I am currently running a zz4 cam in my 305. I need some expert opinions on which cam would turn out the best top end/ ET time.. I want this 305 to pull like a mother up top. Problem is, it has to be below 6000 rpm. I will set my rev limiter at 5950 or so... I already have too much grunt in the middle and not enough up top.. From a dig with literally no launch and doing my best to keep from spinning i can pull on a 03 mach1 5 speed with underdrive, diablo tune, k&n intake, exhaust, short shifter (short no joke), until about 80-90mph until he creeps past me.. I want to reverse this! drivability is not a concern.

Mods are as follows:
305, .030 over, hsr, trickflow 305 heads good to .540 lift , 1.5 roller rockers, hooker headers shorties, 3'' exhaust, spiral flow muffler, 3:70 gears/ T5 tranny, tuning equipment, 52mm throttle body

 

pull on a mach1 untill 80 or so sorry just find it odd a 305 can hang with a mach1. There actually faster then a cobra off the line due to the gears and such but the cobra will come back up top. So if your little 305 has around 350-400hp props to you! i wouldnt change a thing

 

Why only 6000 rpm? You're guaranteed safe to 6200. Set the limiter there. And get some drag radials. A good launch isn't going to break the T5, powershifting second is. Then get the GMPP LT4 HOT cam.

 

yep, it suprises everyone

Atilla, I deffinitely dont doubt your choice, you seem to know your stuff. But you dont feel there is any other cam just a tad better?

 

You want to really push it? call COMP and order this custom grind: 08-000-8, 3015/3037-114. Then install on a 110 intake centerline, with a high-quality chain. You'll be wanting 4.11:1 rear gears.

 

Nice man you got those TFS 175's after all?? I am not surprised it runs hard, just look at those heads. Take it to the track and see what it runs I really want to know. I would love to see a dyno too, I bet you are making that fantasy 400hp that we came up with when you were thinking of buying them.

Tune is suspect to me. What have you done for that? Wideband O2?

You are shifting way early too, those heads are 175cc they are suited for making power at 6000-7000RPM with 305ci. With your intake/cam/exhaust it should be peaking 6250RPM'ish so shifting at 6500RPM in 1 and 2 gear would get you down the track a fair bit faster.

Shifting later not only gets you shifting at higher power but after the shift you are higher in the power band. As an example if after 1-2 shift you are at 3500RPM that's 256HP. But if you go down to only 4000RPM you start the gear at 306HP.

You may net the same effect of the LT4 Hotcam by switching to 1.6 roller rockers with much less hassle and money. That with long tube headers would probably give a good 20+ HP at peak.

 

No, 1.6 rockers with that much spring, you'll be hurting it above 5500 from lifter collapse.
Also, those heads, out of the box, only move 242 cfm. So 6500 absolute max. And that's if you did ARP rod bolts. Any others, 6200.

 

STock bottom end L98 can easily see 6200 shifts and possibly more. Dont see why a 305 cant. I've be curious how that 305 will run with a decent cam with those heads.

Advantage with hotcam is that you can find them used for very cheap and its an effective cam. Its most popular with the LT1 guys and they eventually swap it out for a much larger grind. ebay and camaroz28.com is your place to find them.


not sure what springs are in those heads but if they are anything like AFR 8019s which have 150 seat pressure and near 400 open, a LS7 lifter will handle those loads just fine with 1.6's. They are cheap too. I pulled to 6300 rpm peak and held power to 6600 or so and shifted right then or at 6800 with 1.6 rockers for a total cam lift of .603/.613 on LS7 lifters and those AFR springs shimmed to 165lbs seat.. 1989GTATransAm's motor pulls that high as well with same springs. Stock lifters I would replace

 

a 0.350" lobe in a SBC won't rev as high, with the same lifters and springs, as a 0.350" lobe in an LSx, even with the advantage in rocker ratios, because of the smaller base circle in the SBC.
You might get 6800, I've seen 7000, but it's not how it drives that matters. It's how the dyno result graph gets jumpy at 5800 or at 6500 that matters.
LS7 lifters are no better than ZZ4 lifters from 5 years ago, when it comes to not collapsing.
This is why AFR makes the Hydra-Rev kit. Keep the svalvespring pressure under 300 psi, with 1.50:1 rockers, if you want to reach past 6500 rpm. Choose conical or beehive springs, add the rev kit, and switch from XFI lobes to XE lobes.
That's how you get a HR SBC to be happy reaching past 6500.
I've seen more than enough L98 rods fail from 6200 rpm use. It's very high risk. Later PM rods from L31 and LT1 are safe for 6200, but risky above 6500.
Yes, 305 pistons are somewhat lighter, but SpeedPros are very often heavier than stock.
With ARP bolts in stock, non-PM rods, 6500 is safe. Put ARPs in PM rods, and 7000 is safe. I've done 7000 with ARP in pre-PM, but not for long. You can play roulette with these guidelines, and I can't stop you, but I never hesitate with my "I-told-you-so"s.

 

My cam was on a small base circle without a rev kit with AFR's small diameter valve springs and 8mm hollow stem valves. No problems above 6500 and it would hit the limiter at 7K in a heartbeat if you didnt watch what you were doing. Dyno never got jumpy.

The rev kit however would probably be a better choice in the end and softer on the springs/valves. Probably get more life out of the springs too.

I better tell my buddy not to test that L98 rod to 6200 too often. he's been shifting at 6K but with that 280 XFI cam, it reallly would want to go higher but I dont think he has the spring for it.

 

Doom- reason i dont shift so high is because i was recommended not to with the zz4 cam with them being IR lobes.. stilldont understand that but its gms max recommended too.

Atilla- I will check that cam out, see what they say. Which lifters would you recommend, im still using stock.. The guy i bought the engine off of said it had 142k on the clock before he rebuilt it...

Orr- these are the springs here http://www.trickflow.com/partdetail....98++150&orig=1



im just worried about cap walk which is supposed to be at 6034 i beleive on these engines?

 

the ZZ4 cam should be limited to 5800 rpm.
And if I understand you correctly, you're claiming that someone told you the main caps would start walking at 6035 rpm? That's the dumbest thing ever. I've never once seen or heard of any 305 having a crank, block or bearing problem from being shifted at 6200, regardless of mileage.
I have seen 305s with broken blocks, but ther were shifted around 5000. I've seen 305s with broken cranks. Usually serious-detonation-related, in work trucks.
The cam I specced you is an XFI, 224/236, 537/536.