Hey you over there

Im planning my cam swap and have two cams shortlisted that I'm planning on using and need some advice on.
Those are both single pattern cams.

First cam: Comp Cams 08-420-8 Magnum



or Howards 180885-10



My goals are:
-usable rpm band to 5500-6000 rpm
-still good vacuum and an "ok" idle
-not too much lost on low end torque

My engine:
310cui (305 .030" over) factory roller block
SLP Cam 51002 206/212 in/ex .512/.520" lift @ 1.6 roller rockers, 112 LSA
10:1 static compression
TFS 175cc aluminum heads
ported Pro Flo 4 XT Tunnel Ram manifold
adapted on stock dual 48mm throttlebody with airfoil
1 5/8" shorty headers with two catalytic converters, x-pipe and free flowing mufflers
TH700R4 with 2200 rpm converter, soon swapping to 5-speed manual
modified prom, soon switching to fi-tech

What are your suggestions? Is 225/225 @.050" too much duration for my engine (for low end torque)?
At what rpm will the 215/215 cam peak? Cam Quest said 6000 for the 215/215 and 6500 for the 224/224 with full engine simulation. Is that realistic?

Thanks in advance,
Chris

 

My insight is mostly anecdotal, more like comparing apples to beach *****. In a 355 that's fairly similar otherwise, I had what degreed to be a 225-225 cam and it idled near 750 to the point that I believed it was the 212-218 cam that the card claimed. I don't actually know what all the specs were supposed to be. Powerwise, I didn't fully tune it with a comparable intake and it felt flat with a tpi. It's kinda here nor there.
What's wrong with the cam you currently have. Are you trying to reach an rpm goal? Have you checked with a company like Lloyd Elliott or Jones cam?
I'm curious to hear what people with better knowledge than myself and their take.

 

At first blush, the second one seems like a lot of cam for the 175 heads. And the 110 is going to hurt your vacuum.

It won't be terrible, but as an anecdote I'm running 230/236 110 on a 355, and pull 10" on a good day. Still enough for brakes, but it isn't much.

Were these the recommendations you got from Comp and Howards?

 

There is nothing "wrong" with my cam, it was first installed with the tpi manifold. Now swaped and compared to my new tunnel ram, I could benefit from a cam with more duration.
Some cam manufacturer suggested something around 220 @.050" on intake duration and on a 110 lsa (which is the result if I use david wizards formula to find the right lsa)

I heard and read about the single pattern camshafts and that those should be good with a good in/ex ratio on flow numbers of the heads and with headers.
So thats why I want to try one of them.

Do you have a carb or EFI on top of it?

 

I'm using EFI (Stealthram).

 

Tough call. Idk if the first cam would be enough to warrant swapping over what you have now but i like the extra lift with a 1.6 rocker it will give you.

Cam 2 is abit bigger than you need and would be a little softer on the low end i think, and sound pretty good. Should have enough vacuum tho. I like big cams and lean that way.

 

Could you explain why the 225/225 Howards or 224/224 comp cam will be to much for the 175 heads?

 

It would work, but you'll want to look for parts that complement each other as optimally as possible.

I'd expect that the 224/225 cams will be peaking at a higher RPM than you want with the 175 heads. You may end up losing midrange and not getting any benefit at higher Rs to make up for it, if the heads aren't flowing enough.

 

Hello Folks,

short question: I want to have zero advance on this cam. So if I install it „straight up“, it should have a Ivc of 37.5 according to the calculator, right? I dont want that 4 degree advance. So basically, if I understand it right, if I install it on a 106 degree intake centerline, it has an ivc of 33.5 also known as 4 degree advanced, correct? So installing it straight up would get me to the 110 degree ICL and thus an Ivc of 37.5?

Thanks in advance for Info.
Im tempting to this camshaft for my car. But Im open for other cam ideas.

 

The only problem with that theory is that despite the head having a decent in/ex split (as you stated) having that exhaust hanging off the heads is going to hurt the ability to evacuate the chamber.
Can you post up the flow numbers?

 

Attached are the flow numbers of the heads.
The exhaust of my car includes headers, a x-pipe, free flowing Cats and straight through mufflers.

 

As a reference, my heads have a similar intake/exhaust ratio as the heads posted. Perhaps better considering my heads were flowed without a pipe on the exhaust as yours were. That pipe boosts the exhaust CFM.
I had my cam professionally spec'd (Jones Cams) and even though there's a good exhaust port, the cam still had a 4° split. Further to that, when discussing my objectives with Mike Jones, I stated that I'll be tuning for open headers. And still a split duration spec'd.
The reason being is that the minute you hang something off of the headers, other than a collector extension, you'll reduce the cylinder's volumetric efficiency. Despite having "headers, a x-pipe, free flowing Cats and straight through mufflers." you'll not see all of the benefits of having headers. The exhaust side of the cam timing will undoubtedly need assistance.

 

The advance on that cam is ground in. Installing it on a 106 ICL is as per design. That would be "straight up" or dot to dot as it were. If you install it on a 110° ICL, then you'll have effectively retarded all of the cam timing events by 4°. You're intake valve will now close 4° later.
I can't think of a single scenario where, if the cam is properly specified, that there would be a need or benefit to retard the installed centreline. That will reduce the effective compression ratio and consequently kill off low speed torque.

As for the last sentence in your post, move on from the Magnum and get a lobe profile that's modern. If you want to stick with COMP, at the very least I'd suggest their XR family of cams. Further still, there could be something to gain from the XFI lobes. If the advertised number (at .006" lift) is the same between a group of cams, the cam with the highest .050" duration will give more area under the lift/duration curve and provide more time to fill and evacuate the cylinder.
Similarly, 1.6 ratio rockers will do the same by getting the valve open further and faster.

 

Thanks for the good info to work with!
Then the Magnum cam wont fit my needs. I need an ivc point of roughly 38 degrees to reach my desired hp peak of 5800 rpm.
Im still leaning towards a single pattern for the increased mid rpm torque because the evo is later.

If you could take a look at this cam Card: This cam has no advance ground in, right? So to have an ivc of 38 I will need to advance it at the crank 4 degrees to get it in the range…?

 

How did you come to the determination that the IVC establishes the peak HP RPM? That's traditionally the function of the duration. More duration moves the peaks further up the rev range.
We use IVC to calculate the trapped volume in the cylinder. Work that in with the compression ratio that's built in to get what's referred to as dynamic compression ratio (DCR). That though, in a another rabbit hole onto itself.
As for the Lingenfelter cam posted, it looks to have a decent lobe profile. Not as lazy as some.(.351 lobe lift). I can't say the LSA is something I'd go for but that's just me.

FTR: Using the .050" values for IVC isn't a practical method. Essentially, it means nothing except for comparing one to another. You need to know when the valve closes, not when it's 50 thou off the seat. My cam grinder says much the same but he publishes .050" numbers because that's what people want to see. When you compare cams, look at the advertised compared to the .050 numbers. There can be quite a spread between brands or even between lobe profiles of the same manufacturer.

One method used to select a suitable IVC is to use a DCR calculator. The SBC's I've worked on were (are) very happy for street duty on pump gas with about 8:1. Take your 10:1 static CR and work through a few cams on your list. Then you'll see the effect of different IVC's. That trapped volume resulting from the valve closing is what will make for a responsive street engine.

Those are my thoughts on it anyway. I'm not about to spec a cam for anyone but I can give some insights into what the some of the criteria might be. That said, in or around 270 advertised duration seems like a 305-ish number that works. Tighten up the LSA (say 110 rather than 112) and the IVC is sooner and the recipe is in or around that.

 

Here's a spreadsheet of some cams suggested for a 305 build.

 

Thanks for your Input!
I read something about it here:

https://ls1tech.com/forums/generatio...stion-ivc.html

So for the advertised duration and the lsa the 270 Magnum cam would fit your advice, and for me it also Looks like a good choice.
I just doubted it give me the wishful 5800rpm Hp peak cause of the early ivc.👀🤷

 

I use IVC to determine the engine dynamic compression. That's where the cylinder pressure and the resulting torque come from. The duration is what establishes the RPM peaks and there are other various nuances that come about with split duration or how the LSA is factored in.
Remember too, that unlike duration or the separation angle, the IVC can be moved around. Many, many dyno runs and track testing have revolved around moving the intake lobe centerline. This is also something you'll have to address when degreeing your cam.

As for the 270 Magnum, as I stated earlier, I find it to be a dated lobe profile and consequently you're potentially giving up free HP and TQ. The single pattern is another matter too as there are benefits to having an extended exhaust duration via a dual pattern. One is that power should carry past peak HP RPM and help extend the rev range somewhat. This is what I discussed with Jones when I had my cam ground. It was said peak HP RPM would be about 6000-6200 (with my 357) and carry past that to help my drag racing top end charge.
But back to the Magnum, there are cam calculators all over the internet. Some suggest that an intake duration of 220-222° @ .050" is what's needed for a 311 CID engine to make peak HP at or near 6000. The Magnum 270, with it's dated lobe, falls a little short at 215°. It's said to peak at 5k in a 350 so there's a little something more with the smaller cubes. I think though you might be further ahead with the XR270HR. But that's an opinion though and not something I've researched. The numbers just look better. Installed straight up, it has an IVC of 61° (.006" lift).
The DCR with a 10:1 static CR and a 61° IVC puts that DCR ratio at 8.2:1. I've found that's workable with iron heads so with aluminum, it shouldn't' be problematic.

All in all though, it might be a matter of splitting hairs regarding the cam. Many other variables could get in the way of performance.

 

Very interesting, so its the duration, that determines the hp peak if we just look at the camshaft?
I think, there is more take into account then just the duration @.050 or .006.
And you stated it already: By changing the ICL with advancing or retarding the cam, you also move the valve timing which, according to that video, change the engine behaviour and peak hp point. Of course you also change the EVO point which also determines the torque output of the engine.


oldschool VVT😄

Back again to the ivc: I am neither an engineer nor an expert but can understand the articles I am reading on the internet like summit, onallcylinders or motortrend. And all say the same: The most effecting part of valve timing events for the powerband is the IVC.

https://help.summitracing.com/knowle...SR-05440/en-us

With my installed cam degreed in at 31 degrees IVC ABDC my powerpeak is somewhere around 5200 which holds steady to around 5800.
Thats something I dont need, I want the power to climb to 5800 and the shifting into the next gear. I dont want to loose midrange torque with a split duration just to hold my power peak longer.


enginemasters tested the split numbers of very little to big split and each time the split gets higher, the top end hold on more by loosing midrange torque. Also Richard Holdener tested cams that going the reverse split (more intake than exhaust) route and gain more midrange and loose top end. I THINK if single pattern cams would have been tested, you could see the trend following in between the split and reverse split.

Thats why I think a Single pattern would fit my needs. And of course, the 110 LSA would be the best for my little engine, but I still Need to pass emissions so dont want to go more than -5 degree of overlap @.050.
And the Magnum 270 would fit right in there.

The only concern I have is the IVC of 33.5 degrees which is not much more than I have now.

 

Rhoads V-Max lifters and a 224/224 @ 0.050 grind. Best of both worlds.

EVO has a HUGE impact on low speed torque, emissions and fuel economy just FYI. If you are blowing off the cylinder earlier you rev higher but kill low speed torque, lose mileage and run dirtier.

I have a 10.25:1 L31 with a GM 6492' cam that runs exceptionally clean on a 5 gas analyzer.

 

Some have made of successful career with a contrary opinion.
You seems to have educated yourself so I think at this point, the decision is yours. I've really got nothing more to offer.

 

Single pattern cam is where I would be on a 305 with aftermarket heads. The 305 does not needed the added exhaust duration especially with aftermarket heads that use exhaust ports that could support a 500+ hp 350 in them. Dual pattern grind is just shooting yourself in the foot at lower rpm via added overlap and earliar EVO. The I/E ratio on those TFS heads is substantially better than the older OE castings that most benifit from a dual pattern. There is such a thing as too much lobe intensity as well especially for a hydraulic lifter. I do not even like how aggressive even the Xtreme Energy roller grinds are much less XFI. They require subatantially more spring pressure to prevent lofting the roller over the lobe at higher rpm which beats up the cam and lifters ask me how I know, cause more wear and tear and are noisier which leads to alot of false knock detection issues with knock sensors. Sorry but no free lunch there. 224/224 on a 110 LSA and 106 ICL with V-max lifters is where I would be for a 1.94 valve ~6,000 rpm 305 with those heads. Basically close to where I was with 1.7s and a 218/218 @ 0.050 cam with the Etec170s on the 305 in my Tahoe. That engine sounded nearly stock at idle and lots of vacuum. Cutter Performance literally just proved that even regular Rhoads lifters really tamed out the camshaft at idle and did not effect the ~3,000+ rpm WOT power at all. The sound of them reminds me of the stock Dodge Viper quick bleed down lifters we put in cammed Magnum V8s and my 94 V10 I had as well as well as a tight lash solid roller. The old Mopar Jtecs were basically not tuneable for years and required stock like vacuum and/or a Split Second PSC1-003 piggy back MAP signal adjuster to dial them in when you cammed one. My 94 V10 Ram and 03 Dakota were both setup with the PSC1 piggy back. The 94 Ram had a Mopar Performance PCM and the Dakota had a Superchips 91 octane flash despite being cammed up pretty good. My 97 GM Express van had a MAP ProT MAF translator for a LT1 that had timing control adjustment combined with a Hypertech 91 octane flash for about 6 years too before Tunercats supported the Black Box PCM in it. At the time it was the only way to tune an OBD2 Dodge or GM PCM in those applications. ALL of them passed emissions easily.

 

Both of these engines had aftermarket pushrods in them for proper valvetrain geometry and the in the Hemi engine's case for the correct lifter preload with the non-adjustable valve train. Tick, Tick, Tick, Tick. The Hemi with XFI lobes was so bad you could hear it in the truck at 70+ mph going down the highway. Literally the Rhoads V-Max lifters/Magnum lobe cam in my 383 was quieter and that engine literally resides under the dash.

XE grind cam stock GM lifter.

XFI grind cam with non MDS Hemi lifters

Here is the V-Max/Magnum lobe grind even with a 1.7 full roller rocker from right up against the engine.

https://youtu.be/1xXFPoS3Y2Y?si=lGSzN0KZrDvXKh1s

 

I'm guessing you intend to buy a cam.
So rather than guessing, or watching videos or engaging in conversation with some guy like me, why not fill out a cam recommendation form from Jones Cams? It's not the same as asking some tech line to help because they can't. Send it off and report back. He's reasonably priced and you'll at the very least get a quality cam core (not some suspect thing that COMP currently offers). At best, you'll get a top notch spec based on the information you provide.
Good luck.