69 Z, Headers, VS Stock Manifold and Chambered

[NEW]

I have a 69 Z, it has now a completely rebuilt engine,
0.3 overbore,with standard GM pistons standard Camshaft
and the standard 2.02, 1,60 Heads, The engine has been slightly top decked.

I have for now the oiginal intake, but has also been running it with my Crossram.

Anyway now the qusetion::::

Has anyone here tried swithcing from stock exhaust manifoilds, and chambered exhaust to something like Hooker headers and a little bigger exhaust system like 2,3/4" or 3".???
What is your experiences, there is no punch in the engine and i am thinking it could be the manifoilds that is to restrictive?

And does anyone know what jet sizes is best to run in the stock Z carb, aaaaaaaaand some more, does anybody have recomandations regarding crossram intake, and jetting, maybe it also would be better switching for 1.st design camshaft...

Any tips, or info from people that has tried diffrent things, or people in the know of something pls. Reply..


In advance, THANKS

NEWs,,,
and i know it is not like a Super Super car but it is a super car

[COPO PETE]

I don't believe you will see that much of a gain with headers, but there will be some, nothing really seat of the pants. Sounds like it is geared wrong. What tranny you got???? If it's a M21, you'll need at least 4:88 gears. If it's a M20 4:11 minimum to 4:56. Maybe Mark will chime in on the crossram jetting???
Peter

[Keith Tedford]

Back in '69 Nurse Chev-Olds installed a track cam and cross ram setup on a Z/28. With the stock 3:73 gears there was absolutely nothing below 4000 rpm. 4:56 gears would be the minimum for this combination on the street. The M21 might have been the ticket on the road courses but it didn't do the street car any favours. Tony Pizzi showed what terrors these cars could be on the strip when set up properly. On the stock 780 Holley with power valves front and back #73 primary and #76 secondary jets would be a good start.

[NEW]

Me Again!

I am running M21, and 4,10 in the rear.

Its the 780 carb, but i∆m running 78 on the primary, and 80 on the secondary now.

What timing would be suggested? i∆ve read abt. people doing sometimes like 42 total.

I once had a L88 with stock manifoilds, and stock type exhaust, once i put headers and some less restrictive system on that engine it was like a diffrent engine.

It also have a tendency to get sligthly hot on the exhaust side, LH side.

Has anyone had any problems with the smog system leaking in, and making the engine backfire?,

NEW

thanks for the replys /ubbthreads/images/icons/smile.gif /ubbthreads/images/icons/smile.gif /ubbthreads/images/icons/smile.gif

[COPO PETE]

Stick some 72's or 73's in the front, give it 42 degrees timing, put some 4:88 in it and call me in the morning /ubbthreads/images/icons/smirk.gif L88 with headers will pick you up over 50 horse over manifolds, you will not see anywhere near that on a 302. Do run something like an ultraflow muffler on it.
Peter

[JoeC]

Also try the lightest springs you can find in the carb and dist.

[JohnF]

I am by no means an expert but I have been playing with different set-ups on my Z/28 for almost 24 years. Here is what has worked for me. I run 72 jets on the primary side and 76 secondary side; yellow secondary spring and 25 squirter. Headers do make a difference! I currently run the 1 3/4" Hooker Super Comps, 2 1/4" pipe to a cross flow muffler, and 2" tail pipes. The only muffler, other than stock, that performs better (and is not too loud) is a DynoMax cross flow that is listed for the Buick GN. It is a bit shorter than stock but looks good under the car and seems to flow quite well. As far as timing advance, I run 10 to 12 initial and 36 total, all in by about 2200 rpm. I have never felt that going over 38 did much to create any more power. These are not racing modifications but work very well for me on the street. I have tried everything over the years including the original manifolds, etc. With the quick timing advance you will need good gas. You may want to visit the Camaro.net site and do a search under the name JohnZ. He has studied the original 30/30 cam and gives very detailed instructions on how it should be adjusted. Again, just my opinion, but this works very well on the street.

[NEW]

Hi,,
Basically what you people are saying is ::

72/73 jets front, 76- secondary,
timing 38-42, light springs,
carb light springs.
I∆ll try sometime during christmas or slightly in to the new year..

But back to the Chambered, good, or acceptable or just nice sound?

Smog system, anyone had trouble with this?,


THANKS Great info......

NEWs /ubbthreads/images/icons/smile.gif /ubbthreads/images/icons/grin.gif

[COPO PETE]

Chambered ain't bad, maybe Rob will chime in since he changed his. It is one of the best sounding though! I honestly think to get the best seat of the pants improvemnet is to put a M20 in it. With the M21 you will ring out first gear till your going about 50 MPH. With a M20, you will think you have woke up about 50 horse. I'll put my reputation on that!!!!...what ever my reputation is! /ubbthreads/images/icons/confused.gif
Peter

[Chevy454]

Well, since you asked, Pete:

Factory chambered = Crap

It all depends on what your are going after. Nothing beats the sound of chambered, but the factory system is restrictive...and I mean WAY RESTRICTIVE! Flowmaster offers a 2.5" mandrel system which uses it's own "interpretation" of a transverse muffler, or Dynomax sells a really good transverse muffler that looks fairly close to stock and flows really well, but you'll have to bend the rest of the system yourself. BUT, if I was gonna put exhaust on something that won't be submitted to a tech inspection(!), I would buy the chambered system they offer for the new Camaros/Firebirds. The system is mandrel bent, but is a LOT bigger than the original chambered of the '60s. It supposedly adds power to the late model F-bodys, and is supposed to sound AWESOME, so it must be pretty good, because those late model guys won't buy ANYTHING without seeing what it did on a chassis dyno. That, to me, would be the best of both worlds: the sound and look of chambered, but built using today's technology.

As for tips for your Z-28...I have no idea about tuning it, but don't be afraid to REV THE PISS OUT OF IT! Don't worry, your ET's will thank you for it!

[NEW]

Hi,

In Norway they are very easy to deal with concerning tech inspections on cars older than 71. So i dont have to really worry abt. what i am doing concerning sound, etc..

The engine sound really nice and everything, but it is missing something, it could be that it is breathing to little.. Since it is an original car, and every thing is kept original i am really just not sure what to do..

But i think the exhaust, and the smog system does some strange things to it,,, I∆m not really sure, cause i havent run a 302 in any other form than this,

NEWs
thanks for the help, and if anyone else has any opinions........HIT ME /ubbthreads/images/icons/smile.gif

[Keith Tedford]

The factory chambered exhaust has always had a reputation for being restrictive. If you drive on the highway much, the noise will quickly become annoying. I've run my spare M20 behind our L78 while having the original M21 rebuilt. Even with that engine I prefer the M20, especially in the city. What really helps a 302 to be drivable around town is the L79 cam.

[Salvatore]

Hi new member. Mostly all the things these guys have been telling you I think are right. The chambered exhaust is restrictive. A set of headers is a must for the little 302. Take the smog off and put it into the closet, for now. Put a good set of 2.5in. pipes on it with the cross flow pipe and low restrictor mufflers of your choice. You really do need the M20 with 4:10's or even 4:56's with a taller tire. These 302's have NO torque. I like running the timing around 40 to 42 total advance with the advancement coming in around 2500 rpm's. Jack Podell has a gas additive for 93 octane. You can get as much as 103 octane with the mixture. It is a REAL lead additive. 72 jets in front with 76's in the back sounds good. I don't run the power valve in the front because they are annoying. My car has no problem surging or pulling out. If you set the 30-30 cam a little tighter like 28-28 you can see that it does gain a little more torque with a tighter valve lash. 28in. tires in the back with a 4:10 and a 254 first gear will make your car very drivable and perform well. If you can't find the correct spring tension for your 780 holley you can always install a small nut and bolt in the carb linkage to enhance your secondaries to open quicker without the aid of vacuum. Make sure that your motor does have the correct compression ratio. At least a true 10:50 to 11:1. The smaller the motor the more this helps. Make sure your valve springs are good and REV it to death! Jack Podell is in Hemmings Motor News. Have fun! Sam

[Salvatore]

Tony Pizzi was great! That car flew. 11:68 with 7in. tires. NHRA kept factoring him to death, like they did to Bernie Agaman's 71 454 corvette. The both got out of stock and super stock racing because of that. Jenkins gets some credit for Pizzi running so well also.

[NEW]

Hi again,,

if you guys would like you could i think, if i do it right,
see the car here: www.newsgarage.com/inventory.html (http://www.newsgarage.com/inventory.html)


NEWs
and again thanks /ubbthreads/images/icons/smile.gif
And you know what, here in Norway we get 98 octane at the pump, so some additives easily gets us up to 102-104 octane