nbanwart

How's it going guys, this is my first thread here

I recently purchased a '84 Vette for $2k and am rebuilding the engine. I'm not looking for 'too much' performance, just enough to crush my friends '93 300zx (he thinks american cars suck )

Anyway, long story short, I'm wondering what I should do. I have a set of slightly better than stock heads with large valves, and a lunati barebones 280 cam which should make peak hp numbers at around 5000-5500 rpms. My question to you guys is will the Crossfire system make it that high with ported intake and 1.6rr? I have a Camaro tpi system in my garage, will that make it that high? I could convert to a carb, but I think the crossfire induction is kinda cool. I'm looking to make around 350chp or so with the cheapest viable option, my desktop dyno says that i'll be making 375chp with the setup, but that seems awfully high.

By the way, if it helps my static compression is 10.2:1 and dynamic compression s 8.23:1.

Thanks for the help!

wilcar

There is no way you will get a 280* cam which are usually 230-230 duration at .050, .480 lift and 110 lsa to work properly. Trying to get it to idle even with 10 c.r. will be a real challenge for the TBI or TPI without major mods to the computer. The 280 will pull about 10" of vac at 1000 rpm. Even with a carb conversion you will need some stiff gears and a stall converter with a 280 cam to make it run otherwise your low speed driveability will really suck.

qws

You will get more gain out of a fully ported CFI vs the TPI intake your thinking of putting in there

nbanwart

You sure? Others have said that it would run fine at 800-900rpm with stock converter and the low speed won't be terrible. As long as it won't buck like a mule when I step on the gas I'll be content.


That's what I figured, been reading almost every post you made about crossfires

cv67

Youll need at least a 3.73 gear and a 2800 stall for that cam

Frizlefrak

Hog out the intake fully or find a used X-Ram to take advantage of your increase airflow from the head / cam change, run some steeper gears...and show your riceboy friend to the door.

Tom400CFI

I agree with wilcar about the cam; way too big;
both to run on a stock computer and way bigger than you need to meet your goals. Keep the duration close to stock, port the living bejeesus out of your intake (when you think you're done, do it again!), and do supporting mods. That and the heads you mentioned will get you to ~300 hp and you'll beat a heavier 300zx Turbo (that is stock).

wilcar

I could be wrong on the barebones cam. Since you did not post the actual specs of the cam, I assumed that the 280 would be like their old bracketmaster II cams with the 230 duration at .050 .495 lift on a 110 lsa. Sometimes Lunati specs their seat durations at different rises making them look much bigger than they actually are. I noticed they have a barebones 214-224 112 lsa cam, 280/290 advertised duration, is this the cam you want to use?? If so it might work but think you would still need some stall and some computer mods depending on how much vacuum that cam would pull. Most people I know with a crossfire do not go over 212-212 at .050 112 lsa on a stock motor but since you will have more c.r. and ported intake it could work.

cv67

http://www.lunatipower.com/Product.aspx?id=2505&gid=309

nbanwart

Sorry I didn't post the cam specs, don't know why I left that out.

It's actually the 270/280 cam. But by looking at lunati's website, the ebay seller got the specs wrong....great. But I was thinking about getting the 270/280 cam as it has roughly the same power curve as the 280/290 according to my desktop dyno. That cam should work with no cpu mods whatsoever, right?

Slow_Lane

Not to derail your thread but is your friends 300Z a twin turbo model? I ask because stock those run 300hp and are easy to tweak for more. We all love C4's here and God knows a SBC can be built to whatever output your wallet will allow but I think a HCI update on an otherwise stock C4 will yeild a strong running car but I'd hold off on smack talking your friend until you knw for sure you've got him.

nbanwart

Nope if it was TT I wouldn't even be trying to talk to him lol. He's got somewhere around 250hp (exhaust, intake, bolt on mods) so i'm fairly confident I can smoke him with even a mild build

By the way the .050 duration of the 70 cam is 204/214.

wilcar

The 204-214 has been around a long time and a lot of people have used them in their 350's. I would check with lunati to see if your if your c.r. of 10.2 is going to be okay with this cam. Most guys I have seen run this cam had 8.0 to 9.0 c.r. You may have to run premium gas to eliminate pinging. What heads are you using ? The 84 L83 engine with the stock 624 heads and forged pistons is rated at 9.0 c.r. How did you figure your 10.2 c.r.???

nbanwart

Some heads I'm thinking about picking up that flow better and have 64cc chambers. It is to my understanding that the 8.23 dynamic compression of the cam will bleed off enough compression where I could use 87 fairly easily.

wilcar

If you are going to use 64 cc heads just make sure they have accessory holes because the older "fuelie" heads do not. You stated you have some heads with large valves that are slightly better than stock, which heads do you have?? If you have not purchased heads yet I would highly recommend the Summit 152123 cast iron large valve heads which are really Dart SS heads. They have screw in rocker studs, .525 lift springs and much improved 72 cc combustion chambers. Ready to bolt on for $630 shipped to your door. I just put a set on my 84 and with my ZZ4 intake, 600 carb, 218-218 .450 lift cam and they made a huge increase in power for sure. You might want to check with others that have run the 204/214 cam with 10.2 c.r. or at least make sure that the 10.2 figure is correct. The 204/214 cam will actually close the intake valve sooner than the factory cam which will increase your cylinder pressure so you may have to install it retarded a few degrees if you have 10.2 c.r. You have a tough situation, you cannot over cam the engine because of the crossfire and you cannot under cam it because of your c.r.!!

nbanwart

To be honest...I don't know the casting number. They were recommended by a friend to me and for $300 completely redone, with a one year warranty, I couldn't pass em up The guy who sold em to me had em cc'd at 64 and they have the accessory holes drilled. Anyway, since the l83 cr is 9.0:1 with 76cc heads these new heads will bring it up to 10.2:1 if what i've been reading is correct. I'm leaning towards the 280/290 and if worst comes to worst I'll install a throttle stop screw and idle it a tad bit high.

cv67

use a touch thicker head gasket wit hthe 64cc heads?

Take you to 9xx which will be fine with iron heads

That 204/214 should work well, kind of like the age old "RV type" cams that make good torque.

If you ported your intake and even a little bit of bowl work on the heads /headers that car would really wake up. I wouldnt mess around with large cams/raising idle up wiht the CFI.

Dominic Sopresso really knows these cars well and what works. Maybe someone can send him a link to this thread he can help out...with tuning them too so you only have to do this once and get it right.

qws

When I first started researching for my upgrades on the 84 I first went with the Xram. About a year later went with headers,1.6rr's, Dart SS iron heads and the 2040 cam. I was pleased but still wasnt enough.
I then changed out the cam to a 268H with .510 lift after adding in the1.6rrs and still ran the xram. I was much happier with that combo and still running a CFI style type intake. Of course by that time I could tune the vehicle as well by using EBL/Flash. I also was using a 2500 stall. With that combo I was running 13.3.
I do believe that with that combo you could still satisfy the tune by using the stock ecm just by bumping up the fuel pressure and adjusting the timing.

After that I just got out of control!..

nbanwart

I've heard of doubling up head gaskets, is this a bad idea? Is bowl work on the heads a bad idea to do yourself? I'm kinda short on the cash side as I just paid $1100 for rebuild parts/machine work. I was doing some more research today and bought the 280/290 cam and lifters, people with tbi said they worked great and many others said the 204/214 was too small for it. Playing with the desktop dyno the 280 seemed to have better curves at higher levels of timing retardation where the 270 cam started losing power sharply. I hope I didn't screw up to much

If somebody could link that guy this thread I'd greatly appreciate it. This teenage kid needs all the help he can get.

nbanwart

13.3's huh? Not bad for a cfi car

How hard is tuning with this EBL thing you speak of? Tuning the cpu myself was something I was always interested in but anytime I asked I was always told it was over my head.

I'm also eventually going to switch to a manual trans so I'm too concerned with upgrading torque converters, etc right now.