Road Race Track/AutoCross 351w

General engine tech -- Drag Racing to Circle Track

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GimpyHSHS
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Re: Road Race Track/AutoCross 351w

Post by GimpyHSHS »

MadBill wrote: Tue Apr 27, 2021 12:40 am It's usually not necessary, but builders will sometimes use one half of a 0.001" different diameter bearing pair to 'fine tune' the bearing clearance by 0.0005".
Yeah, I knew that was common in home rebuilds or with used parts, etc. My cousin seemed to think I should wonder about it on the new stuff, but I won't stress over it too much.
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Re: Road Race Track/AutoCross 351w

Post by BILL-C »

If you have the ability to dial in your bearing oil clearances to exactly what you want by mixing half sets why not do it? Nothing back yard or improper about it! We do it often.
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Re: Road Race Track/AutoCross 351w

Post by Walter R. Malik »

BILL-C wrote: Tue Apr 27, 2021 7:01 pm If you have the ability to dial in your bearing oil clearances to exactly what you want by mixing half sets why not do it? Nothing back yard or improper about it! We do it often.
Most of the time, "garage" builders just won't spend the money for two sets of bearings to only use half of each.
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GimpyHSHS
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Re: Road Race Track/AutoCross 351w

Post by GimpyHSHS »

Interesting! I didn't mean to suggest it wasn't proper or was a bad thing, that was my question to y'all because I wasn't sure, I am just only familiar with home rebuilds where I have seen folks do it. Back in automotive in high school, we rebuilt a 350 Chevy engine doing it that way for one of my teacher's trucks. It wasn't a slap it together deal, everything was mic'd and checked carefully, but it was just a bunch of high school kids that did it in the shop (the teacher got a good deal with all that free labor...he still drives the truck today, so I guess we did alright!).

Just didn't know if it was a normal thing with new parts. I couldn't see any other way to do it better, but thought maybe when they started off with a new crank they eased into the machining on the crank to get it very close or something. I dunno, I just wasn't sure to be honest! Thanks for clearing me up there!
1995 Mustang GT (AutoX/Road Course Car)- Missing an Engine at the Moment... ](*,)
Tremec TR-3550 Transmission, 3.73 gears
Maximum Motorsports Coilovers, 400/275 lb/in Springs
MM Torque Arm, Fays2 Watts Link
Way too much else to list...issa money pit.
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Re: Road Race Track/AutoCross 351w

Post by GimpyHSHS »

182423656_296762298618742_4593393727085146633_n.jpg
Getting closer!
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1995 Mustang GT (AutoX/Road Course Car)- Missing an Engine at the Moment... ](*,)
Tremec TR-3550 Transmission, 3.73 gears
Maximum Motorsports Coilovers, 400/275 lb/in Springs
MM Torque Arm, Fays2 Watts Link
Way too much else to list...issa money pit.
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Re: Road Race Track/AutoCross 351w

Post by GimpyHSHS »

I am BEYOND impressed with this new engine!

I got a call from my engine builder last Monday afternoon. He told me that the engine was pretty much finished. He had a guy whose engine was supposed to be on the dyno ahead of me, but they were still waiting on some parts. Asked me if I wanted to run it this past week. Obviously, yes! But I was supposed to be going to Nebraska for work on Wednesday. I was able to delay my trip by a day and go dyno this bad boy. And it didn't disappoint!

Tuesday night, they put it on the dyno and used their 850 cfm carb to test fire and run it in. Figured if it was gonna window the block, they might as well know that before I took a day off work. After a little tuning and timing changes, it ran out to 645HP on 110 octane race gas.
carb number.jpg

When I brought the Holley Sniper to them on Wednesday, we installed it, put in some 93 pump gas, and played with the tuning. Peak power at 635HP!

efi numbers.jpg
power curve.jpg
The slight power loss was pretty easy to stomach. Their carb setup was a little leaner at WOT than we tuned the Sniper for, we were running 93 instead of 110, and the Sniper is 800 CFM compared to 850 CFM for their carb.
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1995 Mustang GT (AutoX/Road Course Car)- Missing an Engine at the Moment... ](*,)
Tremec TR-3550 Transmission, 3.73 gears
Maximum Motorsports Coilovers, 400/275 lb/in Springs
MM Torque Arm, Fays2 Watts Link
Way too much else to list...issa money pit.
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Re: Road Race Track/AutoCross 351w

Post by j-c-c »

So with reliability and on track mileage primary goals, that is a starting point 6500 rpm shift point motor?
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Re: Road Race Track/AutoCross 351w

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j-c-c wrote: Mon May 10, 2021 11:33 pm So with reliability and on track mileage primary goals, that is a starting point 6500 rpm shift point motor?
Autocrossing tries to emulate a road course in a very scaled down venue. Hence, you shift to your nominal gear before the first timing cone and leave it there for the whole run. At least that's the way I did it for time I autocrossed in my TA with an LT1 and 3.91 and close ratio 4 spd. I think in my 5+ years of parking lot racing, I only saw one car with over 500hp and he only brought it out on bigger courses. Gimpy will have plenty of RPM margin for bigger tracks using his favorite gear. Keeping his 200tw tires planted will be a challenge. Sliding is fun, but it's slower than a non-sliding car.
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Re: Road Race Track/AutoCross 351w

Post by GimpyHSHS »

I shift to second pretty quick and leave it there on AutoX runs. Typically don't turn more than 6300 at AutoX, at least on the courses we run. The lowest we pulled on the dyno was 3700 RPM, and it had 504 lb/ft of torque, so I don't think it'll have a problem pulling out of the slow elements. The plan is to not turn more than 7000 RPMs, but I think there's plenty of meat there to make it count.

I will definitely need to upgrade to 315s soon, though. The 275s probably won't do the trick.
1995 Mustang GT (AutoX/Road Course Car)- Missing an Engine at the Moment... ](*,)
Tremec TR-3550 Transmission, 3.73 gears
Maximum Motorsports Coilovers, 400/275 lb/in Springs
MM Torque Arm, Fays2 Watts Link
Way too much else to list...issa money pit.
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Re: Road Race Track/AutoCross 351w

Post by j-c-c »

Rick! wrote: Tue May 11, 2021 2:16 pm
j-c-c wrote: Mon May 10, 2021 11:33 pm So with reliability and on track mileage primary goals, that is a starting point 6500 rpm shift point motor?
Autocrossing tries to emulate a road course in a very scaled down venue. Hence, you shift to your nominal gear before the first timing cone and leave it there for the whole run. At least that's the way I did it for time I autocrossed in my TA with an LT1 and 3.91 and close ratio 4 spd. I think in my 5+ years of parking lot racing, I only saw one car with over 500hp and he only brought it out on bigger courses. Gimpy will have plenty of RPM margin for bigger tracks using his favorite gear. Keeping his 200tw tires planted will be a challenge. Sliding is fun, but it's slower than a non-sliding car.
I guess we see things differently. When OP mentions repeatedly AX & RC events, and then follows with goals of engine reliability and mileage, I disregard the normal AX objectives, as IMO, little carries over between the two.
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Re: Road Race Track/AutoCross 351w

Post by GimpyHSHS »

j-c-c wrote: Thu May 13, 2021 11:07 pm
Rick! wrote: Tue May 11, 2021 2:16 pm
j-c-c wrote: Mon May 10, 2021 11:33 pm So with reliability and on track mileage primary goals, that is a starting point 6500 rpm shift point motor?
Autocrossing tries to emulate a road course in a very scaled down venue. Hence, you shift to your nominal gear before the first timing cone and leave it there for the whole run. At least that's the way I did it for time I autocrossed in my TA with an LT1 and 3.91 and close ratio 4 spd. I think in my 5+ years of parking lot racing, I only saw one car with over 500hp and he only brought it out on bigger courses. Gimpy will have plenty of RPM margin for bigger tracks using his favorite gear. Keeping his 200tw tires planted will be a challenge. Sliding is fun, but it's slower than a non-sliding car.
I guess we see things differently. When OP mentions repeatedly AX & RC events, and then follows with goals of engine reliability and mileage, I disregard the normal AX objectives, as IMO, little carries over between the two.
When I say "reliability", I don't necessarily mean that the engine will last for 10 years, getting run hard most of the time. I fully understand that the engine will probably need some refreshing after 2-3 years. I mainly mean "reliable" in the sense that I'm not sweating bullets while looking at 10 PSI on the oil gauge at every stoplight or worrying that I'm gonna eject a couple rods out the bottom every time I run the RPMs up, or crack a piston, etc. My old engine had 15-20 PSI on the oil gauge when hot, which checks out after seeing the bearings. I think the balance job was pretty bad in that engine, too, it never felt like a finely balanced engine. "Reliability" in the race car sense of the word, where it's strong enough that I can enjoy it and not worry so much that I'm gonna throw a rod.
1995 Mustang GT (AutoX/Road Course Car)- Missing an Engine at the Moment... ](*,)
Tremec TR-3550 Transmission, 3.73 gears
Maximum Motorsports Coilovers, 400/275 lb/in Springs
MM Torque Arm, Fays2 Watts Link
Way too much else to list...issa money pit.
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