibration zone goes up a similar amount. In situations when you have no choice but to run a cast crank, like us poor fellows, a bigger vibration dampener, if avaliable, should help.

As for the stud girdle, its a good idea. There may be some chance of machining one for an OHV I6, but the mains are the wrong size. They tie things together. The alloy sump quietens the car down a whole heap too. The AU and BA run bigger main bearings...it could be the secrete to the higher rev range. The overlap is greater, but I'm not sure how much, sorry.

And as a footnote, Mopar fans with four bearing Slant 225 cranks need to know a cast crank explodes at 4500 plus rpm because there is only 213 thou of over lap. Uggghhh![/i]

 

[Fingers]

And as a footnote, Mopar fans with four bearing Slant 225 cranks need to know a cast crank explodes at 4500 plus rpm because there is only 213 thou of over lap. Uggghhh![/i][/i][/quote]

Its a good thing ma Mopar used forged cranks standard in slants up to 1976 then...

 

[xctasy]

Yup, and at work this morning I remembered the 225 has a 2.2 inch rod journal, and a 2.65 " main. So the over lap with a 4.125 stroke is 368 thou, not 210 thou. I couldn't concentrate at work knowing it messed up my calcs, and put people crook. Ooops, I've stuffed up again!

So I got it wrong again. Oh dear.

They slant is an amazing beast though. What would you do with a four-bearing crank? 280 hp and 13.2 second quarters like a 243 cid LandCrusier pistoned slanter Valiant that a fellow NZ'er ran in pre 65 racing. Game, wasn't he?