Thanks Andreas. I'm going to look into the SOS springs and use the factory Honda retainers and keepers. I want to avoid machining the heads.
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Why don't more owners run cams?
- Thread starter L_RAO
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Thanks Andreas. I'm going to look into the SOS springs and use the factory Honda retainers and keepers. I want to avoid machining the heads.
I used the Supertech valve springs in my old built 3.0 engine. Worked very well
Interesting mix on the valve spring numbers. What did change between the NA1 and NA2 engines is the size of the intake valve. The NA2 engines received an intake that was 1 mm larger in diameter, presumably to deal with the increased gas flow associated with 3.2 l engine. I realize that the correlation may be tenuous; but, the increase in intake valve area (5.8%) roughly matches the change in engine volume (6.6%). The NA2 intake valve presumably weighs more than the NA1 intake (but less than 5.8% more); but, does not appear to have triggered a change in the valve springs.
When reading between the lines in the part number listings, I had interpreted the part number extensions -Axx to reflect updates in the part number or a different vendor - in this case Chuo or NHK springs. The Chuo and NHK springs appear to have different color markers. I didn't see anything in the service manual about having to match the vendors if you needed to change an inner or an outer spring. I had always interpreted the parts numbers that if the root of the part number was the same, you were free to go with different extensions as viable alternates. Perhaps my interpretation of the part numbers is misguided?
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I’m not sure. I haven’t bought engine parts from them.
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Yes, they are. You can find them a lot cheaper elsewhere though.
I purchased all new OEM valve springs, retainers, locks, and seats for my build with OEM valves and cams. They were from the same supplier, but I forget which one now. All springs were measured before installation and were consistent.
However - for the rod bearings there are also two different suppliers. I forget which one I had problems with, but one of the suppliers was definitely screwed up. Honda doesn't provide nominal thicknesses for their colors, so I could only measure what I removed and the two different brands I compared for replacement. This was also around the time that at least two or three other engines spun rod bearings right after their rebuilds. I'm guessing the builders (one of them very well known here) didn't bother measuring the replacements or didn't even confirm with plastigage... They just trusted the suppliers and the colors. That's why I went with aftermarket rod bearings....
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Thanks guys. I've seen the OEM retainers described as "powder metal," though folks like Andreas have been running those for literally decades on high-lift cams. Is it worth going with a billet/lightweight tool steel retainer (I will not consider Titanium, since there are several documented failures of those), or should the OEM be fine on the Comptech cams?
Powder metal? I am guessing that means sintered metal? Sintering can have certain advantages, particularly because it is a good process for forming metals with a very high melting point temperature. It has up and down sides to it. I don't think being sintered is necessarily a bad thing which 'powdered' king of implies.
With respect to titanium, keep in mind that titanium's claim to fame is reduced weight, not spectacular strength. At the risk of gross generalizations about the alloys being used, a titanium part will be slightly more than 1/2 the weight of an equal sized steel part; but, it will in general be a nudge weaker for an equal sized steel part. Up size the part a bit and you can have equal strength with less weight. Don't upsize the part and you might create a problem for yourself. Titanium's soft point might be its softness - compared to steel. You can purchase titanium valves; but, the ones that are any good have to have a special treatment on the tips and seat contact area to prevent them from deforming into junk.
Given titanium's properties and in particular its softness issue, titanium retainers might be good for an ultra high RPM race engine which gets torn down and inspected a couple of times per season. Lightness matters of those vintage 3l 14,000 RPM formula 1 engines. Maybe not the hot ticket for an engine that you want to put together and not worry about. Titanium works fine (other than being super pricey) on the NSX con rods because there should be nothing coming into contact with the rods to test their hardness.
The last time I looked at cams, valves, springs, retainers, etc was about 7 years ago. Maybe there have been some new products introduced since then but I don't know. The springs and retainers are some of the highest-stressed components in the engine, so my personal opinion is to go with a reliable setup that someone else has had long-term success with. The combo Andreas has used seems to have worked very well over the years.
My $0.02!
If you're removing the heads, I assume you'll be upgrading to a MLS-type of HG at least. At that point, you'll need to machine the head surface to a much smoother finish than the factory for a good seal. Sadly, I've seen a lot of engine builds where they omit this important step. Pretty much any engine rebuild will run, but the question is always, for how long?
Also, you'll probably want the valve seats machined, valves polished, new guides, etc. IIRC, I think the Comptech valve springs were from Eibach, so I would be confident running their springs with the Comptech cams and skipping the machining work required to make the OEM springs fit. Here's some more info on this from awhile ago:
http://www.nsxprime.com/forum/showthread.php/166228-Valvetrain-components-OEM-or-quot-upgrade-quot
IIRC, SOS uses, or used to use, Portflow for their engine builds with cylinder head work. Unless you have someone in mind locally to do the engine work, I wouldn't hesitate to mail the heads off to an expert.
You put this better than I ever could have. My father is an engineer and this is exactly how he describes Ti vs steel. Thus, I too counsel folks to avoid Ti retainers on street-driven cars because it really is a race engine part for engines that will be opened at least 2 times a season and where you can visually inspect the retainers for signs of stress or damage. For my NSX, which will be opened once every 7 years for the TB/WP, it's better to stick with steel, I think. My question was more directed at the value of "tool steel" type retainers versus the OEM Honda parts. Considering Honda determined the material based on a need for millions of cycles over decades of time without a failure, I'm going to stick with OEM. I'm not sure the extra lift on the VTEC lobes is going to put that much more stress on them.
I'm going to stick with his setup, except use the SoS/Supertech springs because using OEM springs means cutting the valve spring pocket in the heads. I'd prefer to leave the heads in the stock spring configuration.
Yes, I'm going to be using a Cometic MLS gasket and ARP head studs, mostly because of my prior experience with head gaskets on the NSX
. I have a great machine shop here locally, so when the time comes, the heads will go to them for assembly. I don't have the proper tools for removing the valves and valve seals, so I'll have the shop do it. The Cometic gasket comes with a Viton rubber coating that only requires a 50 ra surface, but I'll still have them take 0.0001" off the head just to get a mirror surface. When milling the heads, you have to be careful about removing too much, as it will move the center bores of the cams closer to the center bore of the crankshaft, throwing off your timing. And, I don't want to mess with adj cam gears, degreeing, etc. The plan is cut the head for 36 mm intake valves, 3-angle valve job, mill the head and reassemble with new springs, retainers and keepers. Do you think I really need to put new valve guides? I don't think I've ever seen one fail, though Kaz has noted some troubling issues on the 3.2L with the guides falling into the combustion chamber... Also, the jury seems to be split on using time-serts for the ARP studs. The recommended torque spec (85 lb/ft) seems to be at the high limit of what the aluminum threads in the block can manage. Though, there are many that go without...
Given the number (low overall but not unheard of) of instances where the head bolts pulled out of the block, I would prophylactically install TimeSerts. Pretty minimal cost if everything is disassembled.
What you and [MENTION=18194]Honcho[/MENTION] are describing is the modulus of elasticity. Titanium elastically deforms a bit more than your typical hard race engine steels at a given stress. For example, as I kept my OEM Ti rods, I had to keep the large piston-head "squish" clearance from the factory, or I could have gone to a better con-rod steel and reduced that clearance a bit for better cylinder combustion.
As you said, you can increase local hardness with some of the common nitriding processes. But, Ti parts are expensive and I didn't want to worry about them later.
In the thread I linked earlier, I compared the Supertech spring rates to the Comptech/Eibach spring rates. Any reason why you don't want to use the Comptech-designed cams together with the springs they specified? The OEM springs Andreas is using has about 2/3 of the Comptech/Eibach rate, yet he doesn't exhibit valve float at sustained redline! I always think it's best to use the lowest valve spring rate as possible because it's less wear/tear... especially on the OEM TB. Regardless, the Supertech springs seem to be just slightly higher rate than OEM, so you should be OK. I'm just wondering why the Comptech engine builders recommended the much stiffer springs. Too bad none of them are left.
Yes, I'm going to be using a Cometic MLS gasket and ARP head studs, mostly because of my prior experience with head gaskets on the NSX
It's good you're following the Cometic instructions. That's their minimum surface roughness, but they'll tell you smoother is always better. My surfaces were almost a mirror finish.
Don't worry about milling off too much of the surfaces to impact cam timing! I've done the math (as opposed to the rampant internet "wisdom" out there), and it's bugdust in the scheme of things. You'll impact cam timing more with the slight tolerance in the camshaft alignment pins than you will with milling surfaces a few thousandths. The reason I did the calcs was because my first engine block "machinist" screwed up. Later I had to grind a bit more than planned on the deck, and I had Cometic make a custom thickness HG for me to get the clearances back to my specs.
I did not put new valve guides in my C30 since they looked brand new. If Kaz has noted problems in the C32 and I had a C32 apart, then I would definitely replace as a preventative measure! It's cheap insurance.
As far as Timeserts, it seems that most of the documented instances on Prime with the block threads pulling out were with C32's. However, reputable engine builders on the West coast do the Timeserts on every block they rebuild. I did it on mine. Torquing the head studs in three passes over a period of two days was nerve-wrecking even with them installed. I've seen cylinder combustion pressures up to 2400 psi, and no problems so far with the Timeserts and ARP studs :smile:
Ask [MENTION=4282]docjohn[/MENTION] about the Comptech (Eibach) valve springs.
Seriously though, they failed on his 96 (using CT cams) and he lost the engine. Thus, for me it's OEM or Supertech.As for the guides, Kaz has mentioned several times on his blog that there is an issue with the C32 heads. In his quiet way, he seems to be implying that there was some kind of manufacturing/assembly issue with the guides at Honda, as several relatively low-mile engines have failed in Japan. The guides literally fell out of the head sleeves into the chamber! Apparently it was enough engines for him to comment that the valve guides should be inspected regularly on the C32 to check for movement. Kind of like with the VVIS screws.
Another reason to leave the valvetrain OEM if you want it to last.
I wonder what the average mileage is for owners that have gone to aftermarket cams and springs/retainers?
I wonder what the average mileage is for owners that have gone to aftermarket cams and springs/retainers?
I know SoS was selling their cams for several years, and I'm sure a few dozen owners use them. No record of any failures on the SoS/Supertech springs. Docjohn's is the only that I know of on the CT/Eibach springs, and it happened at the track.
Here's Kaz's original post on the guides:
http://nsxcb.co.uk/entry.php?72-Potential-C32B-Engine-failure-%96-Intake-Valve-guide
...and I drove home from the glen on 5 cylinders
I would have been having seizures (and mini-heart attacks) the whole drive too. :nightmare:
Another question to consider. Since the CT cams run safely on the factory M/T tune, I wonder if they also would be safe on the A/T maps?
a customer of mine reported that his MT NSX with an AT engine and MT ECU runned to rich (he has broken his origin MT engine and installed an AT engine). Then he swaped the ECU and everything was fine. So I guess it is the opposite when having an MT engine equipped with an AT ECU.
I installed a set of MT cams in an AT engine, leaved the AT springs and putted in a MT ECU. The car revs also just to 7500rpm. It is plug and play, no CEL, etc. The AT transmission ECU is communicating with the main ECU and therefore no higher revs are possible.
My engine tuner once compared the MT and AT spring on a special spring scale and there is very minor difference. Of course the AT engine has no inner springs at the intake side, but according to his info it is fine to use MT cams in AT engine while not upgrading the valve train, unless you dont rev higher than 7500rpm.
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Thanks, Christian, this is very helpful! For me, it's an issue of cost. Ideally, I would swap the Comptech cams into the car, do the 36mm intake valves, SoS Valve springs, change to the 6-speed and tune the car all at once. But, that's a lot of $$$ and Mrs. Honcho has other plans for that money lol. But, at the same time, I really don't want to have to pull the engine twice (especially after a brand new paint job), so it makes a lot of sense to do all of the engine work while the chassis is out for paint.
From what you're saying, it seems like the AT ECU can adjust fuel and timing enough to safely run the car with the big cams and possibly the bigger valves. The 7,500 rpm limiter probably also helps here, right? I'm not going to run the car on the circuit in this configuration (I don't trust my fragile 137k mile auto transmission), so it's really about not damaging the engine internals during street driving. Even if I'm leaving a lot of performance on the table without tuning, as long as the car is not too rich or lean, I think it is a good way to spread the cost. That way, I can drive the car for 1 or 2 years with the auto, save more $$$ and then put in the 6-speed and fully tune the car at that point in time.
Btw, I've been meaning to send you an email. My parts list is growing.
Be careful, I don't think that is what he is saying.
This is correct and we should expect this. The AT engine has lower Ve values in Vtec mode than the MT engine. Therefore, the MT fuel maps will have higher values in them than the AT fuel maps causing it to run rich in open loop. This will be 'safe' operation in terms of avoiding piston and valve melt.
Equally correct. Take note of his comment 'so I guess it is the opposite when having an MT engine equipped with an AT ECU'. I think the interpretation here is that the AT fuel maps will have lower values in them than the MT fuel maps causing an MT engine to run lean in open loop. This may not be 'safe' operation in terms of avoiding piston and valve melt.
If by this comment you are referring to closed loop operation with the O2 sensors, that is not a safe assumption. The first point is that the OEM ECU only works with narrow band sensors and narrow band sensors can only tell you whether you are above or below 14.7. The life mission of the narrow band sensors on an OEM ECU is try to keep the engine running at 14.7 to keep the catalyst happy. Once you are in to high engine power output levels the ECU goes out of closed loop control mode and runs directly off of the fuel map with no EGO correction. You can see this on the AFR values for dyno runs on stock engines which are definitely not running at 14.7.
I haven't been following your thought process in detail lately. But, your initial discussion around using Ostrich to remap / tune the OEM ECU to allow operation with different cams / hardware certainly seemed a viable plan (but, one that does require a trip(s) to a dyno and tuner). Based upon the earlier discussion, my take also was that the OEM ECU has the fuel maps for both the AT and MT engine and that you can switch an AT ECU to the MT fuel maps with the 'resistor snip'. The resistor snip should allow safe OEM like operation of an AT ECU on a stock MT engine. The resistor snip option for an AT ECU may not be safe with bigger cams and bigger valves on an MT engine. Your wording kind of implies that perhaps you are thinking about just dropping the AT ECU in place with no Ostrich remapping and no resistor snipping. If we define safe AFRs as the AFRs that the OEM tune gives you under high engine load, using an unmodified AT ECU on a stock MT engine will take you away from those safe AFRs. Using an unmodified AT ECU on a modified MT engine will take you even further away from those safe AFRs. You will likely be giving up some hp. Will you move far enough away from those AFR values that you run the risk of burning a piston or valve, that is a big unknown. If you wanted to do this just so that you could drive the car around with the occasional short jaunt into VTEC operation (what are the chances of that) then an unmodified AT ECU on your engine might be just fine, particularly if you are always operating in the closed loop region of the fuel map where the AFRs are always 14.7.
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A wealth of information as usual, [MENTION=26435]Old Guy[/MENTION]. I keep forgetting that the ECU goes into open loop at high load/high rpm and runs off the maps vs the sensors. My thought process remains the same as before- when I put the manual transmission into the car, I will use TunerPro and the Ostrich to tune the comptech cams to take full advantage of the larger lobe profiles and all the other engine mods. In fact, I will probably have to take the car to California to tune the load cells above 80%, since I can't do that here at 6,000 ft. . That is going to be a very costly proposition.
In the interest of cost mitigation, I was considering putting the CT cams in and running them on the AT maps with the AT trans. Andreas has been running the same cams on his MT maps just fine for 20 years, so I was thinking there might still be enough safety margin (e.g., fuel) in the AT maps to safely run the CT vtec profile. Especially considering track days are not happening with a 137k mile auto trans lol.
However, the car currently runs just fine and the engine is in great shape, save for a few small oil seeps from old gaskets. If I were to just fix the oil leaks and run the car as is until I install the 6 speed, it would knock over $10k in engine refresh costs out of the 2019 plan. That's an idea I can get behind! I was just trying to determine if i could safely run the CT cams on the AT maps as sort of a compromise measure. But, I think it will be better to just leave the cams on the shelf and install them during the 6 speed upgrade. I have to admit, I'm not feeling great about pulling the engine out of a freshly painted car though...
. That is going to be a very costly proposition.In the interest of cost mitigation, I was considering putting the CT cams in and running them on the AT maps with the AT trans. Andreas has been running the same cams on his MT maps just fine for 20 years, so I was thinking there might still be enough safety margin (e.g., fuel) in the AT maps to safely run the CT vtec profile. Especially considering track days are not happening with a 137k mile auto trans lol.
However, the car currently runs just fine and the engine is in great shape, save for a few small oil seeps from old gaskets. If I were to just fix the oil leaks and run the car as is until I install the 6 speed, it would knock over $10k in engine refresh costs out of the 2019 plan. That's an idea I can get behind! I was just trying to determine if i could safely run the CT cams on the AT maps as sort of a compromise measure. But, I think it will be better to just leave the cams on the shelf and install them during the 6 speed upgrade. I have to admit, I'm not feeling great about pulling the engine out of a freshly painted car though...
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