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Re: The real reason the DZ302 SBC revved so high...
Quote:
Originally Posted by Grim Reaper
jon, I agree with Fast emphatically. Now a 305 has some limitations just because of the very small bore which that limits head selection. And, building an engine to rev so high THAT WILL SURVIVE is another matter again (which you will see after you read this).
Your example would be simpler if it was an L98 (and pretend that you were dumping EFI and going with a carb)...yes the 350 would rev damn near the same as the DZ302 (though max TQ would be higher and peak HP would occur approx 500 rpm sooner). But, the L98s interals would probably not survive very long if you kept taking it to those rpms on a regular basis.
This is when you would want forged internals (crank, rods & pistons) that would be able to handle those high rpms on a regular basis. As well, you would probably be best to have a 4 bolt block instead of a 2 bolt block.
But, as Fast355 just said, with today's modern technology, I would go with a modern solid roller cam; something like a buddy of mine is using ... 248/256* @ .050 with .600" lift as well as modern heads say AFR 195s or maybe even AFR 210s. Lastly, a better intake say a Victor. And to compare all things equal use the 11:1 compression ratio, but on a real engine I would recommend dropping that at least a 1/2 point even with aluminum heads so it can survive on today's pump gas.
That engine will also rev like crazy and probably make around 485 TQ @ 5,000 and 550 HP @ 6,500 ...more than the DZ302 was ever claimed to make.
And if you stroked it to 383, that same combo would make roughly the same HP but 250-500 rpm sooner (which is a good thing in my books). However, TQ would increase over the entire TQ curve, especially the lower RPM range by around 30-35 lb/ft with peak TQ now around 515 lb/ft just before 5,000 rpm. You can see, even when just comparing a 350 to a 383, the HP still remains nearly the same but you get that extra TQ through out the lower rpms and end up with a better engine IMO for both the street & strip.
But you would definitely want good forged internals with a 4 bolt block to ensure it can handle the extreme forces when reving out and "keep it together". And this is where I would have problem trying to do this to a 305 as 305s are all two bolt. If you start getting into the machining costs to convert it to a splayed 4 bolt, the cost alone would make it simple economics to start with a good 350 4-bolt core instead (as well as the fact you cannot bolt on a set of AFR 210s).
You can build a 305 to survive, but it is going to cost you some. I have had good success with the late model GM Powdered Metal rods. I have turned several different engines with them to 6,500+ RPM and put MANY miles on the three. My G20 Vans 350 has them and already has 45K on it. It shifts 1-2 WOT @ 6,500 rpm. It has a factory forged crank, PM rods, and Hypereutetic pistons in it. It is also 4 bolt main.
GM DID make some 4-bolt main 305 blocks. I personally have TWO of them. I would however, in a higher budget build, start with a 2-bolt main block and splay the main caps. You can get away with 6,000 rpm useage with 2bolt mains, good ARP main studs, and a good align bore.
Re: The real reason the DZ302 SBC revved so high...
Quote:
Originally Posted by Fast355
You can build a 305 to survive, but it is going to cost you some. I have had good success with the late model GM Powdered Metal rods. I have turned several different engines with them to 6,500+ RPM and put MANY miles on the three. My G20 Vans 350 has them and already has 45K on it. It shifts 1-2 WOT @ 6,500 rpm. It has a factory forged crank, PM rods, and Hypereutetic pistons in it. It is also 4 bolt main.
GM DID make some 4-bolt main 305 blocks. I personally have TWO of them. I would however, in a higher budget build, start with a 2-bolt main block and splay the main caps. You can get away with 6,000 rpm useage with 2bolt mains, good ARP main studs, and a good align bore.
That was my point too on the 305 as well, that it will cost and you are back at an 'economic' situation. I forgot that the 305 did come in trucks & vans and that is probably where the 4 bolter came from (you learn something every day).
But I was more thinking of the 3rd Genner building his own 305 (which are all two bolt), and with the proliferation of cheap 350 4-bolt blocks (I wouldn't use an stock L98 block either), it makes more economic sense to go with a 350 4-bolt block, especially when it can handle much bigger heads.
As for splaying, I personally wouldn't waste my time with these blocks (LB9 or L98) as well. They are not the best castings. And at these power levels, I want a better casting (there the DZ302 wins).
I am NOT saying "don't build a 305" and refuse to get into that debate (it's been beaten to death and just results in a locking the post). I am saying at THESE power levels which require heads similar to AFR 210 range (and AFR 210s won't work on a 305 without serious machining...and again gets back to simple economics).
And, as I explained in my previous point, I would probably go with a stroker 383 over a 350, as it costs basically the same since you will be changing all the interals anyway. You lose little or nothing in HP but gain in 30-35 TQ all over the lower & mid-range - and that will result in a better motor for both the street & strip (provided you build it right).
Last edited by Grim Reaper; 09-14-2007 at 01:23 AM.
Re: The real reason the DZ302 SBC revved so high...
ok first off i have to say i'm a HUGE fan of the dz 302. Now i'm only 24 but my step dad has an all original 68 Z28. dz 302, muncie, 4.10 12 bolt. the works. His car has no power steering, no ac, no options what so ever. Not even a center consol. Now i have dyno sheets of this and can prove it. Friend of mine has a dyno. We dyno'd this car just to see what it would have. No lie this car made 394 HP at the rear wheels. And thats without thrashing on it. (my dad would kill me if i did) So with respecting the car (and my dad lol) i think that is very impressive for a 53k mile car and not making it scream to its potential. If i'm correct we let off around 6500 rpms. torque was lower as you all would know. These aren't torque monsters. I have built my own clone 302 (283, 327 cranks yada yada yada). Pink rods, have the double hump heads (2.02 valves) you all know what i'm saying. But i also did a little decking to the block, roller cam, rockers, lifters and such. Fully balanced. I had it in a 67 shortbed c10 and my shifter was shot. Missed third gear at the track, revved over 9k by accident. still ran a 12.2 in the quarter. Havent ran it on a dyno yet. Going to put it in my 77 z28 4 spd. If i dont find me a nice 3rd gen first.
Re: The real reason the DZ302 SBC revved so high...
Quote:
Originally Posted by Grim Reaper
...the lack of torque in the 302 was not a problem. Have you ever noticed that the "quick" Mustang 302s are usually 5-speed sticks?
First, if the Ford 5.0 lacked torque, it was only below 1000, maybe 1500 rpm. Having driven both T5 and AOD 5.0s in the late '80s, I can attest to their mid-range torque. They had small valves, and smaller intake ports, plus their runner lengths are about the same as our TPI.
Most of the T5's relative quickness came from how bad the AOD really was, in stock form. The T5 was about a full second quicker just in the first 60 feet, I kid you not!
The AOD torque converter was half to blame, but the AOD's lame 2.40:1 first gear was nothing close to our 3.06:1. And most of the 5.0 / AOD 'stangs had 2.73:1 axles, not the optional 3.27:1 like I drove.
On the other hand, most of the T5 five-ohs had the optional 3.08:1 axle, not the standard 2.73:1 like I drove.
Gearing makes a definite difference. They used a 3.35:1 first, while ours had 2.95:1 first gears.
