Hello and Happy Thanksgiving everyone.

I currently have a GM 502 stuffed in the engine bay of my 69 Camaro. I've run the engine for about two or three years now and I'm becoming bored with the power and need more from my engine.
The engine was ordered by another customer who never took posession of it. The components are slightly different than the standard pieces that come with most ZZ502s'. This car is an everyday driver for me during the spring, summer and fall months. I've never taken it to the track, but would like to have something more potent, but remain driveable for street use with track duty in the future.
I would like to keep the mods to the engine very mild if at all possible - maybe a cam change, injectors too big?? Maybe decrease the size of the injectors? Intake the right one for this setup or should I dump the injection and go with a dual plane carb setup?? Let me know what you think.

Here are the engine and vehicle specs:

Displacement:502 cubic inches

Block: Cast iron four-bolt main

Bore and Stroke: 4.47 x 4.00

Induction: Commander 950 Multi point fuel injection (direct injection).
Four-barrel progressive throttle body with single plane intake
(Holley) with 42lb injectors.
I have the Holley wideband O2 system installed for this system,
but I am currently running open-loop. I've been to two
different race shops to have the systen tuned. One
recommended using the wide-band and the other did not.
When I useded the O2, I always had massive engine run-on
after shutting down. It decreased greatly when I shut off the
O2 sensor and ran open-loop.

Compression ratio: 8.75:1 (compression is usually 9.6:1 with the 110 cc
oval ports which come standard on the 502). I don't
have the standard heads.

Cylinder heads: Performer RPM Rectangular port Marine heads (aluminum)
(118 cc.).
Intake 2:25 Exhaust 1:88 - stainless valves

Camshaft: I'm assuming that the camshaft installed is the factory GM
part that comes standard with the zz502.
Hydraulic roller Lift .527 intake, 544 exhaust, Duration @ .050
224 I, 234 E.

Rockers: Crower stainless full roller rockers. 1.7 ratio

Harmonic dampner: Fluiddamper

Exhaust: Hooker Super Comp tuned headers - 2 inch primaries to 3 inch
collectors. Full length 3 inch exhaust system with crossover and
free-flow racing mufflers.

Ignition system: MSD 6AL. Commander 950 computer is controlling timing.
MSD distributor has been locked out. small cap dist.

Transmission: 4-spd manual Super T-10 (cast-iron nodular case) 2:64 1st
gear. Gear Vendors Over-drive installed - .78 final

Clutch: Centerforce II. Clutch needs to be replaced. Not holding up to
torque very well.

Flywheel: I believe it's somewhere between 33-37 lbs. (steel). I'm not
exactly sure what the weight is, but it's a factory GM part that
was included with the 502.

Rear: Factory 12-bolt with 4:10 gears. Morose Brute-strength posi unit.
Mosier axles.

Car has functioning cowl induction. This car has many options and I believe is quite heavy.

I was told that I could change the cam to make more HP and torque as well as increasing the size of the throttle body to allow for more air with this setup. I really don't know what to do. Can I select a better (larger) cam and still keep my compression this low. Can I continue to use these heads with my combination or are they too big. I know some basics about engines, but not nearly enough to make things work right for me. I just can't seem to get the injection dialed in right and have thought about taking the system off. I'm lost and need some real help here. Please give me some suggestions and get me going in the right direction. I'm not worried about gas milege, I want more uuuummmmmfffffff.

Thanks All,


Paul

One word.. Procharger! My plans are in the works. I am looking at the GM454 , 502 or a shop built engine. I'm having a hard time finding a 454 around here and the 502 doesn't have a fuel pump boss. ANYWAY..The 502 would work great with the procharger. Look at the F1. You can go with the D1 ,but you will get bored of it before th F1. I would go with the intercooled system ,but without would be fine at first. Cost is around $3400 for the Non intercooled though.$$$$. I'd say around 750HP to start... Just an idea. Oh I owned 2 Prochargers so I'm not one of those dreamers... Good luck.

I've done 3 502's with the commander 950 and they all run like a dream. A cam change really wakes these up but with your low compression I'm not sure I could recommend one. A side not, if you send me your MAP file I could compare it with mine and let you know if what I think.

Lee

He, He!!

I can see the dreaded, "more power, Scotty" bug has bitten you bad b/c I figure your motor is a dandy big mild street motor as is.

Anyway, whatever.

Install some 100 cc ROVAL heads on it and then something like a 282S solid cam and I bet she wakes right up AND is still mild mannered, but a lot more powerful!!

Step up to about 10.5 to 1 CR. using better aftermarket aluminum heads and and needed pistons and say a 295 duration solid cam AND more power EASY, imho..

UDHarold has dandy cams that are now sold by Lunati's so just do a search under the cams for 496's and similar sized motors here and over on Team Chevelle.

Per D2K, I figure my 9.8 to 1 CR., "tow-truck", 496 motor with no more than a 282S solid should make close to 550hp!! You talk about midrange grunt!!

pdq67

Why not shave the heads to get a little more compression and then a cam swap. That should wake it up. I like the supercharger idea too, but that is not a cheap fix.

You could put the ZZ502 cam in there (if thats not whats in there) its a complete bolt in. Its sounds like you may have the 502HO, which comes w/iron heads and shares the same cam as the 454HO (something like 211/230 and .511/540 lift?)

Maybe put a dial indicator on there and measure the lift to get an idea as to whats in there.

You have high rpm heads with low compression and a hyd. roller that probably runs out of steam where the heads should be coming on. I think pdq67 is right. Bump the compression up and put in a solid cam. The other option is to put some oval port smaller chamber heads on what you have with 2.19/ 1.88 valves. It depends where you want to rpm to.
In my 454 I have a bigger hyd roller cam than you, .612/.630, 234/242 @.050, 10.3:1 compression and ported oval port 781s with large valves. My engine screams for what it is up untill around 6000-6200 where the cam shows it's colors and starts to roll over. You have better fuel supply then I do. I think that if you match your parts a little better you would be happy.

I forgot to mention that they had a terrible port mismatch and when I ported the intake manifold it reduced our track time by 1 second. Here is a link to my site that better shows you the problem: http://www.horsepowerracing.com/html/holley_mpfi.html

Here is a tunnel ram setup with the same problem" http://www.horsepowerracing.com/Latest_Updates/Tunnel_Ram/tunnel_ram.html

Lee

Hey mnm,
If I had that kinda money, I'd slap a supercharger on in a heartbeat. I've been interested in the Prochargers for years, but times are a little tough right now. As far as the compression, I really didn't want to have to pull the engine to upgrade the pistons. It was such a pain putting the damn thing
in.
I've decided to pull the front of the engine off this weekend and find out for sure what cam is installed. It might very possibly be the smaller cam that sideways suggested. By the way Lee, I did send you both base maps that I currently use. I've tried using the wide-band 502 sysmax basemap. It smooths out a bit and is a little easier to drive on the street, but when I start to step into it a bit, it seems to lean out and begins to burble.
I really should take the intake off and get a look at the ports - I might be suffering from mismatched ports as well. Will mark IV cast iron heads fit on a 502? I do have a set of rebuilt heads from a previous engine sitting in my basement which might work well according to Phels suggestion.
Here's another question - If I were to shave the heads such as Camaroman suggested, kind of compression could I gain. What would be the downside to doing this if any??
Hey PDQ, if I can't make HP and TQ increase happen the easy way, it looks like I'll be following in your footsteps. I hope I can manage with what I have - at least the major pieces. If my luck in the past accounts for anything, I mind as well start looking for the Jegs catalog now.


Please keep the suggestions coming!

Thanks, Paul

What do your intake ports on the heads look like? If they are supposed to be big port than you are trying to run an oval port intake ( the Holley looks like it is made for a peanut port head ) The cam is way too small for a big port head.

Paul - I never got the Email, can you send them again? Also, the 502 MAPs just dont work!

Lee

Hey Lee,

I sent them to you again using the e-mail that's in you signature. Let me know if they arrive.

Thanks again,
Paul

I would suggest switching to a dual plane intake manifold, and a 3.55:1 rear gear.

A cam change will wake it up!
Even something in the 240s duration will work well, and make way more power and be streetable.

Also, you may want to consider some kind of thermal barrier coating for your headers; with uncoated headers in combo with the aluminum heads you are losing waaaaaaay too much combustion heat. Combustion heat = horsepower.

Ran into similar problems with an HO454 motor. Low compression and rect port heads just doesn't work. Go with some oval ports 2.19/1.88, maybe the Edelbrock ones. Get the compression up to at least 10 to 1. you can run a little more with the roller. I run the aluminum heads(milled) with the 502/502 gm cam, coated headers, air gap performer rpm, 750 hollley hp dp. runs strong, not wild, but strong. I'm not sure your intake system will make as much diff as the engine components.good luck.

wilma

Hey Everyone,

I've been checking around, getting estimates for milliing the heads as well as getting estimates for cams, superchargers (just for the hell of it) and etc.. As far as the headers I'm running - they're already coated. Lee is giving me a hand with my fuel maps which appear to be setup incorrectly. I'm crossing my fingers.
I was able to see some old pics that were taken by my friend when we were changing the intake manifold over to the single plane. The ports and gaskets matched beautifully, so that's one less thing taken off the checklist.
One step at a time I guess,

Paul

Hey Lee,

I sent you the newer datalogs using the wideband map. Let me know what you think.

Thanks again, Paul

Never got them! Did you use your Yahoo Email account?

Yeah, sent them twice on Yahoo.

I sent you an updated file...

As far as your heads, cut them to about 110cc. 9.6:1 compression is plenty for a big motor. As far as downsides, the intake will probably need to be machined for proper alignment and check all your valvetrain geometry after its done....especially pushrod length cause these are all things that typically need attention after milling heads. You will probably need shorter pushrods.

As far as the ports in those heads....yeah, they are rectangle ports, but they aint too big. Think about the AFR big chevy heads....you cant get an AFR oval port(even though they advertise em....they probably wont actually be ready til mid next year at best), and nobody complains about the AFR rectange ports.....they friggin rock. Even the description for your eddy heads say that they have long runners and higher velocity. What this means to me is that although its a rectangle port, the inside diameter(mainly minimum cross section) isnt going to be huge and a lot of the port size comes from the stretched out length. On a 502, they probably wont like to do over 6500(and neither will a big block hydro roller cam unless you really put some attention to detail in the valvetrain....like a LOT). Youve got good enough heads that it would be really hard for me to justify spending any amount of money to replace an existing good head like yours. Many(not all), but many of your aftermarket heads will provide fairly similar results....so if you wanted a noticeable improvement youd really have to spend the cash on something good(like an AFR for example). Spending 1500 plus on another descent aftermarket head to replace your descent heads probalby wouldnt make enough of a difference at all for you to be happy with the high dollar purchase. At least it wouldnt be for me. Tis just my opinion. If you were to change heads, consider some performer rpm oval heads(for very similar results, but even more torque at low rpm that you will have trouble using on the street!) or my choice would be either an AFR 305 or a brodix race rite head. The race rites have an option for a 110cc chamber. They dont list it, but you can get em that way if you ask.


About the cam....I too agree that a 240 some degree cam would do it. If your sticking hydro roller, about a 248/255 at .050 on a 110 LSA should have plenty of snap to a bit above 6000rpm. Sorry I cant help more on the injection setup...Im more of a carb guy. However, I woudnt drop the injection for a carbd setup. Since you got it, keep working with it til you make it work cause once you do, you will be better off.

If you change the cam go to a solid roller. I put a comp cams Extreme Energy
in My 502 it sound awsome and runs great. But only once then the lifters
collapse and it runs like stock zz502.

Little more input here. Id check into the voodoo hydraulic rollers. Here is a nice one. Its the 60213 voodoo. Its a little smaller than what I first reccomended, but that shouldnt be a prob. Its numbers are 241/249 at .050 with a 110LSA and .625/.625 lift. I still think in a 502 its not going to requre much over 6000rpm to run best and it would be a good match. On a scale of smallest to largest, low 240's(duration) are the smallest Id go and high 240's are the biggest Id go for a cam.

As far as your lifters go, lots of times you can get away with reusing the stock hydro roller lifters. But, if spring pressures get too high than you wanna ditch em cause they wont survive if you ask too much of them. Sure even aftermarket ones can fail too....but the chances are greater if you try to run stock lifters with lots of spring pressure. I dont know the requirements for spring pressure on that cam....but Ill have a look-see and find out what I can find out.

Springs and rollers are no place to skimp.

Start here first. How fast do you want to go? What is your goal? Is this a street only application? Are you going to do any suspension mods? You can throw money and parts at it and not really get anywhere if your not careful. I have a freind that spent 22,000 on a high dollar motor and didn't pick up 22,000 doallrs worth.

http://www.rehermorrison.com/

Go to the tech section, there is some great reading there.

Just remember that when running aluminum heads you need to run abot a point more compression than when running iron heads due to lee heat retension in the combustion chambers. Your engine running 8.75 with E-heads is like running 7.75 wth the stock iron heads. You need more squeeze. I'd be willing to guess that you dynamic (running) compression is too low, hurting your low and mid-range torque. I'd agree to shoot for 9.75-10 to 1 range.I'm not sure how much you can gain by just shaving the heads though, I'd call Edelbrock and ask them, the should know, they designed them. With 10 to 1 the cam selections you've been given should be just about spot on. It dosen't matter if your running a single plane with EFI 'cause it's just an air box.Actually you don't want a dual plane with EFI. Big throttle bodies never hurt. If you do go with a carb, I'd run a dual plane intake, it should help give you a little more of the seat of the pants grunt.Run atleast an 850 carb, a 950 would probably be even better.IMO.