Wasn't doubting your experience. I just think people need to make the distinction between "stock" heads and "ported" or "worked" stock heads. Or say what kind they are if they're aftermarket. When someone says they made 370 or so rwhp (NA) on stock LT1 heads and stock bottom end, the first thing that comes to mind is that the heads are ported or worked over somehow. Wouldn't you'd feel the same way?


Just to add to the discussion (and keeping in mind what Rich said about cams ^^^): if you were to de-stroke the engine, it would certainly make peak power at a higher rpm since you just upset the balance between displacement and head/cam characteristics. The ports and cam are effectively larger for the destroked engine as compared to the engine in "stock" form so it'll rev higher to make peak power. But then again, that's basically going the other way down the same road as getting bigger heads and cam for the stock shortblock. Not to mention more difficult. Making high revs(6500+) with a "mild" cam on a stock 350 is doing nothing more than hurting the engine and performance.

If you want to rev high, you MUST have the proper combo of heads and cam to feed the bottom end the air it needs for those kinds of rpms. There's no two ways about it. It's difficult to talk about cams without also talking about the heads they're going under and the displacement they have to supply air to. My $.02

 

One thing that I see that's interesting is the rev limit or HP peak of most of these big cams. 6000rpm is about what I see all the time, be it a 305 or a 306 type camcshaft. 230 degs of duration on a LT1 should peak HP alot higher than 6K. My guess is that it has more to do with the rest of the valvetrain not just the camshaft. Just a hunch.

340rwhp is not the limit, I've hooked guys up with cams that are much smaller than a 306 and they made 350rwhp on a cam only setup. I find it interesting to see that a 306 and a 305 make the same mid range TQ on a chassis dyno because on a engine dyno they would vary by about 10 ft lbs at least. Might be part of the fact that the acceleration rate of the dyno rollers is lower on with a 306 equpied car and that will inflate power numbers. Think 4.11 vs 3.08 gears in a car. The 4.11's will make less power on the dyno because they accelerate the dyno faster.

For the guys who don't know here GUMP has a 400rwhp Drag motor with stock non-ported LT1 heads. One of the reasons is that the thing makes peak HP at 6800rpm. That vs a 306 making it at 6000rpm is a big difference. I'm sure he's not going to share his valvetrain secrects but I'll bet that it's not just a huge cam that does that. He even makes the power with 1.5:1 rockers and probably very little lift.

To answer the orginal question Rich has great answer.

Bigger camshafts that are properly setup are going to make more power at higher RPM, that's the easiest way to get RPM. Cylinder heads play into it but when you look at other motors they are not the only limit. Take most circle track stuff. You will use a stock 160-170cc Iron head and spin that puppy to close to 7,500-8,000rpm. Granted they have awesome bottom ends in there to take it, but then again you will have 260 degs of duration or more on your camshaft and solid lifters. They might peak power at 6000-6500 but will not drop off a cliff afterward like these HR cams & valvetrain that guys are running in LT1's

Bret

 

One thing I didn't point out is that what i'm talking about is your average joe street engine, not engines intended only for racing (lightweight/expensive parts, high CR, optimized intakes, etc).

I've paid particular attention to GUMP's posts over the years..... he knows what he's doing and i don't doubt it at all. In fact I've tried to follow the build up of his car..... but he's a LITTLE QUIET about it . KwikistZ said he wanted a high reving "street" engine (which had me thinking stock LT1 shortblock with our "OK" intake) and that's what i've tried to adhere to during this thread. Marcin's stock headed CC306 LT1 hit 348rwhp with tuning while a few others hit in the 330s.... so i figured that somewhere around 340 is close due to differences in dynos.

By all means correct anything I've said thus far.... as long as it applies to "...say I have a stock LT1....and I want it to rev to around 6500-7000 or so " (what KwikistZ said earlier). I'm still learning and am more than willing to listen, so long as we're on the same page

BTW Bret... do you think it could be the LT1 intake that limits the big cams to around 6K? I've wondered about that since our intakes are slated to be less than "optimal".

 

If you took a CC306 and made a SR version of it it would probably peak HP at around 6500-6700rpm.

The LT1 intake with it's short runners actually helps these motors make HP above 6,000rpm.

The reason the intakes are not optimal is the runner length more than anything and they don't flow awesome like a Super Vic does on a cylinder head.

The problem I see with the HR cams peaking early is all valvetrain problems. There are solutions to that, but your not going to get that in a $500 cam kit, it's just not goint to happen. IMHO there is only one good camshaft for stock heads with a stock diameter springs. I don't sell it for $500 though, cause the components to make it work add up closer to $800. (as a bolt in for the average guy) If you want to go with more camshaft then you need to spend more money. For around $1000 you can do a larger camshaft that will run to 7,000rpm and not die off. For a good HR setup with ported or stock heads you are looking at about the same thing. Then you also have more options on the camshaft since you have more valve spring options.

Speed cost money how fast do you want to go? It's true and I hate to say it. It's not just the cam and the specs but it's the whole system. Cam Lobes (this is a biggie), Springs, Retainers, Pushrods etc.... those parts all have something to do with it. You can get by with a low cost setup, it's just not going to be optimal. Every little thing is important here, every detail and making the system work how you want it to takes alot of attention to that.

If we want to make power above 6,000rpm and make it worth while to turn the thing 7,000 then we need to really look closely at the whole camshaft setup.

$1000 is not a cheap bolt in type setup, for that amount you are close to doing a solid roller. The SR is going to be more costly than that because of more expensive lifters and the concern over rocker arm and rocker stud stiffness is going to need a change there. The one thing about RPM is that it cost more money. Either that or you break stuff, which costs more money.

BTW the cam that made that 350rwhp and rwtq was only small because I don't see a need for alot of cam if your not going to make power past 6,000K anyways. Might as well make the most TQ in the RPM range where it's going to make power, with the average stuff out there not working over 6,000rpm why cam it for more than that.

Sorry if I say things on here that are vauge, or not specific like what cam, springs etc you need to run to do X. There is a point where a guy has to make a living and if I just give away the farm why would you come to me for a cam when you could nickel and dime it out to save your self $25 someplace else. Not saying people do that, just saying that it happens.

Bret

 

without a doubt, id let bret design my setup for me......*if* i had the money!

 

Fast Caddie,

Don't take anything that I post the wrong way. If you read my posts you will note that I normally try to talk people out of junking all of that cool factory stuff! (Either that or I buy it from them!).

As far as the original post goes, I am 100% with Fred on this one. It doesn't make sense to rev the tar out of a car that you drive. When I was driving my GTO I used to carry tow money all of the time (and often used it!!).

As far as the intake and throttle body goes, Woodro Josey went 9.9's at Rockingham running Top Stock a couple of weeks ago. His Camaro runs the LT4. It had ported heads, a port matched LT4 intake, 48mm throttle body, and 24lb injectors! I was also there, but had engine problems all weekend. My best run was a 10.7 at only 117 mph. The motor finally grenaded during the first round of eliminations. Both of our cars weigh around 2900 lbs and cam lift is limited to .525.

Best Regards,

Daren

 

Good info here.

I agree the rest of the valve train has alot to do with it as do the ramps on the cams most are using

I made 346RWHP with my stock heads and a Crane/GM#847 cam. The peak was 6,600. I took the car home and ripped the heads off and had them ported. Put the car back together after the heads were done and drove it straight to the dyno without any tuning. The car tripped the rollers at 395RWHP at 6,900 through my full street package.

I use good valve springs and stay on top of my Valve train. after all the only thing keeping a LT1 from shifting at 7,000 is the valve train The stock bottom end can be reved to 7,500 fairly easy as long as the top end stays together.

It is not uncommon for Circle track motors to get over 650FWHP with untouched stock heads and a 500CFM two barrel intake

Now getting the people who build those puppies to tell you how is a whole other story

 

OneFlyn95z28 with youre heads what parts do you have in them i have AI heads gm847 cam to and i peak at 6600rpm i have been to the dyno twice now, i make no more power past it

And do you have a email add that i can talk to you about youre set up i have tryed everting and i get person not found
thx

 

Hehehe you got me man. I even replied

I am running a set of Llyod Elliot heads. I then had them worked over by FlowTechnics. they are sitting with 2.05int and 1.58ext. K-motion K800 valves springs with crane retainers. valves are Si necked down style.

Later!

 

""It is not uncommon for Circle track motors to get over 650FWHP with untouched stock heads and a 500CFM two barrel intake ""


NO not quite! That is not gonna happen now or ever!

They make more like 450 hp and that's with acid ported heads to boot usually!

 

I agree!

450-500hp is about the max you are going to get out of a 355-358 2bbl motor with "unported" ;-) heads.

It takes alot of tricks and attention to detail to get them that high and one BAS *** carb to boot. (i.e. Braswell)

IF the rules were unlimited and allowed the use of any set of cylinder heads, 650hp would be about the max ever. That would be on par with a 9,000rpm Craftsman truck motor using a 390 4bbl and making 700+hp.

Bret

 

Hmmm... It appears I have been miss-informed. I apoligize I was just passing on the info I was feed from when I used to pit on a local winstons west team.

Thank you for the clarifications

 

I have a good friend that races a lot of that roundy-round stuff. To say the least his factory heads are very "special". It is also getting quite common for Stock Eliminator racers to search out heads with "core shift" and "freek" heads with larger than normal ports. That is the main reason that I switched my focus to Top Stock, ported heads are allowed!
For the record, I went 7.10 (1/8 th) with valve springs only and 6.76 with a good valve job, once I figured out my complete set-up (five years). I will continue to work on my Firebird, but the Camaro is currently up for sale.

Best Regards,

Daren

 

OneFlyn95z28,

No problem. Just want to keep it real. Heads are the main thing in the way of most engines trying to make power and rpm on any given size motor. You have to move air to make power so unported heads make a lot less. There are some heads that are very nice as cast but a real 4412 holley (500 cfm@3.0 HG) is gonna kill even those.

 

I under stand. I know we were running brezinsky intakes and I want to say Teea(SP) carbs back then.

They looked stock LOL