I’ve designed quite a few small high-revving overhead cam inline four and straight six engines, but these are my first attempt at designing low-revving pushrod V-8 engines. The standard engines are intended as more budget and economy minded engines, while the S engines are the more high performance models that use super leaded and feature four barrel carburetors. How do these four fare as muscle car style engines? Is it unusual or problematic they all produce far more torque than horsepower?
They feel right on the money for mid 50’s OHV engines. And yes it’s normal to see such high torque numbers compared to the hp output. The hp/torque lines cross at 5252 rpm because power is calculated from your torque output at a given RPM
Any advice on how to improve torque and horsepower output with these engines and others featuring pushrod technology? These are close in performance to some historical pushrod V-8 engines, but I’m wondering if it might be possible to squeeze more horsepower and torque out of them. I’m also designing a 2.7 liter pushrod V-8, if the effects scale differently with size.
Also, when would be a good time to make the jump to overhead technology and multi-valve technology with these engines from a historical perspective? I’m leaning towards keeping them as pushrods, but I’m just wondering for that.
Now this is just my take, but for muscle cars I’d say the cam profile is too aggressive. Only engines like the 426 hemi had torque peak above 4000 rpms, it might cost some hp but try backing off the cam profile till torque peaks between 2000-3500 rpms, that’s a more accurate power band. Also remember that those old engines used gross hp ratings where as this game is in net, gross rating is around 20-30% higher than net.
The cam profile is 45 on the standard engines, and 60 on the performance engines. That’s low relative to every other engine I’ve designed, but I’ve mostly designed high revving small engines with aggressive cam profiles.
Any reason for the 1955 tech year? Muscle cars really didn’t hit their stride until the mid to late 60’s, using a later tech year would allow you to increase displacement and/or revs to give you the power you’re looking for without being unrealistic. I also have to agree about using a smaller cam, those peaky torque curves just aren’t right for these types of engines.
I’m looking for a larger engine for my company. My standard engines come in four different sizes by bore: 60 mm, 75 mm, 90 mm, and 105 mm. The 60 mm designs are direct acting overhead cam inline four and straight six designs for small vehicles. The background for them is that the company started in 1948 with a design for an advanced inline four motorcycle engine and grew from there. The 75 mm designs are direct acting overhead cam as well, but due to technological limitations they don’t enter production until the mid-1960s after years of development (they need the 1965 forged connecting rods to handle the RPM). That leaves a gap for more powerful engines to power larger vehicles, with an inline four being ruled out due to the impracticability of having such large engines of that configuration. However, large straight six engines are also ruled out for many applications at that size because they are too long.
Essentially, I need a large V-8 and/or straight six design, likely of a pushrod design. One reason is that the company will be having some headaches getting the larger direct acting overhead cam designs working for the 75 mm designs, and the other will be that pushrods are a conventional design for the period that have better reliability and perform well at lower RPMs. They’re also legal in more races.
1965 and 1970 are big years for my pre-1975 engines. 
With the engines having cam settings of 45 (performance) and 60 (sport/super fuel designs), what kind of cam setting do you think would fit? I have some rather aggressive cam ratios on my smaller engines, but they are somewhat niche given their size, role, and history.
With pushrods back then I’d make 45-50 your super sport and 30-35 as your sporty. Don’t listen to those present ranges listed on the cam, those don’treally work for pushrods pre 1980. That 7.2 should be pulling 300 torques from idle at least.
Changing the cam profile did drop horsepower somewhat, but torque went up, especially at the low end. I’ll have to see how they do in a car, especially compared to some of the very high-revving V-8 designs I’ve tried.
What would be some good quality settings for a limited production variant of a standard engine, like the famous semi-racing engines sold to the public for homologation purposes? I usually use a setting of zero.
With the right mix of cam (44) and ignition (55) I was able to get a nice little torque plateau. It’s not ultra powerful, but 200 hp is pretty decent for 1955, and the single four barrel keeps material costs low.
4.6L XP 16V OHVRev0.lua (33.6 KB)
I decided to tune with a lower cam profile to give more torque at lower RPM, so 45 is around the cam profile for my super/sport engine. I’ll see if I can incorporate some of this into that design.
What would be some appropriate quality settings and/or end prices for a limited production homologation type engine for a classic muscle car?
Also, when did the transition from pushrods to overhead cam technology start for American automobiles? Obviously it wasn’t in the muscle car era, but when would it be appropriate to consider making the change on production engines?
For the American V8, that would be a big, fat, never. . Look at the C7 Corvette, the new Mustang, the Challenger Hellcat. They are all OHV.
Actually, the Big Three have used SOHC and DOHC quite a bit, but I think it was mostly in the late-90s/early-00s era.
The mustang has been ohc since the end of the 5.0 fox body era (94-95), as have all ford gas engines since the 460 was phased out in 97.
I would put the change to ohc in 4-6 cylinder motors at the mid 80’s, when American and Japanese companies started joint projects. Dodge and Mitsubishi, Chevy and Toyota, Ford and Mazda. Each american company gained at least a few OHC engines, and by the late 80’s each had developed a in-house sohc or dohc 4 cylinder. Though for ford I think they borrowed more from their European branch.
As for v8’s I’d agree somewhere in the 90’s with the Cadillac northstar around 92, Ford modular in 96, and eventually Chrysler with the powertech in the early 2000’s. That said Chrysler still goes with the pushrod Hemi and GM stays with the iconic small block for all major power and truck applications.
Since your power is already peaking at 4k & below, you could probably increase the stroke more to gain low-end torque. Most 'murican V8’s of the 50’s and 60’s idled with enough inertia to liquefy small villages.
You have to take into account that comparing a muscle car engine from 1965 and one from 1955 is like comparing apples to oranges. Pre-mid 60’s V8 engines suffered due to the poorer quality of both the parts and the engineering, then again they would though, especially considering trying to make a 7+ liter V8 at that timewith the whole trial-and-error thing. Chevrolet didn’t come out with the gen I small block until 1955, and there was only one size, 265 CID (4.3 liters i believe). They kept the displacements small in the 50’s and early 60’s because larger engines couldn’t handle higher revving, and sometimes those larger engines would have such a low redline that the engine would be basically useless due to such a small RPM range. Seeing as how most V8’s in automation from the mid 50’s tech years seem to have a safe max of around 400 RPM, you aren’t given much to work with. I however believe that one should still try to get the torque and HP lines to cross in the upper end of the RPM range. All your power in most of these engines is in the top end, and while they have tons of power up there, they will be more susceptible to bogging down and stalling on takeoff. 400 torque sounds great, but if you are sitting at a red light about to race a buddy with a lower profile cam in his and he smokes you right of the line despite probably only having about 300-350 torque you’d probably be banging your hands on your steering wheel in anger.
Basically, when in doubt, build for low end torque.