Okay folks, I continue to learn about all these relationships and now I'm questioning my build. Per the numbers, my 030 over 455 (461) should have a static CR of 9.7, depending on how accurate my combustion chamber measuring was (max 83cc). But I've been unable to tune out detonation. Even with 20* initial, 10* mechanical (limited), and 10* in the vac can (adjustable), and one light spring and one medium on the dizzy weights (so no part throttle pinging), it still pings at WOT. With 30* total initial and mechanical? I try to stick with Shell 93 whenever possible but I've used other 93 as well.
So yesterday I did a compression test on the motor (better late than never), and I get a range of 195 to 205. Now, I've been reading (and hearing from friends) that 200 is really max for a street engine. That's when I started looking at my cam. If I understand correctly, more overlap (a tighter angle) means more cylinder pressure. That seemed backward to me until I read that more overlap means more air pulled into the cylinder and, therefor, more air to compress. My cam's power range is 2400 - 6000 which, again, according to the internet, is a little much for a street motor.
Here are the cam specs (please ignore the blue numbers). I dialed it in at 5.5* advanced even though the cam card said 7.5*, but Mark felt that was a little much and I agreed.





So, with the valve contact pattern issues I've been having and now this, I'm thinking of pulling the motor this winter, if I can raise some more build money. I'd love to go with a roller cam but realistically, that's not going to happen. Any recommendations on cam specs for my car?

455 / Supreme coup
030 over
15cc dish Wiseco pistons (according to the machinist, 012 in the hole)
82-83cc chambers
CompCams roller tip rockers & polylocks
Stock stroke and rods
Stock "N" crank, running .003 clearances (actually, more like .0028")
Ported and polished J-heads with small valves
Running PCV system
Full length Hedman headers
200-r4 trans w/ 2500 stall
3.73 rear gears
Street Demon 750 carb (rated closer to 800, I've heard). Vac gauge easily drops to zero at WOT. Bigger squirter, larger than stock jets, smaller rods.

I'd like to lower the cranking compression just a bit and improve the street manners / idle. I've never been able to get it to idle good enough to put the AC system on.
Mark, feel free to chime-in but I can't promise I'll raise enough money this winter.

 

 

I see you increased jet size but do you know what your wot air/fuel actually is?
Ultimately I’d put a larger cam in it and/or retard it AFTER you verify the wot air/fuel.
For the record I’ve done dozens of builds that had upwards of 200# of cranking pressure. ALL ran fine at 33-34* and on 91 or better fuel. Tuning is key.

 

Ahh yes, head gasket thickness might be important, Sorry about that. 0.038" Felpros.

I don't yet have an AF gauge. CopperCutlass has been bugging me to get one. Mark, are you thinking it's possibly too lean even with the larger jets? And as far as at what RPM its starts detonating; I'm not usually looking at the tach when I've got it hammered so I'll find an assistant (the wife isn't going to be happy about riding along, lol), but I would say it starts around 3500 to 4000 but I'll check.

As for tuning; I started with an MSD spring and weight kit and went from there. I verified that TDC corresponds with the balancer mark and made a timing tape from MDchanic's PDF file. I made bright white marks at 32 and 36 degrees. I've tried many different combinations, moving more and more timing to initial and different combinations of springs. It seems to like a lot of initial for the idle. I can, of course, get rid of the ping but only at the cost of power. I had bad pinging at part throttle until I installed the adjustable vac can.

So the drift I'm getting is that my problems are likely not the cam, but my tune. I should also mention that it's not excessive internal heat. The four row radiator keeps it at a constant 170 degrees. 180 on an extremely hot day or sitting in traffic. Could it be, though, that I'm sucking in under-hood air that is too hot from the headers that aren't coated or wrapped in any way? I had pretty bad problems with fuel boiling with the quadrajet. The phenolic fuel bowl of the Street Demon made a big difference there. And if it makes much difference, I'm running R45S AC Delco plugs. Maybe a cooler plug would help?

I'll admit, my tuning has been a little hap-hazzard. I need to have a specific order of operations. I also discovered/realized that I've been running high resistance plug wires that I made in the early days of this build (the small block), before I knew better. So I ordered 350 ohm per foot wires and a dizzy tune-up kit with matched coil and module. I'll get all that installed and begin again, but with a better plan.

Lastly, I still need to install/test the GN governor I got for the trans. I feel it's shifting too soon. Pressures are good but my weights are really heavy. Part of this could be that I'm not getting into the power band of the motor at part throttle. That wouldn't cause pinging but could explain the lack of power at lower total advance.

Thanks for the input, fellas.

 

Yes get a wide band o2 sensor. Start there.

 

Mac, These are very good points to consider.

 

I had pinging with 9.6 to 1 and 175-180 psi cranking compression on Shell 91. Tuning the carb and very cold spark plugs helped. As said, tune is key and can make a huge difference. I would seriously consider Procomp heads with their more efficient chamber design since you plan on replacing the heads anyways.

 

I'll get the ignition items installed and pick up a wideband and start there.

Are we talking about retarding the cam using a different key on the gear? I hadn't thought about that. What effect would that have on power? The cam card says it should be 7.5* btdc and it's already at 5.5*. Would it smooth out the idle a bit, maybe?

I've been using the Summit compression calculator and, at the time, it was matching what my machinist was telling me. Even if I miscalculated the chambers and they are 82cc instead of 83, it still only comes to 9.73. It's the .012 in the hole I'm not sure of, truth be known. I tried measuring it and I came up with more like .006". I figured it was just me not knowing how to do it. .006 and 82cc comes to 9.84 CR. Still under 10.




I'll admit something here, so give me whatever crap is necessary. I don't have a tach under the hood. I check timing all-in by ear. But honestly, I don't know how one would watch a tach and the balancer at the same time. I'll also double check my timing tape but I know lots of people on CO use that file and there are good instructions on how to print it. But then again, we're talking about home computer tech here. Nothing ever goes wrong with that! But nobody sells an Olds timing tape that I could find. I suppose I could use the timing tab to double check my marks. I have a dial-back timing light but it's kind of a POS, it dances all over the place. I originally thought it was something amiss in the dizzy until I tried my old, regular light and the marks were rock-steady.

I know that cam advance and timing advance are different and honestly, I don't understand cam advance as well as I should, but does advancing the cam limit how much timing can be advanced?

307, I've thought about running cooler plugs but don't you worry about them fouling? I'd love to run 91, 93 is a full buck higher than 87.

 

Okay, I've been reading up. It appears that my cam has 4* advance ground into it (and isn't related to spark advance at all). And that advancing the cam lowers the power band, while retarding it moves the band up. So when I set it at 5.5* btdc, I moved the power band up just a bit. I may try putting it at the recommended 7.5* and see what happens. The rated power band doesn't start until 2400 as is. Am I understanding this correctly?

 

No. When you see an rpm range given it’s for the entire engine family. So that cam’s rpm range will start higher in a 307 than a 455.
You’re running 87?

 

To reduced cranking compress retard the cam 2 to 4 degrees, then before putting the balancer, or timing cover and water pump back on do a cranking compression test to verify its cranking compression has dropped the amount you want.

But this may all come down to fuel ratios or the type of plugs you are running. Check your idle vacuum and make sure with the cover over the metering rods are open enough, to see the pistons they ride on with it running. They need to be down at idle in gear if an automatic. Now blip the throttle in gear and see it they instantly jump up and hit their tops, to enrich it. If not, then stiffer springs are needed under the power piston hold the metering rods. Some use ball point pen springs inside the regular springs, to get the desired results. Stretching the ball point pen springs a little at a time, to get the desired amount in testing.

Another thing a lot of people set the mixture screws at idle, to the highest vacuum or rpms. Turning those screws back out from that point richenning the idle up and and part throttle sligtly is usually a good idea for good driveability.

I would try one range colder for now and see what happens. A little pinging is not that unusual under light loads/throttle to me around town, on a hot day. Low cranking pressures are more of potential problem usually, than higher pressures, For example very old farm tractors use to hit 300 or more.

 

I know the spread between 87 and 91 used to be 10 cents a liter or 40 cents on a US gallon, now a 60 cent spread. What plugs are you running? I went from very hot NGK XR45 or a 4 range to a 5670-8, or ranges 4 colder.

 

The cam has 4* of advance built in and you are adding more advance. Why?

 

Trip, I doubt that's the case.

Macadoo, It sounds like you degreed the cam when you installed it. What was the final intake centerline? Hopefully it was in the neighborhood of 106.
That cam is, IMO, mild to moderate for a street 455. As said, it's all in the tune.

 

It's true. The cam is ground with 4* advance as it sits. If you put it in the engine 'straight up' it will be 4* advanced. I see talk of putting it 5.5-7.5* btdc. That's more advance.

 

Actually the term “straight up” means it’s installed at the same as the lobe sep. So if the cam is ground on a 110lsa then straight up would mean it’s installed on a 110icl, regardless of what’s “ground into” the cam.
Hope this helps.

 

Mac, invest in one of these . You can adjust the advance, see the rpm and voltage. Makes adjusting timing much easier.

 

You could also just buy a 3-3/8 chrome tach for about $40 or less probably at the parts store, and put a few alligator clips on the few leads needed to get the tach signal reading. Then lay the tack on the front of the intake, for viewing while doing a total timing check..Its not one of the timing checks done more than once.

 

I have one of those, works great. I bought it on Amazon for about $80.00

 

Only change one thing at a time and start with the cheap easy stuff. I would put the coldest plugs you can find in the engine first. Its a fresh engine and blowby
and oil use aren't problems right now. Next retard the cam 4 degrees. You should find out you max spark advance. If its more than 34 or 35 degrees at WOT, 5000 rpm it should be brought down.

 

Wow, a lot happened while I was at work. Awesome!

Huh, I wouldn't have thought of this. Seems easy enough. I'm pulling a solid 14 inches of vac at 750rpm idle. The Street Demon instructions say that anything under 10 inches needs a change of springs and I just assumed that would be true. Probably is true but it's worth checking. Thanks dude.

I'm using AC Delco R45S IIRC. I'm thinking of going NGKs but haven't had the time to look at the cross charts.

Hey Trip, how's it going? I don't know everything there is to know about this but the cam card said the intake should be open 0.050 at 7.5* btdc. Straight up was way off (don't recall how much, but a lot), so I used the key that gave me the 0.050 at 7.5* btdc but Mark thought it was a bit much (and he know a jillion times more than me about this) so I backed it off to 5.5* btc. But I'm wondering if I should take it back to 7.5* btdc so I can back off the initial spark advance a little and keep the grunt off the line. Only because Howards says it should be 7.5*.

Unfortunately oddball, I didn't understand the centerline and so didn't check. I just made sure the intake was opening when it should.

Woof, pricey. But well worth the $$ I'll bet. Thanks for the link.

I was thinking the same thing. Or I could have the wife sit in the car and take up the rpms in steps; 2k, 2.5k, 3k, 3.5k, etc. She'll love that

Nah, not more than 34 right now and that's the highest I've had it; except for a brief run down the road at 35. Sounded like rocks in a blender.

 

The Street Demons instructions are not actually reliable IMHO
For example the hole they say is for the TV cable is not in the 1.110 to 1.25 inches away, from the pivot point it needs to be, but they do have a hole that is. Just as example.

They only have/sell springs up to 9 or 10 pounds, so they won't mention maybe needing more or especially ball point springs stretched to fit and used. On the AFB, AVS and Thermoquads a bog lean condition can happen, if the primaries are not coming in fast enough. You should have the green spring at 6 pounds the way it came from Holley.

 

Oh boy, I think I just figured something out; d'oh! Moving from 7.5* btdc to 5.5* btdc actually advanced the events.......right?

Even the center hole isn't quite right; it's a little too far from the pivot point, making for a longer pull on the cable. I've been meaning to make on offset stud to bring it in a little so I can get rid of my cheater spring.

Yup, the green springs are in but I bought the tune kit so I have other options. I might even have a ballpoint pen or two around here somewhere, lol.

 

I was wrong, I did check the centerline. It was 106.25.

 

The first hole is 1.10 (1.10 to 1.250) The middle suggested is not even close.

 

No, you backed it up 2*. And I didn’t see that you answered the question regarding whether or not you’re trying to use 87 instead of 91?

 

87 and I wouldn't have an engine left. I stick with Shell 93 as much as I can but there are other 93 options available.

 

Gotcha, you mentioned how expensive 93 was and I didn’t know where you were going with that.
Save your pennies and buy a wideband then go from there. Don’t waste anymore time on it till then.

 

On correct TV travel and which Demon hole works and why

https://www.1952chevytruck.com/stree...dent_cable.htm

 

Understood. Got any recommendations? I haven't looked into them yet.

I wish I woulda' read this when I had the pan off a month or so ago. I was looking for measurements for the piston but couldn't find them. Are all 200-4r pistons created equal? Anyway, thanks for the link!

 

I can see the advantage of a dual-sensor wideband but if I get one side tuned, wouldn't the other side be the same?

 

2 O2 bung holes, for a choice of which side you want to check out, but for now one side should be enough. A second bung hole on the other side could be done later.

 

Agreed and if it’s a dual plane intake there’s really nothing he can do if it has an imbalance anyway.
Sooo I’d just worry about getting a good O2. The AEM is the fastest and most accurate but there are others that are adequate. Just don't get an Innovate, they’re junk and I can prove it.

 

Funny you said AEM. I was just looking at this unit. And yeah, I have a dual plane which is why I asked what difference it would make.

 

What about this one? I assume by reading Mac's choice has more options?

 

That’s the older model with different face plates. Use the 30-0300, it’s fast, accurate, and reasonably priced.
I really like the AEM stuff, that’s why I’m a dealer for them.

 

I have the older model bought a number of years back and real cheap on price off Ebay.

 

I was actually curious about the range. The older model bottoms out at 11. Any reason to I'd need any lower? I obviously don't know what an ideal AF would be.
Mark, any issues with the 30-0300 being a bit shallower in depth of the housing (although I don't even know where I'd put it yet).

 

I put mine on the steering column with large zip ties, since I use it temporarily for a little fine tuning and then put it up for another day, and pull the sensor and stick an old narrow band sensor, in the exhaust hole to fill it.

Most performance engine like about 14 at idle, and 14 or leaner for steady statecruising above 40..WOT is usually between 13 and 12.5 or so.

 

Remember stoich is no longer 14.64 when using today’s E10. It’s now 14.1 so don’t expect to be able to get much above that at cruise, especially if you have any cam at all in it.
And at WOT I’ve seen the best power numbers in the 12.2-12.4 range.
Hope this helps!