When I modified my z24 with a cam, balanced, intake port and polish, ITB fuel injection, flat top pistons and a 1 mm overbore, I was able to get 140 hp to the rear wheels... That came out to be a 10:1 motor. I'll have to look back and find my dyno sheet but I'm think torque was about 130 lb/ft max with a fairly wide torque band.
I've talked to people who have gotten far more out of the Z24, up over 300 hp, however its a lot of money spent to do so that could be better spent on another motor.
The Z24 was a pretty torquey motor even in stock form, that is for a 4 cylinder of it's day. It's torque was just about equal to the SD22 although at a higher rpm.
The KA24 had more potential on the top end due to the head breathing better. However I'm not convinced it was a better motor overall to the Z24. It had it's own issues. Although it had a lot more aftermarket support since the Z24 was never really supported for racing, not even from the factory.
Although there is a member here that ran a KA24 pretty successfully racing off road up in Canada, first with NOS then a turbo... So it all depends on how you do it, and how it's set up.
And then once you start making a lot more HP, you'll also start figuring out what the other weak links in the power train are which cost more money to address as well.
But a 4 barrel Holley is really overkill for anything other than a fully race prepped Z24. It flows a lot of CFM which can only be used on a 4 banger if running at extremely high rpms. Unless you spend a lot of money on a crank, pistons and rods you'll never get that high in rpm with a Z24. And, it won't be very streetable on the low rpm end and will be very hard to tune. A large 2 barrel is a better choice IMHO.
I think you'll be pleasantly surprised at what you get with the mods you are planning. I'd also suggest a Doug Thorley header, the tri-y design really helps extract torque on the Z24. They're hard to find and a bit pricey, but there are some knock offs around just be careful. And I'm not sure if DT is still making the header for the Z24 so you'd probably have to find a used one if you can, or have someone build one for you using their design... The Pacesetters I've never been impressed with at all. Only marginally better than a manifold IMHO, they rust out very quickly and have thin flanges which don't stay sealed to the head very well.
I talked with James via Facebook, he's the one who ran a Z24 first on NOS with some impressive results for offroad racing, but then he switched to a KA24 with NOS then a turbo setup. He had a lot of success racing that KA24et up against V6 and V8 powered machines. Part of that though is he was running it in a Sidekick which gave him really good power to weight and it was a VERY nimble vehicle.. His input was the KA was better simply because of parts availability which is true. I think the single row timing chain is a weak point myself but I don't recall him ever having any issues there. You may want to get Patrick's take on this, he's done a KA install in a 720 and I'm not sure he was happy with it overall and I think it eventually came back out. But he knows the ins and outs of shoehorning one into a 720 much better than I do.
I'm still looking for my dyno sheet to give you that torque numbers I got. It's been a while since I've dug all that out so I'm not exactly sure where it is at the moment.
33's will always be a power robber on these trucks/motors. I ran 31's for racing and with 5:13 gears they were great, but with 4:11 they are terrible... Then I shattered my 5:13 rears, so now I run basically a 29 to 30 inch tire with 4:11 and it's "OK" but mostly I have to run in low range to stay in the torque band. Most of my racing was short course and tight so I can get away with that. Hard to find gears anymore for the C200 or H190 without spending a fortune so you have to do what you can afford and 4:11's are common in the salvage yards.
I havent been able to find a good Doug thorley, I searched for a long long time. I have a pacesetter header and I actually like it. It may not be a Doug thorley, but I think it's way better than the stock manifold. Right now with 33's and my Weber 32/36 and my nismo cam. I don't think the truck isnt that much of a slouch at all. I went from 30's to 33's and didnt notice much difference with the cam Th carb is a knock kff Weber and starting to act up, so that's why I want a 38. I plan on doing the head work last so illI see how it all comes together.
A dyno sheet would be great for a Z24. I haven't seen anything for the Z series so it's a mystery. I'm curious because I've put a U67 L series head on my old Z24 block. It's been sitting on the lawn under a tree for the past 5 years and it ran so well I'd not want it to go to waste. I currently have a 710 Datsun with L20B which only has 65K original miles so I'd keep this but would love to try an L24B. The reason there is an L20B is because there was an L20 inline six first, so when a 2 liter L series 4 cylinder was made the L20 was already taken. Thus L20B. Well there is already an L24 inline six so I'm callingh this Z24 block with L series head an L24B.
With an L20B oil pan from a 710 and L20B engine brackets and manifolds this will fit the 710 and outwardly look like an L20B, but be 3/4" taller.
So I'm wondering also what the power would be for a Z24 with a much better breathing head on it. Compression is just over 9. An L20B is about 95 hp so scaling it up by 20% displacement should give almost 115. This does not include the compression increase.
The red line on stock parts is about 6,250 so it won't be a revver like the 1cm shorter stroke L20B but it should have massive torque. I don't know what a Z24 has for power or torque and a graph is way betyter than just the top numbers.
I picked up a cam years ago, a re-grind, with .480 lift. Also I have a home made Yamaha R-1 carb manifold that I will 'sort out' on the L20B first but eventually it will feed the L24.
On my mock up head...
I also included a windage tray and crank scraper and an extra baffle in the oil pan. High volume oil pump, studs for the head. The head and both manifolds I port matched and the combustion chambers I un-shrouded around the valves because it's going on an 89mm bore from an 86mm.
Cory, if you can find that dyno sheet.....
I am getting very close to it Mike... I've found some folders of my build info so I know it's there I just haven't had time to sort through it all. I'm fairly certain it's in a stack with my Megasquirt configuration settings... I need to dig this out anyway because I need to do some work on the racer soon.
I'm more into the earlier Datsuns and there is a severe lack of good dyno graphs of a stock engine like the L20B. Usually they are built up. Factory rats them at 110 hp which has top be gross HP. later engines are rated 93HP. This HP @ RPM says nothing about what it's doing at any other RPM and there is no Torque graph either. I did find a reference to a Z24 making 130 @ 2,800 but it might make over 120 all the way to 4K. Peak numbers are rather meaningless and doesn't really give the true measure of an engines capability.
My 620 grew to over 3,400 pounds and I eventually put a Z24 engine in it... had to, the L20B just wasn't cutting it. It ran and pulled very well and this engine was sitting and going to waste. I'm trying to guesstimate was a better breathing head on it would be like. I would guess it would pull at least as well as a stock Z24 so a graph would be nice. Thanks for going to this much trouble.