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).

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.

Originally Posted by Grim Reaper

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).

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?

Originally Posted by camaroz86

this car made 394 HP at the rear wheels

Originally Posted by Grim Reaper

But, in reality, based on what you are describing, you really want the opposite. Assuming a cam with the same duration; the 302 with it's higher bore/stroke ratio, it is better off with a narrower LSA (110 or less) as it is naturally short on torque but high on HP. A narrow LSA will promote the much needed mid-range torque (while sacrificing a little top-end).

Conversely, a 305 with it's lower bore/stroke ratio that is more torque oriented, it benefits from a wider LSA (assuming all the remaining cam specs are the same) as it does not need to promote it's mid-range torque but could use a little help on the top-end HP.

Of course, we haven't even got into the cam lobe profile and retarding/advancing the cam. Which can greatly affect the torque/power characteristics of the cam.

But you are right, there is an interplay in all of this that most people don't bother looking at to see if they have a "good match". The "30-30" cam in the DZ302 was perfect for what it was really designed for: racing.

Frankly, even on a bigger engine like a 383, I feel the "30-30" cam would be completely wrong for a car whose primary use is for the street - even though it would be better on the street than the original DZ302 was. (But it sure would rev - and that is more what I am trying to convey to some of the younger members who believe that the secret to the DZ302 was it's bore/stroke ratio - when it was the cam).

Originally Posted by Grim Reaper

Many times, the younger members of TGO listen to their dads (and grandpas) talk about the famous DZ302 (the original Z/28) engine and how it would rev beyond 7,000 rpm. Most attribute it to the short stroke. But, in reality, it was the camshaft that was the real reason.

I say this because I have helped build and tune a number of engines for various friends over the years (and yes, I actually could drive when the DZ302 was out and actually test drove one). I can tell you that the stroke is not the "magic secret" but the camshaft.

The camshaft was a solid flat-tappet cam with 254/254 duration @ .050 with .485/.458 lift. For those guys who know cams, they know that duration is huge, even on a 383. That is also the reason that car had absolutely no bottom end torque (and why I did not buy the car either).

That cam was designed exactly what GM primarily intended the Z/28 - RACING! GM only sold the Z/28 because it was a requirement to meet the Trans/Am rules.

For those people that doubt me, I suggest that instead of trying to 'destroke' their 350. Instead, install that cam (Crane makes a blueprinted copy which Summit sells P/N CRN-967251) in your 350 instead. It would be best if you could also get a copy of the heads, but with so many great aftermarket heads today, you can easily find a better head that will flow more.

Trust me, that same cam with the better heads we have today will rev just the same as the original Z/28 and though you may not have the same compression ratio (again a good thing as we don't have gas with enough octane to support the original Z/28's 11:1 compression ratio), you will have not only an engine that will make darn near the same power and rev the same BUT you will have something the original DZ302 never had - TORQUE!

But when this cam is installed in a 350 (with decent flowing heads) you can have everything that was great about the DZ302 without it's one weakness (lack of torque). You can now have your cake and eat it.

The stroke was never the secret to the DZ302's ability to rev, it was the cam. But most of us old-timers knew this.

Originally Posted by F-BIRD'88

If you are willing to run the high ratio rear gears 4.56:1 ish you can build a 10:1 - 10.5:1 cr 305 with a .500"-.530" 245-254° @.050 108/110LSA solid cam and 1.94 x 1.50 valve ported heads, headers 750 carb and high rise intake that will rev up just like a 68 302 Z/28 make more power and run like hell.
It will do everything a old DZ302 ever did.
You want to strip down any unnesessary weight from your 3rd gen just as was done on street strip 67-69 Camaros. The T5 manual 5speed will work great.
A Auto trans will want a very high stall 8" -9" race converter 5000 stall target. But it will drive well also.
A th350 will work better overall than a 700R4

Easy 12's just like the street strip 302 Z/28's ran.
You can have a modern 305cid version of this high reving lil solid lifter 302sbc that does exactly what the old guys brag about but run on 92 premium unleaded.

The key on the smaller bore 305 cid version is when choosing and prepping your cylinder heads go with a 1.94" valve VS the 2.02" valve. Once the head is ported and prepped correctly there is no disadvantage at this build level.