Okay here is the baseline...

Chevy 350 Roller Block
Double Hump Heads Shaved
Holley Street Dominator Intake
Compression Ratio around 10.5:1
I run 93 Octane at every fill up

When I'm really getting on it or when I'm running 90+ and give it gas you can hear ting ting ting ting ting it's not in a rhythm it's erratic and bothers me, I've filled up with E-85 completely to see if it would fix the issue and it's still there so from 93 Octane to 110 Octane and the issue didn't change at all. I am starting to think it's not a detonation issue and possibly the timing chain, or possibly the rocker arms are being forced up in such a fast manner they ting on the way down?

I'll try to get a audio sample next time I go out but I'm just trying to get some info where to look because it gets annoying plus I don't want to tear up my engine.

I have tried adjusting timing too it seems to help a little but it takes a lot of power out of it, which makes me think it don't do it as much because the RPM's are not hitting as hard so I don't know...

 

Detonation. Not surprising with those old heads.
No, you wouldn't be hearing the timing chain or rockers as you describe it. Those noises would be more evident at idle.

 

So, I have to dumb down the timing that much till I can get some better heads?
Or could I need bigger jets to add more fuel for higher rpms?

Just need suggestions because last time I retarded the timing it only helped a little.

 

10.5:1 with iron heads? Old heads at that? I'm with LG4Bird on that one. Probably detonation.
Do you have any cam specs? Duration numbers specifically.
I ask that question in a self serving way. I've accidentally (long story about a short block) built a 10.4:1 iron headed small block and have had to crush it's performance by pulling a ton of timing out of it. This off season I've pulled the heads and had some combustion chamber work done to gain a couple of cc's. That, combined with a slightly thicker head gasket will get me to a more manageable 10:1 and when combined with the short cam I'm using should get me to where I had intended to be in the first place.

I've re-tuned my carb in an attempt to supply more fuel (in all circuits) hoping that it would help but there was too much compression to work with to be successful. I ran a mix of premium and unleaded race fuel for a 100 octane total with only marginal improvements.
For what it's worth, changes in timing have a far greater impact on engine performance and efficiency than does the compression ratio. I've learned that it's much better to be conservative with compression and have the timing optimized than the other way around. |There are more than a few technical papers floating around that support this.

 

I don't have the Cam specs, I pulled it a while back and couldn't get the #'s matching which I need to invest in a cam that I know the specs on, but other then that I'm going to attempt to add more fuel with bigger jets and run E-85 with the bigger jets to see if that will solve the issue, I really hate to lose that much power by retarding the timing, there is a big difference in power with it advanced. It don't detonate unless I'm WOT in 3-5th, taking off it's pretty good for what it is but with it retarded it's not got that in the pants feeling.

Any other tips to try before retarding timing to attempt to fix this? I know I probably should get better heads but I'm trying to make due with what I have and the money which is next to $0, I get lucky if I get my bills paid right now, just don't want to see a engine fall apart after all the work put into making it work.

Will attempt bigger Jets "next check" and E-85 next fill up.
Will retard the timing a little just to see if the jets and e-85 with retarding help at all... Maybe cooler plugs? I'm running the R45's right now gapped at .045 I believe.

 

E-85 requires a completely different carb metering plate than gas does, FYI. Just hate to see anything happen to your engine.

 

I've been reading about mixing E-85 & 93, but also about water injection... I've read this basically is almost a cure for this type of issue.

Basically a water pump, water and away to control how much at a pressure so it's a mist at 5% of water 95% fuel makes the ping go away. Is that really the best way to tackle this?

 

Pull the plugs.You need a spark plug inspection tool.Really can't see what you need to with your naked eye.Those tools I think are sold at HF with a light and magnification of X10.Look at the porcelain part of the plug.You'll see specks on it.And for God's sake,don't keep pinging this engine.Each time gets you closer and closer to serious damages.

Water injection??. Would you dilute your gas normally with water??. Of course not. That would serious hurt performance. As much as timing adjustments. These things are a band-aids to a much larger issue that needs to be fixed.

I can't understand a machine shop that would in good faith would cut you heads that much to create this.Need more info to properly advise you.

 

The heads came off another engine which ended up being warped so they shaved them till they would seal properly, unfortunately I have to make due with what I have.

I could double stack head gaskets to help lower compression, I dialed the timing back a good bit and will see what it does in the morning but I don't get on it when it ping's, if it pings I let off and ride but lower gears it don't ping but when in higher gears it'll ping when giving it a little extra gas like in O.D. going from 70 - 80 if I hit it decently to get there in a comfortable manner it'll ping, ping, ping, ping and it's like all of them are pinging because it's not rhythmic at all.

Not to sound rude but why not water injection, everything I read stated it helps a lot with detonation, by cooling the combustion chamber. You are subbing 5% water with 95% gas and allows you to get more timing, and stop pinging and get better gains with the extra timing etc.

Things to try that I've read.
1.) Lower Thermostat
2.) Water Injection
3.) Double Stack Head Gaskets
4.) Retard Timing - (Did this haven't went down the road yet)
5.) Mixing Lead / Octane Booster with gas
6.) Cooler Plugs
7.) More Fuel
8.) *Buy New Heads* which would be idea, and would trade camel hump heads for a set of decent heads.

Any suggestions on any of those besides new heads because if I could buy new ones I would of done it already. I may try to list for sale / trade but want to make it run right.

 

somebody was talking to me about the water/methanol injection the other day, for about the same reasons. i have no experience with it, but it sounds like it makes sense.

http://www.snowperformance.net/faqs_...?type=gasoline

http://www.snowperformance.net/stage...e-car-n-a.html

 

That is a good read, everything I read on water/methanol injection is all positive, it grants you more compression without ping, and allows more timing without ping. I think when I get paid I need to pick-up a cheap or used kit or get a nice 50+PSI pump and get the nozzles and see how it goes. Those kits are really nice though.

 

Well call me dumb, adjusting timing helped top end little to no ping but bottom end was slow and awful... Then did a little research about my distributor and how to change the curve to make it work in my favour. I have the MSD type that is mechanical and vacuum and I had both hooked up. I disconnected the vacuum and plugged the port on the carburetor for vacuum timing and it fixed the curve for me. WOT 1-3rd no pinging and pulls harder then it did before. I haven't got in O.D. for my trip was up to Wal-Mart and couldn't get past 60 mph due to traffic.

Anyway I am a lot happier knowing it's not doing it or that much closer to being fixed. I know I can purchase springs to help the curve even more if needed I believe it's stronger springs and lighter weights to retard the advance on top end.

 

What have you got a timing curve now?
There should no reason why you can't run your vacuum advance provided the spec is right.
Here's a paper that may give some insight into what you can do.

http://classicinlines.com/spark.asp

As for initial/idle timing, what have you got it at?
You've probably been to the MSD site. Lots of good info there too.

 

Okay, did a bunch of research and a few things I need to do is buy a tune up kit for my distributor which allows me to restrict the total timing and change out springs.

Would be nice to have a good timing light but I have the cheapo...

Also I have been using the ported vacuum advance from the carburetor which is no vacuum at idle and increases as you go to WOT, and I read I should be using a non-ported vacuum where at WOT there should be no vacuum is this correct?

 

You want to run more initial and less total. Methanol injection is easy. A windshield washer bottle and pump will do the job , get one from a boneyard car. Run the output hose to unported vac on the carb. You will have to rig a switch. A momentary rigged to the carb which comes on at full open would be best. Fill the bottle with drug store rubbing alcohol, read the label and get 50% methanol.

 

Manifold vacuum connected to the vacuum advance can will provide advance whenever there is manifold vacuum present. That is pretty much all throttle positions excluding WOT. With the carb butterflies fully open there is little to no vacuum being built. Consequently, there is no advance. This is as it should be.
Ported vacuum connected to the vacuum advance can will provide advance from the just off idle position and behave like full manifold vacuum advance from that point on. Again, at WOT, there is no vacuum being produced and thusly no vacuum advance.
If you didn't read the paper I provided a link to, you may find it very informative.

http://classicinlines.com/spark.asp

JaBot has written a thread about ignition tuning which may give you an insight into how it can all come together.

https://www.thirdgen.org/forums/tech...ning-info.html

Unless you have all the parts needed, in both hardware and tools, then full manifold vacuum for the advance is best left alone. Stick to ported vacuum as it will give the least tuning headaches. Using full manifold vacuum for the advance can will initiate the advance at idle. This becomes very difficult to dial in if you don't have a fully adjustable vacuum can. This applies to both the set-point (the inches of vacuum needed to start the advance) as well as total amount. Since ported source does not provide vacuum at idle, it's a non-issue when setting the idle advance.
You say you have a MSD distributor? Then you're more than halfway way regarding the hardware. Use the info you've read regarding the mechanical advance and work with that. Total amount provided by the bushing in the advance mechanism and the springs used will determine that shape of your advance curve. Combine that with your initial advance setting to determine the total. As was pointed out earlier, SBCs like lots of advance at idle. It's conventional thinking to limit the amount supplied mechanically via the bushing in the distributor and set the initial to achieve your total supplied at your target RPM.
I used this kit in my MSD distributor to tailor my advance curve.

http://www.summitracing.com/int/part...8464/overview/

The kit has reasonable instructions and I've checked the results using several methods. They appear to be accurate.
As far as vacuum advance goes, as I mentioned, ported vacuum will provide the least tuning headaches as full manifold vacuum advance can be difficult to dial in at idle. I believe the MSD comes with a non-adjustable advance can so you're stuck with what is supplied until you step up to an adjustable unit. This will let you fine tune the timing. The pinging you experienced at WOT previous to disconnecting the vacuum source had nothing to do with vacuum advance as it's non-functional at WOT. At positions approaching WOT, then it has an impact. You'll want to incorporate vacuum advance into your curve as it assists greatly with part throttle response and fuel economy.

 

get some timing tape.
yep, full manifold vacuum is usually best.
IMO, total timing is way more important then initial.
heres a good video about timing. might help?

 

Problem with that is without all the needed info regarding the specs of the vacuum advance can, you can create more headaches than you solve.
If the idle vacuum and the can specs don't match then it's possible to have a situation where the vacuum advance works wonderfully at idle in park or neutral but when placed in gear or the clutch engaged, the lower rpms and the decline in vacuum start a sort of spiral effect where the vacuum reduction pulls out timing, rpm and vacuum drop further, timing is reduced even more and eventually the engine will barely idle or stall altoghether. It's a careful match betweem idle vacuum values (in inches) and the specs of the vacuum unit that make or break an installation here.
These are my experiences over several decades of messing with this stuff. A lot of people give up and call full manifold vacuum useless and just opt for the ported vacuum source. Every engine is unique.

 

full manifold vacuum vs. ported has been debated forever. it only takes a few minutes to try either and make a decision. manifold vacuum will usually make an engine run cooler, which can aid against detonation problems.

 

heres a good read about ported vs. manifold vacuum.

http://www.corvetteactioncenter.com/...m-advance.html

 

I agree with you 100% on that one.
Once I dialed in my vacuum unit, I found a cooler running engine at idle as well as an increase in the idle vacuum produced in the order of one to two inches.
There was a sorting out process though. As an example, my engine produces about 10 1/2" of idle vacuum at 750 rpm in park, 12 degress initial advance and no vacuum advance connected. I've set my vacuum can to provide full vacuum advance about 2" below that level. Connected to full manifold vacuum it draws in about 20 additional degress of advance for a total of 32 degrees. With the increased timing, idle vacuum moved to 12".
What happened previously when the vacuum unit wasn't properly adjusted was the spiral effect I posted earler. The can set point was too close to the idle vacuum amount (both at 10") and while it would work well in park, once it was placed in gear and the rpms reduced, the whole thing sort of unraveled.
Previously the engine temps would creep up during extended idling however with the vacuum connected, the temps are down about 20 degrees or so. This is a bonus when you're stuck in traffic on a hot summer day.

 

Excellent paper which I've read many times. That and the link I posted earlier from Classic Inline Spark Strageties are both essential reading material if you want an understanding of what's going on and what to do about it.

 

Like to read? Here's another well written article on the whole timing deal.

http://www.contactmagazine.com/Issue...ineBasics.html

 

very good information in there.

 

Knowledge is king. (So is cash but we're talking tech here)

 

Well it seems I was timing the engine to run good at idle / low rpm throttle response vs total timing which if I did total made low and throttle response sluggish and awful.

Moving to manifold vacuum allowed more timing earlier so taking initial and total timing down so no pinging happens the manifold vacuum allowed more timing at idle and fixed response.

Only issue I'm having with it is every now and then it'll get in this stutter mode which I'm not sure if it's a timing issue or something to do with my Holley Carb I've tore it down and cleaned it so many times and I think it helps for a few days but it comes back but the carb isn't dirty fuel looks fine and I haven't figured out what is causing it.

Here is a little video that kind of shows the stutter.

If I got from not touching the peddle to WOT it takes off great, no stutter no issues. If I go from not touching the peddle to hitting the peddle half way it'll stutter like the video, still has decent power but not smooth! If I ease onto the peddle and go up it's a smooth transition like it should be.

I understand the I need to order the kit which may help a lot fine tuning, and possibly an adjustable canister which would help fine tune how much advance the vacuum is pulling.

 

Difficult to tell what's going from the video however since you've been working on the timing and making changes, what's your current timing curve at now?
1) Initial/idle timing with the vacuum advance disconnected.
2) What rpm does the mechanical advance start to come in.
3) What is the total mechanical advance and at what rpm is it all in by.
4) Any vacuum advance specs to might have.
2 and 3 above are easily observed using a timing light (either a dial back type or a conventional timing light used with a degreed balancer) and a tach.
Number 4 will require a vacuum gauge at the very least. To perform this test I tied my advance weights in the distributor in the closed position (using a couple of small zip ties) and then used a hand held vacuum pump connected to the advance can and observed the readings via the timing light as I applied vacuum to the can. Sounds complicated but it works very well.

 

if you dont have a dial back, timing tape, or a degreed balancer,...and your using a 6 3/4" balancer, you can make a mark at 2 inches from TDC. rev the motor to 4,000rpm, vacuum advance disconnected, and set the total timing to the 2" mark. that should get ya in the ballpark for now.

the things Skinny are asking for will really help you get it fine tuned good.

i also found it difficult to tell whats going on in the video.

 

Okay, hesitation was due to me lowering initial timing and it didn't like it at all, I bumped it back up and it drives fine, slight pinging again. I'm going to have to get the MSD Advance Stop Bushing kit and go to the black bushing instead of the factory blue which will drop the advance from 21 to 18 so 3' difference. I hope the 3' will stop it soon enough.

 

It is not beyond the possibility on a old H/B the ring has slipped and the timing marks are wrong.