I'm a bit surprised here. You are all throwing looking at chevys 305 which in my opionion was a boat anchor. Why not compare the Chevy 302 instead. Same stroke as the 283 but with a 4 inch bore. Its to bad we hit emmisions right after this engine came out. It really was an outstanding engine.

But I'm with DOHC, I'll take Displacement everytime. But within a given displacement range I'll take short stroke big bore.

 

You see a 351 based engine in NASCAR, only because of the cubic inch limit. How many "stock" parts are in these engines? Go to any Fun Ford racing event (as sponsored by several magazines), and the 302 based engines GREATLY outnumber the 351. I go to them all the time, and can come up with legit numbers by going through old magazines. I'm REALLY confused by the "grass roots" comment. I go to Emerald Coast Dragway, and Atmore Racepark all the time. Can't get more grassroots then these 2 tracks. On any given weekend, there are just as many (if not more) 302's as 350 Chevy engines, and FAR more 302's then 351W. I'm sure that racing in FL and AL is not so different then in the rest of the country. Finally, when the torque issue is brought up, the word is GEARS, GEARS, GEARS. You can move a freight train with a washing machine motor, given the correct gears are used. Use a light flywheel, low gears, dump the clutch at high rpm's (or use a high stall converter). Keep in the rpm range where the 302 shines, and it's tough to beat. I have a 351 in my 96 Bronco, and the dang thing won't spin the tires in the rain. Yup. I'll agree to disagree.

 

It's the same in road racing too. Everyone is running 302's. It has quietly superceded the SBC as the worlds most popular hot rod motor at the grass roots level. Sure there are plenty of 302 based stroker engines (the 331 being the best combonation) out there, particularly in drag racing, but for the average weekend racer, a stroker kit takes money from the budget that would be better spent on cylinder heads. In time the 302 will probably be superceded in turn by the 3 valve 4.6 modular motor, as the most popular grass roots hot rod engine. Those are just not out there in enough numbers as of yet. The Modular Ford V8 is just proving itself a durable powerhouse in all forms of racing. Robert Yates has been trying to get Nascar to allow the 4.6 in, but that will probably never happen. Yates built some 4.6's for the 24hours of Daytona and was very impressed with the basic design.

All things being equal a smaller engine can't make as much power as a larger engine, but in the real world things are not always equal. The AFR head 302 made 1.38 HP per cube at 6000RPM. A similar 347 stroker makes about 1.24 HP per cube at 6000 RPM. The 302 is converting more mechanical energy from the chemical engery supplied to it. As the RPMs increase so does the difference in effiency between those engines. The 302 not only has a superior stroke/rod ratio but it has less friction at high rpms to overcome because of it's over square bore to stroke relationship.

Another way of looking at it is to calculate the amount of air fuel mixture the engines can prossess in a minute at a given rpm. Both engines with heads and cams will be exceeding 100% volumetric effiency(moreso the 302 at high rpm, but not low rpm), but for simplicities sake we will assume 100% volumetric effiency. At 6000 rpms the 347 consumes 602CFM's. The typical 347 is running out of steam by now, but a built 302 can still rev much higher. By 7000 rpms the 302 is consuming 612cfms, and by 7500 the 302 is pushing 670cfms of air fuel mixture.

A 302 can't make as much power as a 460 though. The 460 has the same rod ratio, and close to same bore/stroke ratio as the 302. Think of it as scaled up 302 with canted valve heads. The 302 can still rev higher due to it shorter stroke, but it can't rev high enough to make up the huge cubic inch difference.

 

The Chevy 302 was indeed a very strong high rpm racing engine. They are extremely rare today. It had two four barrel carbs on a cross ram manifold in Z28 form. It usually beat the experimental Ford tunnel port 302's the first year in trans-am racing, but had a rather difficult time with the Boss 302's, once the Boss 302 came out.

Ironically, the chev 302 may of had too high of a rod ratio. It's rod ratio was 1.90 IIRC. Rod ratios this high are sometimes called slow rods, becaue they move the piston away from TDC so slowly. This makes it hard to fill the cylinder at anything less than very high RPMs. That's probably why the cross ram manifold was used in racing.

 

Dang, I lied!!!

Steve, you're wrong...........In NASCAR you could run LESS cubes...The 358 limits are the MAX. If there was ANY superiority to the 302 combo, believe me, it would be used.

Pro 5.0 is MOSTLY 351 based except for the stock block classes......in other words ALL the fast 7 second cars are 400/408 and up usually turbo cars.........I get the same magazines as you.

Dude.......your killing me comparing 302's to 351's in full size Broncos/trucks. It was sickening trying to pull with a 302 compared to the 351.........been there, done that.

The small circle tracks are still predominatly SBC......and look at the results in most drag racing classes..........there are an occasional Ford in the brackets, but mostly the old SBC.


P, you are an expert at manipulating numbers...........Not only is 6000 RPM safe for a decently built BB, but for a 347 it is down right LOW.......using the NASCAR numbers again, the longer stroke motors turn near 9K.


Your CFM #'s are also flawed.........you aren't taking into account that not only will bigger cubes (especially when done with a longer stroke) allow you to use bigger cam numbers but you also can utilize bigger ports/valves while still keeping the velocity higher.

While I will disagree on the Max RPM's of these engines which I feel is more limited to valve spring technology than piston speed..........the smaller archetecture of the 302 is known to have a SAFE limit of 500-550 HP (yes, I know higher #'s are always out there) the 351 is a much beefier block and when using a 2.75" main is waaaay superiour to a 302. With 3" mains it just a little mo' better.


Check out the winning motor last year in thesmall block Hot Rod(?) engine masters challenge.

Any guesses to what it was???

 

Those 9K Nascar motors are not stroker engines, with the typical short rod ratios of stroker engines, but long rod engines. The Ford engines used in Nascar are based on the 351C, but have longer rod ratios than a 351C. The numbers are not "manipulated", nor are "flawed".

 

No they're not. NASCAR motors use blocks more related to the Windsor block (Windsor oil passages and Windsor front) with the C's smaller mains and the Yates (cleveland style heads)

Dude, you're back pedaling.........you've said the 302 would also outgun the Chevy 350 and 351W(read your posts on page 1) which all have very similar archetecture (4" bore X 3.48/3.5" stroke) Don't get me wrong, Rod ratio and length are important but you are mistaken if you think they can make up 50 cubes......stroker or not, Chevy or not.

BTW, a 347 stroker has a nearly 1.6 RR........not that far off the 1.7 of a stock 302. And as you mentioned the 331 gets even closer.

Check the mags if you wish.......the R block (formerly A302) are almost all strokers to run 9's.......the 351 based motors are in the 8's and 7's (402's/408/427's) and they are now running 800 cube monsters to get into the 6's!!!(I don't know the Rod ratios on these 800 cube monsters but I assure you they are less than the 1.7 optimum )

Listening to you 2, nobody with a lick of sense would build a race motor over 302 cubes...

 

Very few grass roots level 350 Chevy's will survive rpm's above 6K for very long. 5.5K is the more realistic safe limit. You your self have pointed out the problem of the 351w bearing area. You have also pointed out in other threads the plain truth that higher rod ratios are preferred for both power production and durabilty. Rod ratios that result in the rod angle at 90* crank rotation exceeding 17* are simply unacceptable in a high rpm, high performance motor. This would indicate a minimum RR of 1.68. The typical 347 will have a rod angle of 19*. As bad as a 454. Almost 1.60RR is actually a long way away from a ratio of 1.70 when you consider the durabilty implications above 6k. The hundreths matter. The RR of the typical 347 is LESS than 1.6, not 1.6.

The context established in the thread was street engines and grass roots racing motors. That would be guys going to the track on saturday nights, or guys taking their mustangs to a SCCA auto cross and so forth. By bringing in Nascar engines it creates a manipulation of context, and sets up an apples-oranges comparison. It's also a stretch to assume that the typical stroker kit will turn your old mill into something akin to a nascar race motor.

 

I agree with EVERYTHING THAT YOU HAVE SAID...........except for 1 minor detail;

That 45-50 cubic inches will make up for any advantage that RR may have....that is all.

NASCAR was only brought in to say that using your guys' statements, that a 302 based motor (full out race of course) would out perform a 351 based motor.

I'm glad you brough up the BBC.........terrible RR IN THEORY but you cannot argue the success of that motor in almost EVERY form of endurance racing....from off shore boats to monster trucks to 8K drag motors.


When all things are matched; taking into account dwell at TDC for cam lobe ramps, port velocity to the amount of cubes, exhaust etc...........RR is a factor but not the end all to end all.


I've enjoyed this but it is getting counter productive.

An engine building challenge seems to be in order.........I'll let you pick my weapon among the strokers....331-347 or pick a Windsor non-stroker......You must stay with the 302...........what do you think??

 

I picked out one of my old Mustang and Fast Ford magazines at random. Out of every article in the magazine on drag races, a 302 based engine won nearly every race. One race was a 302 cubic inch (the quickest 302 on the planet) against a 812 cubic inch "monster motor". The twin turbo 302 won, with a 6.62 compared to a 6.93 ET. The other car that made it to the finals at the Fun Ford event also had a 5.0 based engine. All others that won, were either 302, 306, 331 or 347 cube engines. The race was called the Fun Ford Challange in Cordova, Illinois. The only class that a 5.0 engine didn't win, was the Street Bandit class. That class was won by a 360 cubic inch small block, and he beat a 396 SBF stroker. This tells me, that size is not everything that matters. The class race when the 5.0 beat the 812, was the Pro class. Money is no object in this class, so it wasn't a case of the person with the most cash wins. There were no mechanical failures or driver errors. The 302 just flat-out beat the 812, even though it gave up 510 cubic inches. In the True Street race, there were 25 cars entered. All were small block Fords. The quickest 351 based engine placed 8th, using nitrous oxide. It barely beat a naturally aspirated 306 (302 bored .030."over) Hmmmm. I wonder what the anti 302 people are going to say now?

 

Study and learn http://www.worldfordchallenge.com/rules_renegade.html



especially in the "street classes where the 310" motors get a 150 pound weight advantage.

Check out the weight advantage of the 302 compared to the monster motors. 700#?


Why would the 302 need a weight break????

 

The twin turbo 302 does not get a weight break over a naturally aspirated monster motor.

 

Whoa, wait a minute- the 302 "has quietly supersceded the SBC as the world's most popular hot rod motor...." Listen, the 302, and all the rest of the Windsors are great engines, but I have to say beyond a doubt, that Chevy small block outnumbers everything 10 to 1 wherever I go. You can't beat what's available in the aftermarket for them. And still quite a bit cheaper than what a Ford costs to build (even though the Windsors are the least expensive Fords to build). I am not saying a Windsor can't be built to keep up with a SBC. Look at how many Deuce Coupes, Fat Fenders, and 50's era Ford pickups are running around with SBC's in them. Oh, and BTW- that P-51D Mustang was a General Motors product- they owned North American Aviation back in WWII.

 

Dude, you bust me up..........twin turbo vs NA..........

 

Okay I'l just concede that bigger is always better no matter what.