Need opinions. FastTA, Inuneer...

[raroZ28]

I have a good chunk of money I'm ready to drop into the Z. I'm going with a Cam, crane 1.6 RR, and headers.

My only real questions are...

LT or ST headers? This isn't going to be a drag car. I just want a 12 second street car. I was leaning more towards LT headers, I hear better things.

What kind of cam? I know there are a lot out there, and I don't know much about lobes and durations and that. Something streetable, but will make me some power.

The main question... Should I go with aftermarket heads, or just have work done to my stock heads? I was talking to my machinist about getting LT4 heads. He said he can make my stock heads better than the LT4 heads. I was wondering if dropping 2K into aftermarket heads is worth it's weight when compared to just having the stock heads worked on. Ported, new valve springs, better valves, etc... What would you guys recommend I do about heads?

I will be putting lower control arms, panhard rod and torque arms on as well.

Thanks guys. I really want to be able to put LS1's down... ZO6's as well

[DeWynter]

Headers are a contentious Issue. The documented facts about headers are theat LT headers with medium to large diameter Primaries will give more HP in higher RPM ranges as they have the abillity to flow more gas. Simple physics. If you go to big of a primary you will lose the resonance of the header which causes pulses to come back up the tubes into the chamber then push out the gases more quickly. takes reading and lots of physics to fully understand what is actually happening. ST headers with small to medium primary sizes will give you more torque at the cost of HP in the upper RPM range. due to the fact that they can not flow as much gas. Another factor is displacment and head design. As to what you want to do with the car is up to what RPM range you are going to drive the car. I cant tell you if your car will be a 12 second street car as there are way mor factors than just the engine when determining that, others here can give you better info on that. I can tell you what an engine will do with a given cam head intake and header combo, and "aproximate" HP/TQ. In reality it comes down to flow numbers at different RPMs to tell you what to do, which has to do with the displacment and flow of intake and head. Less flow less header primary. As for LT vs ST look at the RPM range you want to be in and if TQ or HP is going to be the one that most affects your preformance If you go and look through all the peoples sigs on here and read their Dyno numbers look at where the HP peaks at. Most are in the 5000-6000 Range. You can build a car to have huge TQ and moderate HP and still run with the big dogs of HP. take for instance my 383 TPI, it makes great TQ for its size but mediocer HP. then look at the curve of HP and TQ together and you will instantly see that HP is really low at 1000 RPM(BHP 64.6) but TQ is high(338@1000RPM). I am a fan of TQ so I may be biased. But HP isnt the only mesure of an engine.

[fastTa]

If you could give us your power level goals and what your definition of streetable is it would greatly help to narrow down a few things. Thre reason I am asking about streetabilty is because that term is extremely vague. Some people's version of "streetability" is a 350 RWHP motor with a very mild cam (something 220-ish). Then if you were to ask a person like me...I would say as long as it can steer, roll, and haul ass! I am not scared of a lopey, bangin cam with a 4600 stall, and a 400 shot on the street. However some are.

Contrary to popular belief, head flow numbers don't mean squat. Don't get caught up in the head flow numbers hype. They exist for bragging rights and a mediocre tool for comparing porting work. The volume of air a particular intake runner can flow is nowhere near as significant as the velocity in which the intake runner can achieve.

Port velocity is what makes a cylinder head special. Port velocity is what makes power.

So answer my original two questions (define your version of streetability and how much power do you need) and I will give you some good ideas for parts and how to use them.

[raroZ28]

I want about 400-450 HP to the rear wheels. I'm with you on being streetable, except on the Nitrous. I don't like that on the street. Too cheap. When I say streetable, I just mean, not drag car like stuff. As long as I can roll down the street in it and get decent gas I'm fine.

[Joe 1320]

I'm going to chime in as a user of SLP shorties. Also a random tech high flow dual cat Y pipe. The combo of those two really helped get me to 13.0's @ 107, still using a stock stall speed converter. Ground clearance is great, no scrapes or banging. For a basically stock configuration I think they are the best for a street car and the only way to go on a lowered one. Long tubes may make more HP at certain rpms, torque is where it's at on the street.

[Injuneer]

Need a few clarifications:

Your goals - "12-second car" and 400-450rwHP" - aren't necessarily consistant. A 12-second car can be done with bolt-ons. You need to add 100HP to run mid-12's. A 400-450rwHP car is an 11-second car with either an extremely well done heads/cam setup (note Kevin's question about your definition of "streetable"), or more likely a stroker.

Since you have set your goals fairly wide, and in terms of "rwHP", you need to tell us what trans you are running. 400rwHP with a T56 takes 460flywheelHP. 450rwHP with a 4L60E will require up to 550flywheelHP. Two different engines, particularly when you are trying to do it with a stock displacement and keep it streetable.

Personally, I don't like to think in terms of rwHP... you won't find a lot of difference in performance between a 500flywheelHP engine running a well setup race automatic (<400rwHP) and a healthy T56 (>435rwHP) drivetrain. MPH might run a little lower with the automatic, but ET's will be very similar. Which trans do you have?

Next, what do you plan to do in the way of weight reduction and suspension? There are people who have managed to run closer to the mid 12's with the 107MPH that Joe ran, but it takes an extremely well set up car.

Finally, what emissions requirements do you have to meet, if any? That will affect choice of components, particularly headers.

[raroZ28]

Need a few clarifications:

Your goals - "12-second car" and 400-450rwHP" - aren't necessarily consistant. A 12-second car can be done with bolt-ons. You need to add 100HP to run mid-12's. A 400-450rwHP car is an 11-second car with either an extremely well done heads/cam setup (note Kevin's question about your definition of "streetable"), or more likely a stroker.

Since you have set your goals fairly wide, and in terms of "rwHP", you need to tell us what trans you are running. 400rwHP with a T56 takes 460flywheelHP. 450rwHP with a 4L60E will require up to 550flywheelHP. Two different engines, particularly when you are trying to do it with a stock displacement and keep it streetable.

Personally, I don't like to think in terms of rwHP... you won't find a lot of difference in performance between a 500flywheelHP engine running a well setup race automatic (<400rwHP) and a healthy T56 (>435rwHP) drivetrain. MPH might run a little lower with the automatic, but ET's will be very similar. Which trans do you have?

Next, what do you plan to do in the way of weight reduction and suspension? There are people who have managed to run closer to the mid 12's with the 107MPH that Joe ran, but it takes an extremely well set up car.

Finally, what emissions requirements do you have to meet, if any? That will affect choice of components, particularly headers.

It's an M6. I didn't think 400 - 450 rwhp was an 11 second car. I thought I read somewhere that Jay only pulled off a 13 second et with over 400 hp.

There will be no weight reduction. Not under the hood, and I hate gutting interior, that's part of my definition of streetable. Streetable is a bad term to use, since people use it to describe so many different setups, but anyway, the suspension will be BMR panhard rod, torque arms, and lower control arms. I already talked to my buddy at ramchergers, and he's going to get me all that and subframe connectors, and relocation brackets for around $600. I never thought he could get it that cheap after checking around online, but he was cheaper than everyone else, however, I don't think his torque arms or panhard rod is adjustable... That's with the "coupons" he uses for me though too, so... I will be running drag radials as well.

I'm in MI, so I don't have any emissions, however, they're talking about bringing them back, so I'm going to keep the emissions. My conquest couldn't pass emissions if it had to... No egr, vacuum lines are all gone, no cats, etc... That is a smog monster. I don't want two, just in case it does come back.... The camaro is too hard to work on, it's not like the quest. I can make the quest pass emissions in less than a day, I can only imagine having to pull my headers on the camaro to help it pass emissions....

Any info on what to do about the heads, too?

[Injuneer]

Without the nitrous, my Formula only makes 390rwHP through a TH400 (486 flywheel) and will run high- to mid-11's all day long. It made 425rwHP through the T56, but I could never launch/shift it well enough to run 11's. A good driver could have done it though.

Emissions has 2 aspects.... visual, and tailpipe. To pass a rigorous "visual" you need all the components intact, including AIR, EGR, cats, etc. And to meet the letter of the law, the cats need to be in the same location as when the car left the factory. That rules out long tube headers in many areas. Tailpipe isn't going to make any difference... stock manifolds, mid-lengths, or LT's..... its the tune that governs tailpipe emissions, not what kind of exhaust its flowing through.

An "out of the box" set of factory LT4 heads ($1,250 + $200 intake) will flow approx. 15% more than the stock LT1 heads. But, you can have the stock LT1 heads P&P'd to flow 15-20% better than the stock LT4 heads. Of course, you P&P the LT4's and you'll be approaching 300cfm and flowing 5-10% more then the P&P'd LT1's. Depends what you want to spend. You could get a real good job done on your stockers for $1,000. Buy a set of LT4's an LT4 intake and get them max'd out, and you could be looking at over $3,500. A lot of room in between.

"Streetable" is vague. My car was street driven, weighed 3,760#. The heads flow close to 300cfm. The cam is a very mild 230/242 114LSA 0.590/0.590" solid roller. Starts on the first crank, idles smoothly at 800rpm, gets up to 20mpg, will pass NJ rolling emissions (but not "visual"). I suspect I could pick up a quick 50HP with a more radical cam. Headers are mid-length AS&M's although the collectors have been modified so they run straight back into a true dual exhaust.

[raroZ28]

After reading what you said about the heads... I think I'm going to go with a big cam, and have the stock heads worked on. Midlengths sound good too.. Best of both worlds. Thanks

[raroZ28]

Sweet... Roughly 1000 for head work, 300 for valve springs and rollers, $500 for mid length headers and off road Y pipe, and about 500 for a cam. Nicely! I'm going to be spending about $2500, which is $500 less than I had planned, which can pay for a complete suspension upgrade. I look forward to talking to my machinist about what he can do for my heads. He is a vendor for ls1tech or something I remember him mentioning. He does good work on Chevy's, it's his specialty. LT1 and LS1 anyway... I'm hyped.

[raroZ28]

How does this cam sound?
Comp LT-1 Xtreme Energy Cam, modified heads, intake, headers, converter, gears
Dur@.050 236-242 | Lift .521-.540 | LSA 112 | RPM Range 2500-6000

Any cam suggestions or where to get them? Like I said the lobes and durations and that, I don't really understand at all.

I hope the car blub blub blubs with the new cam. I love that sound. I think a guy named Gunter put a video up of his car after his cam install. Drool....

[fastTa]

To achieve 410+ RWHP with the LT1 castings, you will need to have a stage III porting done. LT1 castings can be made to flow in excess of 300 cfm. If I were you I would go the LT4 route. Most major f-body speed shops will give you money for your old LT1 heads to help offset the cost of the new LT4 castings. They will usually give you anywhere between $200$-$450 for a set of LT1 castings.

My old set of LT4 heads flowed 324 with a full port job. With a fully ported set of LT4 heads, port matched LT4 intake manifold, and a cam with over 233 duration @.050", 440+ RWHP can be easily achieved.

For instance, my old LT4 setup was a fully ported LT4 head, port matched intake manifold, and a 239/245 @.050" , .577"/.576", 112 LSA (hydraulic roller), Jet Hot 1 3/4 LT's, Spintech catback, TH400, aluminum DS, 12 bolt rear, and a belt driven vacuum pump. This combo was plenty streetable and made 488 RWHP naturally aspirated on a SuperFlow eddy-current dyno.

Here is a good list of some common grinds that Combination Motorsports has R&D'ed:

http://www.cmotorsports.com/engine/l...ft-design.html

Here is a pretty good summarization of valve timing and how the camshaft affects valve timing:

http://www.compcams.com/Technical/TimingTutorial/