Race Cam selection

[1795]

The heads have been ported and machined.



Here is the flow sheet for the heads.



The intake manifold for the Webers is being ported to match the heads, new headers will be made this weekend and fitted. Using bushed roller rockers. Lightweight forged cam, 289 with approximately 11.5:1 compression ratio. Running 110-112 octane race fuel depending on availability at the track. 48 IDA Webers.

So what are your thoughts on cam grind?

Jim

[blykins]

Jim, there's no doubt in my mind that I would nail this camshaft.

Contact me through email if you're interested.

[1795]

Brent,

Sent you an email. Taking a look at what different people have to suggest and then making my decision.

Jim

[blykins]

I'm not trying to toot my own horn, so please don't take it that way.

However, I don't generally give out camshafts specs on race cams, because most guys post publicly on forums, and that's where all the "experts" come to demonstrate their knowledge. LOL

I have an extensive history of doing camshaft dyno tests as well as in-car camshaft swaps to find better ways of doing things.

Most guys will say, "I'm very happy with the cam so-and-so ground for me..." but most guys have never tried multiple camshafts on the same day, or at any time at all.

I will say that I'm the only one that has an FE turning 7500 rpm with a hydraulic roller. That's not because I ask around and have people grind cams for me. It's because I spend a lot of time looking at camshaft specs, the overall engine combination, and do lots of dyno testing.

I was approached by a custom cam designer who told me that he would like to earn my camshaft business. I told him that I was working on a particular combination, I already had a camshaft for it, but I was willing to test them both. I gave him the entire catalog of engine data, and even gave him my camshaft specs, but my cam bested his by 28 peak hp and 10 average hp.

One of the members on my Cleveland forum also approached me, telling me that they had a custom camshaft ground for them by Cam Motion. He told me that it made good horsepower but it was soft on the bottom. I had a camshaft ground for him that produced the same peak hp, but also gained him 20 hp at 3500 rpm.

If you have been on the FE Power forum and saw Jay Brown's new cylinder head project, Blair Patrick provided Jay Brown a camshaft for his project. I saw the issues and actually fronted Jay another camshaft to try that was 12° SMALLER than the previous cam and netted the engine more peak hp and torque, as well as up to 20 hp at lower rpms.

Would love to earn your business.

If the other guys are telling you that you need a single pattern camshaft, or a 114-115 LSA because you have Webers, you should walk away.

[1795]

Going only with well known and respected race engine builders/cam designers, who have experience with SBF's and Webers. Brent, I look forward to seeing your specs off-line and for those of you wondering, I will not be posting Brent's specs online.

Jim

[1795]

It is interesting to see the variety of flow numbers that people get from SBF heads. Found a chart online that listed results from a variety of manufactures.

https://www.google.com/url?sa=t&rct=...1SqRFtb-QkdRfS

The results vary significantly from a stock 289 head at 166 cfm Intake (.600) and 125 cfm Exhaust (.600) to a Kasse SVO head at 374 cfm Intake (.600) and 273 cfm Exhaust (.600).

When I was discussing my heads with the engine builder at Cobra Automotive he was saying that their ported race heads are producing over 300 cfm at .700 intake. Heard from several people that my heads in their old form with flowing about 260 cfm at .700 were the limiting factor in my engine. In addition, you have to factor in the carburetor's flow capacity, as while the head might be able to flow a certain cfm, a restrictive carb system will have an impact and the head can only flow what the carb provides.

I have settled on getting cam options from three sources based upon my discussions with them. They are Brent, Cobra Automotive and Shelby Racing Engines. Dema Elgin supplies the cams for Shelby.

Should be able to make a decision soon, as I need to get this engine together.

Jim

[talos]

Just remember, you get what you pay for. Mr. Blykins had a special camshaft ground for my side oiler with the combination I had given him and the results I was looking for. It was perfect for what I wanted. A lot of people asked for my cam specs. His years of experience is worth the investment alone. I went through two previous cam grinds with unsatisfactory results, from other sources, before he assisted me.

[1795]

Thanks for the input. Money is not a consideration, they are all within a $100 of each other. It's just sorting out which one will be the best one for this application. Without going into specific grinds, the lifts for intake and exhaust are all in the low .600's, but from there the departures begin. LSA has a range of 6 degrees between lowest LSA and highest. There is quite a variability in duration @.50 and in lobe shape.

Have to consider multiple factors in determining which one. All of the people giving input and making recommendations are well respected with years of race cam development; there are no slouches in this group.

Jim

[blykins]

Unless you have advertised durations, .200" durations, and .050" durations, the lobe shape would be undefined. I purposely do not give out all of that information.

[eschaider]

Originally Posted by blykins

... Most guys will say, "I'm very happy with the cam so-and-so ground for me..." but most guys have never tried multiple camshafts on the same day, or at any time at all.

This^ and a lack of understanding of the significance of lobe profile aggressivness and the effect of different profiles not just on intake and exhaust cams but on opening side and closing side dynamics makes significant differences in the personality and performance of the target engine — and we have not even gotten to cam phasing yet ...


Ed

[cycleguy55]

Originally Posted by blykins

Unless you have advertised durations, .200" durations, and .050" durations, the lobe shape would be undefined. I purposely do not give out all of that information.

Having that information would allow someone to reverse engineer your cam designs. It's certainly understandable why you wouldn't be giving that out.

[1795]

Originally Posted by eschaider

This^ and a lack of understanding of the significance of lobe profile aggressivness and the effect of different profiles not just on intake and exhaust cams but on opening side and closing side dynamics makes significant differences in the personality and performance of the target engine — and we have not even gotten to cam phasing yet ...


Ed

Ed,

Yes, it is a very dynamic situation and there are a multitude of engine factors that are effected by a small change in any aspect of the cam design. The engine is a system and has to be treated as such. All parts working together to achieve a desired outcome.

Jim

[1795]

Originally Posted by cycleguy55

Having that information would allow someone to reverse engineer your cam designs. It's certainly understandable why you wouldn't be giving that out.

That is true, if someone were so inclined. I am not. I will not be sharing any cam design information, and have not, with any cam designers or anyone else other than the person building the engine (who is not and does not design cams) and ultimately the final decision is mine. My expectation is that they provide me with enough information to make an educated decision based on the merits of their choice, not due to why the other choices are deficient.

As with any field, there is a great variability in opinions and it is up to the buyer to do due diligence in examining the merits of all opinions.

Jim

[eschaider]

Jim, if you don't go to a builder/designer (like Brent) who already has experience with your basic engine package, then you need to start with some more sophisticated than the average bear engine modeling software that allows you to build engine models with detailed cam profiles and then use the modeling software's optimization tools to narrow down the universe of cam profile possibilities for the power and torque curves you are looking for and then optimize them for the engine.

When you get done with that, you need to use a software tool (for the older software probably not with newer software) to optimize the opening and closing profiles for smooth operation. This is a graph of the velocity, acceleration, and jerk curves for the closing side of my passenger side exhaust cam. It is not easy to get them to look that smooth, especially the acceleration and jerk curves.



This is different than the opening side ramp for the cam and in my case because of the different rotation side to side for my cams, it is also different than the closing ramp for the driverside exhaust cam. Your lobe profiles will be a bit easier because of the OHV vs OHC design nuances.

All that said, you will still need access to some modestly pricey equipment and software tools to get your first profile onto a camshaft. The stuff I was fortunate enough to be able to have access to was a generation or more behind the tools that are available today, so some of what I had to do by hand can be done by software tools today.

When you are all done describing your new paper tiger you will need to reduce all he whizzy stuff to a camshaft you can put into the engine and test on the dyno. This step like so many is an iterative process that will be repeated a number of times (read grind more than one camshaft) until you get the power curve you intuitively were looking for way back when as you began this process.

There is considerable value that Brent and guys like Brent bring to the table in this process. As a consumer of his products and services you are buying the literally years of testing, rethinking and retesting he has done to get to the cam recommendations he is providing you as the consumer of the advice and products from him, today.

To duplicate this end result takes lots of time (think years), lots of effort and yes lots of money spent on the process. A good even handed (think realistic) approach to what you are looking for packaged into a dialog with him is an absolute win on your side of the table. You skip literally all of the hard work and sometimes painful discovery process and head to the finished solution without any of the abuse you would have otherwise subjected yourself to.

My best recommendation would be to call Brent, use a cam he recommends and enjoy the engine and driving experience it affords you.


Ed

[cobrakiwi]

Stick with the race engine builders than run the weber induction, they have done it all before and more than likely have the results to back them up.
Nothing new with the small block ford and the weber carburetor.

[1795]

Ed,


I hear you. I am not trying to design a race cam, what I am doing is talking to experts who have designed race cams for SBF's with Webers and then sorting through what they say. I am not even having conversations with anyone that has not designed a cam for more than a few full race SBF's with Webers. I am not going to be someone's guinea pig this time. Weber's do not function in the same manner as a four barrel carb and that has to be accounted for.

As stated previously, I have received three different designs. I am taking what they tell me and doing research and trying to figure out which one makes the most sense given what I know, the engine, car and my driving abilities as a whole. It's not an easy process, but I am someone who loves doing research and have learned a lot in just the last couple of days pertaining to engine dynamics and will learn a lot more before my selection is made.

Thanks. I appreciate your thoughts and comments.

Jim

[eschaider]

Not trying to build your car or engine, Jim but (always a but right?) if you haven't already bought the Webers you might want to investigate the similar looking throttle bodies that are used with EFI. I doubt there is any significant pricing difference when either setup is finished but I suspect you will really appreciate the tunability and throttle response the EFI will bring to the engine without loosing that stunning Weber appearance when the hood is opened up.


Ed

[1795]

Originally Posted by eschaider

Not trying to build your car or engine, Jim but (always a but right?) if you haven't already bought the Webers you might want to investigate the similar looking throttle bodies that are used with EFI. I doubt there is any significant pricing difference when either setup is finished but I suspect you will really appreciate the tunability and throttle response the EFI will bring to the engine without loosing that stunning Weber appearance when the hood is opened up.


Ed

Ed,

Already have the Webers, this is an engine refresh. You have to do that about every 20 hours of race time so that things can be identified and replaced before something catastrophic happens. Vintage racing rules do not allow for EFI unless a car was originally raced as such back in the day. The Webers on an independent runner intake manifold acts more like an EFI system than a 4 barrel carb. The runners are only about 2" long and drop at a slightly angle from the carb base into the intake port of the head. The carbs like a lot of advance, and they want it early. This engine had 38 degrees and it was in by 2500 rpms.

Spent a couple more hours reading up on cams, engine dynamics and flow rates. Read some interesting stuff on the impact of carbs, intake manifold and exhaust on head flow rates and performance. It is easy to get caught up in bench flow numbers of a head, but by the time that you put the engine together the actual flow numbers are not the same.

Thanks.

Jim

[eschaider]

Understand, Jim.

For some reason Ihad it in my head this was a street driven car not a race car and I can't tell you why — brain fade?. Your observations / discovery about the impact of intake and exhaust plumbing on head flow rates is spot on. Pretty amazing when you first come face to face with that particular reality.


Ed

[1795]

Ed,

It happens to all of us. Heck, you are on here replying to so many different threads it's hard to keep them all straight.

I was just on the phone with Jim Inglese, as I have to get new base gaskets for the carbs as we had to do some porting and machining on the intake manifold. Part of the discussion centered around the difference between doing a dyno tune on a stand versus a chassis dyno comparing street/performance engines versus race as it relates to the proper air/fuel mixture. For a street engine, especially on a dyno stand, as soon as you get to WOT and the power start to drop, the engine is shut down and the air/fuel ratio is examined. For a race engine you have to run it at WOT for a longer time and preferably under load because that is how a race engine is run. On the track I may be at WOT for 30 seconds or more depending on the track situation before braking, downshifting and then right back to WOT. It's a lot easier to get to a lean situation if actual race simulation is not tested.

Again, thanks a lot for your thoughts and input. Since retiring I do not get all of the mental stimulation that I need. This research is providing some of that.

Jim