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2026 Rules Updates

Thanks to those who have supported, or plan to support our AutoMeter Wisconsin wingLESS Sprint Series powered by Gandrud Performance Parts.

Following up from our well supported recent meeting, we have come up with a few rule changes and clarifications. Again, it is important to remember that this engine package was chosen as part of a lower cost alternative for teams wanting to race sprint cars in our area. After a decade of competition, it has proven to be an outstanding series providing tremendous and competitive on track action. Our concept has worked. The cost of components has continued to rise however, so we as a group are looking for some ways where we can help find some alternatives, or choices, to allow our teams options, on certain items, from a cost perspective. Nothing we are doing creates a competitive advantage.

Our series is based on a GM604 engine. As no current full-time team is utilizing the "build your own engine" option, we are eliminating it. We are GM604 based only. Gandrud Chevrolet/Gandrud Performance Products are The Official GM parts supplier of IRA's Wisconsin wingLESS Sprints. Our "crate" rules are unique to almost all other crate based race series as we allow rebuilds, drilling of cam to run pumps, and some after-market part options. So, the below will be added to our rulebook for 2026. Much of the 2025 wording will remain. And one item is still being researched before a final decision will be made, though that decision will be made very shortly.

So, in regards to some of the discussion topics at our meeting, this below should clarify.

Engine Blocks: The production GM 800 series blocks have been the standard and will continue to be so. Maximum cubic inches of 355 remains, maximum compression remains at 10.1:1.

Pistons: The Mahle #MHL9301278XX (the XX dictates piston size) piston has proven to be to be an excellent alternative and are available in many different over-sizes to allow for multiple rebuilds. This remains the only alternative to the stock GM piston. Aftermarket piston rings are allowed.

Rods: In addition to the stock GM604 connecting rod, we will allow the Eagle #SIR5700BPLW which is a 5140 forged steel rod with 8340 ARP cap screws. This rod weighs 550g, which is 50g lighter than a GM rod, though we feel has no competitive advantage, though it may require additional crank balancing because of the weight difference. The other new option is the Scat #25700P which is forged steel with ARP 8340 rod bolts. The Scat weighs 605g and is already approved by both IMCA and WISSOTA. It's weight is virtually identical to the GM so no additional balancing will be required.
We are allowing ARP rod bolts.

Oil Pan: While we have allowed aftermarket pans, the Champ #CP100LTRB is specifically made for the 604 application and is solid cost-effective option.

Crankshafts: The GM remains the only legal option. After researching, there are aftermarket part numbers out there, though none are readily available. We stay as we've been on this, stock GM ONLY. Also remember, certain parts such as crank, and rods, should be replaced after four years or so of use.

Cylinder Heads: No change, an unaltered GM "fastburn" cylinder head remains as only option. As we allow freshening, normal procedures for that process are permitted (valve jobs, resurfacing). Any machining that alters the stock design WILL result in disqualification. No change, only stock GM valves, and GM beehive springs allowed.

Lifters: Any mfg, though must be GM factory style, using "dogbone" brackets as anti-rotation devices. No tie bars. Lifters must remain hydraulic roller design. Plungers must depress .100"

Rockers: We have a 1.5 Rocker-arm rule. Our tech tool was purchased from GM and made to check their rocker arm ratios. GM will not guarantee the accuracy of the tool when testing other mfg products, thus the fact this part has a fairly long life span in this application, the current GM 1.5 rocker will continue to be the ONLY legal rocker.

Carbs: We will allow carbs from any mfg. They must be of a Holley 4150 series design and the max size is 750cfm. Carb must have Holley style boosters. Straight leg and dog leg are both permitted, therefore, booster installed height will not be teched. All carbs will be teched with go/no go gauges from BLP Products. Willy's "superbowls" are NOT permitted. Twin blade carbs are NOT allowed, and the screw in boosters such as those found in Willy's equalizer carbs are NOT allowed.

Camshafts: No changes, though an issue that needs addressing is a statement in what some people refer to as the "GM yellow book" pertaining to the specs of the 604 camshaft. Specifically, the sentence that states all cam specs are within +/- .10" or 5 degrees of angularity. GM has a performance tech line available. It's the same line available to dealership technicians. We spent a considerable amount of time on the phone with GM to get clarification on that statement. GM's official stance is that it's a legal disclaimer. GM wrote that in because they can not govern how different engine builders or race series interpret their specifications or how they police a series. The specs on a 604 camshaft are as follows. Lobe lift is .316" - int. and .340" exh. This results in a .474 in and .510 exh lift with 1.5 ratio rocker arms. Duration @ .050" lift is 208 - int, and 221 - exh. Cams will be rolled on our Cam Doctor, and this will be part of our new sealing process. This tool is with 1% of accuracy, there is no leeway on this.

Engine Sealing: Beginning in 2026 we will be implementing an engine sealing program. Teams will be required, and it's a team's responsibility to have a minimum 3/32" holes drilled in 4 intake manifold bolts, 2 timing cover bolts, and 2 oil pan bolts. Oil pan removal will be required during the inspection/sealing process. Pre-season appointments can be made in advance, plus other specific dates announced. Cars racing prior to being sealed will have purse money and points held until the engine is sealed, with a realistic time of doing so implemented. The discovery of seal tampering will result in automatic disqualification and suspension.

Tires: After explaining how our point fund contribution works, the "majority" of teams who reached out after the meeting preferred to stay with Hoosier. But, for those it gets better. We reached out to Hoosier requesting more point $, knowing they should have additional $ in their budget because a few other groups chose to switch mfg or go open. Our request was granted, and we got a 33.3% increase in our per car point fund contribution. We jumped from $15 to $20 per car/per night.
Based on that, Hoosier provided our series $6900 in 2025, at that same car count, that would be $9200 based on 2026 per car amount. So WE WILL be staying Hoosier 4-corner with D15a, MED, or H15 legal RR, and D12a, SC12, or H12 LR and, D12 or D15 fronts.

In 2026, magnetos and ETC rev limiters will no longer be permitted in the AutoMeter Wisconsin wingLESS Sprint Series powered by Gandrud Performance Parts. While we don't feel there was an unfair advantage to those few who used that combination over the years, we just want to get uniform on this rule as this is a crate-based series with strict parameters. All cars will be required to utilize a GM HEI Distributor with an MSD soft touch rev limiter part number 8728 or 8727CT, as the large majority currently do.

Special thanks to Ed Boyd for his time and effort he put into this. I'm truly grateful for his efforts. And thanks to Dennis Spitz for all his research, and of course Kevin Spease, Tony Jenkins, and others such as Craig Campton who I've leaned on over this process.... but special thanks to Eddy. Ed will head up the sealing process and his MLS Auto Clinic location and his proximity to Wilmot should make this process become a much needed reality.

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