New 2056 with big valve 2.0 heads in progress!, I have done various searches and have not found good info on this subj Options

[HAM Inc]

Thanks for the kind words Brett.

I will offer this insight for free. To maintain the optimal port balance for a typical high performance street engine if I spend 10 minutes in the exhaust port I will spend between 30-40 minutes in the intake port.

[ME733]

...The only proper way to compair a camshafts, lift and duration, is to create a lift and duration table for each camshaft you are considering....And before you can do that , properly, ...you must decide at what point you are going to Begin to take measurements...And to do That properly, you must decide , (use a standard) when air flow actually begins to enter the combustion chamber. And to be able to get a handle on that you must know what your valve lash is going to be , and what it will be when the engine is hot and running.(total Lash)....One way to get a handle on all this is to become the engine you are building, to think about how you want air flow (into and out of yourself) to happen and when. And efficent, and effective. It is very easy to overcam( Duration) an engine. it is very easy to over port or over valve an engine. These are easy mistakes that are done all the time. relieing or beliving in "head flow" numbers as the holey grail of head work is fiction to the extent that "head flow" can never replicate the actual engines air flow in operation...Every engine, in my opinion, should use dual valve springs.....all this as food for thought......from murray.

[gothspeed]

lol none of the information anyone has posted is confusing. What is a little strange, is why anyone would think it would be (IMG:style_emoticons/default/huh.gif)

Lobe separation, lift, duration, ramp curves/rates or lack of (straight slope) etc. are easily described as a sine wave (different cam specs create a different shape). Intake and exhaust lobes each create their own wave ....... overlaying these waves on their respective time reference determines where and how much they intersect/interact to describe overlap and lift in relation to TDC and piston travel. How these factors interact with each other in theory on paper, is usually very different than in practice, as practice generally introduces new unfactored variables.

This thread was started to query for first hand experience with various cam profiles vs carbed 914 engine configurations. So if you want to share your experience, it is much appreciated. (IMG:style_emoticons/default/shades.gif)

[gothspeed]

...The only proper way to compair a camshafts, lift and duration, is to create a lift and duration table for each camshaft you are considering....And before you can do that , properly, ...you must decide at what point you are going to Begin to take measurements...And to do That properly, you must decide , (use a standard) when air flow actually begins to enter the combustion chamber. And to be able to get a handle on that you must know what your valve lash is going to be , and what it will be when the engine is hot and running.(total Lash)....One way to get a handle on all this is to become the engine you are building, to think about how you want air flow (into and out of yourself) to happen and when. And efficent, and effective. It is very easy to overcam( Duration) an engine. it is very easy to over port or over valve an engine. These are easy mistakes that are done all the time. relieing or beliving in "head flow" numbers as the holey grail of head work is fiction to the extent that "head flow" can never replicate the actual engines air flow in operation...Every engine, in my opinion, should use dual valve springs.....all this as food for thought......from murray.

Good stuff, I agree (IMG:style_emoticons/default/smile.gif)!!

[Brett W]

I saw something a while back about the port diameter in relation to valve dimension and can't remember off the top of my head what it was. You may run into issues with the 44mm intake valve and the total port dimension ratio being out of sync. I wish I could remember where I read that, since I have been playing with boosted 4 valve heads lately I don't worry so much about the 2 valve stuff like I used to.

On my engine I ran 42mm/36 2.0 914 heads. The heads had been cut down quite a bit, but I also went a little over board opening up the chambers around the valves. I paid for that with a little less compression than I wanted. It was 8.9:1. I also went a little hog wild on the intake ports and thus lost some velocity. Lesson learned. The engine was a little soggy way down low, but I worked around it. But above 3500 it pulled like a raped ape all the way to 7500. Engine made 118hp at the wheels through stock heat exchangers. I think with more compression and decent headers it could have easily done 130 at the wheels. The engine ran great. Also the lightweight flywheel I had tended to affect drivability, it was an 11lb flywheel (On a bathroom scale). (I suspect it was lighter than that)

I was running 44idfs with 36mm chokes and a modified 1.8 dizzy. If I had stuck with the T4 engine I would have gone down to 34s and swapped to a Mallory. That should have made a big difference in the mid range without affecting top end. The gearbox had an S and X 4th and 5th. car pulled like crazy from 70-127. I pulled on a Supra (NA) from 90-127.

Of course a 2270 is a cheap upgrade in the grand scheme of things.


What are you using for your valves? What angles and seat widths are you contemplating? You will find some low lift flow with a nice 30deg back cut on the underside of the intake valve. Some people have found benefit from a 15+degree cut on the face of the exhaust valve but I also wonder if on our engines it causes the valve edge to run hot. I assume you are just running stainless aftermarket replacement valves with stockish dimensions. Not a nice tuliped head valve right?

[HAM Inc]

RAT 9500 cam & lifter kit. Worth every penny.

[gothspeed]

Thanks for the kind words Brett.

I will offer this insight for free. To maintain the optimal port balance for a typical high performance street engine if I spend 10 minutes in the exhaust port I will spend between 30-40 minutes in the intake port.

That sounds about right (IMG:style_emoticons/default/smile.gif).

Of course a 2270 is a cheap upgrade in the grand scheme of things.


What are you using for your valves? What angles and seat widths are you contemplating? You will find some low lift flow with a nice 30deg back cut on the underside of the intake valve. Some people have found benefit from a 15+degree cut on the face of the exhaust valve but I also wonder if on our engines it causes the valve edge to run hot. I assume you are just running stainless aftermarket replacement valves with stockish dimensions. Not a nice tuliped head valve right?

The tiny budget rules my options at this point, so the extra $1500 or so to go 2275, is not gonna happen in this iteration.

The valves are very nicely deburred stainless, with 'tulips' being their first, last and middle names (IMG:style_emoticons/default/wink.gif)

RAT 9500 cam & lifter kit. Worth every penny.

Sounds good (IMG:style_emoticons/default/smile.gif), though without any specs or ball park, I will not know how to set up the heads (IMG:style_emoticons/default/unsure.gif) .......... I do not know why no data is listed with those type 4 store cams (IMG:style_emoticons/default/confused24.gif) ............ that is why I am looking at cams that have 'some' numbers published ......... at absolute minimum, I would need to know the peak lift to make sure my retainers are not gonna kiss the guides, also duration to have an idea where the valves are gonna be with respect to the pistons during overlap/TDC. Personally, I do NOT like the 'slide your money under the door' approach to buying anything. I like setting my own stuff up, so I can take the credit when it blows up (IMG:style_emoticons/default/wink.gif)

[Jake Raby]

Often times big cams, big ports and big valves make LESS power, or they'll create a power band thats virtually worthless for the intended application.

"advertised numbers" for cams and their statements of RPM range are generally worthless. Thats why we have no one line statements about what any camshaft does to the engine, doing so is often times going to send someone down the wrong path.

There have been times here when we've changed cams in the same engine 10 times in a single month to see the effects of those grinds. Hell one of my VW Bus combinations took 14 camshaft deviations to find the right profile and that sometimes was simply a change in lobe separation, other times we just added 2 degrees to the exhaust side of the cam. small changes= large differences in lots of situations.

That said, the camshaft is the LAST component that you buy, AFTER you settle on exact CR and exact port work and have those values.

[gothspeed]

This thread has turned into a circus of sorts, but I am getting useable info on some of the posts (IMG:style_emoticons/default/smile.gif). I thank those of you who posted in good faith (IMG:style_emoticons/default/sunglasses.gif) !!!

Don't judge those cams simply by their .020 and .050 numbers.. To really understand the numbers you need to see what the duration is at .200-.350" lift.

If you consider those numbers some cams magically appear much larger than they used to when you just looked at the advertised numbers. Choosing a cam from just those numbers isn't illustrating the big picture.

FYI- The cam in Len's FP engine that spins 8,500 RPM is actually smaller than all but one of the cams you mentioned if one looks at onl the advertised numbers, thats in a full race engine with 13:1 CR.

The difference is that cam is HUGE between .175-.410" lift. Lots goes into camshaft selection, you can't really make the best choice until you have actual flow numbers from the heads.

NOW we are talking!! Len's cam sounds like a quick ramp rate and stays high for a longer period (IMG:style_emoticons/default/smile.gif). An increased area between the start of the ramp and full lift will indeed feed an engine at higher RPMs, than a slower ramp rate or narrow lobe. Trouble is, there is no way for me to know what I am getting short of buying a ton of cams and measuring them. Which I may have to do, if I do not find what I need.

I may be new to the forum but I am not new to performance engines. One of my passions is in intake and exhaust system design. I have successfully increased HP on many exisiting performance engines (of other makes), for a very long time.

I understand many people build type 4s for autocross and want 'torque' ASAP. My motor will NOT be doing ANY short courses.

FYI one of my other cars does not reach peak torque till 4.5-5k RPM and peak HP till well over 8k RPM, with redline a hair under 9k RPM. It suits my tastes perfectly (IMG:style_emoticons/default/smile.gif).

Often times big cams, big ports and big valves make LESS power, or they'll create a power band thats virtually worthless for the intended application.

"advertised numbers" for cams and their statements of RPM range are generally worthless. Thats why we have no one line statements about what any camshaft does to the engine, doing so is often times going to send someone down the wrong path.

There have been times here when we've changed cams in the same engine 10 times in a single month to see the effects of those grinds. Hell one of my VW Bus combinations took 14 camshaft deviations to find the right profile and that sometimes was simply a change in lobe separation, other times we just added 2 degrees to the exhaust side of the cam. small changes= large differences in lots of situations.

That said, the camshaft is the LAST component that you buy, AFTER you settle on exact CR and exact port work and have those values.

I understand your methodology, but I usually massage the heads, compression, intake and exhaust to match a cam's characteristics/potential first, as those parts are far easier to remove, replace or modify than a camshaft.

I am interested in cam specs similar to Len's, unless it is some sort of a secret or personal custom grind. Then I respect his accomplishment and will find my own way, not a big deal. Thanks for the info so far.

[Jake Raby]

I may be new to the forum but I am not new to performance engines. One of my passions is in intake and exhaust system design. I have successfully increased HP on many exisiting performance engines (of other makes), for a very long time.

One thing you'll learn is that the design of THIS engine is much different than other engines. I work with people who misconfigure these engines horribly and they have experience just like yours, with other engines.
Just be foreqwarned that your previous experience is probably best left aside, you have to start from scratch if you want to be successful.

Trouble is, there is no way for me to know what I am getting short of buying a ton of cams and measuring them. Which I may have to do, if I do not find what I need.

Guess what, thats what I've been doing from day one. I have cam doctor plots for EVERY one of my 65 cam grinds. More importantly I have dyno graphs of each cam (and all its derivatives of split duration, lobe separation/ etc) from all my popular displacements with all of our RS and LE head offerings coupled to them. and CR from 8:1 up to 13.75:1. I just finished sorting those files this week, they tally over 8,000 plots from 1997 to present. Thats not counting the hard drive full that I lost in 1999 to a lightning strike. Pouring over the files and overlaying the average power information all derived on the same two engine dynos and chassis dyno really tells the tale. Having driven all of those combinations is the other pricless bit of data.

Lens cam is a secret weapon, actually both of them are. I was just using that cam as an illustration of how headwork and displacement can turn a race cam into a street cam in two different engines.

I have used the cam I designed for Len in a 2270cc engine with a 200CFM intake port and a 75% I/R ratio and the result was a powerband from 3-6K, instead of a powerband from 5-8.5K like Len's race engine. In the 2270 the cam idled like stock at 950 RPM and had a flat torque curve...

Keep doing your homework.... Just realize that the downfall of many TIV engine designers has been treating this engine like something that its not. Understand that now and make wise decisions.

What do you plan and I'll look through my plots for a similar combo and post the charts with their notes.

This post has been edited by Jake Raby: Nov 5 2010, 09:58 PM

[gothspeed]

I may be new to the forum but I am not new to performance engines. One of my passions is in intake and exhaust system design. I have successfully increased HP on many exisiting performance engines (of other makes), for a very long time.

One thing you'll learn is that the design of THIS engine is much different than other engines. I work with people who misconfigure these engines horribly and they have experience just like yours, with other engines.
Just be foreqwarned that your previous experience is probably best left aside, you have to start from scratch if you want to be successful.

Trouble is, there is no way for me to know what I am getting short of buying a ton of cams and measuring them. Which I may have to do, if I do not find what I need.

Guess what, thats what I've been doing from day one. I have cam doctor plots for EVERY one of my 65 cam grinds.

Lens cam is a secret weapon, actually both of them are. I was just using that cam as an illustration of how headwork and displacement can turn a race cam into a street cam in two different engines.

I have used the cam I designed for Len in a 2270cc engine with a 200CFM intake port and a 75% I/R ratio and the result was a powerband from 3-6K, instead of a powerband from 5-8.5K like Len's race engine. In the 2270 the cam idled like stock at 950 RPM and had a flat torque curve...

Keep doing your homework.... Just realize that the downfall of many TIV engine designers has been treating this engine like something that its not. Understand that now and make wise decisions.

Sheesh ... let me get my boots (IMG:style_emoticons/default/rolleyes.gif) ................ I had no intention of reinventing the wheel with this little engine project, which is why I asked for info on this seemingly friendly forum. But since 'asking' for decent info has proven to be taboo, I will build this little motor to my liking, it is really not that big a deal. I prefer NOT to tout my experience or capabilities ...... and what nanoscopic amount I did mention, will be the end of it.

I thank those few who have posted useful info on this thread (IMG:style_emoticons/default/beerchug.gif) !!!


Consider this thread closed (IMG:style_emoticons/default/sunglasses.gif) !!!!

[Jake Raby]

Have fun. Just wanted to stimulate some thought.