[adamsperf]

I'm up for good conversation in regards to camshaft selection. This is one area that most enthusiasts know very little about.
Most believe that bigger is better and therefore make poor choices (IE: loss of performance for the same dollar) Choosing the right manufacturer, and knowing how/why certain camshaft attributes work, can pay big in terms of power output. Anyone care to elaborate more on this?
We can start off with one of several topics:

1) Duration, what is it, how is it determined and how does it effect engine operation?

2) Lobe seperation, what is it and how does it effect engine operation?

3) Why can't you simply compare durations @ .050 and be sure of an apples to apples comparison?

4) Single pattern profiles or dual pattern profiles, what are they, when and why should they be used?

Lets get technical and learn from each other!

 

[adamsperf]

[No message]

 

[adamsperf]

Ok.. That's a really great topic! Are we building a restricted engine from the ground up? Or are we trying to get more performance out of an already running restricted engine? And do we aasume that we know the specs of the running engine. (IE: actual cylinder head airflow in CFM, runner volume etc.)

 

[351c rules]

Lets build a 302 strickly stock motor for oval track racing.

 

[adamsperf]

This presents a whole different challange as compared to "band aid" fixing a single restrictive component like log manifolds. Here we are faced with multiple restrictions to try and over come. This will get time consuming as a techboard topic because we will all need to know the parameters to follow along like: All stock components or are we cheating were we can?
Dirt or asphalt track? Oval track size?
2 or 4 bbl carb? Minimum weight allowed for the chassis? Do we have access to a flow bench while building this theoretical engine? Once we know this, we can start addressing the restriction to over come.

 

[Oliaar]

I appreciate the knowledge of most of the people on the forum but for someone as myself that is new to the whole thing I would like to hear answers and comments to the initial questions that were asked.

 

[gttorinofan]

I agree with you Oliaar.

 

[351c rules]

lets go with these rules. we must use stock 2bl,log manifolds,flattop piston 4 valve ,0 deck,no lighting,stock heads,cast iron intake. so what individual parts do you think would be the best and how much power?

 

[adamsperf]

I'm also a newby to the forum. Since the postings are under the "technical" heading, I figured I would stir up a technical conversation and learn from you guys.. I see alot of people viewing this topic, but next to none are getting into participating?
Throw in your thought snd ideas for this restricted engine and we'll see what we can get out of it.

We'll say this strictly stock 302 must use s 2 bbl carb, stock iron intake, stock iron exhaust manifolds, stock lift camshaft.
The chassis is 2800 lbs and the track is 1/2 mile asphalt oval. What can we do when we build this engine to help it make hp? Anyone out here have experience with restricted 302's???

 

[adamsperf]

Sounds good 351C.. What stock casting heads flow the best? 1970 351W the "D0VE" castings? I know they have 1.84 x 1.54 valves and a small combustion chamber that will work great with the flattop pistons you provided. Any published airflow specs?
This will play a big part in camshaft selection.

 

[andwrong]

um..... i just read this and the only reason i'm replying is because

I DONT UNDERSTAND ANY OF IT!!

 

[adamsperf]

I would prefere to use a fully ported heads for this application. Up here, strictly stock means NO head work other than a performance valve job. Your right, Ford exhaust ports are some of the worst. We can shorted duration and effectively cut over lap.(but only so much before we shift the power curve against us) However, a severely restrictive exhaust is going to negate alot of the bennifits we would normally get from the camshaft. As you know back pressure kills horsepower period!
A single pattern profile won't help maximize exhaust scavenging in this situation, but it would keep the exhaust opening from intruding in on the tail end of the power stroke. From my experience, most street engines make more torque and Hp with a single pattern profile.
(assuming you have a free flowing exhaust system) Only when the revs come up does the dual pattern profile begin to pay off. For our retsricted engine, I was thinking along the lines of a solid lifter profile with descent lift, (we can cheat and use high ratio rockers to gain a few extra degrees of duration if needed, greater lift and intensity.) LSA on a 106 with 4 degrees advance to 102 I/C. This will put the torque curve at the lower and mid range of our power band and really help the car accelerate off the corners. For those that are less familar with selecting camshafts. The duration will dictate where the power curve is. (IE: Lets say a 280 duration profile will make power from 2000-6000 rpms) But you can determine where in this power curve the engine will make more or less of the power by changing certain things like the lobe seperation angle. Tighten the LSA will open the intake valve earlier in the induction cycle and close it earlier on the compression cycle. This will pay of with greater low and mid range power and a peaked power curve. And likewise a wider seperation angle has the opposite effect and will promote higher rpm power and give a broader power curve. I like 108 LSA for most street engines under 350 cid. How about you guys?

 

[andwrong]

uhm.... i'm going to go get a job at comp cams now... and when i know something about cams.. i will get back in on this

 

[adamsperf]

I was told that Users out here had a good grasp on the basics of cam selection. so I'm sure you're probably just kidding. But a job at Comp Cams would be cool. If you get in, how about getting me a job there too?