Hay guys

Just doing some research. I'm getting a 3.8l fitted into my magna soon. I will be eventually putting a cam into her also. I've talked to a guy who builds 6G 72, 74, 75 engines he's called chapmans autos. Talked to him and he said once I get my 3.8l fitted with a cam and revving Abit more to replace the Rods. He said there to light and small and once I start revving it the Rods will distort and eventually **** up. He said the earlier 3.5l rods he fits to his engine along with the 3.5l bearings. So my question is how strong are the 3.8l rods? I heard there the same as the later 3.5l rods. So yeh just wont people experience and
Opionions?

Cheers kurt

He is correct. The 3.8l rods are weaker, as are the main bearings. The early 3.5's had the thicker rods as he mentioned too. (TH & possibly some early TJ.)

How weak are they? I don't think they're that weak that they require to be swapped just for a cam swap. I'm running cams in my 3.8l with stock rods & bearings at the moment, with no issues so far. If I were to go for a rebuild, then yes I would swap them over but not until then.

Wouldn't bother unless you went big revs. Or supercharged.

I seem to recall reading on here that the IPRA guys are running the 6G75s stock except for cams, and revving to 7300RPM without issues.

My 380 has done 50,000KM supercharged with stock engine & no issues.......

He is correct. The 3.8l rods are weaker, as are the main bearings. The early 3.5's had the thicker rods as he mentioned too. (TH & possibly some early TJ.)

How weak are they? I don't think they're that weak that they require to be swapped just for a cam swap. I'm running cams in my 3.8l with stock rods & bearings at the moment, with no issues so far. If I were to go for a rebuild, then yes I would swap them over but not until then.

Hopefully someone can shed some light.? The early model 3.8l had the not as good bearings but
The later model 3.8l engines had the better 3.5l bearings in them but still the not
As good rod. I'm not shore if this guy I talked to was exaggerating or not. But he said these exact words. I said when I put my cam in it will probably rev out to around 7rpm. He said as soon as u start revving them more those
Rods start distorting in the 3.8l. He then said they replace the rods and bearings with the 3.5l rods and bearings. But then I heard the ipra magnas with there 3.8l are revving out heaps with the standard rod. So don't know Wat to believe.?

The engine will be fine mate unless you sit it on 7000 24/7, even with a cam i doubt you will get much benefit from shifting at much over 6500 anyway.

The rod to stroke ratio dictates a 6800RPM max anyway

Just make sure you use a really good oil, im interested to find out what the IPRA guys use. As well as centrifugal forces, heat can assist in snapping a rod as the metal composition changes. A really good oil stands up better to heat. A diester based oil like those from Neo would be good. Not cheap mind. My clio is getting this stuff in the next oil change.

Just make sure you use a really good oil, im interested to find out what the IPRA guys use. As well as centrifugal forces, heat can assist in snapping a rod as the metal composition changes. A really good oil stands up better to heat. A diester based oil like those from Neo would be good. Not cheap mind. My clio is getting this stuff in the next oil change.

Valvoline VR1 20-50 Semi-syn.

Hopefully someone can shed some light.? The early model 3.8l had the not as good bearings but
The later model 3.8l engines had the better 3.5l bearings in them but still the not
As good rod. I'm not shore if this guy I talked to was exaggerating or not. But he said these exact words. I said when I put my cam in it will probably rev out to around 7rpm. He said as soon as u start revving them more those
Rods start distorting in the 3.8l. He then said they replace the rods and bearings with the 3.5l rods and bearings. But then I heard the ipra magnas with there 3.8l are revving out heaps with the standard rod. So don't know Wat to believe.?

Beleive the guys in the IPRA, DaveTJ is one of them, I have seen one of these cars in person and spoken to the driver many times, they dont touch the motors internally. The guy I spoke to has only ever done damage on massive over revs, normal racing has not had issues

Valvoline VR1 20-50 Semi-syn.

Hay zero do u and the IPRA use this oil? It's Abit thick.

Hay zero do u and the IPRA use this oil? It's Abit thick.

They do!.......i use the 15-40 version.

They do!.......i use the 15-40 version.

Where are they getting it from? As i need to give mine a oil change

My normal supplier has told me that only 10w-40 is now available in VR1. I have been running the 20w50 version like the racer boys

Try the Neo race oils, they are very good

At high revs all the time the oil will be a lot hotter.. and as it heats up its viscosity goes down, so to compensate, a thicker oil is used so that at the higher operating temp the extra thinning down by temperature brings it to the proper viscosity.

Actually wats interesting is that there only using a semi synthetic oil. Wouldn't full synthetic oils be better?

Just checked on those oil weights i mentioned.....:redface: its actually the 10-40 i've been using...so have the IPRA boys. Sorry about that!