Road Race Track/AutoCross 351w

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Re: Road Race Track/AutoCross 351w

Post by Cobra720 »

I also Autocross in a light car 2600lbs. cobra. 3.73 gears TKO 600RR Aluminum fly wheel. I built two motors during the past 10 years. The first motor was a 351W 10.5:1 with Brodix heads that flowed like an AFR 205 and a Vic Jr intake 2-3/4 primaries and a 3" exhaust. So not far off from what you were talking about. Mike Jones ground me a cam HR 233/237 somewhere around .565 lift, LSA 108 ICL 105. Pro-system 780cfm.
The car pulled real nice in 2nd gear from 2000 up to 6000rmps. I just think your cam was too big and your heads were ok. I also had Light Blue springs in the MSD so the advance came in early.

The motor I have now is a 408W Dart block custom SR, ported intake, John Dickey(AED) built me a nice custom carb same heads and It's just an animal. Same exhaust but now I've been told it's too loud, SMH. Good Luck with the new build, should be a big difference. Now you'll have more to deal with, as me how I know.
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Re: Road Race Track/AutoCross 351w

Post by GimpyHSHS »

Tuner wrote: Thu Apr 01, 2021 6:25 pm The cylinder heads on the OP's original engine combo are fast burn and do not at all like advance much over 26 or 28 degrees and that only at high RPM. The WOT low RPM range where he was complaining about the engine struggling may haver been better suited with timing in the 20-22 area. And, the 25 plug is too hot. I have done several mechanical distributors for SBF engines with similar heads and have found they don't like old school timing numbers at all. Timing can be advanced too much for best power and not knock, just have less power than if it were ideal for best output. The above assumes engine is hot to endurance racing temperature, water and oil.
This is very interesting. I called Bill Mitchell at one point and explained the situation to him, and he didn't mention anything like that. I suppose if I had ever had it on a dyno, I might've been able to test that. It just wasn't in the cards at that point.
frnkeore wrote: Fri Apr 02, 2021 1:56 am Well, with that much additional hp, it will be a little harder to control, maybe a lot.

In road racing, it's all about entering a corner and accelerating smoothly out of it. You don't want the tires to spin, a controlled drift, is much faster. Seat time is what will get you to advance your skills and a instructor will help, a lot!

I would suggest two simple things. First have them advance the am, at least 2 more degrees. That will give you a little more average hp and it may not come on so strong as the rpm increases. It won't effect it a lot at higher rpm and it's easily reversed.

Second, put in a 1/2 throttle stop or, disconnect the secondary's, until you get smoother. It will be very frustrating, trying to control the power on the short acceleration areas and having to get set up, for the next corner.

My best suggestion, if you want to be very good at what your doing, is to get the best available driving help, you can afford.

https://duckduckgo.com/?q=road+racing+s ... =h_&ia=web

Find one near you. HP is easy, honing your drivers skills, isn't.
Oh, I imagine it'll be very hard to control. My cousin AutoX's a 99 Firebird with a crate LS3...supposed to be around 550hp. It's a bear to drive unless you're reeeeeeally sensitive on the throttle. All autocross in that car is basically controlled sliding. I codrove it one event and told him I was going back to the Mustang. Never drove it again. He whips it around and places very well in that car, but he's also spent the past...over 10 years making it a great AutoX car for him. It's hard to be a fast RWD American car driver in our AutoX, but he's known for it around us. I just don't have the car control skill he has yet. I don't overestimate my skill level...I know it'll take a while to adjust to big power. Throttling it back may be a good idea to start.

I plan to make a small throttle extension for the Sniper to help with control, too. The old engine was basically impossible to overdo it taking off, but this new engine might benefit from a little more precise control. The Sniper opens the "secondaries" evenly with the "primaries", so not chirping the tires on normal takeoff is a known problem.

I have considered a driving school very heavily, but I'm not racing competitively or anything right now, so it's just cheaper and more fun to learn a little as I go. Normally my cousin rides with me on a run and watches where I'm messing up, and then gives pointers on how to do better. Then I focus on those things and get slowly faster. The nice part about AutoCross is that you can't mess up too bad...worst that happens is you spin out, which I have done my share of in the last year. A little ego damage, but that's all.

They do a driving school at the Hallett event my family goes to in June on Father's Day weekend (Mid-America Ford and Shelby Nationals), but I never get to town in time to attend. I usually get some good tips and pointers from my family. My dad raced ARCA back in the 80s, he's a fairly good driver, and my cousin has done some form of it for 30 years in cars and on motorcycles. So I at least have some good people teaching me. I'm just still working on being smooth...smooth...smooth. I know what to do...now I just have to be able to do it.
j-c-c wrote: Fri Apr 02, 2021 11:37 am A few others have touched on this angle, but Auto-X and closed track road racing are vastly different animals IMO engine wise. So is real(?) road racing ever in the mix, or are we focusing mainly on autox?
Someday, maybe, if I ever get good enough to and have the budget. I've kind of been adding parts to this car with the idea that in...ten years I might want to go run in American Iron and get beat up on.

I mainly do AutoX, since it's a cheap and easy way to get seat time. My cousin also insists that he would've been a much better dirt track driver 25 years ago if he had done AutoCross for 15 years before. But I enjoy track days much more. The plan was to branch out to some other close tracks, Eagle Canyon, Barber, Memphis, maybe even COTA, this year, but the engine deal is going to postpone everything but Hallett until next year.
hoffman900 wrote: Fri Apr 02, 2021 11:50 am Looks like autocross and track days.

For track days, don’t even worry about going faster in a straight line and focus on keeping the engine together. Road racing is very hard on equipment (engine, brakes, etc). Odds are you’ll be driving nowhere near the limit (and shouldn’t be).
Pretty much just AutoX and track days, yes. 15-20 minute sessions at a time. We're not driving at or near the limit, but going faster is more fun. That is why I wanted the strong foundation...something that will handle the abuse for a nice long time. Most of the money is in the Dart block and forged rotating assembly, but I also invested in some longevity things like the deep sump oil pan with windage tray, scraper, trap doors, etc.. An Accusump and oil cooler are also on the plan eventually, before I do anything bigger than Hallett.

Already have the Brembos, Raybestos pads, Motul fluid, stainless brake lines, brake cooling ducts, proportioning valve, coilovers, watts link, caster/camber plates, etc etc.

Tinkering with this car is a labor of love. I don't show up planning to blow peoples doors off, I just enjoy working on the car and getting a little better each time. When I started autocrossing it last year, I spun out on 3 out of 6 runs...then at least once per event for the next 7-8 events. In August, I finally went a whole weekend (2 events) without losing it, and I don't think I have since then.

Thanks for all the advice and opinions. It is always nice to hear other perspectives and things to look at!
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Re: Road Race Track/AutoCross 351w

Post by GimpyHSHS »

Cobra720 wrote: Fri Apr 02, 2021 2:55 pm I also Autocross in a light car 2600lbs. cobra. 3.73 gears TKO 600RR Aluminum fly wheel. I built two motors during the past 10 years. The first motor was a 351W 10.5:1 with Brodix heads that flowed like an AFR 205 and a Vic Jr intake 2-3/4 primaries and a 3" exhaust. So not far off from what you were talking about. Mike Jones ground me a cam HR 233/237 somewhere around .565 lift, LSA 108 ICL 105. Pro-system 780cfm.
The car pulled real nice in 2nd gear from 2000 up to 6000rmps. I just think your cam was too big and your heads were ok. I also had Light Blue springs in the MSD so the advance came in early.

The motor I have now is a 408W Dart block custom SR, ported intake, John Dickey(AED) built me a nice custom carb same heads and It's just an animal. Same exhaust but now I've been told it's too loud, SMH. Good Luck with the new build, should be a big difference. Now you'll have more to deal with, as me how I know.
Very nice! We have a couple guys, the Lousteaus, that Autocross an FFR Cobra here in Arkansas. Veeeery fast. If they're there, virtually guaranteed to be in the top 5, if not setting FTD.
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

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In the shopping cart list of enhancements, I didn't see tires.
Are you running street legal stickies with shaved tread or....?
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Re: Road Race Track/AutoCross 351w

Post by j-c-c »

Still not clear which is your primary application is.
But this is my take engine builds, AutoX you build a motor that is as responsive as possible, everything is about throttle control and low end response. A track car, its very difficult to get needed traction exiting corners from the chassis, and aero isn't yet in the game at most corner exit speeds. Any passing in your mind that occurs exiting from a corner is on a car that is under-powered relative to yours at low speeds, driven by a novice, and/or a lousy chassis or tire set-up, ie, so no accolades there. Passing in road racing is most likely at end of straightaways and/or under braking, that requires HP, not torque, the advantage is a car being set up to be passed is draft-able, and you need all your advantages in speed at the top end from the motor. Peaky HP is relatively OK, if you are chasing another car, but running by yourself without a draft, peaky has fewer pluses. The downside as others have touched on, you are beating on the motor, lap after lap, so its a compromise as to what and how much you compromise these two main goals, HP and reliability.
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Re: Road Race Track/AutoCross 351w

Post by GimpyHSHS »

Rick! wrote: Fri Apr 02, 2021 7:49 pm In the shopping cart list of enhancements, I didn't see tires.
Are you running street legal stickies with shaved tread or....?
I run in CAM-T (Classic American Muscle - Traditional), so we're limited to 200tw tires. I've been running 275/35/18 Falken Azenis RT615K+ on 18x9 wheels, but I got a good TireRack deal on the same size Nexen SUR4G. They definitely aren't the top of the line 200tw, but they work pretty well for now. I figure there's no point going to another, more expensive brand until I'm good enough to take advantage. These tires are better than me right now anyway.

18x11 wheels and 315/30/18s are on the list of upgrades for down the road. My main competitor (and also the friend I am codriving with until my engine is done :lol: ) just made the switch on his.
j-c-c wrote: Sat Apr 03, 2021 2:35 pm Still not clear which is your primary application is.
But this is my take engine builds, AutoX you build a motor that is as responsive as possible, everything is about throttle control and low end response. A track car, its very difficult to get needed traction exiting corners from the chassis, and aero isn't yet in the game at most corner exit speeds. Any passing in your mind that occurs exiting from a corner is on a car that is under-powered relative to yours at low speeds, driven by a novice, and/or a lousy chassis or tire set-up, ie, so no accolades there. Passing in road racing is most likely at end of straightaways and/or under braking, that requires HP, not torque, the advantage is a car being set up to be passed is draft-able, and you need all your advantages in speed at the top end from the motor. Peaky HP is relatively OK, if you are chasing another car, but running by yourself without a draft, peaky has fewer pluses. The downside as others have touched on, you are beating on the motor, lap after lap, so its a compromise as to what and how much you compromise these two main goals, HP and reliability.
Primary application is just going fast and having fun....just a fun car really. I'm not building the car solely for either application. I autocross 1 weekend a month for 8 months. I do a few track days a year. I'm hoping it's reliable enough to take some cruises on the mountain roads...we have some beautiful, fun roads here in Arkansas that I used to drive all the time. But the car hasn't been reliable enough to do that here lately, and it's just not the same in my Focus. It's not really for only one thing. But obviously, the suspension is more suited for track days. Because that's what I enjoy doing the most (and what I am hoping to do more of next year), I just want the car to be better at that.

I didn't want to put just "track" in the title because I was worried people would think I meant drag strip. Where I live, if you say you're going to the "track", people say, "Prescott or Centerville?" (the two 1/8 mile drag strips around here). I suppose putting "Road Race Track" might be confusing too, though.

I'm trying to stay very balanced on the engine where it can do anything I want decently well. It's a 427 with reasonably sized heads, so I am hoping it's very responsive down low, and that is something I stressed to the engine builder. I wanted a lot of low end. I also imposed the RPM limitation, I didn't want to turn over about 6700 originally.

I definitely did not want only peaky horsepower. That's why we're not hogging out a set of large port heads, putting on a Super Victor, running a solid roller, huge carb, etc. Since we're not racing, I'm usually just by myself out there, trying to stay away from everyone, trying to just have my own fun and go fast.

At the same time, I didn't want an engine that ran hard to 5000 and then fell on its face. The engine builder says the current plan will have plenty of power and response down low for the AutoCross days, but make peak hp around 65-6700, then slowly fall off. So he thinks we keep the rev limiter at 7000. I expressed my concern that I would lose the low-end power I was mainly looking for, and he pointed out that he could give it more low end and less top end than he wanted, but that I probably wouldn't be able to lay down the power at the bottom end anyway.
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Re: Road Race Track/AutoCross 351w

Post by j-c-c »

That's all fine and reasonable IMO, except one thing that few seem to understand until they hit the "track", its really hard to put that low end down (traction) exiting a corner, regardless of any tire choice. What you will likely find, once you are straight enough and up to speed, you are out your low end power band. Now if seat of the pants acceleration smile and counter steer power slides are the needed thrill, enjoy, but it will not be fast.
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Re: Road Race Track/AutoCross 351w

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j-c-c wrote: Sun Apr 04, 2021 2:15 pm That's all fine and reasonable IMO, except one thing that few seem to understand until they hit the "track", its really hard to put that low end down (traction) exiting a corner, regardless of any tire choice. What you will likely find, once you are straight enough and up to speed, you are out your low end power band. Now if seat of the pants acceleration smile and counter steer power slides are the needed thrill, enjoy, but it will not be fast.
Having enough power and response down low to be able to use the accelerator pedal as a "rheostat" is very good but, requires a talented driver with an educated right foot.
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Re: Road Race Track/AutoCross 351w

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Walter R. Malik wrote: Mon Apr 05, 2021 12:26 pm
j-c-c wrote: Sun Apr 04, 2021 2:15 pm That's all fine and reasonable IMO, except one thing that few seem to understand until they hit the "track", its really hard to put that low end down (traction) exiting a corner, regardless of any tire choice. What you will likely find, once you are straight enough and up to speed, you are out your low end power band. Now if seat of the pants acceleration smile and counter steer power slides are the needed thrill, enjoy, but it will not be fast.
Having enough power and response down low to be able to use the accelerator pedal as a "rheostat" is very good but, requires a talented driver with an educated right foot.
........ and nevermind the throttle linkage, bellcrank ratios and such...
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Re: Road Race Track/AutoCross 351w

Post by j-c-c »

There is nothing as exhilarating on the track as driving a car well balanced enough in all areas, that the driver can "rotate" the car thru the turn with gentle throttle usage.

I'll resist going further as this is the "engine" forum. :D
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Re: Road Race Track/AutoCross 351w

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j-c-c wrote: Sun Apr 04, 2021 2:15 pm That's all fine and reasonable IMO, except one thing that few seem to understand until they hit the "track", its really hard to put that low end down (traction) exiting a corner, regardless of any tire choice. What you will likely find, once you are straight enough and up to speed, you are out your low end power band. Now if seat of the pants acceleration smile and counter steer power slides are the needed thrill, enjoy, but it will not be fast.
Seat of pants acceleration and countersteering like a mad man can be fun...that's how my cousin autocrosses his car. He came from dirt track racing, where using some throttle steer isn't uncommon. That bleeds over into his AutoCross and track driving.

Making peak power at 6500-6700 and still having plenty of usable power up to 7000, I don't think I'll miss it very much. It's a little higher than I really wanted originally, but the engine builder doesn't think I will be lacking for low end, mainly because of the point you're making. It should make good power down low, but still be able to run a bit higher. That's his goal anyway.
j-c-c wrote: Mon Apr 05, 2021 1:59 pm There is nothing as exhilarating on the track as driving a car well balanced enough in all areas, that the driver can "rotate" the car thru the turn with gentle throttle usage.

I'll resist going further as this is the "engine" forum. :D
We always complained about the fact that you couldn't even use some extra throttle to help the car rotate. You either went full throttle or you got nothing...but even going full throttle, the old engine would not break the tires loose. There was several occasions where the car was pushing a bit and I wanted to use the throttle to get it around a cone, and you just simply couldn't do it. Even tried popping the clutch once when it was pushing in one spot...nothing. I was hoping to make some minor changes and get some power back, but certainly didn't plan to go as far as I am now.

The hope is to get the car pretty well balanced...we want it to be as fun as possible, but not JUST uncontrolled drifting corners fun lol. I've talked about suspension changes we have made elsewhere I think, but we have dramatically improved the car's handling in the past year. The coilovers and Watts Link obviously made the biggest difference. I couldn't get the car to slalom worth a darn before...you had to turn the wheel well before the point where you wanted it to cut to stand a chance of not getting late and then sometimes the rear would stay where you wanted it, other times it would kick out a little extra unexpectedly and take out a cone you thought you were well clear of. After those changes, it was much more controlled...the car set way faster and was much more responsive. Didn't tail wag unexpectedly anymore. I have only driven it once since installing the torque arm, but even just with the driver's side UCA removed and the passenger side left in place, the car was way better. I would have to hope the torque arm is better than the Poor Mans 3 Link.

And there are still some more changes to be made yet. The Maximum Motorsports K and control arms are a decent bit lighter and they move the front wheels forward by a total of 1.5". That's marginally better weight distribution, but significantly improved caster. And we're planning to move the engine/trans back another inch (as long as the new K Member/FCAs and engine arrive in time to do it before the June AutoCross event).

Once I get all the new hard parts, engine, and exhaust installed, it'll go to a local shop for a corner balance (a fellow AutoX guy, I don't have a set of scales and don't feel they're a worthwhile investment right now).
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Re: Road Race Track/AutoCross 351w

Post by rustbucket79 »

The short throttle arm on the Holley Sniper is ridiculous. It’s the only combo I have to change my dyno linkage to accommodate, otherwise it’s more of an on/off switch than a throttle. 1 to 1 linkage isn’t what you want when corners are involved. :mrgreen:

Lengthen that arm as much as possible while still having a comfortable throttle pedal height while achieving full throttle. The longer the travel, the easier it will be to find that sweet spot coming out of the corners.
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Re: Road Race Track/AutoCross 351w

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Some photos that came from the builder a couple weeks ago.
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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 »

Here's a question, probably dumb, so I apologize. I don't know much about engine building. Very familiar with engines and parts, but have never actually built one myself. Is it normal with all new parts in an engine to have to use two sets of bearings to get clearances in the right range?

My builder mentioned it was a little looser than what they wanted, so they would need to match up the right bearings to get clearance down. I didn't think much of it, I thought it was fairly normal to buy a couple of sets of bearings because some of the journals may not be in the range you want. I mentioned it to my cousin, who has more experience than me, and he said he would ask why they were needing to mix and match bearings on brand new parts. Normal? or no?

This is a reputable shop doing the work, so I'm not toooo concerned, but I am curious.
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Builder says 3 weeks to dyno day!
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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 MadBill »

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".
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