Hey folks,
I have a 1982 z28 Camaro, and I'm working out the kinks but I've ran into a few snags maybe you experts can help me with.

Engine specs (i got this off my brother and for all I know it's a bone stock 350, but this is what I was told was done to it.
1986 350 block bored .060
400 crank
X beam rods
"502 crane cam"
305 heads to increase compression (no idea if any work was done)
I bolted the edelbrock rpm air gap intake to it along with a 650cfm mechanical secondary carb and a 65k assault brand clear cap distributor.
Th350 that was "built" and has a shift kit in it.

I've timed the motor vacuum advance unhooked at 14 degrees, with total timing 2800 rpms at 36 degrees. Motor seems snappy, driveability seems decent to me, but I think it could run better.

Question 1. Am I in the right ball park on the timing, I read 36-38degrees is a good start for a mild built motor. When the vacuum advance is reconnected it sits around 19-20 degrees (I'll have to double check that number but it suits my recollection).

Question 2. I attempted adjusting the edelbrock carb, both screws 2.5 turns out from lightly seated. Hooked a vacuum gauge up and the best I can get is 13-14 @800rpms idle. If I adjust the screws out more the idle will go up a little, and once I bring the idle back down to 800 the vacuum gauge reads the same. If I bump the throttle itll jump up and settle back to the 13-14 mark. (I have a power brake booster, distributor, hvac vacuum harness and my PCV valve hooked into vacuum). Do I need to unhook all of these when doing the carb tuning.... or should it hold more than 14 vacuum regardless?

Question 3. I've lost/thrown 4 alternator belts since having this car, all at high rpms, I route 1 belt from the crank to water pump pulley to the power steering pump, second belt is routed from the crank to the water pump pulley to the alternator, power steering pump belt has never came off. The alternator belt feels tight, but once I increase rpms it gets a little floppy in my eyes..... do I need to crank down the adjustment a little more?

I drove the car today, it idles about 550-600 in drive, no sputtering when taking off, I can go from a stop, hit 5500-6k shift to 2nd (drops down to 4k) hit 5500-6k and shift to 3rd (drops to roughly 3500 and starts climbing.)no missing, no pinging or any unusual noises that I can notice.

 

Re.queston 3 ,I had the same problem with alty belts thrown/breaking about every 4th time I went over 5500:fixed that problem with deep-groove alternator pulley meant for 1970.5 Camaro Z/28...

 

Had the same issue throwing alternator belts back in the day on my cammed 305 G20 van. Swapped the crank, waterpump and alternator pulleys off something like an 86 4.3 Astro van that used a multi groove alternator belt. GM went with that style pulley across the board around 1985 or so. I like the deep groove alternator pulley idea but the junkyard pulleys were like $10 including the newish belt that was on it. Plus side is the alternator belt never squeaked after that.

 

Thanks guys on question 3., I've ordered a deep groove alternator pulley and I'll be installing that when it comes in. I appreciate the responses, belt sat even with the lip on the pulley with the V portion fully seated using a 15445 belt from autozone. hopefully sitting a little deeper in a deep groove pulley will resolve that issue.

 

should solve the problem-worked on the old high-revving solid lifter 70-72 LT-1 those also had deep-groove crank and WP pulleys. Totally cured the problem with mine,but I rarely go over 5500.

 

Think I'd need to replace the crank and wp pulleys or just the alternator pulley?

 

nah,alternator pulley alone should solve the problem

 

Thank you sir! I tried a non ribbed belt (like off a lawn mower) after reading some forums. Actually had worse results threw that belt while just cruising around. Gonna order one tomorrow and hopefully solve this issue. Hard to go too far with the alternator not charging lol.

 

It's not a "bone stock 350". It's a 388.

What are the full cam specs? What pistons are in it? With 305 heads its compression might be … just about anything.

Your timing "numbers" seem somewhat OK, FWIW; may have too little static adv and too much centrifugal though. As in, it may run ALOT better with 18 - 20° static and 16 - 18° of centrifugal, rather than 14° static and 24° centrifugal. Subject of course, to whether the marks and your light and measurement methods are accurate. Personally I don't even bother with a light and a bunch of "numbers" until AFTER I get the motor to run perfect; then I just write down whatever randomness "light" says so I can put it back after it's disturbed. After all, I don't know better than the engine does, what it wants; instead I ASK the engine what it wants, by making small changes, and seeing how the engine responds. Forcing some random "number" on an engine is one of the best ways I know to leave capability on the table.

If it's an Edelbrock carb, it's not "mechanical secondaries". It's an air valve system, somewhat similar to a Q-Jet but not the same. I'm not a fan of those carbs (Carter AVS... stands for "Air Valve Secondary") but if it's what you've got then it's what you've got. Edelbrock supplies a kit of tuning parts that gives a great deal of flexibility. I'd suggest getting that and going to work on it in a methodical, orderly, logical pattern that "isolates" and optimizes each subsystem of the carb in the order that they affect each other. DO NOT randomly decide, oh I'd like the secondaries to be richer, I'll just change those; then go back and change the primaries, because then the secondaries will have to be changed AGAIN because the primaries affect their operation. It is CRITICAL when doing carb tuning to do it in the correct order. I can't recall the full details of those, for example whether the main system (rods & jets) affect idle, but their instructions should tell you. If for example the mains DO affect the idle, then tune the mains FIRST, and after they're right, THEN work on the idle. NOT just jump right into messing with the idle, because then you'll just have to go back and tune the idle AGAIN once you dial in the mains.

 

Hey Sofakingdom,

I appreciate the reply, my comment about it being a "bone stock 350" was in regards to me not assembling the motor, or seeing any of the parts I was told were in it, again just going off of what I was told when I got it. I've never disassembled it, had the heads off, or ran a bore scope to check anything.
1. I was told they are flat top pistons
2. I do not have any cam specs, just was told it was a "502" crane cam.

As far as the timing goes (If you have any suggestions, I am entirely open to them): I was looking at that yesterday, and from what I can tell sitting at idle it's sitting at 18-20* with the vacuum advance hooked up. When I unhook that I don't notice a significant change in idle or much (maybe 2*) change in the timing-- light has an adjustable dial on the back and this is where I am getting my numbers, adjusting the dial until the 0* mark lines up with the line/mark on the harmonic balancer. If I leave the hose connected to the distributor and suck on the hose it idles up more (causing vacumm by sucking on the hose). Idling I get roughly 13 on the vacuum gauge, moves up to 14-14.5 sometimes). Almost seems like it's not pulling enough vacuum, if infact it is a big cam, I've heard they don't typically pull a lot of vacuum.

That makes sense on the carb being a air valve system, I do have a holley 750 double pumper on the bench, but I wasn't sure if that would be too much carb or not. According to what I've read about edelbrock, the idle circuit is entirely controlled by the 2 screws on the front of the carb and they do not change any fuel/air mixture above an idle.

 

I too am not a big fan of Edelbrock carbs for a performance orientated engine set up, I always use a Holley mechanical secondary carb on a hopped up motor. I also think you'd pick up a lot of power by replacing those 305 heads with a good set of aluminum heads; they are beyond a doubt the choke point on your build. I'd also be real careful of preignition with those iron 305 heads, depending on the combustion chamber size, you could be running over 11 to 1 compression and you would be really limited to how much timing you can safely run with pump gas; especially with cast pistons.

 

I've (since I got the motor) said that myself, the 305 heads are the choke point. I'd definitely like to look into getting some better heads, I just recently got the car driveable (exhaust, tires, etc.) So now I'm trying to get everything else lined out. I know the easiest way without guessing would be to tear down the motor and see what exactly I have going on, cam, crank, heads, pistons, etc.

My biggest thing at the moment is the low vacuum at idle, ensuring I have the timing in an acceptable range, and I'm not going to tear anything up. I've been running 91 octane pump gas with no ethanol since I've had it, plugs come out a light brown/tanish color.

 

Here's the problem:

4.060" bore, 3.75" stroke, .016" gasket (steel shim), .000" deck clearance, flat-tops w/ 6cc VRs, 58cc chambers: 12.8:1 compression

Same bore, same stroke, .051" (400) gasket, .045" deck clearance (far more likely), 12cc dish, 62cc chambers (305 heads properly unshrouded for 1.94" intake valves): 9.4:1 compression

Which one of those is YOUR engine more like? Iunno.

I'm guessing it's closer to the latter, that being more typical of the real world as we know it, but again, iunno. It's just a guess.

In either case, you're NOT running 38° of advance, no matter what "light" says. The 12.8:1 motor would be COMPLETELY unusable at ANY timing with ANY cam on pump gas; the 9.4:1 motor with that combo would probably not tolerate more than 32° without pinging and other misbehavior if the cam is one that would deliver 14" of idle vacuum, as appears to be the case.

In case you haven't figured out where I'm going with this, (a) I don't believe your timing "numbers" are right, no matter what "light" and "mark" say; and (b) details in the mechanical part of your build matter GREATLY to trying to predict what an appropriate tune would, or would not, look like.

I don't think you have what you think you have. You need to get more/better info on it. And you DESPERATELY need to find out what cam is in it. But, the classic trial-and-error tuning method ALWAYS works, even if it's not the fastest way to get there right at first. It's the ONLY way to dial it in right regardless. A WBO2 helps too but isn't "necessary"; people tuned cars just fine for a century or more before those became available.

The purpose of vac adv is to begin combustion earlier when the mixture is very lean and the density is low; IOW, high speed (cruising) at very low load. The purpose of advance at all, to begin with, is to synchronize the point of peak pressure in the cyl, which occurs just as combustion reaches completion, with the piston reaching or just passing TDC. This combination of events produces the maximum possible downward thrust on the piston as it moves down, with the least possible penalty of continuing its upward motion during combustion against high pressure, which causes less efficient operation, bearing wear, and the possibility of detonation instead of combustion. At a good cruise tuning of the carb, the mixture will be quite lean, and of course the vacuum will be high, meaning there will be very few molecules of air and fuel in there, relatively speaking, which will create very slow combustion, therefore the need to start it earlier. Vac adv usually wants to be at least 12° and as much as 15° for optimum operation (best gas mileage, lack of surging, crisp throttle response, low cooling system temps, and so forth), so if you only have 6°, it's FAR from optimum. Typical junkyard factory distributor crap, and will never really be "optimum" for YOUR build.

Regardless of any of that, the truism (borrowed from one of The Great Ones in a totally unrelated field and paraphrased) to always keep in front of you is:

"If it RUNS good, it IS good."

And conversely, if it runs BAD, it IS bad, no matter what the "numbers" on your "mark" say. And as well, if it runs BETTER when you make some particular change, then it IS better, no matter the "numbers". Results are the ultimate truth: nothing else matters.

 

I forgot to ask: What crank damper is on it? And where, physically, is the fixed side of the timing mark system (the tab) mounted?

If you have a stock damper for the mark setup where the tab is welded to the timing cover at 12:00 or so, as it would have been if this is a 86 motor; but you (or whoever) have put a cover on it that uses a tab that bolts on over at the 1:30 position, then those mismatched parts ALONE create about a 40° error in the "number" you'll read. IOW if it reads 40°, it's REALLY 0°. And that's assuming the damper's inertia ring hasn't slipped.

You REALLY REALLY REALLY REALLY REALLY REALLY REALLY need to find out what's inside your motor if you can. You can tune on it without knowing that, but it would REALLY help. If it was mine, I'd pop the heads off and MEASURE MEASURE MEASURE MEASURE MEASURE MEASURE MEASURE MEASURE. Nothing else works quite as well.

 

Unfortunately I believe the only way I will know what I have inside the motor is to pull it apart. My brothers dad built the engine about 10 years ago. I never had any paperwork, and I don't believe he did either. His dad worked at a local machine shop, and I'm assuming it was a "leftover parts build".

The timing tab is at 1:30 just off toward the drivers side, and the damper looks stock/a typical damper to me.

I have Access to a bore scope, but I don't think that will tell me anything of any use.... unless someone says differently and tells me what I am hunting for.

I assume the quickest and most accurate way is to pull the heads, intake and cam and see what I have.

14 on the vacuum gauge is as good as I can get it, idling anywhere between 750 and 800 and adjusting the mixture screws anywhere from 1 turn to 4 turns out. Best is at 1.5ish. As I said I can apply vacuum by sucking on the hose and the motor revs up, which makes sense more vacuum more advance. But with just the vacuum line attached it has minimal 2-3 degrees of advance with it connected.

idling at 750 rpms vacuum connected it shows 18-20*, if I rev it up I get around 36-38*.

 

This could be your camshaft: 113502
https://www.summitracing.com/parts/crn-113502

 

Are you sure the hose is not connected to ported vacuum rather than manifold vacuum? If you are using an edelbrock their instructions will tell you to hook it up to the "timed" vacuum fitting. Totally wrong for anything other than a stock smog engine. You want the advance hooked to manifold vacuum. Otherwise you will get a secondary advance curve with too much advance when you accelerate the engine and the timing will be too retarded at idle.

 

OK, so your timing "numbers" are most likely roughly 35 - 40° in error. When your "light" says 40, it's REALLY at 0. You can easily verify this with something in the cylinder to detect motion, like a tie-wrap or the like; and turning the crank by hand. Find TDC and create a somewhat accurate timing mark. That's one of the first things I'd do if I was working on trying to tune it.

Needless to say, having your advance set to 40° less than optimum, will make the engine have low idle vacuum, and cause LOTS of other undesirables to happen.

With a borescope you can maybe identify your pistons better, and maybe tell more about your heads. Just getting the casting # off the heads will tell you quite a bit. That's under the valve covers, between the rockers.

 

Well I pulled the valve cover and ran a bore scope in the cylinders. Here is the link to pictures
https://m.imgur.com/a/x2fMdA6


Springs appear to be shimmed to me, appear to be stock springs push rods and rocker arms.
Head casting number is: 14022601 which appear to be a 305 head. Valves dont look oversized to me.

Timing mark pictures include, when piston #1 is tdc mark lines up on the balancer and timing tab.

Pistons say H580 on the top, google says it's a speed pro dish piston. Cannot see a bore size camera isnt that good.

No idea on the cam unless someone can tell me a magical way to check it without a tear down.

 

https://www.summitracing.com/parts/slp-h580cp60

Doesn't matter all that much what the overbore is, it's done to clean up wear, not because it makes any material difference to "performance" or anything.

Compression height for that piston is 1.54". Stock SBC compression height is 1.56". That means they're an extra .020" lower in the bore than "stock". Since the stock deck height of a small block is 9.025" -.000" +.015" or so, that means your deck clearance - the distance between the top of the piston and the deck surface - is .045" - .060", assuming the block hasn't been decked. No way to know that of course. Let's just stick with the .045" number for Ss & Gs. Dish volume is 1.25 cu in which is about 20 cc. We don't know what the gasket thickness is either; let's just guess and put in a stock replacement 350 gasket like a Fel-Pro 7733 which is .039".

601 is indeed a 305 head; 1.84" intakes, 1.5" exhausts, originally. 58cc nominal chambers but that casting tends to be a bit smaller. Maybe 56 or so.

Your compression is 9.5 or a little less; let's say, given the variation possible in the deck height, it's somewhere between 9.3 and 9.5. That's probably close enough for the purpose at hand.

If NoEmissions' guess at the cam is right, which seems reasonable, then it should idle REAL smooth, like stock, and should give 18" or so of vacuum at 650 RPM idle.

I'd suggest trying advancing the timing, until it starts to ping going up a gentle hill in high gear at the slowest speed you would realistically normally try to drive up such a hill in high gear; then back it off until it quits. That probably won't be "right", in the sense that you'd want to leave it there, although you might. But it should give you a fair idea of what the motor can tolerate. See what the idle vacuum is with the idle speed and timing set like that.

Also, try Fast's advice, of hooking up the vac adv to a full-time manifold vacuum port. More often than not, engines run better that way. Only way to know for sure is to try it. It'll speed up the idle for sure, and raise the vacuum; the down side is, it may ping like all Hell at an off-idle throttle tip-in from a stop.

Is this car auto, or stick? What gears are in it?

 

I'm assuming it's a stock rear on an 82 z28, I cant find any markings on the rear to indicate any of that though. It is an automatic, th350 transmission, the edelbrock carb has 3 vacuum ports on the front. One large one in the middle I have capped off, the two smaller ones (one on driver and one on passenger side of the carb) I have tried both of those ports neither seemed to make any difference. The one I am not using I have capped off so no vacuum leaks. I will try going directly to the vacuum tree on the back of the intake if that may help.

Here is a video of it idling after getting exhaust. It's a hedman y pipe that ends under the passenger side and theres a flowmaster 10, then about 8" long piece of pipe and turned out toward the side.