Living with a 2.21....
I titled this thread, "Living with a 2.21" in reference to the gear ratio I have in my 7 1/4 rear.
THE CAR:
Yeah, I know. The car is a '87 Chrysler Fifth Ave. Not an A-Body. But it is has similar drivetrain and a hood ornament.
The curb weight of "Moby" ( I call her that...) is 3750 lbs. After the diet I put on Moby, she sits at 3470 lbs. I know this 'cause I weighed her at one of those Cat scales.
THE ENGINE:
I have authored several threads here on FABO documenting my trials and tribulations about the lowly 318 Roller LA motor. If you did a search you will find I have ported 302 heads with 1.88/1.60 valves I performed my self.
I notched the intake walls of the cylinders and Flex-Honed the bores.
Replace the rings with Chrome Moly and installed new rod and main bearings.
The ignition is interesting. GM HEI but using the MSD Digital 6 ignition controller. It has Start Retard, Variable RPM Limiter and a Two Step should I go with NO2.
The camshaft is the quintessential 20-212-2 from Comp Cams. 218 @ .050 - .454 Lift Single pattern with the appropriate springs.
The highly regarded Edelbrock RPM AirGap serves as the intake. The center divider notched about 1/2".
670 CFM Holley Street Avenger Vacuum Secondary carburetor with 72/74 jets and the lightest spring I have. Short Yellow one I think.
Your typical 1 5/8" chassis headers that merge into a single 3" exhaust.
Average cylinder pressure is 130 psi and with all the cutting and porting to the chambers I would guess static compression around 8.8 since the car was 9.0 from the factory and all I did was flex-hone. No boring the cylinders here.
I'd say the tweener makes 275-300HP.
QUESTION:
But wait you say; why the hell are you running only 2.21 when the 318 with it's 3.31 stroke screams RPMs.
ANSWER:
The car originally came with the 7.25 with the 2.21 gears and I did had every intention of replacing it. As went so far as purchasing a B-Body 8 3/4 with 3.90 gears.
I drive Moby daily and 95% is all highway. She has been running now after I solved all the little "issues" for a month. I'm averaging 19.2 MPG... WOW....
From a stand still, she won't spin the tires unless I'm making a left or right turn.
But...after 20 MPH she will accelerate and accelerate and accelerate.... passing cars isn't a problem and 75 MPH is the sweet spot. Engine goes into some sort of harmonic rhythm and with the single 3" exhaust it is hardly audible.
So would I change all the positives in exchange for lower MPGs, louder exhaust notes and 75 MPH at 3600 or so RPM I'de get with 3.90s......
In a heart beat.....
I titled this thread, "Living with a 2.21" in reference to the gear ratio I have in my 7 1/4 rear.
THE CAR:
Yeah, I know. The car is a '87 Chrysler Fifth Ave. Not an A-Body. But it is has similar drivetrain and a hood ornament.
The curb weight of "Moby" ( I call her that...) is 3750 lbs. After the diet I put on Moby, she sits at 3470 lbs. I know this 'cause I weighed her at one of those Cat scales.
THE ENGINE:
I have authored several threads here on FABO documenting my trials and tribulations about the lowly 318 Roller LA motor. If you did a search you will find I have ported 302 heads with 1.88/1.60 valves I performed my self.
I notched the intake walls of the cylinders and Flex-Honed the bores.
Replace the rings with Chrome Moly and installed new rod and main bearings.
The ignition is interesting. GM HEI but using the MSD Digital 6 ignition controller. It has Start Retard, Variable RPM Limiter and a Two Step should I go with NO2.
The camshaft is the quintessential 20-212-2 from Comp Cams. 218 @ .050 - .454 Lift Single pattern with the appropriate springs.
The highly regarded Edelbrock RPM AirGap serves as the intake. The center divider notched about 1/2".
670 CFM Holley Street Avenger Vacuum Secondary carburetor with 72/74 jets and the lightest spring I have. Short Yellow one I think.
Your typical 1 5/8" chassis headers that merge into a single 3" exhaust.
Average cylinder pressure is 130 psi and with all the cutting and porting to the chambers I would guess static compression around 8.8 since the car was 9.0 from the factory and all I did was flex-hone. No boring the cylinders here.
I'd say the tweener makes 275-300HP.
QUESTION:
But wait you say; why the hell are you running only 2.21 when the 318 with it's 3.31 stroke screams RPMs.
ANSWER:
The car originally came with the 7.25 with the 2.21 gears and I did had every intention of replacing it. As went so far as purchasing a B-Body 8 3/4 with 3.90 gears.
I drive Moby daily and 95% is all highway. She has been running now after I solved all the little "issues" for a month. I'm averaging 19.2 MPG... WOW....
From a stand still, she won't spin the tires unless I'm making a left or right turn.
But...after 20 MPH she will accelerate and accelerate and accelerate.... passing cars isn't a problem and 75 MPH is the sweet spot. Engine goes into some sort of harmonic rhythm and with the single 3" exhaust it is hardly audible.
So would I change all the positives in exchange for lower MPGs, louder exhaust notes and 75 MPH at 3600 or so RPM I'de get with 3.90s......
In a heart beat.....