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Bug53
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Joined: February 22, 2021
Posts: 704
Location: Pawcatuck, CT.
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 Posted: Mon Jun 14, 2021 8:36 pm Post subject: Re: Knocking on hard acceleration and dieseling at shut off |
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I find it hard to believe a carburetor can cause knocking and pinging.
The fuel shut off solenoid could cause dieseling when shutting down the car if defective but the car would have to be pretty hot.
It's all about low octane and advanced timing. The only two knocking factors |
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EODTECH*
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Joined: July 08, 2020
Posts: 142
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| Posted: Mon Jun 14, 2021 9:20 pm Post subject: Re: Knocking on hard acceleration and dieseling at shut off |
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| K. Great. Thanks. I'll take that info to my tech. Maybe I've helped w/adding the octane boost and then refilling w/ 94 oct. |
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Pruneman99
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Joined: February 22, 2012
Posts: 5013
Location: Oceanside
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| Posted: Mon Jun 14, 2021 9:29 pm Post subject: Re: Knocking on hard acceleration and dieseling at shut off |
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| What distributor are you running? That will make a big difference in the static timing. If you have a distributor that has a static timing of 0* TDC, and you have it set at 8* BTDC, you will see like 38* at full advance. |
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RailBoy
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Joined: March 10, 2008
Posts: 2904
Location: Virginia
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| Posted: Mon Jun 14, 2021 11:58 pm Post subject: Re: Knocking on hard acceleration and dieseling at shut off |
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Ok, so you run 87 Octane.
Thing is I saw the original question in the beginning, but Tok 2/3's of the thread to find your answer.
Then I skimmed the rest so may have missed it but here is my question if the answer was over looked?
That is, have you at least put a tank of 93 octane threw it to see how it performs? Why I am not minding my post, that if timing and everthing else has been checked, has the octane been addressed? Could clean up that angle, thing is strokers typically run 93 octane or more, CR thing which we know..
A can of octane boost in my opinion does not match a tank of 93 total performance aspects and for clarity of mind, and used as a tuning aid... RB
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[quote="smitty24"]"HELP, I ported my own heads and now have fire coming out my ass" .[/quote]
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EODTECH*
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Joined: July 08, 2020
Posts: 142
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| Posted: Wed Jun 30, 2021 12:04 am Post subject: Re: Knocking on hard acceleration and dieseling at shut off |
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| RailBoy wrote: |
Ok, so you run 87 Octane.
Thing is I saw the original question in the beginning, but Tok 2/3's of the thread to find your answer.
Then I skimmed the rest so may have missed it but here is my question if the answer was over looked?
That is, have you at least put a tank of 93 octane threw it to see how it performs? Why I am not minding my post, that if timing and everthing else has been checked, has the octane been addressed? Could clean up that angle, thing is strokers typically run 93 octane or more, CR thing which we know..
A can of octane boost in my opinion does not match a tank of 93 total performance aspects and for clarity of mind, and used as a tuning aid... RB |
Yeah. You must have missed what I said about the octane rating. I filled the tank w/Chevron 94 and THEN added 8 point octane boost. I had originally stated that doing that almost completely eliminated the pre-ignition. THEN...I took it to my tech and he reset the timing to 7.5 BTDC...from whatever it was at. Yet still it knocks when I hammer the accelerator at 30 MPH uphill...in 4th.
It takes very, very little backing off of the accelerator for the knocking to stop and STILL increase in speed while climbing a grade in 4th. But it's still there. I basically have to make an appt to make it happen...but I hate that...and my tech says there should be ZERO...pre-ignition no matter what gear your in, no matter what speed, no matter what load you have. It should never, ever knock.
He is now convinced (after burning his fingers on the vaccum advance adjusting the Pertronix distr,) that the engine is overheating,,,,POSSIBLY because the rebuilder didn't use the correct fan/doghouse combo.
I took the wife out for a drive tonight...to cool off with all 4 windows open...(we're under that Heat Dome of Death right now...). I didn't gun it; drove normal, (no hammering on the accelerator this time) and particularly tried to listen for the knocking. Nothing. But after only about 45 min of normal driving....f**k me! that oil dipstick was pretty hot. And on Friday, my tech said..."This engine is COOKIN hot!" The ambient temp out for the last four days has been between 98-104 deg, Cooling down starting tomorrow to about 79 deg at the hottest and then getting even cooler over the next few weeks.
Btw...for the guys that asked before...the compression ratio is 8.8 in each cylinder. |
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Igpoe
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Joined: February 24, 2019
Posts: 853
Location: South Boston, VA
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| Posted: Wed Jun 30, 2021 4:57 am Post subject: Re: Knocking on hard acceleration and dieseling at shut off |
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OK, your timing is set at 7.5°btdc. I'm assuming you mean it was set at 7.5 btdc
AT IDLE. What's the reading at 3000 rpm? What's the reading at whatever rpm you're hearing the detonation, (pinging)?
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mukluk
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Joined: October 18, 2012
Posts: 7020
Location: Clyde, TX
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| Posted: Wed Jun 30, 2021 5:31 am Post subject: Re: Knocking on hard acceleration and dieseling at shut off |
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| EODTECH* wrote: |
| Btw...for the guys that asked before...the compression ratio is 8.8 in each cylinder. |
That's awfully high for what otherwise sounds like a stock 1600DP. What cam do you have?
| EODTECH* wrote: |
| Yet still it knocks when I hammer the accelerator at 30 MPH uphill...in 4th. |
Unless you have really short wheels or short transaxle gearing, you're lugging the engine by running in 4th gear at 30mph uphill. Low revs with high loading are a surefire way to quickly overheat and kill an aircooled engine.
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sb001
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Joined: May 19, 2011
Posts: 10406
Location: NW Arkansas
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| Posted: Wed Jun 30, 2021 5:52 am Post subject: Re: Knocking on hard acceleration and dieseling at shut off |
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| EODTECH* wrote: |
Btw...for the guys that asked before...the compression ratio is 8.8 in each cylinder. |
I'm no expert but after reading some other threads on this setup it seems like that Engle 90 cam is not a good match for a 1641- most everyone I see going to this setup is using a 110. (Don't even know whether this could possibly cause the higher than normal compression ratio you have.) I do agree that I don't think it's the carb causing the pinging, timing or something in the engine internals the builder used. But I don't know squat about engine building so...
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I'm the humblest guy on this board.
1969 autostick sedan, family owned since new
1600 SP engine
Solex 30 PICT 3 carburetor
Bosch 113905205AE autostick distributor |
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Paul Windisch
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Joined: September 02, 2009
Posts: 2546
Location: Clinton Township, Michigan
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| Posted: Wed Jun 30, 2021 5:59 am Post subject: Re: Knocking on hard acceleration and dieseling at shut off |
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I have a couple thoughts, the first one being, 30 mph uphill in fourth gear is on the edge of lugging. I sometimes cruise at 30 mph in fourth, but if I have to accelerate, especially uphill, it's time to downshift.
Second, how do you know your compression ratio? Did the builder give you deck and chamber measurements?
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1984 Mexican Beetle
-1914cc
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-0.040" deck for about 9.1:1 Compression
-Engle W110 cam
-CB Super Stock 1.1:1 Rockers
-Stock Heat Exchangers w/ Tri-Mil Muffler
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mukluk
Samba Member
Joined: October 18, 2012
Posts: 7020
Location: Clyde, TX
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| Posted: Wed Jun 30, 2021 6:02 am Post subject: Re: Knocking on hard acceleration and dieseling at shut off |
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| mukluk wrote: |
| EODTECH* wrote: |
| Btw...for the guys that asked before...the compression ratio is 8.8 in each cylinder. |
That's awfully high for what otherwise sounds like a stock 1600DP. What cam do you have? |
Just reread and found where you said it's a 1641DP with Engle W90. In my opinion the root cause of your issue is your compression is too high to use any typical pump gas with that cam. A recommended CR range of 8.0-8.25 is what I see.
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sb001
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Joined: May 19, 2011
Posts: 10406
Location: NW Arkansas
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| Posted: Wed Jun 30, 2021 6:08 am Post subject: Re: Knocking on hard acceleration and dieseling at shut off |
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| mukluk wrote: |
| mukluk wrote: |
| EODTECH* wrote: |
| Btw...for the guys that asked before...the compression ratio is 8.8 in each cylinder. |
That's awfully high for what otherwise sounds like a stock 1600DP. What cam do you have? |
Just reread and found where you said it's a 1641DP with Engle W90. In my opinion the root cause of your issue is your compression is too high to use any typical pump gas with that cam. A recommended CR range of 8.0-8.25 is what I see. |
Mukluk, with that cam is it possible to just switch the rockers out with another size that would lower the CR and use regular gas? Or does the cam need to be swapped? AS I said in my above post I know jack squat about engine building
_________________
I'm the humblest guy on this board.
1969 autostick sedan, family owned since new
1600 SP engine
Solex 30 PICT 3 carburetor
Bosch 113905205AE autostick distributor |
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mukluk
Samba Member
Joined: October 18, 2012
Posts: 7020
Location: Clyde, TX
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| Posted: Wed Jun 30, 2021 6:59 am Post subject: Re: Knocking on hard acceleration and dieseling at shut off |
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@sb001
Swapping the rockers wouldn't change the static compression ratio, that can only be done by changing the swept volume, deck height, or chamber volume. If stock 1.1 ratio rockers are swapped out for 1.25 ratio it will change the dynamic compression ratio slightly, but not likely by enough to make a difference.
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sb001
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Location: NW Arkansas
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| Posted: Wed Jun 30, 2021 7:17 am Post subject: Re: Knocking on hard acceleration and dieseling at shut off |
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| mukluk wrote: |
@sb001
Swapping the rockers wouldn't change the static compression ratio, that can only be done by changing the swept volume, deck height, or chamber volume. If stock 1.1 ratio rockers are swapped out for 1.25 ratio it will change the dynamic compression ratio slightly, but not likely by enough to make a difference. |
If he swapped the Engle 90 out for a 110 (what I am seeing most people use in a 1641) will this solve the CR problem? (related: How do you calculate the effect that a certain cam has on CR?)
Promise no more hijacking questions after this one 
_________________
I'm the humblest guy on this board.
1969 autostick sedan, family owned since new
1600 SP engine
Solex 30 PICT 3 carburetor
Bosch 113905205AE autostick distributor |
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MuzzcoVW
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Joined: February 21, 2018
Posts: 1460
Location: Westfield, MA.
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| Posted: Wed Jun 30, 2021 7:39 am Post subject: Re: Knocking on hard acceleration and dieseling at shut off |
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| Yes the 90 cam is close enough to stock that 8.8 compression is very high. Also at 30 mph up hill you shouldn't be in fourth anyway. They weren't designed to do that...it wasn't a power issue it's a cooling issue. Running high compression lugging up a hill is a recipe for these issues. And you need to be especially careful running a 1641. It's SO easy to get too hot and oval the Jugs. IMO Not at all worth it over a 1600 |
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Paul Windisch
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Joined: September 02, 2009
Posts: 2546
Location: Clinton Township, Michigan
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| Posted: Wed Jun 30, 2021 7:42 am Post subject: Re: Knocking on hard acceleration and dieseling at shut off |
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I tend to think that the increased duration of the 110, and the one extra degree of lobe separation, would reduce if not eliminate the knock due to high CR.
I am running a 110 in my 1915 with ~9.1:1, and it only knocks a little bit at certain loads, at high ambient temps, with low octane fuel. If it is below 70° F, it runs on 87 just fine. Any ambient temp higher than that, and 93 octane is the ticket.
EDIT: But as I said earlier, is still think 30mph in fourth gear uphill requires a downshift.
_________________
*ASE Recertified Master Automotive Tech*
1984 Mexican Beetle
-1914cc
-L3 Heads 35x32 valves 52cc chambers
-0.040" deck for about 9.1:1 Compression
-Engle W110 cam
-CB Super Stock 1.1:1 Rockers
-Stock Heat Exchangers w/ Tri-Mil Muffler
-Dual Weber IDF 40s w/ 26mm venturis
-034 SVDA Distributor
2013 Chevrolet Volt DD
2005 Pontiac Montana SV6
MAHLE Service Solutions
Applications Engineer |
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MuzzcoVW
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Joined: February 21, 2018
Posts: 1460
Location: Westfield, MA.
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| Posted: Wed Jun 30, 2021 7:47 am Post subject: Re: Knocking on hard acceleration and dieseling at shut off |
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| Paul Windisch wrote: |
I tend to think that the increased duration of the 110, and the one extra degree of lobe separation, would reduce if not eliminate the knock due to high CR.
I am running a 110 in my 1915 with ~9.1:1, and it only knocks a little bit at certain loads, at high ambient temps, with low octane fuel. If it is below 70° F, it runs on 87 just fine. Any ambient temp higher than that, and 93 octane is the ticket.
EDIT: But as I said earlier, is still think 30mph in fourth gear uphill requires a downshift. |
Agreed Its either that or shims to take care of it. I run a CB2280 in my F.I. 1600. Had to raise the compression to 8:1 for it to run right (used flat tops in place of the dished pistons) but I wouldn't want to go any higher with my cam. I believe the 90 is quite similar to the 2280 |
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EODTECH*
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Joined: July 08, 2020
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| Posted: Wed Jun 30, 2021 11:07 am Post subject: Re: Knocking on hard acceleration and dieseling at shut off |
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| unitedracing wrote: |
| Paul Windisch wrote: |
I tend to think that the increased duration of the 110, and the one extra degree of lobe separation, would reduce if not eliminate the knock due to high CR.
I am running a 110 in my 1915 with ~9.1:1, and it only knocks a little bit at certain loads, at high ambient temps, with low octane fuel. If it is below 70° F, it runs on 87 just fine. Any ambient temp higher than that, and 93 octane is the ticket.
EDIT: But as I said earlier, is still think 30mph in fourth gear uphill requires a downshift. |
Agreed Its either that or shims to take care of it. I run a CB2280 in my F.I. 1600. Had to raise the compression to 8:1 for it to run right (used flat tops in place of the dished pistons) but I wouldn't want to go any higher with my cam. I believe the 90 is quite similar to the 2280 |
Thanks all for the info/suggestions. I just want to clarify a couple of things. First, I never intentionally lug my engine. I only drove it in 4th, uphill and then hammered the accel... (and only twice) to see if I could recreate the knocking and when and where it happens. The moment it happened, I immediately eased off the accel and the knocking stops. Not trying to insult anyone...but I've been driving Bugs for almost 45 years. I know exactly when to downshift,,,yada, yada, yada. Never ever had a knocking issue in any Typ 1 engine in any of my previous Bugs.
I had a 1980 Z28...that started to knock after about 4 years. Changed the fuel pump...and changed from using low grade leaded gas (back then) to Hi-test. Solved the problem But that was Chevrolet. Pretty simple engines to work on. You didn't need a tech back then. Just common sense and the ability to read the official Chevrolet manual.
How do I know the CR is 8.8? Because I asked the builder directly. He's the shops 1600 DP designated builder and has been for years. They have ppl for 1200;s...1500's...etc.
Remember when I mentioned that the builder said he used a W90 cam "because it was the closest thing we could find to stock."
Is my current tech thinking in the right direction? He says it's definitely overheating...which is most likely the cause for the pre-ignition. "Something is causing this engine to run really hot...and I think that's why you have detonation. But I have to find out WHY it's overheating."
The engine builder is 300 miles away...and it's a ferry crossing to get to him. And with the apocalypse virus and it's variants still going on...it's not practical to drive it all the way there. My current tech is a local guy who's been doing nothing but Typ 1 maintenance for decades.
The last two fill-ups were Chevron 94 octane w/a booster added to that. As I said...as soon as I filled it up the first time w/94 and 8 point octane boost...it almost eliminated the knocking....but not TOTALLY.
And finally, in all other respects, this engine fires up beautifully...every time...cold or hot...idles beautifully...(when he reset the timing, he set the idle so that it that rpm is now somewhere btwn 990 and 1010.) |
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Paul Windisch
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Joined: September 02, 2009
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Location: Clinton Township, Michigan
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| Posted: Wed Jun 30, 2021 11:31 am Post subject: Re: Knocking on hard acceleration and dieseling at shut off |
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Did they say how that compression ratio was achieved? Flat top pistons? Smaller chambers? Reduced deck via turning down the cylinders?
Only asking, because a stock 1600 CR is around 7.5:1, so your increased CR is quite a bump from stock.
I am not doubting anything you have told us. I'm just trying to paint a clearer picture.
And the comment about lugging in fourth gear wasn't to insult you (if you took it that way). Rather, from my experience, I can induce the same behavior out of mine under similar circumstances.
So, at this point, I think you have several good suggestions. Mechanically, get a different cam; slightly reduce compression with shims; slightly retard the timing until the knock goes away; bigger jets. Or, on the fuel front, run extremely high octane fuel. As far as retarding the timing, this is a completely viable option. Increased compression and cylinder pressure do not need the lead time of advanced timing. The number of degrees advance, in general, is irrelevant. The engine wants and needs what it wants and needs. If it runs great and efficiently with 0° initial, and 20-22° all in, then run it that way.
The only unknown is the "overheating" condition. I didn't see any mention of any temperature measuring gauges, so that would likely be the next step. Cylinder head, and more importantly, engine oil temperatures should be measured.
I may have overlooked it, but is all of the factory tin in place with thermostat and flaps?
EDIT: Another thing just occurred to me; you said the 1200 came out and a 1600 went in. What year is your car? And does the decklid have cooling slots in it?
_________________
*ASE Recertified Master Automotive Tech*
1984 Mexican Beetle
-1914cc
-L3 Heads 35x32 valves 52cc chambers
-0.040" deck for about 9.1:1 Compression
-Engle W110 cam
-CB Super Stock 1.1:1 Rockers
-Stock Heat Exchangers w/ Tri-Mil Muffler
-Dual Weber IDF 40s w/ 26mm venturis
-034 SVDA Distributor
2013 Chevrolet Volt DD
2005 Pontiac Montana SV6
MAHLE Service Solutions
Applications Engineer |
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EODTECH*
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Joined: July 08, 2020
Posts: 142
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| Posted: Wed Jun 30, 2021 12:42 pm Post subject: Re: Knocking on hard acceleration and dieseling at shut off |
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| Paul Windisch wrote: |
Did they say how that compression ratio was achieved? Flat top pistons? Smaller chambers? Reduced deck via turning down the cylinders?
Only asking, because a stock 1600 CR is around 7.5:1, so your increased CR is quite a bump from stock.
I am not doubting anything you have told us. I'm just trying to paint a clearer picture.
And the comment about lugging in fourth gear wasn't to insult you (if you took it that way). Rather, from my experience, I can induce the same behavior out of mine under similar circumstances.
So, at this point, I think you have several good suggestions. Mechanically, get a different cam; slightly reduce compression with shims; slightly retard the timing until the knock goes away; bigger jets. Or, on the fuel front, run extremely high octane fuel. As far as retarding the timing, this is a completely viable option. Increased compression and cylinder pressure do not need the lead time of advanced timing. The number of degrees advance, in general, is irrelevant. The engine wants and needs what it wants and needs. If it runs great and efficiently with 0° initial, and 20-22° all in, then run it that way.
The only unknown is the "overheating" condition. I didn't see any mention of any temperature measuring gauges, so that would likely be the next step. Cylinder head, and more importantly, engine oil temperatures should be measured.
I may have overlooked it, but is all of the factory tin in place with thermostat and flaps?
EDIT: Another thing just occurred to me; you said the 1200 came out and a 1600 went in. What year is your car? And does the decklid have cooling slots in it? |
Exc. Thanks. I will bring up all these points to my tech, The Bug is a 63 Deluxe. The decklid is stock and has no slots in it. And no...there has not been any actual measurement yet...of the head, or oil temp. When I bring it in to him next week...I will print out this thread and hand it to him and let him judge. And yes...all tins and flaps are properly in place.
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Paul Windisch
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Joined: September 02, 2009
Posts: 2546
Location: Clinton Township, Michigan
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| Posted: Wed Jun 30, 2021 12:56 pm Post subject: Re: Knocking on hard acceleration and dieseling at shut off |
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Because it is cheap and easy, you may try the old tennis ball trick to open the decklid a smidge, just to see if it helps.
Please keep us posted! You'll get it sorted out.
Wow! Very nice looking car!
_________________
*ASE Recertified Master Automotive Tech*
1984 Mexican Beetle
-1914cc
-L3 Heads 35x32 valves 52cc chambers
-0.040" deck for about 9.1:1 Compression
-Engle W110 cam
-CB Super Stock 1.1:1 Rockers
-Stock Heat Exchangers w/ Tri-Mil Muffler
-Dual Weber IDF 40s w/ 26mm venturis
-034 SVDA Distributor
2013 Chevrolet Volt DD
2005 Pontiac Montana SV6
MAHLE Service Solutions
Applications Engineer |
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