Hello all! My 77 Z28 is bone stock.(LM1/M21/3:73)My plans are to do mild modifications to the engine.I have the following: Edelbrock Performer manifold which I plan to use with the stock carb.I have purchased a L-82 camshaft(made by Speed Pro) Lift .450/.461 Duration .224/.224 Lobe 114/114. The heads are stock (333882)with 194/150 valves.The heads have been milled but the block hasn't been decked so I assume that C/R is still 8.5 to 1.(Is this correct?) My question is since I am not going to race the car and use it for cruising am I wasting my money by installing Chrome Molly roller tipped rockers(1.5 ratio) or just leave the stamped steel ones in? Any other thoughts,suggestions would be great. Not sure yet if I will install headers or not but since I heed new exhaust,I will go with 2.5 inch Flowmasters. Thanks Laurence(Laurie) Potter

I wouldn't use that cam. Use something more modern. Check out the XE262 by Comp. And, IMO, those roller tipped rockers ain't worth squat. Go full roller ($$$) or stay with the stockers. Lastly, a set of headers and dual exhaust would really wake that engine up -

Roller tip rockers are not worth the money, unless you are doing a completely new valve train and want to minimize wear on the tips of the valves where the rockers make contact. Full roller rockers reduce friction in the valve train and let you pick up a few RPMs, and a few Hp at higher RPMs. If you are not going to the track with the car, you probably will not notice any difference.

I agree that more modern cam grinds offer some advantages over the older muscle car cams, but there isn't anything like that nice lopey idle of the old cams for that muscle car vibe. I run the GM 350 hp 327 cam in my 80 with a 327, and it sound great.

Thanks for the reply guys! Funny thing happened today...I called Flowmaster and asked about 2.5 inch exhaust and the answer I got was that because the engine was basically stock,I should 2.0 inch or at the most 2.25 inch exhaust. As posted earlier,I was thinking of using their 50 series muffler and going to 2.5 in pipes.Now i'm not sure what I will do.Any thoughts please! Laurie Potter

2.5" you'll be alot happier

Just my 2 cents, but higher flow and less back pressure is bad for mild stock cams - they need that back pressure - for mileage and lower rpm torque. If your plan on running a more free flowing exhaust with that L-82 or performance style cam, then you should be fine with 2.5" exhuast.

I run a similar cam (I use the term lightly) @ .442/.462 112LS - with 1 3/4" headers and 28" long glasspacks welded straight to the collector - there 2.5" straight through. So my exhaust is pretty much 28" long free flowing. 1k to 1.8k rpm is kind of soggy due to almost no back pressure. Needs more gear in the rear to help compensate for this.

Also found out that large headers and tiny exhaust, 2", don't match. I guess its because the headers scavange but don't have the flow to push it out? 'Dunno for sure.

Hope some of this info helps.

[This message has been edited by malducci (edited March 24, 2005).]

Low backpressure has absolutely nothing to do with soggy bottom end torque. If your engine displays low bottom end torque after an exhaust change it is because the air/fuel curve in the carb will now be leaner, and will need to be richened up to compensate. If a ton of back pressure was needed for bottom end torque then all those after-cat exhaust companies would be out of business, as the stock high back pressure exhausts from the OEMs would be as good as it gets.

Next time you see a UPS truck go look under it - they have a full 3" exhaust but only use a GM 4.3 litre V6.

The L-82 cam will work in your '77 Z, but it does require a bit more than 8.5:1 CR to work optimum. At least 9:1 would work better, but if you have it you can use it esp. considering you got the heads milled, have the 4-speed, and are running a 3.73 gear. I'd advance it about 4 degrees in the motor which should help out bottom end power. The rest of your combo looks okay. The one advantage to those older cam grinds is they are easy on the valvetrain and will last a long time. And, they do make power, contrary to what those who jump on the Comp XE bandwagon would have us believe. I would also suggest the Comp roller tip rockers will work fine and last a long time in a street motor with a mild valvespring like the GM LT-1. In fact Dave Vizard uses the Comp Magnum roller-tip rockers with huge solid-lifter cams running 350 lbs over the nose and recommends them. They key is to use a quality roller-tip rocker arm like the Comp Magnum. I would not use a cheap import roller tip rocker arm. Go with the 2.5" exhaust.

------------------
'Silver Bullet' 1977 Z-28 413" SB
11.73 @ 115.10 on drag radials
Old Vortec combo:
12.15 @ 110.52

Thanks for the info Dirt - must have been urban legend pass from father to son. I did notice a lean change in air/fuel ratio - so your more than likely right.

Sorry, Z169 - didn't mean to hi-jack your thread.

Imho, and I'm old-school too, the old -151 and -962 hy-cams need at least 10 to 1 CR. to run good AND stock motor 11 to 1 is right-on!!

(And fwiw, I ran a -151 cam in my stock, L-48, 295hp/350 motor that is from 10 to 10.25 to 1 CR. as a daily driver for several years after 1,200 miles from new back in the spring of '67!)...

With the old -151 cam, my motor had a middle of second gear to top of third that pulled like a freight train with my M-20, 3.31's and recap, real 8.00-14 slicks back then!!! AND on cheap, 25 cents/gallon, regular LEADED gas!!! Those were the day's!!!!!!

Go with any of these if you want to.

A CC 260HE at what CR. you are, and 268HE to 9 to 9.5 CR., then a 270 Magnum if you can get the CR. up to about 9.75 to 10 to 1.

Crane 266/266 Energizer at what you are up to 9 to 1 CR. and 272/272 Energizer up to 9.5 to 10.....

Isky 270 Mega at 9.5 to 10 to 1 too....

I think you may be able to change heads and run Fel-pro, .015" thick shim headgaskets and get up to about 9.5 to 1 CR. fairly easily.

If you want to learn about this stuff: The deal is that you have to pick a cam that creates a dynamic/effective compression ratio that is from 7.75 to 8 to 1 for pump gas use!!

This is found by playing with a Dynamic/effective compression ratio calculator like either Pat Kelley's great site or the "Boost Calculator" site.

Open Pat's great site up that you get to through his sig. AND read it at least 4 times!!!!!!!!!!!!

Dynamic/effective compression ratio is calculated by taking into account the intake valve's closing point, rod length and motor size and static CR.

I play around with this all the time for the fun of it.. That's why I have a good old CC 282S solid cam in my 550hp at 5500rpm, 496" BB "tow-truck" grunt motor!!!!!

pdq67

<font face="Arial,Verdana" size="2">Originally posted by pdq67:
[BI think you may be able to change heads and run Fel-pro, .015" thick shim headgaskets and get up to about 9.5 to 1 CR. fairly easily.
[/B]</font>
Even with 64cc heads and the 1094 gasket, he would still only be around 9:1.

Z169, what shape is your engine in? How is the oil consumpion, and overall wear. A cam change is pretty involved, and It might be worth it to freshen up the whole motor while you are at it.

Gee Thanks for all the info Guys! The engine was reciently rebuilt(1.5 years ago) back to stock specs.I bought the car from Camaro Heaven just out side of Toronto.I know that the heads have new valves,guides etc and the engine has a new crank(cast or steel I don't know).I don't know if pistons were changed to flat tops or original ones were used.Motor doesn't snoke and sounds real quiet when it runs.(no valve train noise)Car is really really clean.Original trunk,doors,fenders,1/4panels.I just I would wake it up just a bit with some mild additions. You guys have really been helpful.Sorry to take so long in responding..I work shift work. Laurie Potter