C4Callum

Cheers. Great advice. So these mild cams won't flow more than my standard 113 heads?

Getting really amped about getting the motor built now.

bjankuski

This statement is misleading at best. In general you can increase performance and gas mileage at the same time (as long as you stay out of the throttle, increased engine efficiency will increase gas mileage and power).

The ZZ-4 cam should provide you more power and better gas mileage then stock, if it is installed correctly. The cam should be installed at 108 ICL and at this installed position with its fast ramps it will close the intake valve quicker than the stock cam. The earlier closing will build more dynamic compression for better gas mileage. In addition its area under the curve is increased since it has fast ramps and much more lift then the stock cam. This combined with the tighter lobe separation (112 degree) will cause the engine to pick-up low and mid-range torque. The extra exhaust duration will also help blow down the cylinder quicker and scavenge the cylinder better. The only downside to this cam is that it will idle rougher at 550 RPM because the overlap is much greater than stock. You may need to raise your idle RPM to 750 RPM to smooth out the idle. It will work even better with a low restriction exhaust and better flowing intake.

I have run 1.6 rockers on the ZZ-4 cam in the past and had no issues with noise or life of the valve springs, in general it is a good cam for a TPI engine. You can get better cams but it will not cause you a loss of power or mileage. If you study the specs of this cam you will notice it is similar to the ZZ-9 cam from TPIS.

If you decide to use the cam make sure you use the correct valve springs and make sure you have enough retainer to guide clearance. The stock cylinder heads usually require some work once lift exceeds .480 lift.

GREGGPENN

I agree that mounting a cam advanced is the best way to address MPG concerns. The more advanced a cam, the sooner the valve closes and begins to build pressure. (I was remiss in not mentioning that option).

I suppose we could debate the issue of more vs less overlap getting better mpg. Less overlap gets more cylinder pressure and better idle, More gets more power -- and VE (efficiency). I doubt anyone has studied the effect of a few degrees overlap for mileage. Aftermarket cams are geared toward making more power. And, MPG isn't going to be [significantly] different either way.

Don't install a cam if you're worried about .5 mpg.

I assume the OP knows a bit about cam basics, but, if not....
http://www.chevyhiperformance.com/te...ics/index.html

Since we have contradictory opinions on the validity of 1.6 rockers with ZZ4 ramps, just be safe and use plenty of spring. Some think stiffer springs lose a couple of ponies. OTOH, in a valve train, as one spring is resisting opening, another is helping to close a valve -- making it insignficant for most people. Valve control is way more important than a hair more power.

If it was me (considering the OP's situation), I'd use a bit more duration, sacrifice any MPG loss that MAY happen, and be happier with milder ramps. (It might be why Brian mentioned the ZZ9 cam.)

One last point....In my 89, the stock cam is not installed advanced. I think it's to make more power top-end (under the long-tube runners). After you read the link above, you'll see less overlap and retarded cam positions create a more linear power curve (with better top-end). That's a big reason aftermarket cams have the potential bump mid-low power and actually improve mpg.

Since HP is bragging rights, taking a bit away from top-end potential often leads to an undesireable result. By going big enough (vs stock), you restore top-end, create enough overlap to consider eliminating the EGR (due to charge dilution), and increase TQ/HP from idle to to the peak hp rpm.



Now for the $64 question....I'm betting the OP will opt for less overall expense, avoid the cam install, and settle for the rocker mod -- calling it good. Am I right?

C4Callum

wow, food for thought. great information there. i understand the basic mechanical principles of a cam eg lift and duration but know nothing about the other effects that can occur.

your probably right saying i will stick with just roller rockers for the time being. the big factor for that would be that i would have to get my motor tuned right away and i dont plan on getting it done till after i have installed my hsr. which wont go on for a little while after the rebuild.

this is my first engine rebuild and unfortunately i dont know anyone else who has done anything like this.

GREGGPENN

You mean you don't know anyone personally? Locally?

Neither did I. Have the cam you want installed the first time. Have the intake you want installed the first time. Pay for a mail order tune (and tweak) to get it running.

I got my help/advice from here. You can too.

85 Vette Kid

I have been thinking about doing a cam swap and longer headers in my 85... Just looking for a way to make it a little more fun to drive. Any suggestions? And im not so concerned with gas but it is an everyday driver.

GREGGPENN

Do a search and start a new thread is my first suggestion. Its the best way to view/review your personal build issues.

Look for a couple of build threads and read up. This helps with the type of questions you need to ask -- and members will be asking you.

BADDUCK

Do the cam NOW if you are going to do it at all. If all you are doing is adding the ZZ4 cam now a mail order tune will work fine and can be adjusted later. I did just 1.6 full RR's on my 1989 and it cost more than a ZZ4 cam. More labor and trouble to do it later.