BTW . . . what brought this about? Are you going to be new car shopping? Or are you trying to win some kind of bet with a beer drinking buddy?
I was reading an article about ways to increase the HP in a Chevy ZZ-5 engine. It’s configured stock as a V8 w/670 cfm Holly carb, HEI distributor, mild-profile roller-cam/roller lifters, and dual plane intake. Of the things they tried — single plane intake, various different carbs, different ignition systems, different cam profiles, & roller rockers – it seemed like roller-rockers brought the most bang for the buck. So then I got to thinking that this rocker business seem like yesterday’s news. Why use rockers in modern engines at all? If the engine designers went with overhead cams and no rockers, I got to wondering if that would have solved most of what was limiting the power to begin with. But from the interesting discussion above, maybe it isn’t as simple as all that, since even overhead cam designs still use rockers sometimes.
Being just a driveway diyer, when I read these articles about high performance engines there’s often stuff I simply don’t understand what they are talking about. But I still find it interesting to try to figure out. For example, for the life of me I don’t see how the camshaft can just be slid in from the front like that, by hand. It seems like for it to fit in so easily, the bearings would have way too much play. Then I got to wondering if the camshaft bearings, for it to fit like that, maybe it had different bearing diameters front to back, with the smaller diameter ones in the back so they’d more easily poke through the ones in the front. And since it seems like the camshaft bearings must be hollow cylinders, sort of donut shaped, how do they get the bearings inside that camshaft hole in the block and located in the right place?
For example, for the life of me I don't see how the camshaft can just be slid in from the front like that, by hand. It seems like for it to fit in so easily, the bearings would have way too much play.
If you look closely at some good photos of camshafts for pushrod V-8 engines, I believe you will see that the edges of the journals that ride in the bearings are beveled slightly to provide a lead-in to center the journal in the bearing shell. If they were left with a sharp razor edge, you would shave babbit metal left and right while trying to insert the cam.
George, all you have to do is go to youtube and search “sbc cam bearing installation”. Plenty of videos showing you how they’re done. All bearings are the same, it’s a snug fit, but precision machining will let it slip right in.
Just curious, what kind of camshaft bearings are used in V8 pushrod engines? Bushing/sleeve one-part type? Or does it use a two-part bearing, where the inside part moves with respect to the outside part, and there’s either ball bearings or needle bearings in between?
I Installed my own camshaft in the Olds engine in my ragtop. The cam bearings fit quite snugly, thank you. I threaded in an extra long bolt to the front of it to give me a “handle.” Applied plenty of assembly lube, and slowly snaked it in.
All Top Fuel and Funnycars are using engines based on Mopar 426 Hemi architecture, even the ones that say Ford or Chevy. I guess that is even more fake than Nascar. Nascars cars are identicle but the engines are sitll designed by the various makes, even though the engines don’t have much to do with the their cars on the street .
I don’t think there is a single Mopar component in a top fuel car engine, not even the block. The same goes for Nitro-Harley drag bikes and Harley Davidson parts.
what kind of camshaft bearings are used in V8 pushrod engines</b
Sleeve bearings very similar to connecting rod bearings, except one-piece. NASCAR engines use needle bearings for the cam to reduce friction.
NASCAR engines from all 3 manufacturers are designed by Toyota, Ford and Chevy to a strict rulebook that limits a lot of the design. The parts, heads, blocks, intakes and sometimes crankshaft blanks and camshaft blanks are made available to the race teams to build however they see fit within those rules with those base parts. The teams are the engine builders with help from the manufacturer.
All run the same throttle body fuel injection with limits on intake air passages to further limit horsepower.
None of these companies sells compete engines they developed in passenger cars or trucks.
Installing camshaft bearings requires a special tool and some close attention to details such as ligning up the oil feed holes. Some engine’s cam bearings are all the same diameter while others use bearings that are progressively larger from rear to front which makes installing the camshaft somewhat easier.
Good info there @“Rod Knox” & all. Thanks. If I were given the job to offer an opinion on the design a camshaft bearing arrangement for overhead valve v8’s, I’d never have thought to do it that way. It seems problematic, prone to failure, and nearly impossible to maintain, putting it inside a long inaccessible hole only open at the ends, & to have enough room between the bearings & journals to be able to just push it in like that. Seems like it would be spun-bearing city. But it seems to work great. I’ve never heard any complaints about overhead valve camshaft bearings going wobbly. Or it getting stuck in the hole. hmmm … maybe that’s why nobody ever asked me for my opinion … lol … Anyway, thanks all for the interesting and informative comments.
Where in the heck have I been ?Didnt think I was locked up that long ,they use fuel injection in NASCAR now ?The last I remember was 4bbl carbs,with some as small as 390 cfm(when are they going to use airbags and VSA ?)
I understand the space efficiency of a cam in block arrangement, but why aren’t we replacing pushrods with engine oil？ FCA has been using that for 5 years already and has been combining variable valve timing and valve lift in such design. Such cam activation also allows multiple valves per cylinder and pent roof design
BLE - That is why I said 426 Hemi ARCHITECTURE. They started using 426 Hemis but added more aftermarket parts including big inch blocks that there are no original parts as you said. That doesn’t change ther design. They are clearly not based on Big Block Chevys or Fords.
I liked the good old days of stock car racing when the handling of a was even more important than the type of engine. Hudson Hornets had a flathead 6 engine, but the Hudson had much better handling than other cars of the time and won many races. Also, there was a driver whose name I can’t recall, that won some races wifh a 1950 Plymouth coupe. That Plymouth was lighter than the other cars and didn’t have to stop as often for tires. Plymouth had a short wheelbase line back then that consisted of a single seat business coupe, a fastback coupe and an all metal 2 door station wagon called the Suburban. The senior Plymouths were on a longer wheelbase. It was the Plymouth business coupe with its flathead engine that won a couple of races.
@Mustangman Sprint Cup cars use port fuel injection, one injector per cylinder. It does visibly look like a throttle body setup though. NASCAR mandates a top mounted throttle body so the teams wouldn’t have worry about changing the air filter housing or type and it makes fitting restrictor plates more or less the same as it was when carbs were used.
I recall Juan Pablo Montoya saying that NASCAR cars were difficult to get used to after driving F-1. The NASCAR handling was a lot less sure than F-1 cars. He marveled at how the successful drivers could go so fast with poor handling compared to F-1.
jtsanders: Exactly. F1 or Indy car compared to NASCAR is apples and oranges. Those who say I could drive in a circle have no idea. To be anywhere near competitive NASCAR drivers are always on the razors edge of tire adhesion. I prefer NASCAR road courses which tasks the masters of the circle tracks. I have been a automobile racing fan since 1964. I have problems with idiotic regulations but still watch and enjoy.