Camshafts: What effect does increased lift have on performance?

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Yeah, this will be my first ever roller cam engine. I want to put roller cams in my other V8 cars too.
This 360 was intended to be just a refresh job. I thought I'd just replace the head gaskets and run it but the guy let water sit in it. I've had a few cams/lifters fail so the chance to build a roller cam engine was one I wanted to take.
I have a 318, 340 and another 360 here that are all non roller blocks that I may or may not ever build.
Can you expound on how the rest of this engine will go? Static compression ratio, what heads, intake and exhaust? Automatic? Gear ratio?
 
This is the cam that was in the engine:

View attachment 1716356064

It is a cast iron core so it also has the standard stock oil pump drive. I rode in the car that had this engine, it ran great but that car only had a 3.23 and he ran it with 360 cast manifolds. My Dart has a 4.10 and will have headers. The 308 heads had springs to match the cam, there were no signs of piston to valve issues or detonation.
I'll need new pistons but will use this cam again. I just noticed that the Hughes cams had more lift than other brands of cams that I have seen.
I forget, what rockers were on that motor? I'd think that cam would need something more than stock stamped rockers.
 
Absolutely.
It appears to have been approximately .010 below deck with 5 cc valve reliefs. .020 over, stock 3.58 stroke. I don't know the exact chamber size but online sources show between 63-72 ccs for a '308 head.

360 CR 1.png


The first and worst case scenario comes in at 10.52 to 1, way too high for an iron head engine on 91 octane. If the pistons were .020 below deck, it gets slightly better:

360 CR 2.png


If the heads are closer to 65 ccs AND if I used a piston with an 18 cc dish, the C/R gets around where I'd feel comfortable.


360 CR 3.png


I don't want to always have to run 91 octane with this car:

67 R.jpg


The Dart has a 4.10 gear SG 8.75 axle. The intake that came with this engine will go back on it.

IMG_8407.JPG


Buried in that is the RPM Air Gap. I'll also use 1 5/8" headers and 2 1/2" pipes with an H pipe and Flowmaster mufflers.
 
Absolutely.
It appears to have been approximately .010 below deck with 5 cc valve reliefs. .020 over, stock 3.58 stroke. I don't know the exact chamber size but online sources show between 63-72 ccs for a '308 head.

View attachment 1716356070

The first and worst case scenario comes in at 10.52 to 1, way too high for an iron head engine on 91 octane. If the pistons were .020 below deck, it gets slightly better:

View attachment 1716356071

If the heads are closer to 65 ccs AND if I used a piston with an 18 cc dish, the C/R gets around where I'd feel comfortable.


View attachment 1716356072

I don't want to always have to run 91 octane with this car:

View attachment 1716356077
Let's dispel that myth. 10.2 isn't too high for pump gas and iron heads. I run 10.6 on premium all the time when I drive Vixen. It's all in the tune. So yeah, you can do it just fine. And not with a large by huge cam, either.
 
Absolutely.
It appears to have been approximately .010 below deck with 5 cc valve reliefs. .020 over, stock 3.58 stroke. I don't know the exact chamber size but online sources show between 63-72 ccs for a '308 head.

View attachment 1716356070

The first and worst case scenario comes in at 10.52 to 1, way too high for an iron head engine on 91 octane. If the pistons were .020 below deck, it gets slightly better:

View attachment 1716356071

If the heads are closer to 65 ccs AND if I used a piston with an 18 cc dish, the C/R gets around where I'd feel comfortable.


View attachment 1716356072

I don't want to always have to run 91 octane with this car...

Your 308 heads probably have 72 cc chambers. Not that I have measured a set, I gave up trying to find a set that wasn't cracked. J head chambers measured 74 to 72 cc if i am remembering correctly. With that hardware on the engine you bought I'd measure the chambers and deck measurement myself before you buy pistons. You can also adjust CR with thinner or thicker head gaskets available today.
 
Show us an example of head flow the same at .400 and .600. I swear, I'm gonna send your wife a new baseball bat cause she musta lost the last one.

I can’t find the flow sheet this instant but my OEM Magnum heads do this. I didn’t go to .600, IIRC Between 500-600/650, it floated in the 210 area.
 
Now cam numbers make my head spin, so nothing but confuse me, especially when you dig deeper like overlap,

Another question does lift or duration play more of a part in how much vacuum a given engine makes
Valve timing events.

That nano second, is the difference between an advertised 252/.425 & a 208/.600.

The difference between a OEM .410 lift and a 252/.425 can be 5-20 hp, all things being equal, good question. The variables are to many. Interesting question. I know with rebuilt engines it has been done and tested. Steve Dulchich did this before.
 
Daily driver street/strip car.

Someone needs to explain how lift is bad. It’s such a ridiculous statement but that’s what it is.

Lift is bad.

Lift is good (that’s what I say) and I can’t think of a reason where more lift is bad.

Again, it’s 2025 and .600 lift is the new .480 lift.

It’s hilarious that people continue to say lift is bad and they mean anything over .500 lift is bad.

That’s asinine.
Like an X coworker of mine. “.500 is big lift….”

Me: “Ummm, noooooo, I’m daily driving a .575 right now.”

Him - Mind explodes!
 
This is the cam that was in the engine:

View attachment 1716356064

It is a cast iron core so it also has the standard stock oil pump drive. I rode in the car that had this engine, it ran great but that car only had a 3.23 and he ran it with 360 cast manifolds. My Dart has a 4.10 and will have headers. The 308 heads had springs to match the cam, there were no signs of piston to valve issues or detonation.
I'll need new pistons but will use this cam again. I just noticed that the Hughes cams had more lift than other brands of cams that I have seen.
That cam you have circled is a fine everyday driver. I e used very similar specs on a HFT with very good results. Even in low compression 318’s that turned high 14’s in the 1/4 w/3.21 gears on stock size tires.
 
Holy crap...Really? That ought to be fun!

It was. Even more so the comp ratio spaced in at 7.8-1 on the 318. It also got headers, Jets exhaust, LD4B and a 600. Orange box ignition. Tires, IIRC, were BFG’s OEM size. No shift kit in the transmission, no recurved distributor. Just a cam and bolt on parts. Not to shabby. Spun a lot at the starting line at Atco NJ.

First run fresh off the road was a 15.01. Literally, I came off the highway turned in paid my fee and the guy says you better hurry up they just called but you’ll be running in. I drove directly to the study line and wait a less than five minutes. Engine was hot and toasty borderline of overheating. It was hard to start back up that day. Hot outside.

A member way back, Mike Beck, ran the same Crane HFT @216/228-.454/.480-112 in his drag on well lightened Duster into the 12’s with that cam and a well put together car.
 
Want to see the flow numbers for my heads? I think from .500-.700 they flow pretty much the same.
A friend who does port work flowed my J heads whe I got done with them. Just as a favor and I didn’t get a full written report. He said he got 262 at 500 and the same at 600. I had heard that these heads don’t improve past .500. Just my experience. I put 1.6 rockers with my .484 lift Mopar Performance cam to up the lift a bit and quicken the opening. Duration at fifty as I remember is 238. My performance goal is to be respectable. Not a race car.
 
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A friend who does port work flowed my J heads whe I got done with them. Just as a favor and I didn’t get a full written report. He said he got 262 at 500 and the same at 600. I had heard that these heads don’t improve past .500. Just my experience. I put 1.6 rockers with my .484 lift Mopar Performance cam to up the lift a bit and quicken the opening. Duration at fifty as I remember is 238. My performance goal is to be respectable. Not a race car.


And I’m going a cam for a street car right now that will be in the .550-.560 lift range depending on the lobe.

It will be reliable and make more power than if I gave up .030ish in lift. In fact, I may look at some lobes in the .580 lift range so my net lift is closer to .550.

This nonsense that when a head breaks over you stop lifting the valve. That’s incorrect.

If more guys were flowing heads with the intake manifold on they’d learn the heads don’t break over nearly as much or not at all.

And…never mind.
 
But you cannot increase lift and have the same duration. Mathematically impossible. The extra lift increases the duration or you have an awkwardly weird ramp rate.
Howard’s has a 266/.558 solid. 238@.05. Builds a lot of torque, but it’s over at 5400 in a 360.
 
And I’m going a cam for a street car right now that will be in the .550-.560 lift range depending on the lobe.

It will be reliable and make more power than if I gave up .030ish in lift. In fact, I may look at some lobes in the .580 lift range so my net lift is closer to .550.

This nonsense that when a head breaks over you stop lifting the valve. That’s incorrect.

If more guys were flowing heads with the intake manifold on they’d learn the heads don’t break over nearly as much or not at all.

And…never mind.
This is a Schneider solid grind. Keven or Jerry will get you fixed up.
image.jpg
 
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The MP cams are designed in a certain parameter of thoughts which I find accurate in their description of balancing the track performance with still be streetable.

The key to this camshaft thinking is how the engine responds to the camshaft in making power and where you want to make the best and most power for your particular situation.

Duration allows more or less air and fuel into the cylinder with the cylinder head (only the cylinder head for this exercise) being the limiting factor.

Now for say, the cylinder head flows well to only .500 lift. More lift has the flow rate tank badly. Here, you don’t need more lift, so finding more power comes with duration. Holding the valve open longer allowing more air and fuel. But we know this raises the rpm level of performance and can be a draw back to the track being raced among many things.

Now! If the cylinder head flows really well to, let’s say .750. Lifting the valve up higher to get into the superior air flow characteristics of the cylinder head will allow more air and fuel to get in thus creating more power. Obviously.

Being that the duration hasn’t changed, the operating rpm range really doesn’t change much. It will rise some but the bulk of power remains the same in the same area but just with superior high end power being made. There should actually be an increase of power everywhere as in a broader and fatter power curve.

A slight loss of torque will happen. This has been seen before. Someone above wished for this test and it has happened before.

To continue my answer, I will also address the below quote:



Not exactly true. The duration and lobe of the cams opening and closing points are not changed but what changes is the area under the curve gets fatter. The valve rises quicker and higher to stay within the opening & closing points. The cam lift becomes quicker which equals more aggressive.

A quicker opening valve almost always equals more power. There is a point that you can open the valve to quickly to take wastage of what it can/could offer. Mostly, it’s a intake track issue that won’t allow the air and fuel in generously quick enough to match the valve action.

This is also why you can see/read at the Hughes web site on how the intake track (intake manifold) should flow more than the cylinder head. IIRC, Hughes wrote something along the lines of greater than 15% better. Probably higher. I’d go higher if possible. (Often it is not.)

Ok, let’s go back to the cylinder head that kicks *** with great flow to .750 and beyond with an intake and carb set up, up to task.

Lift will directly effect HP.

Crap head and intake.

Lift doesn’t help anything. Will probably just simply hurt the engine and/or combo.

The old saying of you just can’t get THERE from HERE Iis due to the equivalent of everyone driving their car at 90 and maintaining speed as you neck down from an 6 la e interstate hwy to a one lane exit.

It’s just not happening. Everyone gets jammed up.

This is kind of where the low lift cams come into play very well. While I normally suggest getting as much lift as possible , sometimes this possible is limited to a stock head.

A stock 340/360 head flows around 210 cfm @ .520 lift on the intake.
(Just for argument sake)
Then simply get a cam that lifts the valve up to a maximum.500/.520, then hold it there for as long as possible (duration) to allow the most A&F to get in.

Most stock, as cast OEM heads, will flow well to about .500. In general, the valve job is responsible for lifts to 400-450 area. After that, look at the under valve area.

If you happen to have an old MP engines book, they don’t recommend a (bowl) ported head (340/360 engines) until you want to achieve ET’s in the lower 12 second range. The bowl ported head gets coupled with the MP mechanical cam, 284/.528.

This doesn’t mean you NEED a bowl ported head to run low 12’s, it’s just a better more efficient way rather than tax the head with more lift and/or using more duration with low lift.

I hope that wasn’t to confusing and answered your question.
Thanks but that WAS confusing. It reminds me of the old saying....I asked him what time it was and he told me how to build a grandfather clock.
How about boiling it down to simple terms?

360 that is .040 over, 9.5 to 1 compression, stock '308 heads, RPM Air Gap intake, 1 5/8" headers and 2 1/2" exhaust.
This is a roller cam block with a Hughes 218-228 with .544 lift @ 1.6 rocker arms. I might swap back to stock stamped steel rocker arms for simplicity. That would put me back around .510 lift.
 
I haven't read the 4 pages worth of replies, but if you're thinking you'll gain a bunch of performance from increasing the lift, aka: like going from a 1.5 to a 1.6 ratio like a lot of guys do thinking they'll gain 30 HP it's not going to happen. Duration has far more to do with increased performance than .050" -.100" extra lift. Hanging the valve open longer is where you'll get more substantial power gains.

Tom
 
I have a set of 1.6 rocker arms that came with an engine that I am rebuilding. I was wondering if at my level, did the extra bit of ratio make measurable amount of power.
If not, I’d just sell off this rocker arm set.
 
I have a set of 1.6 rocker arms……..I was wondering if at my level, did the extra bit of ratio make measurable amount of power.
Define measurable.

Engine dyno, probably. Well controlled track testing maybe. Street butt dyno - absolutely not.
 
I haven't read the 4 pages worth of replies, but if you're thinking you'll gain a bunch of performance from increasing the lift, aka: like going from a 1.5 to a 1.6 ratio like a lot of guys do thinking they'll gain 30 HP it's not going to happen. Duration has far more to do with increased performance than .050" -.100" extra lift. Hanging the valve open longer is where you'll get more substantial power gains.

Tom


I was doing some testing on a 340 last week. It has a very small cam in it. Too small but it was picked for “drivability”.

Anyway, when it was last in the car we installed 1.6 rockers. With a geometry correction kit.

The cam was supposed to lash at .028/.032. I never lash anything that loose. But when the rockers went on, I did the math and it came back some big number.

So set them, against my better judgment at .028/.032 and went to the track and it was Sloooooooooooooow. I didn’t want I work on it at the track so we finished the day and left it alone.

On the dyno it was a P-I-G PIG.

I decided since it was on the dyno I’d tighten them up.

I could tell when it lit off it was much happier. Idled better, took load better. It was just better.

First pull was up 40 hp.

In this case the cam is so small that it will respond to anything that makes the cam bigger.

I killed any power gain by opening up the lash more than it should have been, regardless of what the math says.

So between the lash decrease in the lash and the 1.6 rockers it showed a nice gain.

Obvious had the cam been correct, or at least been closer the gain wouldn’t have been as big. If any.
 
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