z28 vs boss 302
07-09-2007, 01:26 AM
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z28 vs boss 302 in terms of the 67-69 z28 and 69-70 boss, how much different were these engines, in terms of being underrated and such. it just seems odd of rating both cars identical
07-10-2007, 10:59 AM
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Z28 ONLY came with the 302 and 4-speed in the first gen. I had the chance to drive a '69 of my buddy's rebuilt to stock specs some years back and it was amazing! I do not know what the cam specs were, but it was built to rev! Decent down low (but ran slightly rough until you got a few thousand on the tach) and positively fierce up top. I have driven high compression big blocks and they were all the other way around, all torque down low and falling off up at the top end.
A good running 400 block in a muscle car would probably give it a run for it's money on the strip, but these cars were built to handle a road course, not a drag strip. The Ford's (as I recall, memory gets fuzzy in this old mans head from time to time) never had the success of the Chevy's on the track (and they both probably spent about as much modifying the cars for racing) and I suspect that it is Ford's recurring problem, they overrate engines while GM underrates them. Ford may have been hurting for cash during developement as they had spent a ton of cash trying to beat Ferrari at about the time they would have been designing the engine. Just conjecture on my part.
Been years and years since I have even seen a Boss 302, but as I recall the street cars were more luxury oriented than the Z28, heavier too. Never driven one, but it would have to be damn good to make me spend my hard earned money on one over a Z28.
A good running 400 block in a muscle car would probably give it a run for it's money on the strip, but these cars were built to handle a road course, not a drag strip. The Ford's (as I recall, memory gets fuzzy in this old mans head from time to time) never had the success of the Chevy's on the track (and they both probably spent about as much modifying the cars for racing) and I suspect that it is Ford's recurring problem, they overrate engines while GM underrates them. Ford may have been hurting for cash during developement as they had spent a ton of cash trying to beat Ferrari at about the time they would have been designing the engine. Just conjecture on my part.
Been years and years since I have even seen a Boss 302, but as I recall the street cars were more luxury oriented than the Z28, heavier too. Never driven one, but it would have to be damn good to make me spend my hard earned money on one over a Z28.
07-11-2007, 08:45 PM
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In terms of engine performance potential the 69 and 70 Boss 302's was built with features that form the basis of the engines Ford uses to this day in Cup racing.
The Boss 302 and later 4 bbl. Cleveland based engines featured large canted valve cylinder heads with 1.73 rocker and a solid lifter cam in the case of the Boss 302's. The blocks were 4 bolt main with screw in pipe thread freeze plugs. The 289 length connecting rods had 3/8" bolts and the 3" stroke crank was forged steel. The points distributor featured a factory installed rev limiter box that I believe limited the engine to 6250, which naturally limited hp output along with the dual plane intake manifold. The '69 Boss 302 head had a slightly smaller combustion chamber, if I remember correctly it was 49cc and 2.25 intake valves. The '70 head had a slightly larger chamber and 2.19" intakes. Most Trans Am type engines featured inline Autolite carburetors in either a single 4 or dual arrangement. These carburetors formed the basis (appearance) for BG's new inline 4bbl for street rod guys. The Boss's were reported to make in the neighborhood of 430 HP from the factory with the point grounding rev limiter bypassed.
The '67-early '68 Z28 302's were 2 bolt blocks with 11/32" rod bolts, same as the 327. The later 68 and 69 302's were 4 bolt medium journal engines with 3/8" bolt rods. All had forged cranks. The '492 heads had a much lower flow capacity and 160-165 cc runners with a 2.02" intake valve. The mechanical cam was 254 @ .050" single pattern on a 114 deg lobe sep. Like all 1st gen SBC's the heads featured a 1.5 rocker ratio. These engines weren't spark rev limited but limited in rpm capability by the valve springs. Both the Boss and Z28 used a 780 cfm Holley carburetor.
I have a 302 and can tell you its no low end powerhouse and was never meant to be, I wouldn't build another one for performance reasons. A good 350 is better everywhere up to 8000.
I used to have a '70 4bbl 351 Cleveland in a Fox mustang and it was simply badass everywhere you revved it to, but think the Boss 302 would suffer from horrendous low end response, again not what it was designed for. Besides Ford let you have a 4.30 gear in the mustang with 3.73 being most common in the Z.
The Boss 302 and later 4 bbl. Cleveland based engines featured large canted valve cylinder heads with 1.73 rocker and a solid lifter cam in the case of the Boss 302's. The blocks were 4 bolt main with screw in pipe thread freeze plugs. The 289 length connecting rods had 3/8" bolts and the 3" stroke crank was forged steel. The points distributor featured a factory installed rev limiter box that I believe limited the engine to 6250, which naturally limited hp output along with the dual plane intake manifold. The '69 Boss 302 head had a slightly smaller combustion chamber, if I remember correctly it was 49cc and 2.25 intake valves. The '70 head had a slightly larger chamber and 2.19" intakes. Most Trans Am type engines featured inline Autolite carburetors in either a single 4 or dual arrangement. These carburetors formed the basis (appearance) for BG's new inline 4bbl for street rod guys. The Boss's were reported to make in the neighborhood of 430 HP from the factory with the point grounding rev limiter bypassed.
The '67-early '68 Z28 302's were 2 bolt blocks with 11/32" rod bolts, same as the 327. The later 68 and 69 302's were 4 bolt medium journal engines with 3/8" bolt rods. All had forged cranks. The '492 heads had a much lower flow capacity and 160-165 cc runners with a 2.02" intake valve. The mechanical cam was 254 @ .050" single pattern on a 114 deg lobe sep. Like all 1st gen SBC's the heads featured a 1.5 rocker ratio. These engines weren't spark rev limited but limited in rpm capability by the valve springs. Both the Boss and Z28 used a 780 cfm Holley carburetor.
I have a 302 and can tell you its no low end powerhouse and was never meant to be, I wouldn't build another one for performance reasons. A good 350 is better everywhere up to 8000.
I used to have a '70 4bbl 351 Cleveland in a Fox mustang and it was simply badass everywhere you revved it to, but think the Boss 302 would suffer from horrendous low end response, again not what it was designed for. Besides Ford let you have a 4.30 gear in the mustang with 3.73 being most common in the Z.
