Slight Knock/Ping

1966-300 · Oct 28, 2012

OK back again for free advice. After I rebuilt my 383 and got all the bugs worked out she is running really good with one small exception. When I really jump on it and accelerate moderately hard there is a ping/knock. I backed off the timimg to the 10-11 degree range and it mostly went away but still an occasional knock/ping especially after it is really warmed up. A friend has suggested rejetting the carb, suggesting more fuel for the .30 over cylinders. The rebuild was not a performance build, just a slightly bigger cam, and bored .30 over. The compression is likely in the 10-1 range maybe a little higher. What is the opinion of rejetting the carb? Currently it is a standard Carter AFB with the stock jets. I am dubious that this will have any effect on the pinging situation, and believe it to be entirely timing. I am going to try to post some pictures but have had no luck so far as they are all really big files and unable to upload. Any way let me know your thougts on the rejet?

commando1 · Oct 28, 2012

Jetting has nothing to do with knock.
10:1 CR? You are using 92 octane, right? You've already backed off on timing. At the loss of more performance, you might have to go another few degrees.
Also, the rebuild may actually left you with a higher CR than you're guessing. Last resort: add another layer of head gaskets to lower the CR.

(Sent using Forum Runner)

70NPORT · Oct 28, 2012

I didn't know 66 383 had that much compression...is that the stock motor?

Bryan · Oct 28, 2012

1966 383 was 9.2 for the 2 bbl car and 10.0 for the 4 bbl car.

Newp · Oct 28, 2012

commando1 said:
Jetting has nothing to do with knock.
10:1 CR? You are using 92 octane, right? You've already backed off on timing. At the loss of more performance, you might have to go another few degrees.
Also, the rebuild may actually left you with a higher CR than you're guessing. Last resort: add another layer of head gaskets to lower the CR.

(Sent using Forum Runner)

'' add another layer of head gaskets to lower the CR.'' What?...

Newp · Oct 28, 2012

1966-300,
You have a timing and/or octane issue.

commando1 · Oct 29, 2012

Newp said:
'' add another layer of head gaskets to lower the CR.'' What?...

Seriously, you NEVER heard of that?
OK, to calm you down:
Change to a SINGLE head gasket that's .050 thicker than the one being used now to lower the C.R. 1 point.
Better?
Stock head gaskets are between .030 and .040.
The rebuilder may have used an .020. Not good.
That's why I don't buy rebuilt engines. They are a box of chocolates.
If he did, replace with an .040 to .050
If there's an .040 in there, he'll have to double up.
Bottom line, he HAS to know what gasket is in there now.
Or live with the slight pinging and just accept that today's 10% ethanol garbage is just that: GARBAGE. Today's 92 octane is NOT 1968's 92 octane. It's more like 1968's 89 octane.

Newp said:
You have a timing and/or octane issue.

Thanks for confirming my diagnosis.

Newp · Oct 29, 2012

commando1 said:
Seriously, you NEVER heard of that?
OK, to calm you down:
Change to a SINGLE head gasket that's .050 thicker than the one being used now to lower the C.R. 1 point.
Better?
.

Much better..

70NPORT · Oct 29, 2012

commando1 said:
Seriously, you NEVER heard of that?
OK, to calm you down:
Change to a SINGLE head gasket that's .050 thicker than the one being used now to lower the C.R. 1 point.
Better?
Stock head gaskets are between .030 and .040.
The rebuilder may have used an .020. Not good.
That's why I don't buy rebuilt engines. They are a box of chocolates.
If he did, replace with an .040 to .050
If there's an .040 in there, he'll have to double up.
Bottom line, he HAS to know what gasket is in there now.
Or live with the slight pinging and just accept that today's 10% ethanol garbage is just that: GARBAGE. Today's 92 octane is NOT 1968's 92 octane. It's more like 1968's 89 octane.

Thanks for confirming my diagnosis.

I'll will testify today that...today's gas is ABSOLUTE garbage. I found out the hard way while dealing with an vapor lock issue last summer. I stay on 92/93 octane with and additive.

Newp · Oct 29, 2012

Newp said:
1966-300,
You have a timing and/or octane issue.

The first thing you need to do is make sure your timing is correct.

If your dist. has an advance curve and/or adjustable vacuum advance, initial timing specs no longer apply (example 10 deg. at an idle).

You need to time the engine for ''total'' timing which is in the 2500 rpm range.

Newp · Oct 29, 2012

commando1 said:
Thanks for confirming my diagnosis.

Your welcome, just trying to help.

rexus31 · Oct 29, 2012

Put a little race gas in it to see if the condition goes away. 10-1 is too much compression for 92 octane.

1978 NYB · Oct 29, 2012

rexus31 said:
Put a little race gas in it to see if the condition goes away. 10-1 is too much compression for 92 octane.

Google CAM2 to find a gas station near you that sells that race fuel. Most sell the 100 octane Cam2 which is clear in color or I've seen 110 octane Cam2 (which is purple in color) for sale at a gas near my local racetrack. They usually sell CAM2 with a short hose that won't reach your gas tank. CAM2 is intended to be pumped into a race fuel can and then poured into your race car. You don't have to have a race fuel can, any fuel can will work.

1966-300 · Oct 30, 2012

Thanks to all. I know for sure the head gasket was .040 as I installed it. At the time I was on the fence about going thicker but that is what I have. I dont really want to dismantle it just to go a little thicker on the gasket, even though I know it would have a benefit. As for using higher octane fule that is certainly the way to go and I was going to do that as well. I still think I can tweak the timing just a bit more and just keep checking to get optimal results. I was just curious about the idea that rejetting the carb would have any effect. My opinion from the start was IT WOULD NOT. But my buddy is a master Toyota Tech and he is emphatic but it is my engine and I just think he is wrong in this case. This is NOT a major deal it is a very minor ping, and only if I jump on it. So not a really bad problem in my opinion. Thanks for the input from all.

1966-300 · Oct 30, 2012

One last thing I read was you can add toulene to 92 octane and get an octane boost. Any confirmation to this and at what ratio?

commando1 · Oct 30, 2012

1966-300 said:
my buddy is a master Toyota Tech and he is emphatic.

That is the scariest thing I've ever seen posted on FCBO....

66-300: have you been using 92 octane?
(Sent using Forum Runner)

1966-300 · Oct 31, 2012

Yes using 92 octane which is the highest octane I can find locally.

1978 NYB · Oct 31, 2012

1966-300 said:
Yes using 92 octane which is the highest octane I can find locally.

Must be a dragstrip close by. They'll let anyone buy race fuel.

commando1 · Oct 31, 2012

Having a car that needs you to find race fuel or av-gas is dumb. Cut back on the timing until the detonation goes away or turn up the radio.

(Sent using Forum Runner)

Newp · Oct 31, 2012

Newp said:
The first thing you need to do is make sure your timing is correct.

If your dist. has an advance curve and/or adjustable vacuum advance, initial timing specs no longer apply (example 10 deg. at an idle).

You need to time the engine for ''total'' timing which is in the 2500 rpm range.

..........

Slight Knock/Ping

New Member

Old Man with a Hat

Old Man with a Hat

Well-Known Member

Active Member

Active Member

Old Man with a Hat

Active Member

Old Man with a Hat

Active Member

Active Member

Senior Member

Warfighter

New Member

New Member

Old Man with a Hat

New Member

Warfighter

Old Man with a Hat

Active Member

Similar threads