Facts you may not know

Hi everyone I don't have any street racing stories because I am currently deployed overseas. I have spent a good bit of time on the internet however and have been reading the AF threads alot.
I have read a few times people question chevy's persistant use of pushrod motors, and a few times suggestions that they switch to the Northstar. I read into it and this is what I found about why they have maintained their famous small block.
First off if you think about it, why use overhead cams? Over head cams come in as a benefit when you have 4 valve engines. It would be impossible to have that many pushrods going through the middle of the block like that and it would be over complicated. So if you want 4 valves just put the cams on top and have one for intake and one for exhaust. If you only have 2 valves per cylinder you don’t really need to have an over head cam, its still doing the same job as a pushrod when you have SOHC.
Second, the having multiple cams on top of the engine adds weight to the over all engine and all that weight is basically moved up to the top of the motor, raising the center of gravity, and we all know we want low centers of gravity.
Lastly, and in my opinion the most important, it makes for a more compact engine to use pushrods. If you look at the physical size of an LS-1 vs. 4.6 SOHC or DOHC engine, or for that matter a 5.4 DOHC, the LS1 is far smaller despite its larger displacement. The size will affect the chassis of the car it goes into. For example, the Corvette has a double A-arm front suspension like a race car would have. The 2005 Mustang has a far improved front suspension than the 2004, but still it lacks the double A-arm front suspension that its Lincoln LS brethren (which it shares many design cues structurally). This is because the 4.6 liter engine it uses takes up too much space for that kind of suspension. The Lincoln LS has a smaller V8. Ford wanted to do the same but lowering engine displacement wasn’t an option (can’t argue with that).
Just wanted to let everyone in on some information I had, stick up for Chevy a little bit (even though I have never owned one), and hopefully pass some new information onto others. Maybe you knew some of this maybe not. I don't drive a chevy either so this isn't some pro V8 thread. Its just some knowledge.

... that was kinda random...

But... welcome?.. to AF.

Maybe a little random but I thought it could be of interest to someone :lol:

of course the benefit of a push rod engine is weight and size, but it also lacks refinement. but thats also part of the attraction ( in its rawness ) but i would take my high tech dohc engines anyday even though they cost more, but trust me, i love hte way a 350 sounds or a 305 sounds with flows and a mild cam.

pretty interesting.

too bad i dont care about cams.

... that was kinda random...

But... welcome?.. to AF.
Kinda random???????
Well being this is about things you may not know, here goes.

Did ju no Juneau was the capitol of Alaska?:loser:

BlackGT2000, sorry to hear you've been deployed overseas. I was abrod once...:eek7:

I've been drunk and shot but never deployed. I guess I missed that when I was in VietNam.

i would take my high tech dohc engines anyday

I use to be all about the American pushrod muscle. Now I see Ford's DOHC engines kicking butt and taking names so I'm starting to change my views here.

even though they cost more

I hear you there. I know this guy at church who races Indy cars professional. He isn't in the Indy 500 or anything like that but he does races kind of like it. Anyway he was telling me the pushrod engines are about $100,000 a piece and the DOHC will run you around $175,000.

but trust me, i love hte way a 350 sounds or a 305 sounds with flows and a mild cam.

:iagree: You forgot one engine though, Ford's 302 :biggrin:

interesting! I was only wondering why some manufacturers still use only 2 valves per cylinder and some use 4? like why do american cars still use only 2 and jap cars go for 4. I saw fords commercial about the new Explorer and how it has 3 valves per cylinder, well why are they bragging about three when an eclipse has 4?

the real reason I'm asking is cause some guys make fun of my Starion since it only has 2 valves per cyl.
will it make as a DOHC? I know my valves are bigger then the avarge DOHC valves but will it affect timing in any way?

Maybe a little random but I thought it could be of interest to someone :lol:

thats very interesting

interesting! I was only wondering why some manufacturers still use only 2 valves per cylinder and some use 4? like why do american cars still use only 2 and jap cars go for 4. I saw fords commercial about the new Explorer and how it has 3 valves per cylinder, well why are they bragging about three when an eclipse has 4?

the real reason I'm asking is cause some guys make fun of my Starion since it only has 2 valves per cyl.
will it make as a DOHC? I know my valves are bigger then the avarge DOHC valves but will it affect timing in any way?

usually less valves means bigger valves. thats the recipe for low end torque.

usually less valves means bigger valves. thats the recipe for low end torque.

Is that why american engines only rev to like 6K rpms, and some honda and nissan engines go to like 7500 rpms?

Hey blackgt2000 i know how you feel. Im overseas in iraq. Im not sure where your at but your not home. I hate iraq. Welcome to the forums

Actually the benifit of and OHC engine over pushrod is lower rotational mass, engines using pushrod design have a camshaft located in the engine block near the crankshaft. Rods linked the cam below to valve lifters above the valves. There are more moving parts there is also more lag between the cam's activation of the valve and the valve's lifting motion. Where as an ohc engine activates the valves directly thus there is no lag in the actuation of the valves.

I use to be all about the American pushrod muscle. Now I see Ford's DOHC engines kicking butt and taking names so I'm starting to change my views here.



I hear you there. I know this guy at church who races Indy cars professional. He isn't in the Indy 500 or anything like that but he does races kind of like it. Anyway he was telling me the pushrod engines are about $100,000 a piece and the DOHC will run you around $175,000.



:iagree: You forgot one engine though, Ford's 302 :biggrin:


oops i didn't mean 305 becasue those are crap, what i meant to say was a 302. heh

I have read a few times people question chevy's persistant use of pushrod motors, and a few times suggestions that they switch to the Northstar. I read into it and this is what I found about why they have maintained their famous small block.


I would never buy a Chevy if the got rid of their SB's for Northstars...

Northstars are crap, they constantly have to be resealed and are only good to about 30K miles before needing new rings and pistons.

Really? I thought the northstars were Gm's pride and joy...wow thats really interesting Z28 Josh

Thats the thing with pushrod and DOHC is that yes the pushrod has a lower center of gravity which is ultimately good for the car...but 4 smaller valves can allow more air in and out faster than 2 larger valves, and thats why a DOHC can rev higher and breathe easier at high rpm

well fords 4.6 engines are really starting to impress some people, they really can take some power. the 4.6 is a better motor than the 5.0. and im not sure what the idea is with 3 valves but i think it has something to do with engine effieciency, less gaps in motor and stuff idk. and ford is just exploring a new idea. the ohc engines are more efficient and are newer technology, i think ford is very smart by making the switch sooner rather than later. and the reason theyre mustangs are 2v is so they can save the 4v ones for the more powerful cars like the cobra. you gotta remember you have 8 cyl here, not 4 so even a 2v engine can be quite powerful.

Hey blackgt2000 i know how you feel. Im overseas in iraq. Im not sure where your at but your not home. I hate iraq. Welcome to the forums

I am in Iraq too. Trying to make the best of it you know. I think these days if your not in iraq your in afghanistan.

Everyone here as added alot of good points about the OHC layout as well, I wasn't saying that pushrods were better I just thought that if someone viewed them as old tech, than maybe I could offer some information on some of the benefits. As for fords 4.6, I think its finally catching up to where it needs to be. The new all aluminum 3 valves are a definate improvement over the 2V that I have. I still havent been able to test drive one as of last month though, see how they measure up to a LS1.

i just thought it was wierd how chevy had the C4 ZR1 motor making more power than the Z06 at the time, and they didnt continue using that engine. Was it too expensive to produce?


btw this should be in non-spec

i just thought it was wierd how chevy had the C4 ZR1 motor making more power than the Z06 at the time, and they didnt continue using that engine. Was it too expensive to produce?


btw this should be in non-spec
I dont know much about the ZR-1, but could be that its cheaper to make an LS6 which is just the standard LS1 with different heads and cam, rather than producing a whole different kind of engine with different mounts and acessories to go with it. Just a thought :dunno:

i just thought it was wierd how chevy had the C4 ZR1 motor making more power than the Z06 at the time, and they didnt continue using that engine. Was it too expensive to produce?


btw this should be in non-spec



The ZR1 ran from 1990-1995. The motors were extremely expensive to produce. The ZR-1's main feature was the LT5, a highly modified version of the 350 V8, developed with the help of Lotus, and built by Mercury Marine. The LT5 featured a very modern dual overhead cam, 32 valve design which put out a whopping 375 bhp. The ZR-1 also featured a distinctively wider back end and square tail lamps. The main problem was price. The ZR-1 cost nearly $59,000 (and many sold for much more than MSRP), compared to the base coupe priced at $32,000.


They made 375 bhp @ 6000 rpm, 370 lb-ft @ 4800 rpm. In 1993 they bumped the power to 405 bhp @ 5800 rpm, 385 lb-ft @ 4800 rpm.

Oh, and there was no C4 Z06 if that's what you mean. The Z06 didn't debute till 2001 and it produced 385 bhp @ 6000 rpm, 385 lb-ft @ 4800 rpm. In 2002 the Z06 got bump in power to 405 bhp @ 6000 rpm, 400 lb-ft @ 4800 rpm.

I dont know much about the ZR-1, but could be that its cheaper to make an LS6 which is just the standard LS1 with different heads and cam, rather than producing a whole different kind of engine with different mounts and acessories to go with it. Just a thought :dunno:


Well, figuring the LT5 was designed back in the late 80s... and the LS series of motors didn't come out till 1997...

Two totally different beasts, designed in two totally different decades with eons of technological advances.

Really? I thought the northstars were Gm's pride and joy...wow thats really interesting Z28 Josh


Pride and joy huh?? I wouldn't think it was anything to be proud of. The service department i work at, we've already done GM Factory warrantee on resealing and replacing rings and pistons and whatnot on 6 different northstars..2005 alone, what's sad is that we're a Buick/Pontiac/GMC dealer, the local Chevy/Cadillac dealer doesn't want to mess with them, and we have yet to have an unsatisfied customer yet with our rebuilds. Northstars are just...pathetic..

Is that why american engines only rev to like 6K rpms, and some honda and nissan engines go to like 7500 rpms?

Thats part of it. Larger valves tend not to close as well at high RPMs as smaller valves.

Pride and joy huh?? I wouldn't think it was anything to be proud of. The service department i work at, we've already done GM Factory warrantee on resealing and replacing rings and pistons and whatnot on 6 different northstars..2005 alone, what's sad is that we're a Buick/Pontiac/GMC dealer, the local Chevy/Cadillac dealer doesn't want to mess with them, and we have yet to have an unsatisfied customer yet with our rebuilds. Northstars are just...pathetic..
They sure have. My dad's the one that's been doing them :smile:.

:iagree: You forgot one engine though, Ford's 302 :biggrin:

351 > 302 :grinyes:

pretty interesting.

too bad i dont care about cams.

lol, i hear you...i wish i had the money for insurance on an RX-7...but i dont :mad: .
But you have to worry about apex seals :p

edit:
but it must be fun being able to have an engine stable at 11,000 RPM with some modification in a daily driver... :lol2:

351 > 302 :grinyes:

427side oiler>351


but it must be fun being able to have an engine stable at 11,000 RPM with some modification in a daily driver... :lol2:

that would be a neat feeling...

lol, i hear you...i wish i had the money for insurance on an RX-7...but i dont :mad: .
But you have to worry about apex seals :p

edit:
but it must be fun being able to have an engine stable at 11,000 RPM with some modification in a daily driver... :lol2:


it doesnt rev THAT high. on my n/a motor redline is 7k and power falls off around 6.5. The limitation is the stock port size. If the ports are made bigger than it'll rev that high and actually make power up there.

with my turbo motor, it has porting so the redline could be higher than stock but the stock turbo (which i'll be using for a while) falls off around 6500 rpm as well.

and i dont worry about apex seals too much cuz i take care of my shit!


btw my insurance is actually fairly low.

edit: red my fault about the z06 comment. i was trying to refer to the higest performing corvette under the ZR1

I was under the impression that sohc were typically three valves per cylinder. Two intake and One Exhaust in that case it does make sense to have an sohc engine.

I find it funny that the new 4.6 just now came out with three valves.
Honestly I didn't know the old 4.6's were two valves till I just looked it up. I guess they made it so just for a smoother running engine, and for the advantages already stated.

I thinks it's cool how the ZR-1 was so far ahead of it's time. Granted the new Z06 is nothing to scoff at it would have been interesting to see where they would have been now with the dohc set-up.

the v8's rev limit is limited to the weight of the internals plus the stroke of the engine. my proffessor got his 500 ci mapr block to rev to 8K in his hot rod. the main problems that i would think is hydraulic liftes sticking at higher rpms, and such, that is also another factor that might limit a v8's rev limit.

it doesnt rev THAT high. on my n/a motor redline is 7k and power falls off around 6.5. The limitation is the stock port size. If the ports are made bigger than it'll rev that high and actually make power up there.

with my turbo motor, it has porting so the redline could be higher than stock but the stock turbo (which i'll be using for a while) falls off around 6500 rpm as well.

and i dont worry about apex seals too much cuz i take care of my shit!


btw my insurance is actually fairly low.

edit: red my fault about the z06 comment. i was trying to refer to the higest performing corvette under the ZR1

i said it can, with modification...well more than some, but Wankles can do 11,000 RPM in a "daily" driver (more like a weekend driver) no problem. ive seen some take redline as far as 12,000 but for the most part you only take it that high because your powerband is naturally so high and you have to have such a large turbo to run massive ammounts of boost that it doesnt even start making boost untill pretty hgih RPM's... but 12k is pretty excesive. either way...my insurance for my truck is around 1300 a year...for a 2nd gen 7 it was going to be over 2k a year.

well wouldnt an ohc engine also rev easier due to less moving parts, less weight. nascars (yes i know theyre racing motors) rev to 10k in v8's. and those indy cars, well they rev to rediculous amounts if im not mistaken

but indy engines are deisgned to last 500miles, no longer, they also cost hundreds of thousands just for the engine and are short stroke wide bore V10's that are limited to 3.0l and only rev that high because they are trying to make 700+ HP with only 3l of displacement and no FI. Nascar motors are also only deisgned to run one race before they are rebuilt... hardly compareable. and Indy cars use electronic valve timing, from what i understand it is 100% controleld by a computer, nothing mechanical connected to the crank involved.

also, from my understanding indy engines IDLE at around 4,000-5,000 RPM and dont hit their power band untill between 10,000 and 15,000 and redline as high as 21K RPM.

i said it can, with modification...well more than some, but Wankles can do 11,000 RPM in a "daily" driver (more like a weekend driver) no problem. ive seen some take redline as far as 12,000 but for the most part you only take it that high because your powerband is naturally so high and you have to have such a large turbo to run massive ammounts of boost that it doesnt even start making boost untill pretty hgih RPM's... but 12k is pretty excesive. either way...my insurance for my truck is around 1300 a year...for a 2nd gen 7 it was going to be over 2k a year.

if your peak power is 11k then its probably a bridgeport or half bridge. Thats close to being unstreetable. you have like no power below 3k in that instance. you have to understand that rotary engines have linear powerbands (the power rises as rpms rise, thats the reason why the engine design was originally used as a supercharger). when you port it, it shifts upward. you lose the first 3000 rpm but gain them uptop. it also causes you to idle higher as a result (and you get that fucking badass idle). i hope that makes things more specific.