I'm contemplating doing a little upgrading of the engine in my 73 Nova, because 'Merica, and could use some opinions from more experienced folks. The car is not a daily driver, street use only. No plans for anything at the track. I just want a fun car to drive in good weather. Currently, the suspension of the car is stock with long term plans to change it. The rear end is 2.73 geared, but I'm open to changing that and am considering a 4 link rear end. The next set of tires will be summer performance instead of the old all seasons that are on there now, and I'll go as wide as I can as I already have zero difficulty breaking the tires loose.
The current engine is a GM ZZ4 turnkey kit with the Holley 4160 750cfm carb. It is all factory ZZ4 with no significant changes, dual plane mid-rise intake manifold included.
The published specs on the factory heads (GM pn 12556463): Combustion chamber: 58 cc Intake runner: 163 cc Int Valve diameter: 1.94 Exh valve diameter: 1.5 Rocker arms are 1.5:1, D shaped exhaust port, and angled plugs. Thats about all I can find on the specs for those heads.
The factory cam is as follows (GM pn 10185071) Intake lift: 0.474 exhaust lift: 0.510 Intake duration: 275 Exhaust duration: 280 Int duration @ .050: 208 Exh duration @ .05: 221 Int centerline: 108 ATDC Exh centerline: 116 BTDC Lobe centerline: 112 Operating range: 3500-6500
A coworker offered me a set of heads that he pulled from a 73 chevy pick up that he built up years ago. He wants about $450 for the heads. Here are the specs:
Dart 127322 Combustion chamber: 64 cc Intake runner: 200 cc Exhaust runner: 75 cc Intake flow @ .5 264 cfm Exhaust flow @ .6: 180 cfm Int Valve Diameter: 2.02 Exh valve diameter: 1.6
Square exhausts port, straight plugs.
From what I've read, if I really wanted to take advantage of the new, better breathing heads I'd have to change out the cam to something a bit bigger. The ZZ4 factory cam is apparently pretty mild. I contacted COMP and they suggested the following cam for use in a ZZ4 street car with the DART heads ($300 new):
He says his cam is more geared for a truck than a car and that I'd probably be slightly happier with the one suggested by COMP. I can be a cheap-skate at times, but I'd probably spend the extra 150 and go with new if all agree it is a better choice.
Can I get some opinions on the heads as a potential upgrade and which cam would be preferable?This message has been edited. Last edited by: thumperfbc, October 05, 2019 12:15 PM
October 05, 2019, 10:30 AM
VictimNoMore
In all honesty, if it were my setup, I'd look at changing the rear end gears (3.55 or 3.73) and maybe up the stall speed on the torque converter (if it's an automatic) first, before getting into the cam/head combo. The ZZ4 is a great crate engine, as-is. You'd be surprised at what a good set of gears and a torque converter can do, in terms of driving fun/acceleration/etc.
October 05, 2019, 10:30 AM
SigJacket
2.73 is what I have in the 57. Good cruising ratio.
Do a TBI kit, tweak the exhaust note to suit, and do the Power Tour.
-- I always prefer reality when I can figure out what it is.
The 202 heads flow really well. If it were mine, I'd get the set of 202 heads and change the cam - and then see if you *really* want to get into the rear end. I've personally ruined too many nice cars by putting too low (numerically high) rear end gears.
I can't say enough good things about the 202/Dart heads; great choice.There's lots of room to work in the engine bay, an easy weekend swap. Headers at the same time since the heads are coming off?
October 05, 2019, 12:12 PM
thumperfbc
quote:
Originally posted by VictimNoMore: In all honesty, if it were my setup, I'd look at changing the rear end gears (3.55 or 3.73) and maybe up the stall speed on the torque converter (if it's an automatic) first, before getting into the cam/head combo. The ZZ4 is a great crate engine, as-is. You'd be surprised at what a good set of gears and a torque converter can do, in terms of driving fun/acceleration/etc.
Rear end is at the top of the "long term" list, but I'm holding off to do a new modern suspension back there and wrap it up as a single project. I haven't done a ton of research yet, but initial looking points to a 4-link system. I'd just do the ratio at the same time... either with a swap out or if I really want to get crazy and convert to a Ford 9".
quote:
Originally posted by aileron: The 202 heads flow really well. If it were mine, I'd get the set of 202 heads and change the cam - and then see if you *really* want to get into the rear end. I've personally ruined too many nice cars by putting too low (numerically high) rear end gears.
I can't say enough good things about the 202/Dart heads; great choice.There's lots of room to work in the engine bay, an easy weekend swap. Headers at the same time since the heads are coming off?
It's already got headers... hopefully they work with the new heads if I snag them up. The GM heads are D port, angled plug. The Dart's are square port, straight plug.
It took me a minute to figure out (maybe) what you meant by "202 heads". It is a reference to the intake valve size, correct?
Both links are the same... I went looking for Blueprint crate engines, but there are a bunch.
quote:
Originally posted by Excam_Man:
quote:
Originally posted by thumperfbc:
It took me a minute to figure out (maybe) what you meant by "202 heads". It is a reference to the intake valve size, correct?
That would be a yes.
Thanks.
October 05, 2019, 01:22 PM
Excam_Man
quote:
Originally posted by thumperfbc:
Both links are the same... I went looking for Blueprint crate engines, but there are a bunch.
Yeah, I caught it before you posted, but obviously not BEFORE you hit the reply button.
It is fixed. Most if not all of the Blueprint SBC engines have the same specs for the cam.
BTW, Comp Cams has a cam called Thumpr cam... seems appropriate.
October 05, 2019, 01:32 PM
Russ59
Can you buy a new ring and pinion that could be transferred to your future rear end set up?
I have a 3.70 with the old Borg Warner overdrive in my 59 with the 2- barrel 283. Final drive is closer to 2.7(?). I’m sure there are online calculators that would give a suggested gear ratio.
Is your 2.73 stock to your car and transmission? Seems kind of odd or at least set up for Max fuel economy.
I’ve been on chevytalk.org for 20 years. Great resource for stock and hot rod options.
P229
October 05, 2019, 01:51 PM
thumperfbc
quote:
Originally posted by Excam_Man:
quote:
Originally posted by thumperfbc:
Both links are the same... I went looking for Blueprint crate engines, but there are a bunch.
Yeah, I caught it before you posted, but obviously not BEFORE you hit the reply button.
It is fixed. Most if not all of the Blueprint SBC engines have the same specs for the cam.
BTW, Comp Cams has a cam called Thumpr cam... seems appropriate.
I waited a few minutes before posting seeing if you would update... guess I should have waited 1 more!
The specs you linked to seem significantly different than the one COMP recommended I use. I guess "bigger"?
It is kind of rough when everybody used relative terms like "big" and "mild" when you don't have the background context due to ignorance! lol
quote:
Originally posted by Russ59: Can you buy a new ring and pinion that could be transferred to your future rear end set up?
I have a 3.70 with the old Borg Warner overdrive in my 59 with the 2- barrel 283. Final drive is closer to 2.7(?). I’m sure there are online calculators that would give a suggested gear ratio.
Is your 2.73 stock to your car and transmission? Seems kind of odd or at least set up for Max fuel economy.
I’ve been on chevytalk.org for 20 years. Great resource for stock and hot rod options.
To the best of my knowledge the rearend is stock, as is the TH350 transmission, to the vehicle. The transmission was rebuilt years ago and they put in some sort of shift kit, but I couldn't tell you anymore about that.
October 05, 2019, 02:03 PM
greco
I agee with the guys that a gear ratio change would make a considerable difference. A 310 or 356 would be a good compromise. I have built a lot of muscle cars over the years. Some friends wanted 4.56 and 5.56 ratios which were not good for the street. Imagine a GTO going down the hiway going 70 mph at 4500 rpm. All the other suggestions are good too. Heads and cam, yes. EFI system, good. Different intake manifold is nice. Then the brake up grade and suspension redo. It never ends. It’s only money.
Never be more than one step away from your sword-Old Greek Wisdom
October 05, 2019, 02:42 PM
FN in MT
I'd go 3:55 if not even 3:73 or 3:91.
I ran 4:56's in a big block Chevelle for a few years. GREAT in town, but hell on the highway. And those were the 55MPH days!
October 05, 2019, 03:45 PM
.38supersig
If you change the heads and need new headers, consider some that have mounts for an O2 sensor in case you decide to shop for a dry intake and MPFI later.
How are the brakes? If the four link is in the works, it would be a good time to shop for rear disc brakes and not buy some of the parts twice. If you don't have disc brakes in the front, I'd shop those first.
quote:
Originally posted by thumperfbc: if I really want to get crazy and convert to a Ford 9".
The PI Crown Vic will have the 9" you want and the disc brakes too.
October 05, 2019, 04:49 PM
thumperfbc
quote:
Originally posted by .38supersig: If you change the heads and need new headers, consider some that have mounts for an O2 sensor in case you decide to shop for a dry intake and MPFI later.
How are the brakes? If the four link is in the works, it would be a good time to shop for rear disc brakes and not buy some of the parts twice. If you don't have disc brakes in the front, I'd shop those first.
quote:
Originally posted by thumperfbc: if I really want to get crazy and convert to a Ford 9".
The PI Crown Vic will have the 9" you want and the disc brakes too.
It's got disc up front now. Hoping to not have to change the headers... I think it should work.
The rear 4-link might be in the next 2 years, maybe 3 if it grows to include the brakes and a swap out to a Ford rear end.
Longer term is the front suspension/steering. It seems you can buy an entire quasi-assembled front subframe assembly with modern suspension and steering that is *supposed* to slide in and bolt up relatively easily. That'd be awesome, but is significantly expensive. That might be a retirement project after relocation.
Gonna have to look into the swap from a PI to the Nova... Hadn't considered that. Probably much cheaper than buying a kit.
October 05, 2019, 05:35 PM
Oz_Shadow
Note you may need a special set of gears or a 3 series carrier. I went with something about 230 duration at 0.050 in a 350 years ago and thought it was very streetable with a mild stall converter, 10.5 to 1 compression, 4.10 gears
October 05, 2019, 07:22 PM
64dodge
GM claims 355 HP and 404 lbs./ft. for a ZZ4. What power level are you looking for?
October 05, 2019, 08:09 PM
thumperfbc
quote:
Originally posted by 64dodge: GM claims 355 HP and 404 lbs./ft. for a ZZ4. What power level are you looking for?
Whatever these heads and an appropriate cam bump it to. It’s fun to drive as it is but if I can upgrade the heads for $400 and have a fun project over the winter, why not?
October 06, 2019, 08:38 PM
64dodge
quote:
Originally posted by thumperfbc:
quote:
Originally posted by 64dodge: GM claims 355 HP and 404 lbs./ft. for a ZZ4. What power level are you looking for?
Whatever these heads and an appropriate cam bump it to. It’s fun to drive as it is but if I can upgrade the heads for $400 and have a fun project over the winter, why not?
I asked because you'd be making a couple of trade-offs with the new heads. Yes, the Dart heads will flow more but with the bigger chambers, you'll be giving up almost one full ratio of compression. The cam you said was recommended is pretty similar to what you already have. A cam with more lift and a longer duration would probably provide a bigger gain, provided your piston-to-valve clearance doesn't get out of control. Your 750 CFM carb has the potential to support 500+ HP but you make no mention of the intake manifold. If that part isn't up to the task, you could easily see little gain with the new heads and cam.
The previous advice about new rear gears and a converter upgrade is sound and would probably be your biggest bang for the buck.
You also stated you're considering a 4-link setup. If you're looking for the Pro Street look, that's one thing. It certainly isn't necessary for a street cruiser. There are lots of crazy fast cars out there with leaf spring suspensions and components from Calvert Racing.
