Fuel System Tuning Q's

Thanks Bob. We have a guy down here in TX that is running 6.20 in his TD. I watched him make it several rounds and dialed the dang thing from 6.20 to 6.21 all day. His name is Mike Manners. He just bought a turnkey TAD to run also and has a Quick Rod dragster running about 213mph at 8.90 which is crazy. He owns the QR speed record.

My buddy's dad has a Pro Mod that runs and they are turning the AFC into a Fuel Altered right now. Driven by Dal Denton and tuned by Larry Reap. Only thing is I really dont help mess with them so I am not learning what I could be. We are too busy with 2 TD's and 2 TS cars. I have a friend that is also our TS tuner that built the Pro Mod and has a lot of blown experience that I am going to turn to for some help up front. But I want to learn everything myself for tuning later. Even though this "friend" that plays golf and poker with us all the time and hangs out with us and is a close friend, he will not give his knowledge up. He will tune it and you run it without teaching you anything. Thats what I dont like. He's really good but I want to learn it all.
So back to the point. I guess that a tune up in the middle range would work and then I could change shift points to adjust the ET if needed. It really doesnt need to be adjusted though. I just need to know what the new ET will be with the current air given. So hopefully no changes have to be made. I guess only time will tell and making some laps to see what it is going to do.
If this helps, it is a Reher-Morrison 565 bbc with close to 15-1 compression. I am going to run it for now with the current compression to save money. Using an 8-71 with hat and port injection. I talked to our motor guy at RM and he said maybe a max of 10% overdrive would work so I plan to start at about 5%and work our way up. I plan to change the pistons next year maybe so I can get the compression down a bit. I am also running my 7al3 box with my current ignition setup. I can change timing pretty easily during the run with timers. I was already thinking of pulling some timing out at launch so it might leave easier and then bring it back up after about .5 sec or so. I'm just wondering if this could be used to tune it as well. I dont know how critical timing is for these motors either.

 

middle of road tuneup

I met Mike Manners when I was writing for IHRA. Great team. Difficult to drive against an 8.9 sec competitor who always flies by you at the finish such as he does.
Regarding middle of the road tuneup, I previously referenced our tune up as in a linear range. That is when we increase the shift point, our ET is proportionately lower. That is a result of a whole bunch of characteristics from our combination, some intentional and some accidental. I recall a setup many years ago that was not linear. If you raised the shift point in some cases, you slowed down. The cylinder heads were small and acted as the limiting factor in the combination. The subject of linear is an extensive one. Keeping everything moderate is a good step in that direction: moderate timing, launch point, shift point, and fuel enrichment. In our case, we know what our air to fuel ratio is from jet area and air calculations. We know our rich air to fuel ratio limit and our lean air to fuel ratio limit and we keep in the middle. It is difficult to get there without record keeping and some calculations or data measurements. And we found that method to be very repeatable year after year after year.
Regarding your setup with the high compression BB, the detonation can be controlled with enrichment and air to fuel ratio control. However, I am not sure about the mechanical strength of the components. I asked a friend with BB experience, and he supposed that at that high compression with a blower and a wedge head, the power stroke starts on one side of the dome. If you are using short skirt pistons or pistons that are not full circumference below the ring groove, you may have a problem with skirt deflection, breaking a piston, or galling it. Anyone else out there put a blower on a NA engine with high compression? Incidentally the 8-71, at 10 over, theoretically pumps the same amount of air as an engine approaching 900 ci. Stuffing that into a 565 gets a lot of boost.
Bob Szabo, author Fuel Injection Racing Secrets and 5000 Horsepower on Methanol
www.racecarbook.com

 

High Compression and 8's

An 8-71 from the 80's or from today, big big difference.

My understanding is the OD limited straight rotored 8's on monster truck motors are in the 15:1 range. But they probably aren't conventional headed BBC's. The conventional head BBC, big compression and boost = $$$$ of detonated broken parts.

If it were mine, an old 8-71 and 10 over, I'd do it. But watch it closely.

Another option would be to mill off some piston dome.

Let us know what you do!

 

WOW. 900 ci. That sounds great, but dangerous for the motor. I plan to start it at about 5% over and see how it works, Run it a bit rich and easy on the timing. As you stated above. I'm only going to run this combination for a short time since the motor isnt built for it at all. The plan is to go to a blower piston and new rods for the next season. That should make it safe. BTW The heads are Dart 355 cnc.

 

heads?

Are they water heads or solid?
Bob Szabo
www.racecarbook.com