I am looking to add some juice to my L98. The motor has about 30,000 highway miles on it since its first rebuild. The motor was bored 20 over, raised the compression to 10.78.1, port matched the stock heads, and balanced the entire rotating assembly and installed a 12-256-4 flat tappet comp cam.
12-254-4 - 212/218 449/456 112LSA installed at 106 intake centerline

I added the big mouth intake manifold but never finished off the hipo TPI set up. Magna Flow exhaust, ram air, airfoil, modified MAS and stock PCM. Adjustable fuel pressure regulator set at around 46psi. At the time the car was a daily driver so the mild set up was a compromise. The engine builder was excellent and really did a good job. The car is a real torque monster and even with the stock runners It will pull strong to 5000rpm shifting at 5300-5500 depending on temp. The tranny was rebuilt also with a stock convertor and 2.59's out back.

I am looking at installing a comp roller cam R12-601-8
235/249 522/509 107LSA

In addition I was going to increase the valve size to 2.02/ 1.60, fully port the heads and top it off with a Mini Ram and 52mm throttle body.
The addition of long tubes, x pipe as well as elimnating the pre cats to finsih off the exhaust. I am planning to use a TPIS stage V prom. My goal is 400hp at 5800-6200 RPM.

I know the 2.59 rear and stock convertor is going to kill the performance but other than that what do you guys think? Also, do you think I can get away with a 3.07 rear or is 3.54 a minimum with this cam.?

 

Thats a decent sized stick for a 350, I would gear it even lower if it were me.(although 3.54 will probably work ok.) Heck, you have the mini, take advantage of the RPM. get a stall, too.

Edit:Looking at those specs from your post, that isnt one of those thumper cams is it?

107 LSA can be tuned but it may be tough. Id go with a little wider lobe center.

 

I agree, a steeper gear would compliment your planned combo. 3.54 would be a good choice, or even steeper if you can live with the slight mileage decrease/RPM increase.

Unless you are getting a killer deal on enlarging the valves and porting the stock heads, you'll probably be better off going to a new casting all together. A decade or so ago, the stock L98 aluminum heads were about as good as it got when a competent porter worked them over, but with todays technology there are out of the box after market heads that will smash anything a ported stock head could even think about doing. Trick flow, dart, canfield, and a few others make some pretty budget friendly heads that should produce quite a bit more power than ported stockers.

If you're looking for 400 HP at the wheels, I don't think your current recipe will get you there. With a well ported set of stock heads, I'd be surprised if you were able to make more than about 330 at the wheels. With any of the heads I mentioned 350-360 isn't out of the question. 400 out of the stock cubes is tough, but it can be done. You'll need some more radical components and more RPM to get there though.

For an honest 400 RWHP 350, you'll probably need to step up to an AFR or Brodix head, probably with a 200+ CC port volume. I think your cam specs are OK (that is the lift with 1.5 rockers, right?), but I would step up to a 1.6 or even a 1.7 rocker and take advantage of the awesome springs that AFR or Brodix will install on the heads. Plan to buzz the engine close to 7000 and you should see peak power around 6500-6700.

If you can keep the quench down below .040 and get someone to lay a killer tune on it, the high dollar heads and your planned cam should put you very close, if not over, 400 at the tires.

There are some stock bottom end LTX combos out there making 425-450 at the tires on www.cz28.com, you might want to look into those combinations to get some idea's on what it takes to make big power on the stock cubes.

 

If this is an 86, it has a 2000rpm TC already, which is not a terrible match to this combo, but still good on the street. 2400-2600 would be better, but further would be a bit much for street use.

If you can get 3.45s in a D44, I would do that. I wouldnt do the 3.54 or 3.07 if I was sticking with D36.

Do NOT spend money on that Tpis chip, have one customized for your setup.

I would NOT spend another dime on the stock heads, with that camshaft you need much bigger and better heads, otherwise tone down your cam selection, because the stock heads..even if ported..cant feed that cam to its potential.....nowhere close.

 

This will give you the best "bang", especially with a MR. I would think about something like a 2,600-3,000rpm TC.

I don't think the 2.59s will be an issue. If you can get up to 3k RPM to launch these gears will let you pull "forever", well at least to 6k RPM with a stock bottom end.

Take a look at TPIS "Insider Hints" to see where the MR power band is located. To take full advantage you really need to pull to ~6,500rpm.

 

 

for a street/driver I think that is a lot of cam

 

Yes, it is a thumper

 

I wouldnt go over a .500 lift cam on stock head for one reason. The rockers are going to hit the guides. Thats way to much cam for stock heads unless you have the guide machined.

 

Wow, old thread...what did you end up doing?
Hopefully you didnt choose that cam to use with any long tube runner intake or 113 head. Mismatch city.