Delta Cam? Anyone?

[maverick75]

Anyone running one of their cams? Also whats the biggest cam i can run with 91 octane?(its a weekend car so i wanna go on the wild side). Mods are in the signature. I already have adjustable rocker arms. Later on I will be swapping a 80` 250 head, with two small 2bbl carbs. Hopefully hit 9.0:1 comp ratio. Also i'll be making a header with dual collectors, 1 5/8 long tube.

 

[maverick75]

Oh and its got a rebuilt C4 with a new(remaned) converted.

 

[MustangSix]

Years ago I ran some analysis on EA 3.0 of various combos of cam, exhaust, carbs, and compression to see what would happen. What we learned was that of all the things you can do to pick up power in one of these engines, the one thing that made the most difference is the cylinder head. Unless you can get more air in and out of the head, you are pretty much stuck at about 160 hp with a stock head. And the only difference a cam makes is how little torque you get while making that hp.

That's why it was so amazing that when we saw guys putting the Aussie 2v head on a dyno they were picking up 35 hp with no other changes. And that's why Mike spent so much time and money to develop a new head. That's where the power is - not in the cams or carbs.

So anyway, on to your questions....

octane requirements are more closely tied to compression ratio and ignition timing. If you have a high static CR, sometimes you can get by with lower octane by using a bigger cam that doesn't build a high dynamic CR. Or you can crutch it a bit by backing off the timing or reducing engine operating temps. But cam specs and octane alone don't correlate. In any case, with only 9:1, you should be ok with any cam on 91 octane.

Two 2bbls on a log are fine if they are progressive. If they are normal 2bbl carbs, you'll be better off if the intake is isolated 123 from 456.

If you are already running a 260 cam, you should see a big boost in power if you port the intake and exhaust runners. A stock log head of any vintage or casting number flows very poorly.

Finally, install a good ignition. DS II, Pertronix, or DUI all have shown good results.

Good luck.

 

[rbohm]

8) to simplify what jack wrote, dont look for the biggest cam to run, but rather the best cam for the rpm range you plan to run in 80% of the time. too much cam timing can be worse than too little cam timing. also the only factor of cam timing that has any effect on fuel octane is in fact valve over lap, and lobe separation angle. a lot of valve overlap or narrow lobe separation angles will reduce compression pressure at lower rpm and prevent detonation. going the other way will increase compression pressure, and increase the possibility of detonation.

in the end your best combination is one that is planned out carefully, and all parts selections compliment each other.

 

[maverick75]

Thanks for the throural response guys. Im still learning about these motors, im 21 so I never grew up with these motors. I normally work on an build sbf`s and Dseries Hondas. Im kinda a maverick expert so im always on that forum and Gene posted something about cams being one of the best upgrades. In my original post i already stated that im going to swap to the largest port head, and im already running duraspark. As for the dual carbs, if i use sidedraft carbs will the divider still be needed? I have access to a plethora of Honda sidedrafts. The ones used on a 2.4. My planned rpm range is idle-4400. Im hopping these will be big enough for my planned rpm range.

 

[aribert]

Back to your initial question about Delta Cams - I use one in my Isuzu Amigo (2.3L). In order to get more valve lift, the cam gets the valve springs too close to coil bind. I learned this the hard way when my engine developed an internal rattle after about 65K miles that I could not find (I was not looking for an internal rattle - I was looking at both ends of the engine). After 25K miles of ignoring the rattle, while idling out of a gas station there was a very terminal noise followed by an abrupt lockup. Turns out the valve spring had been broken (for 25K miles) and the keeper finally came loose the valve dropped, the valve head seperated from the stem and the valve head ventilated the piston twice before getting stuck in the head. http://i290.photobucket.com/albums/ll27 ... 280018.jpg
http://i290.photobucket.com/albums/ll27 ... 280023.jpg

I am still running the cam (I like the results), with a new head & piston but now I plan on replacing the valve springs every 30,000 miles.

 

[maverick75]

I've already ran some of deltas cams in other cars. And for 86 bucks you can't beat the price. I have no questions about the quality, i already know that its good. I'm thinking of getting a customish one, its basically a mix between two. Any input? duration: 264/274, lift: .455/.480 With a Lobe center angle of 114.

 

[59F100]

8) ...the only factor of cam timing that has any effect on fuel octane is in fact valve over lap, and lobe separation angle...

...and IVC or intake valve closing point. It is important to degree your cam when you install it. This will determine your dynamic compression ratio which is based on the volume of air in your cylinder when the intake valve closes*, not at bottom dead center (BDC). (*Note: take that statement with a grain of salt)

Earlier closing (closer to BDC) will increase your DCR and your effective compression will change less over the rpm range. With a mild low revving engine, you could loosely base your octane requirements on the DCR.

A later IVC will lower DCR but you will see (if you could monitor it) more of a change in compression throughout the rpm range as the "ram effect" starts pushing more air into the cylinder prior to the valve closing. With a hotter higher revving engine, you could loosley base your octane requirements on you SCR value, or higher if you have a very efficient engine.

At least that is how I see it...much more to the whole story of course. And unless you are entering the engine masters six banger challenge...you might not need to be concerned with it. If you are, someone smarter than I w :| ill have to answer your questions...

 

[maverick75]

Is there a six cylinder challenge? Haha. I'd love to see that!

 

[Gene Fiore]

If I said a cam swap was the best upgrade then I must have been half asleep or something. As has been said in previous posts on this thread, the head is where the biggest gain will be seen on these little motors. A big log head with 1.75/1.50 valves installed and some porting in the bowl area and smoothing of the exhaust ports will give you a big improvement in breathing...which is what these engines need. A cam similar to the classicinlines 274 cam with a 110 or 112 centerline should work well. Putting a big cam with lots of overflap and an operating range much past 5000 rpm will not work well with the oem cylinder heads since the head just can't flow that much. Now put on the classicinlines aluminum head and now it's a different ballgame!

Oh, and if you still have a stock converter in that tranny you may need to step up to an aftermarket higher stall converter depending on what camshaft you end up with. Just my 2cents.

 

[MustangSix]

Is there a six cylinder challenge? Haha. I'd love to see that!

I'd like to see that too. Anybody want to ante up $20k to build and dyno a couple of engines?