engine woes
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I like your style my friend, stick around here.
Last edited by 80 Rocket; Mar 13, 2015 at 12:29 AM.
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From: Fuquay Varina NC
I woke @ 3:00 this morning with the 2 points being made in this thread going around in my head.
Timing problem is mute because of the compression issue.
Get the engine dialed in before you address the compression issue.
I came to the conclusion that it is a "chicken or the egg thing"
He can address the compression and install new heads. That will do nothing to reveal what is causing the unsteady timing. How frustrating will it be when he takes it for the first test drive he hears the pinging because he didn't address the timing issue. Both need to be taken care of.
Timing problem is mute because of the compression issue.
Get the engine dialed in before you address the compression issue.
I came to the conclusion that it is a "chicken or the egg thing"
He can address the compression and install new heads. That will do nothing to reveal what is causing the unsteady timing. How frustrating will it be when he takes it for the first test drive he hears the pinging because he didn't address the timing issue. Both need to be taken care of.
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From: Poteau, Ok
I'm wondering what the total timing is set to, both with vacuum advance and without. Is it pinging under both light throttle and wot? I understand about the compression, but the voices are leaning towards a cam timing or distributor issue.
Does the engine run smooth or does it shake at idle? When you raise the idle manually is it smooth or does it chug up. What I'm getting at is it possible the cam was not setup correctly?
Does the engine run smooth or does it shake at idle? When you raise the idle manually is it smooth or does it chug up. What I'm getting at is it possible the cam was not setup correctly?
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Joined: May 2012
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From: laingsburg mi
easy compression check,find someone with one of these..
http://store.katechengines.com/whist...ster-p174.aspx
any race tracks near where you are?
http://store.katechengines.com/whist...ster-p174.aspx
any race tracks near where you are?
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Joined: Mar 2015
Posts: 66
From: Washington AC
easy compression check,find someone with one of these..
http://store.katechengines.com/whist...ster-p174.aspx
any race tracks near where you are?
http://store.katechengines.com/whist...ster-p174.aspx
any race tracks near where you are?
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Joined: Nov 2008
Posts: 8,477
From: Central Fl
I have stood right in front of, on the side of, in the same room as an Olds that had too much timing in it, yet it didn't "ping" once, not once. How do I know? Simple, when you lose significant hp on one pull vs another, with the only change being the timing, then regaining that lost power retarding the timing back to square one, then you know.
I've said this before, detonation is called the silent killer. There's a reason for that, cuz it's true.
Verify your cranking compression at operating temp, not cold, and go from there.
Thank you.
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From: Fuquay Varina NC
[QUOTE=cutlassefi;
Verify your cranking compression at operating temp, not cold, and go from there.
Thank you.[/QUOTE]
What would you expect the maximum cranking compression range to be in an engine without detonation?
Verify your cranking compression at operating temp, not cold, and go from there.
Thank you.[/QUOTE]
What would you expect the maximum cranking compression range to be in an engine without detonation?
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From: Washington AC
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With iron heads and pump gas, somewhere around 180.....and that is with the engine up to temp. I believe I read in one of David Vizards books that he says 200-220. I don't know how he does that.
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http://www.eastwood.com/gas-comp-tester.html?fee=7&fep=48094?fee=5&fep=4990&SRCCODE =1SE1528&creative=5461472965&device=c&matchtype={M atchType}
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From: Washington AC
165-220 rings being seated in is a variable though. can lower the pressure somewhat.
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From: Washington AC
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From: Poteau, Ok
Ok here's where the misnomers come in.
I have stood right in front of, on the side of, in the same room as an Olds that had too much timing in it, yet it didn't "ping" once, not once. How do I know? Simple, when you lose significant hp on one pull vs another, with the only change being the timing, then regaining that lost power retarding the timing back to square one, then you know.
I've said this before, detonation is called the silent killer. There's a reason for that, cuz it's true.
Verify your cranking compression at operating temp, not cold, and go from there.
Thank you.
I have stood right in front of, on the side of, in the same room as an Olds that had too much timing in it, yet it didn't "ping" once, not once. How do I know? Simple, when you lose significant hp on one pull vs another, with the only change being the timing, then regaining that lost power retarding the timing back to square one, then you know.
I've said this before, detonation is called the silent killer. There's a reason for that, cuz it's true.
Verify your cranking compression at operating temp, not cold, and go from there.
Thank you.
I cannot run my car for fear of blowing the motor. Pinging/detonation is scaring me. Engine is a 1971 olds 350, .30 over. Block zero decked. #7 iron Heads milled and polished. Flat top pistons. 10.1:1 compression ratio(calculated). I have felpro head gaskets. Cam is a Comp XE268H. Plugs are AC Delco 45s. Stock Distributor with Pertronix installed under the cap - stock springs/weights. I tried re-curving but was not happy with the results. Stock coil. Timing is dialed down to 8 initial. 1000 miles since built. Pings so bad I can't drive it. Even on 93 octane it sounds like an army shaking spray paint cans. Suggestions?
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From: Central, IL
I applaud your debate skills. You are a gentleman and scholar.
Again, who cc'd the heads? What heads were on it before the Machinist decked the block?
He should check his work. He should not waste a set of head gaskets et al until he has. That's where I am coming from. You can't establish the true problem until you have eliminated all other possibilities. I wouldn't tear into that fresh engine until I could confidently say I did everything right. JMHO
Again, who cc'd the heads? What heads were on it before the Machinist decked the block?
He should check his work. He should not waste a set of head gaskets et al until he has. That's where I am coming from. You can't establish the true problem until you have eliminated all other possibilities. I wouldn't tear into that fresh engine until I could confidently say I did everything right. JMHO
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From: Central, IL
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From: Central, IL
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Here is another option that may allow you to keep the heads you have. Cometic offers multi layer steel head gasket that are .060" thick. They are pricey (around $200 for the pair) but they are reusable. I have had the heads off my dragster motor about 3 times now with the same gaskets.
Step number 2 would be to polish your combustion chambers in the heads. This will net you an additional 2-3ccs, and will also help reduce hot spots in your combustion chamber, which can ward off detonation or pre-ignition. It's like a win-win there.
These two thing will bring you down to around 10:1 (or slightly less) depending on where your combustion chambers size out cc-wise. And you get to keep your freshly worked over heads.
Step number 2 would be to polish your combustion chambers in the heads. This will net you an additional 2-3ccs, and will also help reduce hot spots in your combustion chamber, which can ward off detonation or pre-ignition. It's like a win-win there.
These two thing will bring you down to around 10:1 (or slightly less) depending on where your combustion chambers size out cc-wise. And you get to keep your freshly worked over heads.
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From: Central, IL
oldcutlass - Yes. I am actually not running any vacuum advance currently.
80 Rocket - Heads were previously polished. Milling brought the CC back down.
I have another set of 7a heads - unmilled, I could polish and try.
80 Rocket - Heads were previously polished. Milling brought the CC back down.
I have another set of 7a heads - unmilled, I could polish and try.
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Do you know how much they milled your current heads? It sounds like they would have had to take off about .040"-.060" to end up at 64ccs after polishing the combustion chambers.
How did your intake fit on the engine when you put it together? Did the mating surfaces have to be milled or slotted bolt holes?
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Dynamic compression is a tricky thing, affected by a variety of factors (intake volume, head flow, ring seal, and on and on). I agree with Don, IMO, cranking compression should be 180 tops for a street car unless you are a VERY good tuner.
Also, no engine will detonate at idle, if it did, it would not start when at operating temperature.
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From: Central, IL
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Something is amiss there with a 152 and 198.
For reference, my dragster motor was pumping 180 across the board with a tired 385" small block Chevy. The motor is 11:1 compression.
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Out of Line, Everytime😉
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From: Melville, Saskatchewan
How many miles on this build? One high and one low, hmm. I am wondering if the rings are properly seated yet? Did you try a spark plug like a NGK 5670-8? I would try atf in all the cylinders. The Cometic head gaskets can be ordered to .140" thick but $50 more per gasket above .051" thickness. Over .100" thick is another $100 each.
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From: Central, IL
How many miles on this build? One high and one low, hmm. I am wondering if the rings are properly seated yet? Did you try a spark plug like a NGK 5670-8? I would try atf in all the cylinders. The Cometic head gaskets can be ordered to .140" thick but $50 more per gasket above .051" thickness. Over .100" thick is another $100 each.
Cometic prices - gaskets must be made of gold!
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Thread Starter
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From: Central, IL
I told the shop 10:1 over 6 years ago. Shop calculated compression to 10.1:1. They cc'd the heads after milling. They built the bottom end. I assembled top end. Have been battling a tune ever since. I'm going to drive this motor till it blows. Not enjoying the car as I should. I have the numbers matching motor on a stand. I will put a stock build on it - a stock grind cam, original 4 bbl and drive it. Thank you all for your help and input.
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From: Fuquay Varina NC
That sure sucks. You have a lot of money and time invested in your build. You will have a lot more invested in rebuilding the new one. I would consider trying to get the rings seated and investing in the Cometic Gaskets. Good luck with whichever route you choose.
