Pushing to the NA limit

[MPGmustang]

well then what is the best camshaft for my motor? I'm miss understanding something here... so I'm askign in this category...

I honestly don't know what I want out of the motor, as I'm not sure what I feel when I feel it...

off the line I like quick accelration, I want to spin tires, not just chirp them... and I want passing power with ease, along with good mileage (18+ mpg)

currently
9.3CR
264/274 110* cam .450 inch lift with stock 1.5 rockers
78 head with 2bbl directly mounted
holley 2300 series 350cfm carb

Head flow
http://i897.photobucket.com/albums/ac17 ... AN0001.jpg

Current Dyno Run (best result with 87* air temp)


now, what would be better? is there a better cam that will give more torque or HP and not loose drivability? should I go get the head milled more and bump the CR up?

my goal with this engine is always more power, but right now I would like reach 150hp. I'll set up a dyno run a few weeks from now, as it's getting colder it would be a great time to test the enigne with the best temp of air.

but what do you guy's think?

 

[170-3tree]

Did you ever try a bit of a spacer on the carb? I believe that your cam could be bigger, but not sure if the 274/274 would ruin driving characteristics.
If you are tryin to hit it this time, and willing, another .1 or .15 compression might get the bump. Also, recall that using more can might need more compression to be drivable. Am I reading that a/f area wrong or do you go lean at high rpms?
Does your 350 have annular discharge? Would a cfm equivalent autolite with annular boosters get you where you want to be?

Just kinda tossing ideas out there for anyone to stomp on or agree with.

 

[xctasy]

There are no wrong cam combinations, only wrong engine specifications. Any cam will have an ideal engine specification that it will suit.

Copy what MustangGeezer is doing. I advocate the highest compression you can get, then optimise everything to suit the existing cam profile. Definately a flat top O deck piston with very close to valve piston clearance. So that cam you have can then work at its best.

The soft head concept of engine is where 1) the comp ratio is amped up, and 2)the cam duration wound back to get a cold cranking compression reading low enough to avoid massive detonation. If you can then 3) wind off ignition advance, and 4) concentrate on making the engine at 250 thou lift make 95% of the cfm flow at 450 thou, you'll get the power you need. A 5th requirement is paddle wheel rpm...an attempt to get mixture motion into every cylinder by promoting swirl. These five things are what GM used to get more power out of its all alloy 4.8/5.3/5.7/6 liter engines. Alternative takes on the soft head process are the changes that Classic Inlines headshave over regular 2v heads. They work with extra mixture motion, better cylinder to cylinder flow efficency, better port shapes, better combustion shapes. At present, compression ratio is kept at stock, but that's only because Mikes heads have to start somewhere. Where MustangGeezer is headed, is to a more soft head Larry Widmar configuration.

Most people here who are making power are tending towards the five of the six sides of the soft head corner stone. The sixth is the one that everyone messes up on, reducing exhaust port volume to increase exhaust port flow and low rpm torque. That's why some modified log heads fail to deliver good fuel economy...the exhast areas shouldn't be touched, as the cam can balance the intake:exhast flow to the 65 to 80% that makes power...anything more, like 89%, is too much flow, and there is no scavenging at low lifts.


At the moment, you have 140 cfm at 450 thou, so the target cfm at 250 thou is 133 cfm, 17% higher than the 113.8 cfm you have at the moment. If you can make changes to the piston to a flat top, and then run it 45 thou away from the piston at the closest, then you'll get cummulative gains in the lower end, with no disadvantage up high. Down here, our alloy Honda headed cross flows sit at around 145 cfm, and flat line at 196 hp when given the best 2-bbl carbuation, so an iron head non cross flow should be able to match that if the intake manifold porting allows each cylinder to flow 85% of the best port flow...that's the hard bit on the log head. That and port area is why the Classic Inlines and 2V heads yield so much extra power. Inter cylinder flow efficency in cfm should be 95% of the best port flow to get the hp the cfm figure implies.

So optimise what you can with the parts you've got, and you'll be really happy.

 

[MPGmustang]

the AF Ratio does go lean, but only because I let go of the pedal then... other wise when it went under the line it was right on target for max hp. I could richen it up to 12.8 but I figure that I'm close enough on the AF at WOT. IDK if a space will help, but I'm sure I can get my hands on a 1 inch spacer and try. it never hurts to try.

so the 6 things to consider

1)the comp ratio is amped up
I'm thinking close to 9.7-10 CR, I still have to use 91 oct as I don't get 93 oct down here and I don't want to spend 5$ for a bottle of oct booster

2)the cam duration wound back to get a cold cranking compression reading low enough to avoid massive detonation
my cam timing is 4* advanced I'm using the clay smith cam, and they say it's best @ 4* advance, what should I set it too?

3)wind off ignition advance
using the DUI, I have it set to 14* static, and it has 24* mech advance @ 3k rpm, what would be the best setting? I've always thought I can do something about this, but don't have anythign to do it with so I'll have to send it out and have it done, so I'd rather tell them one thing and have it done right. alos I guestimat a 12* vacuum canister to retard the timing... under full vac it's retarted 12* under zero vac it's fully advanced.

4) concentrate on making the engine at 250 thou lift make 95% of the cfm flow at 450 thou
this is easily said than done, IDK how to accomlish this, it's already ported to the max, and any more I'm told will risk head integity as it's close to the water ports and exhaust walls... I could try that molten hot sand and run it through to smooth it out, but don't think i'll get that extra cfm, beside it costs almost $1500 to run it through, and I'd rather spend that on an alum head... wouldn't you? so for arguments sake I have to put my foot down on this one, as it's too costly

5) requirement is paddle wheel rpm...an attempt to get mixture motion into every cylinder by promoting swirl
I'm also told that dished pistons are best swirl efect... so it's why I have dished pistons... but what else can I do? also explain little about the paddle wheel... I'm very young at this.

6) reducing exhaust port volume to increase exhaust port flow and low rpm torque.
as compared to the exhaust, it looks like I messed up, I have mostly 87%-90% flow when compared to the intake flow, there's nothing I can do about that except get a different head... which is too costly... my .100 lift to .200 lift goes from 75% to 87% flow rate, so lower lifts are good just not higher lifts... IDK if this helps... but then agian I have a header so I kinda don't have any restriction now. darn.

I have .010 deck block, and 7cc dished pistons... don't think I can must up the dough to fix these...

so in the end, It really comes down to more CR(milling head), less cam timing, less ignition timing, these three I can do

the milling and the cam will be done the same time. what's the goal to shoot for is the next question. as I have a dual grind camshaft (which apparently I don't need or use to it's advantage) I can or can't (i forget which) go to a higher CR safely and still use pump gas (91 oct), I'm even hard to understand what my dynamic CR is, even though I understand that it's when the valve closes and it when I actually start building compresison, as compared to the static CR.

So Xctasy,
out of milling head, cam timing, and timing, what should I aim for? those I can work with. in a reasonable amount of time.

 

[MPGmustang]

I guess instead of guestimating the timing, I'll spring for a dial back timing light and get some accurate readings... just to fully tune the engine.

 

[xctasy]

Camshaft is the answer. You can get your distributor sorted easily, and if the log heads exhast ports have been opened out, then the cam you have won't make good torque anymore..it'll be "cammy"

Save up for another cam profile which suits your head and compression desires, and spend 400 bucks for a designer cam profile, and have Clay Smith make you a special from its masters.

This is classic Engine Analyser stuff, and you'll find a cam which lights up with that heads cfm figures.

Then ask Farron for a distrubutor calibration, and Bill for a killer Annular Holley.

So long as you match compression, carb, cam and head flow, you'll make up for the flow efficiency issues. The American way is to take a too small carb, and optimise the cam to suit the head, carb exhast. I don't like a split high scavenge exhast unless its a specific Cobra Jet 428 FE, where the iron headers were quite restricted.

 

[MPGmustang]

Okay Xctasy, I'm bitting for more info...

with the head info I have and the fact that I would like to stick to 91 oct pump gas (cause that's the highest in my area), what is the best bang for the buck?



Camshaft, need a diffrent one cause this one is limiting me... how do I figure out wha duration's I need, and lift?
Farron from where? getting the distrubutor dialed in should be easy and quick

If these two don't push me to 150hp, then I'll change the carb... going for the billet meter block, and the annular mod.

 

[FalconSedanDelivery]

I'm Faron , I recurve Dists you can PM me

 

[170-3tree]

Richard,
If I were in your position, I would look into gettin a custom ground cam. I actually think that the same durations, but switched, on 112* centers, maybe with a bit more lift. Maybe more like 270/264 would be more suited, I am sure there is a science to figuring it out, but I am lost beyond that. You have a free flowing exhaust and a restricted intake. I would get a cam that favors it.

Lift, in theory, should be around 1/3 of your intake valve size. According to vizard, but knowing that your log won't flow much over .450", I would only say go higher, maybe for higher average lift.

 

[MPGmustang]

actually, I was thinking of getting rid of the dual grind altogether and go a single pattern grind.

FalconDedanDelivery, can you do DUI'?

 

[170-3tree]

That would be cheapest and easiest. I was just thinkin, if you really wanted
to optimize what you have.

I believe Faron will do the DUI though, I think next time I decomission my car I will have him do mine if he will.

 

[MPGmustang]

it will still be a custom grind, but the dual grind I have now will go away, maybe sell it to make some losses back from it... I'm thinking of a custom grind with a single pattern... but maybe dual is better IDK. I figured I don't want dual as I alread have a good enough exhaust flow (the purpose of a dual grind in a cam) but oh well, it's all cool.

 

[FalconSedanDelivery]

I can recurve almost any distributor that is or has been produced , with a few exceptions and a DUI/HEI is Not a problem

 

[xctasy]

it will still be a custom grind, but the dual grind I have now will go away, maybe sell it to make some losses back from it... I'm thinking of a custom grind with a single pattern... but maybe dual is better IDK. I figured I don't want dual as I alread have a good enough exhaust flow (the purpose of a dual grind in a cam) but oh well, it's all cool.

I'll buy your cam. I need it for my 3.3 log head engine. My engines are independent runner, so my log heads don't have reworked exhasts, they have really good induction with big carburation instead.