02/10/2026
๐บ๐ธ A VERY NICE MUSTANG THROUGH THE DOORS AT KN CUSTOMS! ๐บ๐ธ
Weโve had this absolutely stunning Mustang Fastback in with us after the owner contacted us with concerns over what sounded like a serious engine knock.
Before bringing the car in, the customer carried out an oil change and thankfully the serious knocking noise disappeared. Understandably though, he still wanted us to have a good look over it and give him some peace of mind before continuing to enjoy the car.
After running the engine from cold and carrying out our checks, we found what appears to be a slightly lazy hydraulic lifter on initial start-up. Once the oil pressure builds, the noise settles down and the engine sounds healthy.
For the time being weโve advised trying some Lucas Oil Stabilizer to see if this helps quieten the lifter down, with the option of addressing the lifters properly in the future should the noise become worse or persist.
The next issue was how rich the engine was running.
This isnโt a standard Mustang engine either! Itโs running performance heads, a high-lift cam, Edelbrock intake and a Brawler carburettor, so unfortunately there isnโt a factory setting we can simply put everything back to.
We hooked up our vacuum gauge and made some adjustments to the carburettor, getting the idle mixture and general running considerably better than when it arrived.
We also checked the ignition timing. With the engine having an unknown-spec high-lift cam and performance heads, we canโt accurately work from a standard factory timing figure. Based on where the timing is currently sitting, how responsive the engine is and how strongly the car performs, weโre happy with where it is.
And it certainly doesnโt hang about! ๐
There is still a very slight hesitation/misfire when holding the engine around 2,000โ2,500rpm. With the engine having been running considerably rich, the spark plugs may have become fouled, so weโve advised the customer to replace the plugs first and see whether that clears the hesitation before carrying out any further diagnosis.
The carburettor also still appears to be delivering more fuel than the engine needs under acceleration, so weโve advised that a less aggressive/more appropriately sized carburettor may suit the setup better.
Thereโs only so far we can accurately tune a modified carburetted engine in the workshop without being able to see exactly what the fuelling is doing under load. The ideal next step would be a proper rolling-road session with a wideband lambda/AFR reading, allowing the fuelling and ignition timing to be dialled in accurately throughout the rev range.
Most importantly, though, weโve found no indication of the catastrophic engine failure the owner was understandably worried about, and he can hopefully get back to enjoying this absolutely gorgeous Mustang! ๐
Safe to say we certainly donโt mind when things like this turn up outside the workshop. ๐๐บ๐ธ
KN Customs Ltd
๐ง Servicing โข Repairs โข Diagnostics โข American & Classic Vehicles
