Long box vs short box tracks

[Halifax]

Hi Gents,

Question here about long box vs short box tracks. My Lynx B has a short box tranny and, of course, I live 20 minutes from Lime Rock, a long box track. From what I have gleaned, NHMS and WGI are short box tracks, while LRP and Pocono are long box tracks. What about Summit Point, the NJMP tracks, and others?

What makes a track a long box vs a short box track?

Second, I've heard that there are wheel options when one has the long box ... can anyone comment on this?

Lastly, do most Vee racers have both trannys in their garage, and swap them out as necessary? Or are people avoiding the tracks that are not compatible with their gearbox?

Thanks!
Harry

[Matt King]

Lastly, do most Vee racers have both trannys in their garage, and swap them out as necessary? Or are people avoiding the tracks that are not compatible with their gearbox?

Thanks!
Harry

I can't speak fo other areas of the country, but here in Cendiv we have two primary tracks, Blackhawk Farms (short box) and Road America (long box) and every FV racer I have met who runs both tracks has both boxes and does the swap. But there are definitely some guys who stick primarily to BHF, although I'm not sure needing to swap transaxles is the reason. I just bought a long box last week and I will be swapping it in before my next race at Road America.

[Halifax]

I can't speak fo other areas of the country, but here in Cendiv we have two primary tracks, Blackhawk Farms (short box) and Road America (long box) and every FV racer I have met who runs both tracks has both boxes and does the swap. But there are definitely some guys who stick primarily to BHF, although I'm not sure needing to swap transaxles is the reason. I just bought a long box last week and I will be swapping it in before my next race at Road America.

Hi Matt,
Might I ask what a long box is running these days?
And is it a major project to do the swap?
Thanks,
Harry

[Matt King]

Hi Matt,
Might I ask what a long box is running these days?
And is it a major project to do the swap?
Thanks,
Harry

I think Lybarger gets about $1300 for a new one complete, drum to drum. Used ones are quite a bit less. I got a deal on one locally. The work to swap it depends a lot on the car and type of rear suspension. It's not something I would want to do at the track, but definitely no more than an afternoon's work on my car (Citation XTC).

[budawe]

I agree with Matts answers but will add that Road Amercia is the only track that I know of that requires the long box. You can run RA with a short box but be prepared to be off pace on the long straight aways and be careful of rpm in a drafting pack. The first year at the Sprints I ran a short box, pedaled the throttle in the draft and finished 4th, so it can be done. At BRM Engineering we can provide center sections ( without axles and backing plates) less expensively but it will increase conversion time.

[FVRacer21]

Harry,

How is the car coming?

For this year leave the short box in. Only one more race at Lime Rock and that is at the end of the year. NHMS is a short box track and you probably can get away this year at LR with a short box (especially if it keeps raining.....)

Someone will jump in bout the NJ tracks.

We don't really have a tire choice the way we used to have.

ChrisZ

[Hardingfv32]

IF you are not in the front of the pack normally, don't worry about it. A short box is much easier to drive if you are still error prone.

Brian

[problemchild]

By the same token, you will need a longbox anyway, why abuse your engine when you're not at the front? Lime Rock is easier to drive with the long box. The number of longbox tracks are much reduced these days .... there must be many sitting around unused.

[Halifax]

Harry,

How is the car coming?

For this year leave the short box in. Only one more race at Lime Rock and that is at the end of the year. NHMS is a short box track and you probably can get away this year at LR with a short box (especially if it keeps raining.....)

Someone will jump in bout the NJ tracks.

We don't really have a tire choice the way we used to have.

ChrisZ

Hi Chris,

Thanks for the great instruction at SCCA school.. I really appreciated your tutoring.

Dick has my Lynx and is working his way through a few issues, but it looks like it will be ready by the end of the weekend. Are you heading up to NHMS next weekend?

The short box stays in this year. What are you running in your Vee? Are you swapping long and short boxes according to the track or ?? Maybe I should install a shift light as an extra measure of protection when running the FV w/ short box at LRP? I guess the real question is, how disciplined can one be to back off the throttle on the front straight in a racing situation?

Still curious about NJ and Summit Point ... long box or short box?

Thanks!
Harry

[FVRacer21]

Harry,

From my chart it looks like with the short box you would be around 6600 on the main straight if you do it right. Others can chime in if I am way off. You can run 1:03s with a short box easily - I did it when I first got my car - no problem on the back straight you just shift early. The problem is that you don't have a lot to pull out in the draft. If you are going to do the NARRC runoffs later this year, leaving the short box in will be the best if your engine will take it.

Right now I am running a long box everywhere, which is painfull up the hill at NHMS - If I do the race in September I will probably put in the shortbox.

Right now I am down until I fix the bent things on the car - going to start working on that tomorrow.

ChrisZ

[Halifax]

FYI, I was told today that Summit Point is a shortbox track, too.

I ran the Aug 4 test and tune at Lime Rock explicitly to see how the Vee would perform with the shortbox. I had to shift into 4th in the middle of the right hander onto No-Name, which complicates things, and I was backing off around 6200 in the front stretch because I am unsure of the "normal" top RPMs for my motor (an SR Racing rebuild from 2007).

Which leads to the embarassing question ... what is that rattle that starts when one starts to approach over-RPM? Valves?

[FVRacer21]

No rattle is good, but some rattles could be harmless. It could be anything from bodywork to exhaust system.

In the very old days, when we ran stock springs, some engines used to float the valves from 6000 to 6200. But since we have been allowed better springs, 6800 or more is okay (but not recommended on a ? engine.) I assume you have the good springs.

If you are only seeing 6200, I would not think that was a problem. Gene Grimes used to run Lime Rock with a short box and run 4th all the way around. The theory was you only needed to race to the finish line; however, today you need the pop into the first turn.

What was your oil temperature and pressure?

If the rattle was a rod or crank bearing - they don't last too long. Then it usually gets very quiet. How sensitive is your gauge? Oil pressure at idle, at full rpm and in the turns.

What about your oil level?

I would also check your valve lash - some valves go tight and some go loose.

If you have C Clips on your rocker shafts you want to make sure that the are still there and the washers take out most of the play. If you have the bolt setup instead of the clips, make sure there is a little play but no too much.

Throw out bearing? Did you try and touch the clutch when it rattled and did it go away?

Sorry, Right now can't tell much more.

ChrisZ

[Halifax]

Hi Chris,

It's the same sound that I heard in Dick's Protoform when I rented it from him in June ..when I got near 6600-6700 before shifting in the right-hander a couple of times. I'll take a look and Dick's going to be doing some work on it, primarily an alignment, so I will ask him about it. I don't think it's a problematic issue at this point, maybe it is just the valve lash. BTW, I would like to watch you do an alignment on your Vee sometime as well as some other work including the shortbox/longbox swap.

I generally am at or close to 6000 by the trackout point of the downhill turn right now, if I remember correctly. At test and tune day Aug 4, I was backing off at about 6200-6300 to be cautious.

Oil pressure full on about 50 - 60 midway through a session, dipping to 40 at times, and after the last race it was 10-15 at idle when returning to the garage. Oil temp 225-250 but not certain because my checklist/notes sheets did not have that category and I did not log it (they do now). Cyl head temps 250 with one entry 275.

I would really like to race at the LRP Runoffs.. just can't figure out if I will be the sweeper car or not. It seems like I'm going to have to fund a long box over the winter ... the track is so close to us, it's nuts not to be able to run there, plus I like the test and tune days, too. I'll hopefully find a complete rear end to make the process simpler.

Your next race is...?

Kind regards,
Harry

[Daryl DeArman]

I had to shift into 4th in the middle of the right hander onto No-Name, which complicates things, and I was backing off around 6200 in the front stretch because I am unsure of the "normal" top RPMs for my motor (an SR Racing rebuild from 2007).

Which leads to the embarassing question ... what is that rattle that starts when one starts to approach over-RPM? Valves?

Top rpms and top HP number are two different things. Are you shifting at 6200 from 3-4th? Because of the huge drop in rpms on the 3-4 shift and where you are wanting to shift to 4th, I'd suggest carrying the rpms up to the 6700-6900 range if possible.

Are you sure that rattle you hear isn't detonation? A/F mixture and timing---check them.

[FVRacer21]

I'd suggest carrying the rpms up to the 6700-6900 range if possible.

Are you sure that rattle you hear isn't detonation? A/F mixture and timing---check them.

He is running an engine with an unknown history. Since Lime Rock is a momentum track holding to 6700 for him would not gain much. Depends on if he has a 1.22 or 1.26 third gear.

Good idea on the timing. I assume Dick checked it but it can change with point wear. Harry, what gas are you running?

ChrisZ

[sracing]

It is highly unlikely that you heard detonation at that RPM. Detonation occurs the most near peak torque which would be much lower. Sounds more like valve float.

Also the typical HP curve and gear ratio spread on a Vee dictate shifts at closer to 6500-6600. If you shift anywhere near 6900 you upshift to 4th will put you at or over the peak HP curve, thus "wasteing" much of the HP under the curve. Some short 3rd gear straights will require leaving it to 6700 or maybe above, but that's not optimum.

Jim

[SOseth]

Most people use a short box.

SteveO

[Daryl DeArman]

Also the typical HP curve and gear ratio spread on a Vee dictate shifts at closer to 6500-6600. If you shift anywhere near 6900 you upshift to 4th will put you at or over the peak HP curve, thus "wasteing" much of the HP under the curve. Some short 3rd gear straights will require leaving it to 6700 or maybe above, but that's not optimum.

I wasn't suggesting it was optimum, I was suggesting it was a solution for the corner he is finding himself shifting in the middle of (I'm not familiar with the corner and don't know how long it is or if the exit is downhill). If he doesn't need to carry the RPMS that high to get through the corner fine, but if need be he isn't going to do any harm.

____________

In a typical FV motor how much more torque (percentage wise) do I have at 4700 rpms than at 6700?

[budawe]

Geeze guys I don't know where to start. That noise youre hearing at high rpm is probably valve train seperation or float. These engines not only do not make less hp over 6500 but they will self destruct the valve train in the process. Either shift early in that turn or pay the consequences. Try to pick up the mph pace to compensate for the rpm problem.

In response to Quckshoe: Torque at those rpms is about 2/3's of max which is achieved down in the 4k range.

[sracing]

In a typical FV motor how much more torque (percentage wise) do I have at 4700 rpms than at 6700?

About 66lbs of torque at 4700 and about 48 lbs at 6700.

But this is a non issue. Wheel torque is what you are concerned with. The transaxle converts the engine HP to any wheel torque you want. You can convert max torque to the wheels at peak HP. So you are typically able to develop the most torque at the wheels when the engine is in the 5100 to 5600 range.

[Halifax]

Hi Jim,

Since you're in this thread, my engine was rebuilt by your shop in what I was told was 2007 ... Mark Bartholomew was the owner at the time. Would it be possible to find out the nature of the rebuild, the type of valve springs used, etc.?

I'm running at NHMS at the end of the month ... my video cam should be able to pick up the noise. I'll go through some of the existing vid and see if I can find the sound, too. Come to think of it, my tach is usually wildly oscillating/bouncing at top RPMs so I should probably try to figure that one out so that I have more certainty about upper RPM readings, too.

[sracing]

Hi Jim,
Since you're in this thread, my engine was rebuilt by your shop in what I was told was 2007 ... Mark Bartholomew was the owner at the time. Would it be possible to find out the nature of the rebuild, the type of valve springs used, etc.?

Not in 07. I have sold some parts to Mark in 07 and beyond, but no engine rebuilds. Sure it wasn't well before that or under another name? Anyways if you have more info you can call the shop and I can probably give you flow numbers from the manifold and carb, HP and the parts used. We always use a HD valve spring and measure them at install height. However in many cases an engine might come in where the springs are decent and we simply shim them a bit to get proper pressures. It is certainly possible that was the case with that engine and after 2 or 3 years, you probably are weak in the springs.

.., my tach is usually wildly oscillating/bouncing at top RPMs so I should probably try to figure that one out so that I have more certainty about upper RPM readings, too.

This is more than likely point bounce and/or a bad condensor and points. (or of course tach). Make sure your dwell and timing is correct and I would replace the condensor and points since they are cheap.

Give us a call and we might be able to determine more about the engine.

Jim
859-252-2496

[sracing]

Just found the Bartholomew engine sheet. It was October of 05!

Don't have the dyno sheet anymore or specs. It was dyno'd at that time and obvioulsy run up to 6700+. And it doesn't look like we put new valve springs in it at that time.
It looks like someone had just rebuilt it before we got it, since the bearings and dowels were installed incorrectly and the case was destroyed. The engine had blown. Crank was replaced due to journal destruction. It also looks like we didn't charge him enough for what all we had to do to it. So you owe us some money.

If that is really the engine you have and it hasn't been gone through since then, you might have some valve float. Or maybe even some other stuff.

It's good to know that it's been running for 4 years though.

Hope that helps.

Jim

[Daryl DeArman]

About 66lbs of torque at 4700 and about 48 lbs at 6700.

But this is a non issue. Wheel torque is what you are concerned with. The transaxle converts the engine HP to any wheel torque you want. You can convert max torque to the wheels at peak HP. So you are typically able to develop the most torque at the wheels when the engine is in the 5100 to 5600 range.

Jim,

Thanks for the response. It is exactly what I was looking for because I wanted to know if the 40+% difference in gear ratios was going to make up for the difference in engine torque.

Looks like 48 x 1.26 (the 3rd I always used) = 60.48 ft.lbs at the axle.
and 66 x .89 (4th gear same road speed) = 58.74 ft. lbs at the axle.

Close, but better off in 3rd if valve seat and valve train life is not a concern. Perhaps the "about" numbers and the more common 1.22 3rd gear make it such a wash as to why not just put it in 4th and let the motor live a little longer....that is unless you are in the middle of a corner or on the uphill side of a crest and you don't want to shift at that point in time.

Thanks for the info--you have a ton of knowledge FV's--all I had was a bunch of seat time and ignorance about all things FV when I started in FV. Didn't know what the accepted practice was and just went with what worked for me. More than one way to skin a cat.

[SMac35]

NJMP Lighting- the shorter track, is a really fast track that requires the long box
NJMP Thunderbolt- longer of the two, is a short box
Summit Point- Short box hitting 6500+ RPM at end of front straight, but definately do not want to run a long box there

Steven

[budawe]

Is the math really that simple? Mulitiply the torque by ratio? I'm not good with math but that seems too simple. Jim, could you explain how the tranny converts torque. Is it a matter of leverage?

[sracing]

Is the math really that simple? Mulitiply the torque by ratio? I'm not good with math but that seems too simple. Jim, could you explain how the tranny converts torque. Is it a matter of leverage?

Pretty much. HP = Torque x RPM / 5252. If you use the drive train ratio of 8:1 to leverage the Torque x 8 and the RPM /8 you have done it and the HP remains the same.

That is why we can chassis dyno an engine at any gear (with a few caveats) 1st, 2nd, 3rd, or 4th and the HP is always the same. (The caveat is that with greater ratios there are slightly more thrust losses especially in a angled cut VW trans gear set.) (Off the thread, but it is quite amazing how efficient the VW trans is. A good one compares quite favorably to a Staff, Hewland, etc. with straight cut gears in our low torque application.)
(I am designing a trans dyno as we speak.)

[Daryl DeArman]

(I am designing a trans dyno as we speak.)

Very cool!

Budawe---a couple of things about my math.....I'm not accounting for the final drive ratio nor the radius of the tires, I am assuming those remain the same (constants) so I can just compare the effect of 3rd vs 4th at the same road speed given where the torque is at the corresponding rpms.

The other issue is that I'm considering that the trans is just as efficient in either gear and that nobody has done anything 'funky' to the assembly.