Rochester M4M rods
Thread Starter
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
Rochester M4M rods
Is there any way to get primary rods for my '79 Q-jet? Is there maybe a tutorial on making them from "M" rods? Does someone have them for sale used? what's the deal here? Thanks,
Scott
Scott
Melting Slicks
Joined: Oct 2000
Posts: 2,142
Likes: 195
From: Englewood FL
Thread Starter
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
The M4M can use those .036 powertip rods, but you have to use a huge jet along with it, I'd rather just use a .026 powertip rod, but nobody makes 'em, seems like. What size .036 rods do you have?
Scott
Pro
Joined: Feb 2008
Posts: 556
Likes: 13
From: C3 Forum, Colorado
They all have the .026 power tip but are short rods measuring 2.40" end to end.
41 J
41 K
45 P
51 P
50 Y (.036 tip)
And one set not stamped measuring;
2.40" length X .026" tip X .039 cruise.
You probably already have this information but here's a quote from Lars in 2007. I know this is old information but I don't have his current tuning papers on this computer. But I believe this reference is still accurate.
Pre-’75 (up through ’74) Q-Jets use metering rods that are approximately 2.47” long overall (total length from the metering tip to the extreme top of the rod). 1975 and newer Q-Jets use rods that are about 2.40” long. The early rods typically also have just a plain number stamped into them (like, “44”), or will often have the letter “B” after the number (like, “44B”). The later rods will often have the letter “K” or “M” after the number. If an early rod (long rod) is installed in a post-’75 carb, the actual shank (body) of the rod will be stuffed down into the jet, resulting in a severe lean condition with associated marginal drivability. Likewise, if a late rod is used in an early carb, there will be virtually no lean-out from the power piston at idle or cruise, and the carb will suffer a severe rich-running condition.
