Raising the Dead
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Raising the Dead
After 25 years and 270,000 miles my truck - my child - died . New engine time. It curently has a 302 2Bl Auto but I am thinking of going with a 351 for the extra available power. However, I have two questions. First, pardon my ignorance, what is the difference between the Cleveland and the Windsor? I looked in teh tech articles first before I posted whatis sure to be an oft asked question. Second, my primary concern in rebuilding is mileage. My truck was a daily driver and it got to be damn expensive. Is the best bet leaving everythin stock? How does the fuel economy of a 302 vs a 351 compare? What should I take into consideration in rebuilding to achieve the best possible milage? Your insights are greatly appreciated.
GAB
GAB
Tuned
Joined: Jun 2001
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Raising the Dead
>After 25 years and 270,000 miles my truck - my child - died
>. New engine time. It curently has a 302 2Bl Auto but I am
>thinking of going with a 351 for the extra available power.
>However, I have two questions. First, pardon my ignorance,
>what is the difference between the Cleveland and the
>Windsor? I looked in teh tech articles first before I
>posted whatis sure to be an oft asked question. Second, my
>primary concern in rebuilding is mileage. My truck was a
>daily driver and it got to be damn expensive. Is the best
>bet leaving everythin stock? How does the fuel economy of a
>302 vs a 351 compare? What should I take into
>consideration in rebuilding to achieve the best possible
>milage? Your insights are greatly appreciated.
> GAB
The big difference between a Cleveland and a Windsor is the heads. Cleveland heads have a canted valve design, and breath much better than Windsor heads. I expect that you could get similar performance from a Windsor with aftermarket aluminum heads.
Mileage depends on a lot of variables, including gearing, average speed, driving style, altitude, etc. Cleveland engines are not known for their high gas mileage - but if your 302 was struggling to move your truck, the 351 may be loping and may actually get slightly better mileage. It also depends on how you build it - what cam, intake, carb, exhaust, etc.
Unless you can find a decent fresh 351C, you will have to rebuild it anyway so why not pep it up a bit. Performance and mileage are not necessarily exclusive. Anything you do to improve efficiency would improve power and mileage. First of all, for a truck I would strongly encourage you to seek a 351C with the 2V heads, since the smaller ports are designed for low-end torque. The larger ports of the 4V heads sacrifice low-end torque for high-end HP.
I would pay specific attention to letting it breathe, and a good ignition. So make sure the air induction system breathes well, the intake and carb flow sufficiently (600 CFM or so), and the exhaust system is free flowing. Headers are not mandatory but would improve things a bit. Make sure you go with a dual-plane intake such as the Performer 351c-2V. Install a 'straight-up' (0 degree) timing set, and an RV type cam. Remember to choose your components for low-RPM torque unless you are mudding.
If rebuilding the heads, have some typical 'clean-up' done, but no need for full porting. You could put slightly larger valves in. As far as compression ratio, if you have to replace the pistons you could go up to 9,5:1 or so on pump gas and that will gain you a bit. If you got ahold of some Aussie heads and used flat-top pistons, you would be running around 10.7:1 compression and this will reportedly work on pump gas as long as you pay attention to timing and carefully select the cam.
In the end, I can't really say what your mileage would be but it sure will be more fun! I don't suspect it would be much worse and with some tuning you should be able to do at least as well as the 302 on mileage...
>. New engine time. It curently has a 302 2Bl Auto but I am
>thinking of going with a 351 for the extra available power.
>However, I have two questions. First, pardon my ignorance,
>what is the difference between the Cleveland and the
>Windsor? I looked in teh tech articles first before I
>posted whatis sure to be an oft asked question. Second, my
>primary concern in rebuilding is mileage. My truck was a
>daily driver and it got to be damn expensive. Is the best
>bet leaving everythin stock? How does the fuel economy of a
>302 vs a 351 compare? What should I take into
>consideration in rebuilding to achieve the best possible
>milage? Your insights are greatly appreciated.
> GAB
The big difference between a Cleveland and a Windsor is the heads. Cleveland heads have a canted valve design, and breath much better than Windsor heads. I expect that you could get similar performance from a Windsor with aftermarket aluminum heads.
Mileage depends on a lot of variables, including gearing, average speed, driving style, altitude, etc. Cleveland engines are not known for their high gas mileage - but if your 302 was struggling to move your truck, the 351 may be loping and may actually get slightly better mileage. It also depends on how you build it - what cam, intake, carb, exhaust, etc.
Unless you can find a decent fresh 351C, you will have to rebuild it anyway so why not pep it up a bit. Performance and mileage are not necessarily exclusive. Anything you do to improve efficiency would improve power and mileage. First of all, for a truck I would strongly encourage you to seek a 351C with the 2V heads, since the smaller ports are designed for low-end torque. The larger ports of the 4V heads sacrifice low-end torque for high-end HP.
I would pay specific attention to letting it breathe, and a good ignition. So make sure the air induction system breathes well, the intake and carb flow sufficiently (600 CFM or so), and the exhaust system is free flowing. Headers are not mandatory but would improve things a bit. Make sure you go with a dual-plane intake such as the Performer 351c-2V. Install a 'straight-up' (0 degree) timing set, and an RV type cam. Remember to choose your components for low-RPM torque unless you are mudding.
If rebuilding the heads, have some typical 'clean-up' done, but no need for full porting. You could put slightly larger valves in. As far as compression ratio, if you have to replace the pistons you could go up to 9,5:1 or so on pump gas and that will gain you a bit. If you got ahold of some Aussie heads and used flat-top pistons, you would be running around 10.7:1 compression and this will reportedly work on pump gas as long as you pay attention to timing and carefully select the cam.
In the end, I can't really say what your mileage would be but it sure will be more fun! I don't suspect it would be much worse and with some tuning you should be able to do at least as well as the 302 on mileage...
Senior User
Joined: Jan 2002
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Raising the Dead
[updated:LAST EDITED ON 21-Jul-02 AT 07:42 PM (EST)]To give you some idea of POSSIBLE difference...
A friend of mine has a stock 351C 2v motor (with Aussie 4bbl 2v intake and carter thermoquad carb), and in his 1700kg car with 2.9:1 gears and a FMX auto he gets around 20L/100km.
In my 1400kg car, with 3.89:1 gears, and single plane intake, 750 holley sqr bore, interference headers and dual 2.5" exhaust, as well as cam upgrade and c4 auto, i get 15-16L/100km. So not much difference, especially considering weight differences, and if I put the boot into it my economy goes out the window; ie 35L+/100km.
(ps my motor also has stock 2v heads)
For economy I would suggest upping compression and fitting headers+dual exhausts.
A friend of mine has a stock 351C 2v motor (with Aussie 4bbl 2v intake and carter thermoquad carb), and in his 1700kg car with 2.9:1 gears and a FMX auto he gets around 20L/100km.
In my 1400kg car, with 3.89:1 gears, and single plane intake, 750 holley sqr bore, interference headers and dual 2.5" exhaust, as well as cam upgrade and c4 auto, i get 15-16L/100km. So not much difference, especially considering weight differences, and if I put the boot into it my economy goes out the window; ie 35L+/100km.
(ps my motor also has stock 2v heads)
For economy I would suggest upping compression and fitting headers+dual exhausts.
Elder User
Joined: Sep 2001
Posts: 887
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From: Jax FL
Raising the Dead
Here is the rub.
A 351w has better after market support and a mild built one will give about the same milage.
A 351c will make more power but cost on gas, with a gear change you can compensate for some of it.
A 400 will make more torque, but cost on gas and need to change the tranny as well.
An old engine builder once told me you can build an engine for power/torque or for torque/fuel milage. but you wont get all three.
A 351w has better after market support and a mild built one will give about the same milage.
A 351c will make more power but cost on gas, with a gear change you can compensate for some of it.
A 400 will make more torque, but cost on gas and need to change the tranny as well.
An old engine builder once told me you can build an engine for power/torque or for torque/fuel milage. but you wont get all three.
