Question: E4ME: Secondary metering rods

[Feltman]

Just not quite right. I have posted previously the work I have done on my 81. Because, I am never really satisfied a trait must of us vette owners possess (in a good way), I would like to get some feedback on the following. I have reviewed past post on this information and did not see or maybe understand what I am about to ask.

Modifications to my engine (increase compression from 8.2-1 to 9.5 -1, more robust cam, roller lifters..etc..etc....the engine, intake and carburetor or original for the year. Here is the issue. I installed a 700R4, changes the rear gears from 2.82 to 3.55, removed stock air cleaner (not enough airflow after the engine work) and have put about 600 miles since the car was down for about a year. Car will pop and hesitate when WOT is applied from 55-60-65-70, while in overdrive. Will pop once or twice and then goes away for period of time (normal performance), I feel the car is running to lean. I removed the carb and change the factory primary metering position from 3 full turns out to 4. That should help. I want to change the secondary metering rods. Anybody know what the factory specs are for the secondary rods.

 

[GerryLP]

Just not quite right. I have posted previously the work I have done on my 81. Because, I am never really satisfied a trait must of us vette owners possess (in a good way), I would like to get some feedback on the following. I have reviewed past post on this information and did not see or maybe understand what I am about to ask.

Modifications to my engine (increase compression from 8.2-1 to 9.5 -1, more robust cam, roller lifters..etc..etc....the engine, intake and carburetor or original for the year. Here is the issue. I installed a 700R4, changes the rear gears from 2.82 to 3.55, removed stock air cleaner (not enough airflow after the engine work) and have put about 600 miles since the car was down for about a year. Car will pop and hesitate when WOT is applied from 55-60-65-70, while in overdrive. Will pop once or twice and then goes away for period of time (normal performance), I feel the car is running to lean. I removed the carb and change the factory primary metering position from 3 full turns out to 4. That should help. I want to change the secondary metering rods. Anybody know what the factory specs are for the secondary rods.

Feltman,

Did you return the stock computer-controlled carburetor and distributor to the car?

And what do you mean by "I removed the carb and change the factory primary metering position from 3 full turns out to 4."?

If you are getting back-firing out of the carb, then your a right to guess a lean mixture, but before we can help you, we need to clarify the points above.

But just in case, here is some information on metering rods...

http://www.oldengine.org/unfaq/leadfoot/qrodpri.htm

I have the AC-Delco 9A-100-3 (1980 - 1981) Carburetor, Parts, Power Kits & Emission Control Parts manual, and for the 1981 E4ME Rochester jets and rods, they match the Rochester part number with a Jet & Rod Package Part Number. So for example, for Rochester carburetor part number 17081217 and 17081218 (L81 carbs -Federal), it lists the same Jet & Rod package part number of 17067801. Therefore, perhaps the only way to tell which jets and Rods the L81 is supposed to have would be by obtaining one of these Jet & Rod Packages.

I suspect that you read Lars Grimrud's "How To Tune a Q-Jet", and that is why you are asking. If not, then do a search in CAC for the link. I found my copy of his informative paper here.

Nevertheless, a sensible way for you to solve your backfiring problem now would be for you to find out what metering rods you have there, and perhaps experiment with some rods with a smaller tip diameter (to en-richen the mixture at WOT).

If you know which rods you have, then perhaps these will help you:
http://cgi.ebay.com/ebaymotors/quad...013QQitemZ230260989384QQrdZ1QQsspagenameZWDVW

 

[Sensei]

The stock secondary rods were CH. Edelbrock makes replacements:

PN 1952 (CK). A good bit richer than stock

PN 1951 (CE). A bit richer still. This is what I use with my modified engine.

PN 1950 (CC). Stupid rich

If you are using an open air filter element, the thin, hot under hood air might be contributing to your lean condition. The stock dual snorkle set up is a very good design, it is usually a performance mistake to replace it.

God bless, Sensei

 

[Feltman]

Adjustment on the Primary metering jets was successful. No more back firing, dramatic increase in performance......now on to the secondary rods..thanks GerryLP and Sensi....