Harness fit my IO360 perfectly. Only #1 cylinder was marked, but no problem there. Cranked right up and ran perfect.
Johnny W
Verified Purchase
Shielded Ignition Harness 12304-33
August 19, 2025
We purchased this product for my school’s run and taxi Cessna 150. This fixed the mag drop issue and the product looks great. Very pleased.
Adam
May 9, 2025
David H
Verified Purchase
Shielded Ignition Harness # 12304-31
April 24, 2025
Purchased for my experimental O-200. No cylinder markings i.e. T3 etc, but very easy to future it out. A bit thicker cable than OEM, which created bigger loops in the wire, (couldn’t bend as tight) but again, no biggie. Fit well, good connectors.
Carl O
Verified Purchase
Shielded Ignition Harness # 12304-31
June 26, 2024
These were a perfect fit for my O-320 D3G
Paul R
Verified Purchase
Shielded Ignition Harness 12304-33
June 8, 2023
Works well
Norman S
Verified Purchase
Shielded Ignition Harness 12304-33
May 20, 2023
Pending installation cant tell yet.
John B
Verified Purchase
Shielded Ignition Harness 12304-33
March 25, 2023
fit perfectly
Jason B
Verified Purchase
Shielded Ignition Harness # 12304-31
November 23, 2022
Installation was simple, the leads fit perfectly, and each length was exactly correct.
Dr. A
Verified Purchase
Shielded Ignition Harness 12304-33
November 10, 2022
Magaero L
Verified Purchase
Shielded Ignition Harness 12304-33
August 23, 2022
Magaero L
Verified Purchase
Shielded Ignition Harness 12304-33
June 16, 2022
Everything fit as advertised. Price was right, didnt break the bank
James T
Verified Purchase
Shielded Ignition Harness # 12304-31
June 1, 2022
Would not purchase, the mag side of harness connectors are to short,and cause it to miss fire. Surefly Mag does not recommend it!
Dale L
Verified Purchase
Shielded Ignition Harness 12304-33
December 8, 2021
Rod K
Verified Purchase
Shielded Ignition Harness 12304-33
November 17, 2021
The harness was too short for the#1,#3, and very short for the#6 cylinders. Very disappointed.
Michael W
Verified Purchase
ACS Ignition Harness Lyc-O-540, Slick Mags
November 2, 2021
Gary D
Verified Purchase
Shielded Ignition Harness 12304-33
October 8, 2021
The best
Texas S
Verified Purchase
Shielded Ignition Harness 12304-33
June 16, 2021
No comment. Perfect job !
Vojtech J
February 19, 2021
Fit perfectly, had to reuse old cap screws so if yours are worn may want to order new. Caps are just a hair taller than the old ones. Came with a collection of adel clamps and screws and nuts and zip ties. However did not come with replacement rubber cushions that go around wires beneath the metal clamps on intake runners. Had to fabricate those from the cushions on the adel clamps.
Charles A
November 4, 2020
Really nice set of wires at a price BUT, if your mag is very tight to the fire wall, the shoulders they use to keep the wires straight coming out of the mag cap, adds about 1/2 to the length of the magneto. Only a problem if you were already against the fire wall.
Dave
September 14, 2020
Delivered promptly in good shape
Danny B
September 8, 2020
The parts arrived about a week after ordering, and were a perfect fit. There were no machine screws, so I used the old ones. Otherwise there were no problems.
Daniel K
May 11, 2020
I found this item to be well made and of very nice quality for my RV-4
Roger A
May 6, 2020
Fast delivery and perfect fit. No problems at all with installation.
Dwight H
July 27, 2019
They fit well and perform great. The shielding is encapsulated in a silicon outer coating/sleeve making them stiffer and larger in diameter than the original. This is a very good value compared to OEM product offerings.
Dr
May 11, 2018
fit perfect ,ran much better after install
Rick
April 5, 2018
Purchased for my Archer IIs 0-360 (M2363) p/n 12304-33. Wires were just long enough to route w/o kinking but were a tight radius out of the cap. A couple more inches in their lengths would help. As others stated, the plug hexnuts are not marked! They should be as my mechanic inspecting the installation said. Was able to make aluminum tags for each cylinder wire. Also marked the hexnut with a permanent marker.
Mark
November 22, 2024
It fit well to my Lcy. 0-320 & slick mags. However, the ignition leads didnt have a tag or label to what cylinder they were to go to. At least the cap had a #1 one for cylinder #1, and I used the old harness to figure out how to route all the leads.
Blue S
Verified Purchase
Shielded Ignition Harness 12304-33
August 16, 2022
It installed ok leads are a tight fit. Leads should be numbered.
Bill
August 28, 2020
It looked like a well made part but was the wrong harness. I need the harness for Bendix mags p/n 12301-22. The harness I received was for slick mags 12304-33. I have sent the slick harness back with an explanatory note including the required code number for returning a part, now I await shipment of the correct part.
Robert R
August 16, 2019
Dont know yet not starter engine, however hardware is not useful. plug ends not labeled. price is great if all goes well. Thank Jerry
Jerry C
February 5, 2018
Be advised, the terminals that fassten to the tops of the sparkplugs is about a half inch hgher than the original Slick harness.
Bruce C
Verified Purchase
Shielded Ignition Harness # 12304-31
November 27, 2025
Although it appears to be a quality product, I was a bit disappointed. Wires were not labeled. My main problem was the supplied adel clamps. The provided adel clamp holes were too small for the valve cover screws. Unfortunately, it required a trip home to retrieve my step drill bit.
The A
August 5, 2025
Perfect fit on my 4300 series mag
Five R
Verified Purchase
Shielded Ignition Harness 12304-33
June 5, 2024
The harness is largely of good quality, but overall the leads are short and tight on the engine. They need to be at least 8 inches longer per lead. I have a o540 engine and the application is for a o540 Lycoming,, I complained to Spruce about it, but the rep was not helpful at all
Joseph A
Verified Purchase
ACS Ignition Harness Lyc-O-540, Slick Mags
September 28, 2023
Didn’t work with my surefly, Caused it to miss fire, replace with a Kelly harness and the surefly works fine. The cables were also short, with very little slack
Steve M
August 28, 2022
Great product but leads are not labelled for cylinders.
Mark F
Verified Purchase
Shielded Ignition Harness # 12304-31
October 14, 2021
The first set of wires came with a defect at the spark plug end, however staff was quick to remedy the situation by shipping a replacement. Overall, the product seems to be great.
Bob H
August 16, 2019
The leads were not labelled and the harness caps are plastic, but other than that it was okay for the price.
Norm
November 28, 2018
I ordered this unit, needing it asap and was informed that it was out of stock in both east and west locations and that it would not be available for some time. Of course i could of cancellede the order and bought it elsewhere, but I chose to keep the order in effect. What puzzles me is that if this item is so popular, why would your company allow the stock deplete. I was told by your customer relations dept that it was the fault of the vendor, but I would say FIND ANOTHER VENDOR. I did finally get my order after about 3 weeks. A package of clamps was included, but are useless for installation because all rocker cover screws are 1/4 in dia, but the included screws were 3/16.
Try explaining this to an irate customer.
I also found that some of the wires were not of the correct length
Stanley S
September 18, 2017
I ordered this item for the two Slick magnetos that I purchased from ACS. There were no machine screws included with either the magneto or the wire harness !! So, I had to locate and purchase the appropriate screws so that the harness could be attached to the magnetos. Another delay.
Byron E
May 25, 2017
I enjoy the price, but this is no an exact replacement. Ferrules on the spark plug end stick up a critical additional ¼” and I will have to add bump outs to avoid squashing the wires. Why they don’t simply put 90° bends at both ends? Fortunately I have enough space at the firewall, but many plane installs don’t. With OEM caps it is possible to swap leads and use the right for the left, but these don’t appear to be able to be relocated. It would be nice to be able to buy just the right or left harness.
Kevin L
February 2, 2021
not approved for certified aircraft a&p would not install got a rma order and have sent back for credit
Tom K
August 7, 2020
The harness was way too short and none of the spark plug leads were marked for the cylinders they went to
Paul
Air F
February 10, 2021
Did not work out of the box. Going back two leads dead out of the box cost me tons of MX hours troubleshooting a new harness
Rob H
January 19, 2021