Ok guys I've been looking at new cams for my LT1.. Currently I have a Comp Cam 230/236 .580/.590 110 LSA.. The cam does pretty good.. I've been looking at the Comp 242/248 cam .589/.590 1XX LSA.. But I have a stock bottom end car.. Some say go for it, others say it's too big.. I'm looking to gain a little over 2 tenths at the track.. I saw that Hot Rod magazine (ya I know but it's the only data I have) did a test on four cams and two of the cams are VERY similar to what I'm talking about but on a 377ci LT1.. The 230/236 made more peak torque but the 242/248 made more peak horsepower.. What's your thoughts??





http://www.hotrod.com/how-to/engine/...lock-and-cams/

 

What heads are you running? What's your shift point? A4? M6? Gears?

 

Stop reading those magazines and call LLoyd or AI. Tell them exactly what you just told us and take their recommendation. Those magazines are promo platforms for the big companies, and those dynos are very generous. I usually subtract about 10% from whatever numbers they post. Prime example...with those heads, Edelbrock claims a flow of over 270 cfm on the intake and 180 cfm on the exhaust. The most I have EVER seen them flow on many tests back in the day of the LT4 rage is about 225-230 in the intake and MAYBE 150-160 on the exhaust....BOTH of which are about 10% less than advertised. Now, I can see 500 hp from a 377 LT1 engine, but I dont see it happening with no stock LT4 heads, which is basically what those edelbrock LT4s are. If that were the case, EVERYONE would be running those heads on their stroker motor, those off the shelf cams, and 11s. If you running 11s and trying to go faster, I doubt that too much of anything off the shelf will work for you.

Oh and BTW...that 07-468 cam is a beast from what I read.

 

AFR 180cc, the shift points are set for 6400, it's an A4, and has 3.73 gears..

 

I understand it's a Magazine artical and that could be true what you say about the heads BUT I'm looking at the way the different cams behaved in those test.. And trying to see how would it compare in a 350.. Btw I specd my own cam that's currently in my car.. And most likley Llyod or AI will tell me the cam is too big and recommend something similar to what I have already in the car.. I know one guy who ran this cam and he ran a tenth faster than me with his stock short block.. Just trying to see if it'll worth me switching to a bigger cam.. I'm kinda worried about not gaining anything at the track by pushing my car to it's max..

 

https://ls1tech.com/forums/lt1-lt4-m...ants-some.html

 

Call a place that does custom grinds.

 

Why not add spray?

 

Whats the advance on the cam? Compression ratio? It's similar to my build, except I'm forged 30 over (11.8:1 compression M6). I ask because you may be shifting too soon for your current cam (according to my dyno pulls I should be shifting at 7000 rpm, but am limiting it to 6800 due to my 3/8 SA RR), and a bigger one will require more dispacement or higher rpm still. What stall are you running?

 

I'm running 11.0:1 on the nose or VERY close too it.. My tuner and I agreed to shift it at 6400 with a 6600 redline according to the Dyno graft. He says I won't pick up much if anything from shifting higher and HE didn't want to risk me blowing the motor either and ME being pissed at him like other people has done in the past.. But I have a 4000 Edge converter.. On the Dyno I saw the horsepower peaked at 6250 and never fell off even at 6600 where we stopped the pull as it just kinda stayed level (this was with mid tube headers)... But I guess it's not good to shift TOO high also because your too far from the touque curve.. I think I'm just gonna make another pull on the Dyno to see where my car is making power at now with the long tubes (all my track times are with the long tubes).. It might want to shift a little higher now.. But I don't think it'll be 2 tenths.. I'm trying to get in the 10's N/A without touching the heads and without going the tin can route..

 

You said stock bottom end right? Stock rod bolts and pistons too? Machine work like Balanced? Line honed? Etc? If all stock, 6400 is pushing your luck.

If your power is still holding up at 6600 though, you're probably short shifting it. But I can't tell you for sure without actually seeing the dyno curve. If it's similar to mine, you'll still have tons of torque there.

 

The bottom is 100% stock

 

I don't know if I'd do even 6400 rpm if that's the case.

The thing is you're RPM limited. But you are a stalled auto. So, going with a bigger cam will require more displacement or higher RPM or both to maximize it's power output. BUT that doesn't mean you won't go faster within your current limitations. If you increase power from 4K to redline, you'll go faster than you are now. A bigger cam should do that, at the sacrifice of worse driveability. But, I don't see you gaining much power with any cam larger than you have now to hit your goal.

If you decided to rebuild the bottom end to handle 7k (more would require a different PCM or going to carb and points), you'll likely gain more than you would with a cam swap. If you did do the bottom half, with your current cam and shoot for a 383 ~12:1 SCR with a small advance (like 2-4° or so), and make sure you have the valve train to handle 7K, you could very well hit your goal. And you could go bigger on the cam on top of that.

My cam is 6° advanced, see sig for the rest of the build details, and with that I still need to rev to 7K (PCM limit) to maximize it's power band. That's with a tighter gear spread in my M6 to your A4. The gear spread from 1st to 2nd in the 4L60e is huge, you want as much RPM as you can get in 1st for the A4. 2nd to 3rd isn't nearly as bad.

 

It will ET worse with that 242 cam.
You don't have enough head flow, TC, and gearing to make use of it, not even considering your bottom end.

Those "magazine" article heads are pretty crappy or they did something else wrong, with a tq peak way up at 5200 rpm and a measly 6400 rpm power peak with that much cam.

 

I can change the TC and gears in a snap.. It's the bottom end mainly, and the heads kinda, that has me worried..

 

Well.....all it takes is missing one of those items. You're missing two, so that bigger cam is no dice.
If you want ET, stick with your present cam.
...I just looked beyond your first post in your other thread and saw you changed to an Edge TC. What stall?

 

It's a 4,000

 

Like Pat stated......that cam will result in a slower ET.....or it may equal your current ET if you're lucky.

That cam is best suited for a stroker engine that sees about 12:1 compression ratio.

The 19 degrees of overlap from that cam will put a crush on your low RPM (below 3500 RPMs) torque, so you'll lose a lot coming off the line.

A cam with that much duration will want a lot more lift to flow the air necessary to take advantage of the overlap; it really needs at LEAST.600" of lift, and your heads should be able to handle that lift. But as it stands, this looks like a poorly designed cam.....

So.....if you feel that you MUST go with a cam with that much duration, you'll really want to go with a custom grind, do some head work to increase compression, and redo the valvetrain to something that can handle the lift and the RPMs (read, shaft-mounted rockers or steel NSA rockers). Also, such a cam would mostly shine in the 6500+ RPM range....so there's that!


So.....that's what you're looking at with this cam....needs more compression, not enough lift......and like I said......this is really a stroker cam.

Just sayin'......

KW

 

With a 4000 RPM converter, you want a cam & combo that makes your torque peak very close to 4000/4200 RPM, to run it's best ETs at the track. Go by what it actually flashes to at launch. A 4000 converter in one car may be a 3800 or 4400 in another car. You have tobe able to log it to know. Your engine's torque and car weight & gears effect that. The vehicle has to recover from shifts quickly. You want to gear it and shift it, so it falls back close to (not below) your torque peak RPM. When you get it right, it will feel like a surge at the shifts, not flatten for a mili-second or so. I see a lot of guys with too much cam & injector. They aren't like boobies & peckers. Bigger is not alway better. And, we don't race dynos.