1978 442 clone

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Hi Everyone,I have a issue on my car pinging it’s a 1978 Oldsmobile with a 403 I back the timing off and I tried octane booster
i run 87 non-ethanol can’t get 90 here in S Carolina
The heads are 1971 7 A heads and are 9:1 compression ratio
I’m told I can run regular
any idea what would be causing this
Thank’s
Steve
 

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Olds 307 and 403

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Oct 4, 2018
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Melville, Saskatchewan
What cam is in it? I ran my 9 to 1 350 with 214/214 cam on 87 with 22 base, 38 in by 2600 with a 30 degree vacuum can on manifold vacuum. No pinging, just low speed bucking, a 20 degree can fixed it. Stock pistons .025" in the hole with .028" thick head gaskets. With the right cam, you will be fine.
 
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Rocketman269V

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Feb 26, 2020
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I think that the issue here is the fact that he is running a 403, which had ~83 cc. combustion chamber volume and switched to the '71 7(A) heads, which are ~64 cc. That will definitely bump the compression up, depending on the head gasket thickness and if the heads have been milled. Do a cranking pressure (compression) test and see what kind of pressure you have in the engine. Be sure that it is warmed up, disconnect the (+) wire to the distributor and wire the throttle wide open to get sufficient air into the engine. Don't forget to remove whatever you use to hold the throttle open after you're done. Don't ask.:rolleyes:
 

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What cam is in it? I ran my 9 to 1 350 with 214/214 cam on 87 with 22 base, 38 in by 2600 with a 30 degree vacuum can on manifold vacuum. No pinging, just low speed bucking, a 20 degree can fixed it. Stock pistons .025" in the hole with .028" thick head gaskets. With the right cam, you will be fine.
Not sure but it’s a mild edelbrock that’s all I no. I’m having a hard time finding amy over 87 Non Ethanol gas
 

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I think that the issue here is the fact that he is running a 403, which had ~83 cc. combustion chamber volume and switched to the '71 7(A) heads, which are ~64 cc. That will definitely bump the compression up, depending on the head gasket thickness and if the heads have been milled. Do a cranking pressure (compression) test and see what kind of pressure you have in the engine. Be sure that it is warmed up, disconnect the (+) wire to the distributor and wire the throttle wide open to get sufficient air into the engine. Don't forget to remove whatever you use to hold the throttle open after you're done. Don't ask. I
I won’t lol
 

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Nov 27, 2021
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Hi Everyone,I have a issue on my car pinging it’s a 1978 Oldsmobile with a 403 I back the timing off and I tried octane booster
i run 87 non-ethanol can’t get 90 here in S Carolina
The heads are 1971 7 A heads and are 9:1 compression ratio
I’m told I can run regular
any idea what would be causing this
Thank’s
Steve
This is what the engine was built on
403 specs:

- 1979 Oldsmobile 403 small block

- 1971 7A heads

- Edelbrock mild cam

- Comp roller tip rockers

- Nodular crank

- Dick Miller main girdle

- ARP Fasteners

- 9:1 compression ratio
 
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Olds 307 and 403

Well-known member
Oct 4, 2018
846
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Melville, Saskatchewan
Even the 204/214 Edelbrock should work Ok. Were those heads rebuilt? Was the block bored oversize? They aren't 64cc, that is the factory spec, most are actually 68 to 70cc uncut. The factory pistons will be .020" in the hole and probably .042" compressed Felpro head gaskets. It actually means less than 9 to 1. Try an adjustable vacuum advance canister, set it at 10. The factory is probably a 30 degree unit.
 
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Steve[email protected]

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Even the 204/214 Edelbrock should work Ok. Were those heads rebuilt? They aren't 64cc, that is the factory spec, most are actually 68 to 70cc uncut. The factory pistons will be .020" in the hole and probably .042" compressed Felpro head gaskets. It actually means less than 9 to 1. Try an adjustable vacuum advance canister, set it at 10. The factory is probably a 30 degree unit.
Not sure
 

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What cam is in it? I ran my 9 to 1 350 with 214/214 cam on 87 with 22 base, 38 in by 2600 with a 30 degree vacuum can on manifold vacuum. No pinging, just low speed bucking, a 20 degree can fixed it. Stock pistons .025" in the hole with .028" thick head gaskets. With the right cam, you will be fine.
I found the cam number
 

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Olds 307 and 403

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Oct 4, 2018
846
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Melville, Saskatchewan
That is the larger 214/224 duration cam, that should help even more. If your heads were milled and are actually 64cc, a 0 piston to deck with a stock bore, you could be at 9.6+ to 1, which could be a little tempermental. I ran the 204/214 Edelbrock cam in a 9.6 to 1 Olds 350 with terrible quench, around .070" piston to head. It needed cold plugs and less timing or it pinged on 91 non ethanol gas.
 

Olds 307 and 403

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Oct 4, 2018
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Melville, Saskatchewan
What intake, carb and distributor on are this motor? Try setting the timing back to spec. Then remove and plug the vacuum advance hose. If that fixes the pinging, get an adjustable vacuum advance.
Like I said an adjustable vacuum canister at full advance only puts out 20 degrees max, you can adjust down to 2 degrees. Your factory vacuum advance canister has a stamped number on top, it tells the degrees of advance. It could be 30 or more. Good luck.
 
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Olds 307 and 403

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Oct 4, 2018
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Melville, Saskatchewan
The carb will be on the lean side, especially with the bigger cam and higher compression. If the adjustable vacuum advance canister doesn't fix it, a custom tune on the Qjet should be next.
 

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Here’s some more information The guy who built it sent me this

The heads are 7a from a ‘72 Cutlass 350, they were redone with better springs, resurfaced and have adjustable rocker arms from Comp Cams. They raise the compression from 8 to 1 about one point 9 to 1. Stock 403 heads are 83 cc and the 7a heads are about 70 cc give or take a little bit. I would back the timing back a couple degrees.
 

Olds 307 and 403

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Oct 4, 2018
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Melville, Saskatchewan
Resurfacing usually removes 2 to 3 cc. So they are probably in the 65 to 68cc range currently. If put them on an undecked, stock bore 403, you will be around 9.25 to 1. I think you will be good with less vacuum advance. You want to keep the base timing at the stock 20 degree setting, if at all possible. It will idle and run smoother. The stock advance springs are pretty stiff, you won't usually get full mechanical advance till 3000 rpm, even with lighter, aftermarket springs. Accel and Crane sell adjustable vacuum advance canisters, just make sure it is for a HEI. We are lucky, our 91 Premium is non ethanol, our 87 is 10 percent ethanol, with 89 in between.
 

Olds 307 and 403

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Oct 4, 2018
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Melville, Saskatchewan

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I found a place today that sells 90 non- ethanol I filled up sat with 87 non- ethanol
Do you think I need Higher that 87 octane
thanks for the info
I’ll put the 90 in this weekend after I use this 87
up
Thanks Again
 

Olds 307 and 403

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Melville, Saskatchewan
You may need the 90 octane. All our 91 Premium is non ethanol, so far. But it is nearly $1.20 more Canadian per US Gallon vs 87 with 10% ethanol. My current 357 Olds 350 build with the new small chamber Edelbrock heads should be fine with 87, if necessary.
 

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A buddy of mine told me take the hose off to the vacum advance canister and block it and if the pinging stops problem solved Rt
I would have to get a different one like that one you sent me
what do you think
thanks