LS7 265cc 4.000" (+) Bore - Single Black Label CNC Cylinder Head - Bare

Marsoni

M251S

$1049.50

Get it in 3 business days with 1 day shipping. Friday, May 29

LS7 265cc 4.000" (+) Bore - Single Black Label CNC Cylinder Head - Bare>Download the cylinder head spec sheet< The Mast Motorsports cylinder head product line is completely manufactured from a raw casting to a finished cylinder head in the USA located in Nacogdoches Texas. Mast refuses to compromise on materials and methods that may jeopardize longevity, performance, and quality. When buying Mast Cylinder heads, you are getting the highest level of quality and performance on the market. Full Send, no compromises, no

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We offer a 30-day return/exchange service after receiving.
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Used it as directed. Down to an eighth of a tank. Poured it in and added enough gas to get back to one half a tank. Wanted to get it mixed in really well. Immediately jumped on the interstate and ran 75 MPH for 40 miles. Stopped and filled the tank and when I restarted the engine, the light was off. Coincidence? Not a chance. Light had been on continuously for weeks. AutoZone said I needed a catalytic converter. Nope. One thing I found out the hard way. If your gas filler has a flap at the top, make sure it is easy to push aside. Mine had a little release button near the top that the filler hose would depress before the flap would release. Dumped the first bottle right on the ground. Twelve bucks wasted. No one to blame but me, I guess. Still a bargain, even at twice the price.

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Reviewed in the United States on February 17, 2026

Verified Purchase

Brenda A DeRouen

Los Angeles, US

★★★★★ 1

Before use on March 15 two days later March 17 engine light still on

Size: 1 Count (Pack of 1), Size: 1 Count (Pack of 1)

I read the specs on this product and it was guaranteed to cleanse as well as turn engine light off in vehicle. I received it March 14.2026 and used it on March 15.2026 I took a picture on Sunday before I entered it into the gas tank engine light was on at that time. Today is March 17.2026 and engine light is still on. The truck was driven for one hour on the 15th 45 minutes on the 16th and 50 minutes on 17 March. Still the engine light is on. Got home parked the vehicle took a picture again to show engine light is still on product guaranteed it was shut it off, but unfortunately product does not work.

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Reviewed in the United States on March 17, 2026