Going with a custom grind and need opinions on the specs. I do not want to go above 216 on intake duration. That is really the only limitation. I also have my reasons for setting it there which some may not agree with-please don't comment on the cam being too small and no I do not want to hear about the hotcam at all.

I'm thinking of going ~210/230 @.50 ~.550/~.590 w/ 1.6 and the tightest lsa possible without losing vacuum and lowend torque. I think a bigger exhaust split will help on STOCK HEADS (no plans to port. no nos). My car is an a4 dd. Needs to run on pump gas so if anyone could play with those specs to get around a 9.0 dcr I would greatly appreciate that! (unmilled stock heads w/ stock gaskets stock motor.)

Thanks let me know what you think of having a big split and if that will help torque etc.

 

That ain't gonna get you there.... the 210/230 split? Do you have something REALLY suffocating the exhaust? There is absolutely no reason that a NA motor in a street LT should ever have that split, NEVER EVER.

Your quest for a 9.0 DCR is not the best idea either, you can cram that IVC point really early and the motor will not make good power, only way to get there is add more compression. FWIW plenty of the high compression pump gas motors I build that push the envelope do not even get near 9.0 DCR, but they are able to make some serious TQ per cube.

Basically so far you have a bad idea brewing, you have some good ideas but not all the knowledge to finish it.

Bret

PS A Critque should be a honest opinion on another ones work, so if you don't like it... well at least I wasnt lying.

 

How about we make this simple and I just sell you my old ZZ4 crate motor cam.
208/221 .474/.510(with 1.5s) on a 112.

 

No not at all. I respect and appreciate your advice. I am trying to do a custom cam that improves upon the crane 227 or 210/224 which has a healthy exhaust split. I was wondering if increasing the split would help but I guess not. I am curious to know the dcr of the crane 227 on stock engine lt1. A lot of people like this cam because it is powerful throughout the rpm range. Someone said it was because of the split (maybe stock exhaust port doesn't flow that well?)? Why wouldn't you want that split?

Bret, I was wondering what is your opinion of the crane 210/224 on a 110 lsa with more lift (same duration steeper ramps)? Will this be an improvement for more power? BTW does a tighter lsa improve power all across the rpm range or hurt it? Can you go too tight and lose power down low (I assume you could)? What is your opinion of small duration/high lift/tight lsa cams?

Thanks.

John

 

Good question.

 

That whole crane cam thing working because of the split is funny... the real deal is that most times when someone has that much split it's not because that it needs more exhaust duration, it's because it needs more overlap. So what do you think that says about your question of:

"What is your opinion of small duration/high lift/tight lsa cams?"

FWIW if you just increased the static compression ratio and evened up the intake and exhaust durations of that cam you would have the same or more TQ down low and more HP up top.

Don't worry so much about the DCR. I've been kicking myself in the *** a lot more lately for even talking about that 4 years ago on the forums. By no means did I invent the term, or was I the first to talk about it... I just think putting that putting this into the general engine lingo of the day has good and bad results. Guys put way too much stress on DCR when what they should look at is valve events and gettting them correct. Then dial in the SCR to get you into a safe DCR range for the motor thru it's RPM range. I do a lot of stuff in the low to mid 8's and it works great. You could dial more compression into the setups but that can cost time and money for customers and maybe problems as well.

So how does that relate to camshafts and your question.... well let's take a 350 LT1. 2600 stall, 3.23 gears, something pretty tame. Now you only have 10:1 compression to work with here, and DCR is important, but there is no way in hell that you can get 9.0:1 DCR with 10:1 compression, you would basically have to close the valve a little after BDC to get there. That would give you such a low duration and/or ICL that you really cant get there from here. So what you need to focus on is getting the valve events correct and keeping an eye on the DCR. Your more likely to be around 8.0:1 DCR than you will be 9.0:1 but you can always increase that afterwards with a static compression ratio change. With a stock motor changing to a much thinner head gasket would really help that out a bunch.

Now as for LSA, it's basically a byproduct but yes you can go to narrow and to wide and hurt average power for the RPM range you are running the motor in just like you can with duration.

Basically what I do is find the amount of overlap I want, find the right intake duration for the RPM range that I'm running in, look at the dynamic E/I% for the exhaust duration and figure how much lift I need to get the curtain area that is needed to feed those cubes at the max RPM that I want to make power. That's going to get me the valve events I want and then from there I can get the duration and LSA. More importantly I have to work in the real world with what lobes are given to me and what the valvesprings can do so the valvetrain can be produced. I do think in terms of duration and LSA, not IVC and EVO, but I do look at the setup and try and optimize each event for what the motor is going to need/like. So yeah I do think I need XXX duration @ .050" intake and exhaust and put it on a 1XX LSA, but at the same time that's all relative to the rest of the specs and that i've seen that situation, time and time and time again. That gives me a good starting point and I tweak from there.

Bret

 

I've always appreciated the "less is more" approach to camshaft design too. Curious to see what comes out of this.

 

Clean out your PM box

 

good info