[enkeivette]

In the past three months I've taken the head off of two different 420A engines.

The first motor (mine) was bought with 72K miles on it. Since it's a cheap car, I feel I'm safe to make the assumption that it saw nothing other than organic oil and cheap 87 gas. Since I've owned the car, I've been running Mobil 1 but still 87 octane fuel. The head was taken off at 80K miles.

The second motor (my friends) was bought with very low mileage, around 20K. Since then it has only been run with Mobil 1 synthetic oil and 91 octane fuel. The head was taken off at 113K miles.

The first head (80K - organic) had usual signs of scoring on the cam bearings and the cylinder walls. The pistons were caked with nearly 3/8" of carbon.

The second head (113K - synthetic) had barely any signs of scoring on the cam bearings and the cylinder walls were shiny and glazed. The pistons needed no cleaning, there was basically no carbon build up.


This is obviously by no means a scientific test to which I can publish results. But I think you all get the point. Running good gas and synthetic oil makes a big difference.

[SeanPlunk]

Originally Posted by enkeivette

In the past three months I've taken the head off of two different 420A engines.

The first motor (mine) was bought with 72K miles on it. Since it's a cheap car, I feel I'm safe to make the assumption that it saw nothing other than organic oil and cheap 87 gas. Since I've owned the car, I've been running Mobil 1 but still 87 octane fuel. The head was taken off at 80K miles.

The second motor (my friends) was bought with very low mileage, around 20K. Since then it has only been run with Mobil 1 synthetic oil and 91 octane fuel. The head was taken off at 113K miles.

The first head (80K - organic) had usual signs of scoring on the cam bearings and the cylinder walls. The pistons were caked with nearly 3/8" of carbon.

The second head (113K - synthetic) had barely any signs of scoring on the cam bearings and the cylinder walls were shiny and glazed. The pistons needed no cleaning, there was basically no carbon build up.


This is obviously by no means a scientific test to which I can publish results. But I think you all get the point. Running good gas and synthetic oil makes a big difference.

As far as I know, the octane rating should have nothing to do with the quality of the gas.

[enkeivette]

Originally Posted by SeanPlunk

As far as I know, the octane rating should have nothing to do with the quality of the gas.

I honestly don't know, but I do know that Arco gas can cause carbon/ mineral build up. And the second motor has never taken a sip of that treacherous gas, while mine probably lived off of it.

[vonage6591]

Originally Posted by enkeivette

I honestly don't know, but I do know that Arco gas can cause carbon/ mineral build up. And the second motor has never taken a sip of that treacherous gas, while mine probably lived off of it.

I've heard that a couple of times but have never seen any evidence to back it up and just assumed that because it was the cheapest that people made that up. Is there proof showing that it does??

[SeanPlunk]

Originally Posted by vonage6591

I've heard that a couple of times but have never seen any evidence to back it up and just assumed that because it was the cheapest that people made that up. Is there proof showing that it does??

I've looked into this - there is NO proof I can find.

[Vettezuki]

Originally Posted by enkeivette

. . .The pistons were caked with nearly 3/8" of carbon. . . .

3/8? Are you sure? My mind cannot comprehend that. Maybe 1/16 . . . I want pictures

[enkeivette]

Originally Posted by SeanPlunk

I've looked into this - there is NO proof I can find.

I've seen proof, but for you it will just be more hear say. Matt used Arco gas in his quad for one day (nothing else was available), and then stored the quad for a week. Took it out again, and it wouldn't fire. Took the carb apart, and the main jet was closed off due to mineral deposits.

My friend Mike has a few first hand stories that I've heard aswell.


Ben, yes, it was ridiculous. I'm sure that I lowered the compression by scraping it all off. It was so bad that the height of the build up was limited by the cylinder head combustion chamber.

[Vettezuki]

Originally Posted by enkeivette

. . . Ben, yes, it was ridiculous. I'm sure that I lowered the compression by scraping it all off. It was so bad that the height of the build up was limited by the cylinder head combustion chamber.

Ouch. BTW, SeaFoam is awesome stuff for cleaning up carbon deposits in combustion chambers. We did it on my brother's truck and holly crap over I've never seen so many pillowing clouds of smoke come out of a tail pipe.

[enkeivette]

Originally Posted by Vettezuki

Ouch. BTW, SeaFoam is awesome stuff for cleaning up carbon deposits in combustion chambers. We did it on my brother's truck and holly crap over I've never seen so many pillowing clouds of smoke come out of a tail pipe.

Had to be great for the catalytic converter.

[Vettezuki]

Originally Posted by enkeivette

Had to be great for the catalytic converter.

No problem. It's just emulsified carbon. It's not like lead additives, or tons of NOX that destroy the catalyst.