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Old 03-26-2010, 12:49 PM   #1
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Default Got Head? RPM Question.

The new head I'm building for my 1.6 NA will be the first head on this car that I've devoted so much time and money toward. It's getting 32mm and 27mm valves dumped in it with dual valvesprings (rate is 12 flat per mm and lift is 125.3 @ 10.3). I don't really care about the inertial stress (read: rotational effort) caused by the dual spring setup. My question is what kind of RPM can I expect to get from this setup before I get valve float with cams that have around (I say around because I'm not set on a profile yet) an 11mm lift? The springs are good for 15.8 max lift. Yes, I know, I put random information all over the place and it's hard to read, but hey... I can't spoonfeed you guys. Geeze.... Oh, I'm sticking with the hydraulic setup because I'm cheap.

Any insight is appreciated... even the useless, misleading and generally non-constructive posts are encouraged for daily humor. Thanks in advance.

Oh, and yes it will be ported and polished and port-matched and have a 5-angle job and blah blah blah. That may all be a given but I figured I'd throw that in there just in case.

Also note that I have talked to the machine shop and they are suggesting using the camshaft RPM power-range specs, which is stupid because those change based on timing and the Mazda guys say nothing helpful at all: "You should never, EVER exceed the RPM specified on your tachometer that is indicated by the red warning lines." I'm pretty sure everyone that I call hates life in general and feels like being a complete douche, so here I post.
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Old 03-26-2010, 12:57 PM   #2
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Did last night. Might I ask what kind of motor build/turbo you are working on to need more than 7500 RPMS?
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Old 03-26-2010, 01:05 PM   #3
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I don't see anything mentioned. But anything over ~7800 causes all sorts of fun Harmonics and the oil pumps blow up and ruin nicely done motors.

Might want to take that into account.
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Old 03-26-2010, 01:06 PM   #4
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^ The higher your RPM celing in terms of effective breathing, the wider your powerband. A wider powerband means more time in the lower gears and much better acceleration. In the end the only really significance of HP is that it indicates how TQ and gearing (in terms of RPM capability) work together to accelerate you up the road.

I am definitely interested in this too. Having power start well below 4K is great, but if it continues to 8500 or something, then your gearing gets much much more useful. Imagine if you can stay in 2nd and 3rd for an extra 1000 rpm without power dropping off
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Old 03-26-2010, 01:19 PM   #5
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Originally Posted by miatamania View Post
I don't see anything mentioned. But anything over ~7800 causes all sorts of fun Harmonics and the oil pumps blow up and ruin nicely done motors.

Might want to take that into account.
Good point. Something like an ATI might be a good idea. Boundary pump is probably a given too.
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Old 03-26-2010, 01:22 PM   #6
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Originally Posted by adamhershner View Post
Did last night. Might I ask what kind of motor build/turbo you are working on to need more than 7500 RPMS?
Forged, maybe 0.60 over, but at least 0.40, sleeved if it's 0.60 over, 8.5:1, I think the head gasket is .2 thicket but I'm not sure. Inconel exhaust valves, OEM HL's... I dunno what else to tell you. It's going to remain small displacement so I'm going to stick with a small compressor but get it all polished out so I can spin it a bit faster, so a 28 series will be biggest that I'll go. I'm shooting for low torque, high power (obviously at high[er] RPM).

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Originally Posted by miatamania View Post
I don't see anything mentioned. But anything over ~7800 causes all sorts of fun Harmonics and the oil pumps blow up and ruin nicely done motors.

Might want to take that into account.
I'm not using an OEM pump, so hopefully that fixes the problem.

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Originally Posted by Sparetire View Post
^ The higher your RPM celing in terms of effective breathing, the wider your powerband. A wider powerband means more time in the lower gears and much better acceleration. In the end the only really significance of HP is that it indicates how TQ and gearing (in terms of RPM capability) work together to accelerate you up the road.

I am definitely interested in this too. Having power start well below 4K is great, but if it continues to 8500 or something, then your gearing gets much much more useful. Imagine if you can stay in 2nd and 3rd for an extra 1000 rpm without power dropping off
That would be ideal and that's sort of what I want to get at. But I don't know how much the OEM HL's can handle before RPM increase becomes a mute point. That way I can get more out of a close ratio and have the duration of a wider gearset... kind of, ha ha.
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Old 03-26-2010, 01:24 PM   #7
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Your rods/rod bolts will limit you long before valve float will. By limit I mean, fly out of your block.

This has been discussed adnauseum, you are not the first person to modify a 1.6 head. You haven't even spent a lot of money yet. Search.... You'll find some posts, I know because I made a bunch of them like 3-4 years ago.
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Old 03-26-2010, 01:30 PM   #8
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Originally Posted by neogenesis2004 View Post
Your rods/rod bolts will limit you long before valve float will. By limit I mean, fly out of your block.

This has been discussed adnauseum, you are not the first person to modify a 1.6 head. You haven't even spent a lot of money yet. Search.... You'll find some posts, I know because I made a bunch of them like 3-4 years ago.
Three to four years? Damn... that's lots of searching. The block it's going on is going to be built to withstand well over 10K RPM and loads of boost. Everything's being balanced and I'm getting the crank knife-edged, even though it does bad things down the road. I'm not putting a built head on a stock block or even just a block with forged internals, that's a waste of money.
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Old 03-26-2010, 01:49 PM   #9
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Searching is only as good as the user inputting the search terms.
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Old 03-26-2010, 01:50 PM   #10
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Searching is only as good as the user inputting the search terms.
I know, ha ha. I'm still searching. You just recently blew your engine didn't you? What went wrong?
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Old 03-26-2010, 05:46 PM   #11
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I fully built my 1.6L and kept it at 7800-8000rpm above that im not making anymore power so its useless.
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Old 03-26-2010, 05:48 PM   #12
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First of all if you are going to put this head on a well built bottom end, why would you skimp on lifters? Do not do that. Second, it is better to match the camshaft with the proper springs. Anything too week and you get valve float, and loss of horsepower. Anything too stiff will also result in a loss of horsepower. Keep in mind that if you use a lightweight shim under bucket lifter, you will need less of a spring to keep the valves from floating. It adds horsepower too. It is a good investment. My best advice, is to contact your cam manufacturer on the best combination of portwork, valvetrain components, and camshaft.

Another thing, there was no mention of duration. What will the duration be, particularly at .050 inches lift? The duration is what will effect the rpms the most.
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Old 03-26-2010, 06:18 PM   #13
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Originally Posted by stranges12712 View Post
I fully built my 1.6L and kept it at 7800-8000rpm above that im not making anymore power so its useless.
How fast did your power taper off past 8K and how much did you play around with cam timing? It wouldn't be hard to make 8K a target as opposed to higher, especially if cam timing is essentially beat out my physics beyond that point.

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Originally Posted by miata2fast View Post
First of all if you are going to put this head on a well built bottom end, why would you skimp on lifters? Do not do that. Second, it is better to match the camshaft with the proper springs. Anything too week and you get valve float, and loss of horsepower. Anything too stiff will also result in a loss of horsepower. Keep in mind that if you use a lightweight shim under bucket lifter, you will need less of a spring to keep the valves from floating. It adds horsepower too. It is a good investment. My best advice, is to contact your cam manufacturer on the best combination of portwork, valvetrain components, and camshaft.

Another thing, there was no mention of duration. What will the duration be, particularly at .050 inches lift? The duration is what will effect the rpms the most.
Duration is 287... I think, ha ha. I'll have to get back to you on that. So get the cam manufacturer to suggest components and porting, hmmm. Would I be better off just going to Wiseco (first name that popped in my head) and getting them to cut me cams based on what I want and letting them deal with components and giving me an outline for porting? I guess any place can make me springs and valves based on what I want. I'm skimping on lifters because I think it's going to exceed my budget to convert to solid. If I exceed budget, then no engine goes into the car, which saddens me.
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Old 03-26-2010, 06:30 PM   #14
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Wiseco makes pistons, maybe you meant Web Cam or Integral.

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Old 03-26-2010, 06:54 PM   #15
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Integral has some very good packages under a grand.

I was considering a pretty serious head build when looking at building a motor, but am now just sticking with some basic porting.

Anyhow, they can easily tell you what combination of their 3 levels of cams are for you, match springs and lifters, and tell you what their operating range is.
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Old 03-26-2010, 09:34 PM   #16
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Forged, maybe 0.60 over, but at least 0.40, sleeved if it's 0.60 over...
Just curious, but why would you sleeve an iron block?
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Old 03-26-2010, 10:01 PM   #17
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Old 03-26-2010, 10:05 PM   #18
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You are getting in a little over you head. You need to learn more before posting. It sounds like you are portraying knowledge that you do not yet possess.

The wolves can sniff out weakness, and the stench is strong.
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Old 03-26-2010, 11:50 PM   #19
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Originally Posted by E-NA6CE View Post

Duration is 287... I think, ha ha. I'll have to get back to you on that. So get the cam manufacturer to suggest components and porting, hmmm. Would I be better off just going to Wiseco (first name that popped in my head) and getting them to cut me cams based on what I want and letting them deal with components and giving me an outline for porting? I guess any place can make me springs and valves based on what I want. I'm skimping on lifters because I think it's going to exceed my budget to convert to solid. If I exceed budget, then no engine goes into the car, which saddens me.
If you want a max effort 1.6L motor, you need to maximize the airflow of the 1.6 head. You are going to have to spend some money to get maximum flow out of the 1.6 head; oversized valves, professional porting and converting to a solid lifter setup capable of supporting a lot more lift than the stock HL buckets. The port work to be done differs if you stick with stock style HLs; no need to work on flow at higher lift rates (.400-.450) if you can only get to .380 lift with HLs. Cam choice can't be properly spec'd (e.g., running a simulation) until you know cylinder head flow at various lifts, compression, intake, turbo map etc. Springs and retainers can't be selected until you know the lift specs and lobe acceleration specs of the cam.
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Old 03-29-2010, 09:59 AM   #20
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Originally Posted by TurboRoach View Post
Just curious, but why would you sleeve an iron block?
I don't know, ask the guy who is going to be doing the machinework.

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Originally Posted by miata2fast View Post
You are getting in a little over you head. You need to learn more before posting. It sounds like you are portraying knowledge that you do not yet possess.

The wolves can sniff out weakness, and the stench is strong.
Duh, why do you think I'm asking? I have an idea for cam profiles but I figured I'd ask about the limitations of the factory HLA before I went RPM happy and wrote my new engine's demise. Someone asked for the duration and I gave them an idea of what it may be. It's not like I can give anyone a specific number when I haven't chosen, yet. How about this: I'll PM you progress of the build (both what I do and what the shop does) and then a video of the end result (after tuning). Then, when you are satisfied and see that you, nor I, are not a wolf, you can start a thread telling everyone how much you love me and that you wrongly judged me. I think that seems fair.

Oh (to the other guy), and no I did not mean Web or Integral. I said Wiseco because that is the first company that popped into my head. Geeze. I know they don't make cams, I just threw a name in there for an example. I'll be specific next time in case you don't read what I typed in the parenthesis after.

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Originally Posted by sn95 View Post
If you want a max effort 1.6L motor, you need to maximize the airflow of the 1.6 head. You are going to have to spend some money to get maximum flow out of the 1.6 head; oversized valves, professional porting and converting to a solid lifter setup capable of supporting a lot more lift than the stock HL buckets. The port work to be done differs if you stick with stock style HLs; no need to work on flow at higher lift rates (.400-.450) if you can only get to .380 lift with HLs. Cam choice can't be properly spec'd (e.g., running a simulation) until you know cylinder head flow at various lifts, compression, intake, turbo map etc. Springs and retainers can't be selected until you know the lift specs and lobe acceleration specs of the cam.
This is starting to sound like I should tell the shop what I want and tell them to make it work. And I don't want a max effort 1.6 that I'm going to have to rebuild every ten thousand clicks; I'm going to drive it around when the weather is nice.
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