GM fixed the water passages in the Gen VI block and made the Mark IV heads interchangeable with the Gen VI Block. Gen V block had the water passage incompatibility with Mark IV heads. Trust me...I'm running Mark IV heads on a Gen VI block, and water temp is constant 180

 

So,

I am hearing that Hooker 1 & 7/8" headers, true 2 &1/2" (i.d.) duals w/ X pipe and Super Turbo's with 2 &1/2" inlet & outlet is too small for a 502?

I respect everyone's opinion here.

However, isn't there some loss of torque when you go to a larger exhaust? Isn't some backpresure a good thing? At least this would be a lot better than stock manifolds, right?

As stated, this isn't going to be a 7000 rpm screamer.

Regards, Mark

 

I'd suggest option 6: RamJet 502. I believe fuel injection is the only way to go for all out performance...include an ignition timing control in it and a computer to tweak all the power out of it that you can!

 

In the GM book I have about Big Block Chevrolets, the factory recommendation for the 502 is a 3" exhaust system. I ignored the suggestion and installed Hooker 2 1/8" primary side mounts and Hooker side pipes with 2" glass pack inserts. On the first 2 baseline dyno runs, there was a drop of 95 Horsepower when using the 2" diameter inserts in the 4" sidepipes. The guy doing the dyno runs couldn't believe it, so he ran it again- same results. So there's some hard numbers for you. Believe what you want- but the key to the power of the BB Chevy is its breathability.

:yesnod: :chevy :chevy :yesnod:

 

I was gonna run a merlin 509 shortblock with these heads
pro topline 360s -- flow almost as good as AFRs but not quite as much http://www.protopline.com/12419000360.asp

and maybe the edelbrock dual quad setup -- hopefully will fit under the hood of my 73.

Havent run it through DD2000 yet but I figure it should be good for 600ish hp

 

Rock N Roll, that would be nice but won't fit my hood I don't think.

MassVette, Thanks for the info. I was talking about a conventional straight exhaust system. I've read/heard that sidepipes are inherently more restrictive.

That said, your 95 hp drop is substancial. Did the torque #'s also drop a similar amount? What was the previous exhaust set-up that you used as a "base" comparison (before the side pipes, or was it still side pipes but w/out the 2" inserts?).

If I was to use the 502 w/ the smallish exhaust I listed I suppose I would be in for a similar drop in power. Perhaps I could get away with a 454 w/ that exhaust set-up. Of course, another rebuild of the 427 is always an option too.

I only started looking at the GM 502 crate after the rebuild I got 2 years ago wiped a camshaft lobe (#6 exhaust to be specific). This was from a Crane H-272 flat tappet hydraulic.

After you add in all the "go-fast" goodies that are on the re-build wish (roller cam, alum heads, forged internals) list you get into the same price range as these crate motors (well ,not quite but pretty close).

A basic re-build is still cheaper of course and may be the right answer for my situation. At least I would pick up some power with a slightly bigger cam and the addition of the Hooker Headers. Perhaps 35 hp and 70 lbs ft torque?

Thanks again to everyone who responds as I need to hear the "real world" experiences you have had.

Gotta go to work now.

Regards, Mark

 

This is not MY experience, but I saw it with my own eyes:
Easter Saturday, my local track. A guy tows a mid-'70s Vette to the strip. It's a bone-stock ZZ502, headers & side-pipes, THM400 with an 'on-sale' converter, 3.90 gears & 28" M&H slicks.
He goes 12.03 @ 112 on his only run; he shells the rear on his 2nd launch! I helped the guy (a stranger) load his Vette; it idled very nicely, and the needle on his tach was set at 5300 RPM.
I detected no 'whiff' of race-gas coming out his pipes, and the car, while not 'cherry', wasn't cut-up or butchered in any way at all (amazing what 567 ft/lb of torque'll do for ya!).
With stock LS1s running mid-13s, and stock ZO6s running mid-12s, a ZZ502-equipped C3 would train-length either of these (and, arguably, LOOK BETTER doing it)!
Will it get 25+ MPG highway? Would it have the 'creature-comforts' of a C5?
Can it handle a winding road like it's current brethern? Does it cost $50,000?
NO!!!
Does it provide the basis (aluminum heads, 540" capacity) for future, high-horsepower (600+) applications? Can you build this type of power with 'off-the-shelf' parts, in your own garage? Will the 'WOW-potential' of it's sheer size (as John Force used to say) "scare the other guys"? Will it blow the doors off of stock, new Corvettes (and Z28s, T/As, Rustangs, and 'rice')?
Hell, yeah!!!
How's THAT for 'real world'?
:thumbs:

 

real world experience for ya....hooker sidemounts....in Cleveland is a metro park system, called The Valley, and as the name indicates, the park is deep in a valley, and to enter the park, one has to drive down long steep hills, and and to exit, one has to drive up the same steep hills. Ok so far? So, how steep is steep? Probably no less than a 30 degree grade. The speed limit is 30 mph in the valley, because it is a wild life preserve. For me to drive 30MPH, in 5th, I am cruising around 1000-1200 rpm.

It was time for me to exit, and I was following a line of cars, so, being too lazy to downshift, I just left it in 5th, and thought I will downshift when the vette starts to bog, well, I'm going up the hill, not missing a beat, and tach is at 1000. Half way up the hill, the light is still green, so I thought I better step on it, and I did, and the vette just took off, in 5th gear, accelerated like there was no tomorrow, did not skip a beat. Now, if there is a loss of torque using 2.125" tubes, you will never convince me, not in my lifetime.

My suggestion is for you to go on your gut insticts. It is your $$$$$$, your car, and remember, we live and die by the decisions that we make. As you said, you are not building a 7K screamer, and maybe a redline of 5,500-5,800 is more than enough. Me, I have the best of both worlds, I idle all day long at 800, pull 14" of vacuum, can scoot up 30 degree grades taching 1000 in 5th gear, water temp around 180, and have the kahunas to climb to 7K R's on demand....what more can a man want? Eh? Don't even say it....:D

 

What would you need to change modify to drop in a BB into a SB vette(1973)

 

If money is a concern, then the crate longblocks may be the way to go. Otherwise, the crate shortblock would be great and then add your own heads, intake, carb of your choice.

As 427 Hotrod (Jim) stated, I am very pleased with my mild-mannered combo, and it makes plenty of power. It's a 454 HO with the AFR 305 heads (cnc'd chambers), smallish 230/230 hyd. roller cam, Performer Air-Gap intake, 950 HP carb, and Hooker 2 1/8" sidemounts. It's characteristics sound a lot like GDaina's 533. Idles at 800rpm, pulls plenty of vacuum (haven't verified it, but I've owned cars that pull 10-11" at idle, and this one is way better than that... probably 14-15"+.), gobs of low-end and midrange, and pulls til I want to shift it. It's still making power at 6400rpm, but being a hyd. roller, that's as far as I'm pushing it...which is almost never anyway. 3.36 rear gears and a Richmond/Doug Nash 5-speed (no overdrive). This car is incredibly streetable. Granted it only gets ~10mpg, but that doesn't bother me in the least. 434rwhp/450rwtq... ~510hp at the flywheel, and this is with a "year 'round" tune. It is rich right now in this 95^F heat when I dyno'd it (12:1 A/F ratio). It will lean out in the fall/spring and be over 450 probably without touching it. IOW, its not even set to "kill" and it makes excellent power for the manners.

Only ~9.5:1 CR, so it runs fine on pump gas. I don't have a vac. advance distributor (I have an MSD Pro-Billet mechanical unit), so timing is only at 33^...probably a bit low for max full-throttle performance.

A 240+ duration cam would get me ~460rwhp probably with the tune set more precisely.

In a 502, this combo (with something like a 240-246^ duration cam ... I like hydraulic rollers...call me wimpy) I have would make ~475+rwhp easily and make all that power before 6k rpm. :) It would also idle great, and have good driveability and manners. More aggressive cam would yield more top-end power.

You can run a low-rise intake (I was running the LS6 intake when it was a stock 454 HO crate motor), but on my combo it would have cost me 20-30hp easily. The bigger the inches... maybe it doesn't matter as much, as in GDaina's case.

I know you don't want to worry about the exhaust lining up. My Hooker sidemounts were fine...the main thing was having to dimple them a bit to gain spark plug access. Didn't bother me. The performance of the AFRs is worth it. But, all these cars are different, and maybe they would cause a problem with other cars????

Your desires are close to what I wanted out of mine, so hopefully some of this helped. The car does NOT need EFI to be streetable, or to drive it around a metropolitan area (I'm in N. Dallas). It also does not need an overdrive. Those things would be gravy, and really nice, though. Your 4-speed will cost you some bottom end torque multiplication if you stay with the 3.36s, but with my 5-speed I'm probably going to step down to 3.08s b/c my first gear is useless now. Getting them spinning in 1st, I can short shift into 2nd and then into 3rd and the tires just stay lit for a couple hundred feet. :)

I applaud the research you're doing. I did the same thing and these guys on this board were extremely helpful, and it paid off with a combo I am very pleased with. Good luck!


[Modified by WA 2 FST, 3:34 PM 8/30/2003]

 

Glen, GDaina and WA2,

Those were some excellent posts! I can't thank you enough.

I guess my limitations ($ for the project, hood, intake and exhaust) will dictate what I decide to do in the end.

It sounds like I picked out too small of a header. Although it might be the correct size for my exhaust pipe & muffler combo. Also, the exhaust was done by the previous owner (although I added a few touches) and it's in too good of shape to consider trashing at this point, not to mention the $.

The intake side of this deal would be the other limitation. So, perhaps the exhaust size limitation might be offset by the inefficiency of the intake, if you follow my logic. Less air in requires less exhaust volume (does this make a bit of sense?).

So, if I go the 502 route I could always upgrade these areas if I needed to in the future. If I found that the performance was what I was hoping for despite my limitations then I wouldn't have to do any changes. Going the 454 route as WA2 has done might be the best solution. I think I saw in Chevy Hi Perf. Magazine that GM was going to start offering the 454 as a shortblock like they do the 502. That would save some $ that then could be spent on heads.

Thanks again, I sincerely appreciate the help.

Regards, Mark

 

another option for you to consider.....buy a 502 bare block, and assemble the unit yourself. If you go that route, you have choices in strokes from 4" to 4.5", internal balanced, all identical in cost. Rod length from from 6.135 to 6.535, again all identical cost, and the beauty about the rods, these are h beam, stronger and lighter than GM's 7/16" I beam.

There are a number of sites offering complete kits, fr0m cast to forged, to build up 454, 502 blocks. Prices vary from 1,200.00 to 2,200.00.

Before you make up your mind on a crate motor, do some research on individual components. You can pick and choose to your hearts content, and end up with a cam, piston, crank combination that YOU want, not what someone thinks you should have. This is the route I took when I built my 533.

If you are not comfortable assembling a short block, ask a competent individual if they will assemble the shortblock....the charge should be around 200-250 for the work.

The downside to this, no guarantee, but then again, you are not going to be twisting the thing to 7K r's either.

Again, do some reasearch, make a spreadsheet so that you can see what each option costs you. Also, check ebay, and http://www.mortec.com for 454's and 502's, or internal components that may appear on their sites.

I know a complete 502 for sale, from intake to pan, fresh rebuild, but that is a Gen V, and has limitations to the cylinder head options, but is reasnobly priced. At least I think it still for sale.

 

:iagree: with GDaina,.....to an extent.
If you begin with a bone-stock ZZ502, you'll find out if you REALLY 'want', or 'need' more displacement in the future (seriously; how many of us have ever TRULY dealt with 567 ft/lb of torque under the skinny pedal?).
If, after a while, you decided you have enough hair on your back-side to 'handle' more power, you can 'poke' the 502-block to 4.500" bore, and stroke it another 1/4", resulting in a whopping 540"!!!!!
But, in the mean-time, $7500 puts the ZZ502 between your fenders, and you down the road, with no assemby hassles, AND a GM warranty stuffed in your pants!!!
Is THIS a great country, or what?????
:thumbs: :flag :chevy :flag :thumbs:

 

Well, I did a bit of research from some old books on hot rodding big block chevys and it would appear you all are correct about the exhaust set-up being too small in my application.

My apologies for questioning the experienced ones who replied.

So, unless I want to choke off the 502, I guess that may not be the way to go.

A 427 re-build or maybe the 454 HO (or some version of a 454) might make more sense for my set-up.

Thanks again for all the advice. I certainly needed it !!!

Regards, Mark


[Modified by marky mark, 11:34 AM 8/31/2003]

 

mm, isn't basing your engine & displacement on what EXHAUST you have a bit bass-ackwards? :confused:
Check with GM Performance Parts & see what kind of exhaust THEY used to get the 502/567 numbers. I think on the 'original' 502"/440HP version, they used some puny pipes; maybe the ZZ502 was dyno-tested with the same exhaust.
I'm guessing it'd be cheaper to re-do the exhaust NOW for the 502, than to re-do a 454 to 502-or bigger specs (AND the exhaust!!!) at a later-date.....
Just my $.02 worth.....
"There is NO replacement.......FOR displacement!!!"

 

Glen, that's a valid point. I don't have the budget really to do everything over including new headers & custom 3" exhaust, new 3" mufflers and stainless tips. And then add a new crate motor. Just can't do it. As it is now those pipes under my car are indeed 2&1/2" inside diameter and there isn't much room left. I would think 3" would be a very tight fit. Not sure it's worth the hassle or expense.

I expect trying out the 502 with my set-up would be a bit of a gamble.

Not sure I need all that anyway.

But, tomorrow I may change my mind!! Haa ...

Thanks, Mark