Why would you presume that anyone on this forum can speak to what any given insurance company would or wouldn't cover?
This is an enthusiast forum, a place on the web for an exchange of ideas and knowledge amongst those with a common interest. Sure, sometimes a question will be asked by an individual that seems obvious to most of us. But if this is a true open forum for early Ford V-8 automotive enthusiasts (whether longtime & knowledgeable or new and curious), as a whole the members/participants of the forum should be positive & forthcoming with their thoughts, ideas and solutions. Simply put, if you don't have something positive to ad to the conversation, keep it to yourself. Lastly, we shouldn't assume there isn't anyone on this forum that can't answer a particular question, because as this thread shows, there are folks out there weighing in with positive responses to the original question.
Now, as for the original question, yes, one should let the insurance company know if they make a performance upgrade to their vehicle relative to the power of the engine if is would significantly increase speed. As is customary in automotive insurance coverage the vehicle with the V-8 powerplant is more of a liability than a vehicle powered by a 4-cylinder engine. Having said that, there may be a gray area. For example, if you have a stock flathead V-8 engine in your pre-48 V-8 vehicle (let's say, a 1940 Ford pickup) and you upgrade the top end w/alum. heads, dual carb induction, headers, cam change and an ignition upgrade, my opinion is that the HP increase is going to be nominal as opposed to swapping in an OHV V-8 like an OHV 351 Windsor V-8. In that case, I wouldn't say anything, unless one feels that these upgrades increased the value of the vehicle significantly enough to warrant an increase in the replacement value on the policy.
As stated earlier in this thread, most (not all) collector car policies, whether antique, restored or modified generally require numerous photographs of the vehicle from all angles outside, the interior and the engine compartment along with details about the modifications and materials used (i.e., leather interior, candy paint, magnesium wheels, etc.) so the underwriters can review and approve/deny coverage and how much the premium is if they approve. I went through this w/AAA in So. Cal. with one of my cars which is modified and has a high replacement value in contrast with some antique/restored vehicles. They took their own pictures and physically inspected it while I had to provide a detailed list to justify the replacement value and it was approved for coverage. I also have a stock "beater" w/OHV V-8 power & stock driveline currently under a regular auto policy which I'm trying to get covered through the same collector car program my other car's insured with because up to now AAA So. Cal. would only insure "show room finish" cars & not weathered, "patina" vehicles under their collector car policy.
The point is this: If the change to the vehicle is significant (i.e., changed flathead to OHV engine power, changed wheels & added WWW tires, reupholstered in leather, etc.) and changes your vehicles value, then update your vehicle description with them. But, if the change isn't significant in terms of liability issues (i.e., went from single to dual carbs, installed dual exhaust, changed radiator, etc.) then an update may not be necessary. However as for liability issues, anything that could give them an angle to deny a claim (such as changing over from a flathead engine to and OHV engine w/out upgrading the driveline, brakes & rolling stock to accommodate the HP increase) should be brought to the insurer's attention regarding ones collector car insurance policy. That's been my experience and observations regarding this subject.
Lastly, just a point regarding collector car policy's and angles to deny claims: Closely examine the fine print on one's policy relevant to when, where, how long or how far the vehicle can be driven. Some policies aren't very "permissive". In other words, there can be limitations where you can drive you vehicle to. For example, your policy may only allow the insured vehicle to be driven only to certain venues, such as a swap meet, organized national event, parades or other organized automotive related events. If your just out for a "Sunday drive" and get in an accident, they may deny the claim. That's the reason after long research into collector car policy's from Grundy , J.C. Taylor & others I settled with AAA So. Cal.'s collector car policy because it IS permissive. If I so choose, it allows me to take my "collector car" out and drive my family out to the beach to have dinner or any other type of excursion that isn't an official organized automotive related event. Maybe some of the other provider's of this type of auto insurance have changed their policy rules, but don't take it for granted. Ask them and even then, check the fine print yourself. Good luck!
