Arizona Mike

David, Like I said, I plan to set the rev limiter to 6,800.

Here is an example of custom 1 3/4" 4-into-4s for a vintage SBC in a Cobra. The 4 tubes in the side pipe before the collector are 2" each! LS1 headers would probably not be much different. People are getting significantly more power with 4-into-4s than with performance shortes (with or without cats) I doubt I'll loose much!


The Shelby's had a 4-speed. The 6-speed allows you to cover both ends. Cruise rpm is more of a noise issue than fuel economy. A lot of Cobra people try to stay under 2,000 RPM. In AZ we are 65 mph (effectively 70) on rural highways and 75 (effectively 80) on interstates. With such a light car, I wanted to keep my first gear final drive under 10:1 so I went with 3.73:1 instead of 4.10:1. Aren't these two ratios the hot cam ratios for 3,800lb F-body cars?

You probably missed it above. Arizona registers replicas by nearest body style year, I'd be smog exempt statewide registered as a 1965. I'm also smog exempt on all my cars in my country but probably not for long!

I don't want to go off-topic for too long, but to answer your question: I'm planning on using a Factory 5 since I love the space frame and the aluminum panels. The only fiberglass in non-stressed. Also, I can make the most custom build choices with the kit format vs. buying a roller. I'm planning a Wilwood brake setup, and IRS with Konis, and some bump steer and Ackermann mods in front. I picked the F-body drivetrain based on cost and weight. There's enough money to be spent elsewhere!

Mike

s346k

iTrader: (4)

setting your rev limiter at 6,800? you have many cam choices. i think the most radical cam you could use with that rev limiter would be the ms3, offered by texas speed. if you get a cam any larger than that, you will be leaving hp on the table. also you'd lose out on your mid-range. i believe the specs to be 237/242 - .603/.609 - on pretty much any lsa you want. to keep the cam fairly tame, i would suggest the default 113 lsa. also, this particular cam is known for its excellent reaction to n2o, should you choose to spray it.

the items you mentioned changing will easily support that particular cam. rod bolts aren't NECESSARY, especially on an 01+ shortblock, as they received upgraded rod bolts (compared to 2000 and older) from the factory. however, since the bolts are easily accessible, swap them out for a set of katechs.

hope this helps..

ThirdGenLS1

iTrader: (11)

Give Trevor at TSP a call, i talked to him for almost 30 min today about a cam for me...AWSOME guy, prolly the nicest guy i have ever talked to.

Arizona Mike

s346k, I think g5x3 or ms3 is the upper bound on what I am considering.
ThirdGenLS1, I actually fired off an e-mail earlier today to Jason and Trevor.

These roadsters are light and have a 15" high center of gravity, so they don't tend to transfer a lot of weight. You can lift in a launch from drivetrain inertia alone and thus make about 1G on street tires through most of first (I've seen logger data to confirm this), as soon as you shift to 2nd, you go back to steady state weight transfer. My math shows a little less than 0.6G on street tires, real world logger data seems to top out at 0.7G.

I calculate my traction limits as follows:

1st gear: 2500lb *1.0G = 2500lb force at tire --> 2335 lb-ft at wheel (25.7" tires) --> 626 lb-ft at tranny (3.73:1 rear) --> 781 lb-ft at tranny accounting for 20% drivetrain loss.

2nd-4th: 2500lb *0.7G = 1750lb force at tire --> 1634 lb-ft at wheel (25.7" tires) --> 438 lb-ft at tranny (3.73:1 rear) --> 548 lb-ft at tranny accounting for 20% drivetrain loss.

Gear...Ratio.......Traction limit (FWTQ).....TL(RWTQ)
1st......2.66:1...........294 lb-ft........................235 lb-ft
2nd....1.78:1............308 lb-ft........................246 lb-ft
3rd.....1.30:1............421 lb-ft........................337 lb-ft
4th.....1.00:1............548 lb-ft........................438 lb-ft

On racing slicks, we are looking at something ~50% higher (353/369/505/657 RWTQ) which is why I might want to use some juice if I ever get serious about drag. I probably won't since I'm not setting up the suspension for drag (I'm going independent) and might break the tranny on slicks. If I can get more than 340 lb-ft of RWTQ through the power band, I'll be traction limited through highway speeds and would probably never want to add nitrous. I might not even need that much cam to reach this goal!

I'm leaning towards the TPS 233/239/.595/.603-112 Rev. 2 given my RPM and torque goals.

Mike

james562

iTrader: (35)

I want pics when this setup is done. Sounds like a hell of a setup
Cammed LS1 in 2800lbs cobra =

s346k

iTrader: (4)

any of the aforementioned cams will perform very well. i think you'd get the best performance out of the x3. however, almost every x3 dyno i have seen shows the cam making power to 7k. i think it would be an awesome street/strip cam, especially in a car that light. also, i believe that the x3 would give you the most driveability, assuming you chose the 114 lsa.

DavidNJ

Arizona has nice emissions laws. The Cobra headers are junk. Way too long on the primaries which don't even try to be equal length, no merge collector, no x-pipe or crossover. Might be faster with zoomies.

If it is an NHRA track (and probably if it isn't) you won't be allowed to drag race unless you have a custom roll bar (or a FFR Spec Racer). Under 14 (or is it 13.5 now) you need a roll bar that has a side bar alongside the driver. The bar also needs to be 3" above your helmet. And be as wide as the driver's shoulders or within 1" of the door. And have 1 3/4" tubing.

That said, for cruising at 1600rpm all these cams are too big. Your car would be fast with a 250hp engine. And the exhaust will ensure it is noisy. And you probably would only see the difference from the cams at idle, which will be lumpy, and sub-2000 rpm throttle response, which may be soft.

You might get alot of what you want by just adding 1.8 rockers (maybe inexpensive LS7 exhausts or even the Crane Quick-lift), new valve springs with Ti retainers, and a good tune. The LS1 is already in a bit of a performance tune.

The stock '02 cam was 197/207/116 with .47 lift more or less. Newer grinds can be .58 to .66 lift. The '02 LS6 was 204/218/117 with .55 lift. I'm suggesting something like 218/224/114 .55 to 224/228/112 .59.

To people running 236/242/110 combos, what is your compression ratio, header, and head look like? Who did the tuning? And what engine speed to you use on the highway?

P.S.
Everyone has their own combo with their own sexy name. A few don't publish specs. All are getting them from 3 or 4 cam grinders who publish catalogs. Find a tuner who has built combos similar to what you want and see what they suggest. Then pick one who can order the cam for you.

P.P.S.
6th gear in a T-56, except the $6k 2.22 first racing one, is for fuel economy or the Bonneville Salt Flats.

Arizona Mike

Junk of not, the header design is largely determined the fact that the car is wide and the engine is set pretty far back (mid-front).
The Hooker headers for the Ford application have 4 different lengths. The collector, btw, is in the side pipes.

Mike

PS. I see you've posted on a Cobra forum about this. Have you come up with a solution?

DavidNJ

The design is a copy of an awful early 60's design. The only redeeming factor is it is better than the Daytona coupe.

Exhaust manifolds have a scavenging function. One factor is having the tubes the correct length. Merge collectors, which are maybe a 1995 technology and not a 1964 technology, significantly increase the scavenging by managing the flow around the junction.



But that still doesn't deal with the firing order which places 4&6 and 3&1 next to each other. There are three fixes for that. A flat crank, which some Ferrari's have but no LS1s. A crossover header which takes one pipe from each bank and crosses it over to the other bank's collector. These are available for stock cars but a real pain to deal with.

So the common solution is a Y-pipe or an X-pipe (which functionally two Y-pipes joined) that lets to two banks scavenge each other.



There is more than enough space to the side of the engine, in front of the engine and in front of the footboxes to work out an appropriate header in a Cobra replica. But few did. This is a picture and link to someone who added a header (abit short though), X-pipe, and mufflers to an FFR Daytona coupe:

http://www.ffcobra.com/cgi-bin/ultim...t/002403.html?

NicD

iTrader: (7)

For a nice driver with no major issues, go with a nicely balanced cam the TR 224. If you are thinking about nitrous or FI in the future, get it on a 114 lsa otherwise for just N/A get it on a 112. I think it will make plenty of power for you in that car and have a nice broad torque curve and you would be shifting around 6600 rpm. If you want more top end power get a slightly larger cam in the low 230 duration range. No point in having a huge cam in a car like that unless you like the big lumpy stuff and the smell.

MAJBush

Do the engine mounting points match up with the LS1 or do you have to fab where the engine mounts are going in the frame? I was curious about this b/c I am considering doing the same project. I was just curious how the LS1 and T56 fit and what modifications needed to be done.

Thanks

Arizona Mike

MAJBush, people have to fab their own motor mounts. In the case of a Factory Five, the tranny mount is very flexable (with a bunch of holes and slots in it) and rather universal. Modular guys have used the plate for their builds, but still need to fab the motor mounts. LTx guys seem to all fab their own tranny mount and motro mount. There are only a handfull of guys who have done LSx builds, not very active posters, and a couple of the from New Zealand (the Holden cars/LSx engines have a great reputation down there).

I'm planning to build the bulk of my roller durring a paid sabatical from work at the end of next year, I just want to know what parts I'll need so I can look out for bargains over the next year.

DavidNJ, I replied to one of your posts in the Cobra forum. This is turining into an external engine discussion and I want to try to bring it back to topic. I'm just staring to put much thought into these issues. When you said 1&3 and 4&6 above, did you actually mean 1&3 and 2&6? I thought the firing order was 1-8-7-2-6-5-4-3-1.

Mike

DavidNJ

I'm thinking of doing the same thing your are, however I might get the parts separately. In NJ, I would have to deal with emissions in an LS1. But a strong all aluminum injected motor for that price is very hard to ignore.

Yes, I made an error in the firing order. There are few oval track LS1s and I have never seen a 180 crossover for them.