Any experts recognize these rods? 2.8 race motor

[jmz]

Amy of you experts recognize who may have made these rods?

They are ~141mm and came out of my trick 2.8 Race motor.

[Magyar Kiwi]

Hi
Those nice rods were shot peened at manufacture.
Shame that someone attacked the caps with a Centre Punch one to six times !
Cheers

[dannobee]

They look like Crower Maxi-Lights. Could be something else, but the design looks the same.

[jmz]

Thank you, Deep Google search told me that might possibly be the builder. Original build was back in the 80s I think.

[jmz]

These are somewhat unique in that the rod bolts thread into the cap leaving more clearance around the big end. Most are the other way round.

[safe]

Looks like every I-beam rods made in China. Not implying that they are bad, only that there are just a few factories and they do tonnes of rods for different brands.

[jmz]

Originally Posted by safe

Looks like every I-beam rods made in China. Not implying that they are bad, only that there are just a few factories and they do tonnes of rods for different brands.

While I agree that they look like them, think this build pre dates China made rods.

[phunt]

You know China is older then the U.S.

[targa72e]

They look a lot like the rods offered by MittelMotor in Germany. Not sure who makes theirs.
https://www.mittelmotor.de/racing/de/webshop



john

[safe]

Originally Posted by targa72e

They look a lot like the rods offered by MittelMotor in Germany. Not sure who makes theirs.
https://www.mittelmotor.de/racing/de/webshop



john

Definitely China. I got some Mittelmotor rods for a 924,

[917_Langheck]

Looks like some didn't actually spot the difference in their boy's life books....

[jmz]

Originally Posted by phunt

You know China is older than the U.S.

…was china building rods for Porsche racing engines in the 1980s?

[jmz]

Originally Posted by 917_Langheck

Looks like some didn't actually spot the difference in their boy's life books....

WTF? I Just want to get these old school rods re-bushed/rebuilt and go racing again, -thought I might reach out to the brain trust here.

[917_Langheck]

JMZ, are you the one comparing your rods to chinesium that look nothing like your rods? No sir. That observation wasnt directed at you; why would it have been, you're the one asking for help, and not really getting it with comparisons to parts that are clearly not identical. Sheesh.

[Henry Schmidt]

I'll come at the question from a slightly different perspective.
I don't know who made these rods. In 40+ years of building these engines, I have never seen that design used in an air-cooled Porsche.
That said, does it really matter? If you were thinking about buying these rods, "who made them" becomes far more important. You own them, they look to me to be well made and you have a history of success with them.
If this is a 2.8, that would suggest that the B&S is 70.4 x 92. Very common in the day. Whoever built this engine was looking to improve the rod length to stroke ration in an attempt to help it rev. 141:70.4 = 2:1. This odd length may also suggest that the rods were designed for another application. Carefully measure the journal size.
2:1 is considered by many (including myself) the optimum ratio for NA engines for a couple of reasons. Increased rod angularity causes additional wear and often facilitates the need for off-set wrist pins. Longer rods reduce angularity and create additional piston dwell improving horse power output. With longer rods, the pistons dwells longer at TDC and it dwells less at BDC. The decreased dwell BDC can cause detonation. The perpetuity towards detonation in a Hemmy head engine means attention to dynamic compression becomes more critical.
Knowing who made them is a nice foot note but not required to rebuild your engine.
Obviously the long rod will create the need for custom pistons, so look to that issue carefully.

[jmz]

Originally Posted by 917_Langheck

JMZ, are you the one comparing your rods to chinesium that look nothing like your rods? No sir. That observation wasnt directed at you; why would it have been, you're the one asking for help, and not really getting it with comparisons to parts that are clearly not identical. Sheesh.

My bad! Sorry, took that the wrong way!

[jmz]

Henry, thank you for your response.

I asked the question so maybe we could send back to the shop that made them to have them re-bushed.

This engine uses 2.8 factory RSR 92mm pistons and a 70.4 crank with clever use of spacers, longer chains, modified fan shroud and a splice welded info the Weber cross bar.

You might be about to help with another question. …cams are Elgin 306 288 102. Current heads that have been used for many years have I think 38 or maybe 39 intake port size. …not close by to measure. It is currently very easy to drive and if you set it up right pulls quite well out of corners.

I have another set of heads that appear to have been loved on a visited by Captain Airflow …41.5 intake and 39/40 exhaust depending on where you measure. (D shaped exhaust)

Compression with current heads measures 12-5:1 need to verify with the big port heads still.

In my quest for more power I am considering using these. -should probably leave well enough alone but…

Anyway, any thoughts on using the big port heads?

Originally Posted by Henry Schmidt

I'll come at the question from a slightly different perspective.
I don't know who made these rods. In 40+ years of building these engines, I have never seen that design used in an air-cooled Porsche.
That said, does it really matter? If you were thinking about buying these rods, "who made them" becomes far more important. You own them, they look to me to be well made and you have a history of success with them.
If this is a 2.8, that would suggest that the B&S is 70.4 x 92. Very common in the day. Whoever built this engine was looking to improve the rod length to stroke ration in an attempt to help it rev. 141:70.4 = 2:1. This odd length may also suggest that the rods were designed for another application. Carefully measure the journal size.
2:1 is considered by many (including myself) the optimum ratio for NA engines for a couple of reasons. Increased rod angularity causes additional wear and often facilitates the need for off-set wrist pins. Longer rods reduce angularity and create additional piston dwell improving horse power output. With longer rods, the pistons dwells longer at TDC and it dwells less at BDC. The decreased dwell BDC can cause detonation. The perpetuity towards detonation in a Hemmy head engine means attention to dynamic compression becomes more critical.
Knowing who made them is a nice foot note but not required to rebuild your engine.
Obviously the long rod will create the need for custom pistons, so look to that issue carefully.

[Henry Schmidt]

Any competent machine shop familiar with Carrillo rods should be qualified to rebuild those rods. They may have to fabricate the pin bushings.

The pistons used in your build have the 12.5 compression ratio because they were designed to run in a completely different chamber configuration. RSR heads had a considerably different combustion chamber (much larger volume with different valve angles). That means, the valve pockets in the RSR piston do not match the valve angles in the 2.7 head. Is that OK? well, it's OK until you start measuring valve to piston clearance with any real accuracy.
The 2.8 RSR was designed to run 10.4:1 and that number was always very optimistic.

[jmz]

Originally Posted by Henry Schmidt

Any competent machine shop familiar with Carrillo rods should be qualified to rebuild those rods. They may have to fabricate the pin bushings.

The pistons used in your build have the 12.5 compression ratio because they were designed to run in a completely different chamber configuration. RSR heads had a considerably different combustion chamber (much larger volume with different valve angles). That means, the valve pockets in the RSR piston do not match the valve angles in the 2.7 head. Is that OK? well, it's OK until you start measuring valve to piston clearance with any real accuracy.
The 2.8 RSR was designed to run 10.4:1 and that number was always very optimistic.

Race engine, 110 octane always. -No issues so far and while I cannot say that the valve to piston clearance is optimal I can say that I've not had a problem with the occasional mis-shift and pistons and valves making bad things happen.