Cams cams cams...

Tech tips and how to's

Moderators: notoptoy, S Allen, Solex68, bmccarthy67

User avatar
Gregs672000
Roadster Fanatic-Site Supporter
Posts: 8324
Joined: Fri Aug 07, 2009 11:47 pm
Location: Tacoma, WA

Cams cams cams...

Post by Gregs672000 »

Ya, I can never seem to stop messing, and for those who like this stuff I through the I'd post and get some input, and just document how this progresses as I investigate. As I noted yesterday here on the site, I decided to replace my Isky Z-197 cam (278 duration/246 at 50 thousands, .531 total lift) with what I have understood to be a Racer Brown cam ground by Delta Cam in Tacoma (341-R: 280 duration/248 at 50 thousands, .478 total lift. As a comparison, a B cam has the same duration and .460 lift). Reason 1 was I had surmised that the tapping sound I heard from the motor was the valves (likely intake) tapping against the block (long story that involves the 48mm intake valves in my head, custom reliefs cut into the block but there's limited depth you can go before you expose the upper compression ring. This time I had the machine shop do it, but apparently not enough). As I was looking into this, I had come across some technical/engine expert write-ups that had advised that using a total valve lift of over 15% of cylinder bore size tended to create turbulence in the intake tract by creating "shear" where the intake charge starts to separate from the valve and go from smooth flow to turbulence, reducing the ability to fill the cylinder. The Z-197 lift is 15.5% of bore, and the RB/341-R is 14.5% (that was considered to be quite good). That became reason 2. The head already flows more than normal, so I figured that I'd actually be gaining power and avoiding any damage, so I had Delta surface the rockers and polish the RB cam and installed it yesterday. I've since driven it about 50 or more miles, allowing the computer time to adjust the fuel map, and have checked lash etc.

Results? Pros: Tapping noise is gone. The engine seems to rev a little smoother, and it revs well to 7000+
Cons: Lost power. At first I wasn't sure, but I just took it to my test hill where I push it hard at 3200 rpm in 4th gear. I use this spot to listen for knock when setting up my timing map, and I do have to progressively pull a fair amount of timing out at high loads (drops to 22.5 degrees advance at 2500rpm, 24 at 3000, 26.5 at 3500, 30-32 at 4000 at 70-100% of throttle. For comparison, low load/cruise timing is 28 degrees at 2500, 33 at 3000, then 37 from 3500 onward). Before, if I hit it hard at 3200 on the hill it pulled (as long as it didn't knock! Thus the above adjustments); now, it goes flat, and has that flat blaaaa kinda sound where pushing the pedal makes no difference in the car, and then it begins to catch up. The engine doesn't strain (in fact it feels "safe"), it just seems "thin" there, like it's off the cam. You can feel it on the flats as well, but that's what makes the engine feel smoother. Top end may be the same, I need to try some high speed runs in my test place for that, but the 3200 rpm grunt is missing.

Then I realized, it's a feeling I've felt before. And sure enough, I looked back through my previous posts about dynos and cams etc, and there were my own words talking about how much better the Isky was at 3200 rpms. Then I looked over my own dyno charts from over the years, and while the engine has evolved in many ways run to run, I did have an early 2004 run with the RB cam with 48mm SK RACING carbs w/39mm chokes, stockish compression, ported head but standard valves. At 3000 rpms it was making about 120lbs torque. But then it dropped down to 105 at 3500, before climbing back to about 128 at 4000 then peeks at 130lbs at 4600. Then it drops off to 120-118 at 5500 (believed to be carb related at the time). That first drop at 3500 seems to still exist. Why? Not sure, but that's what happens. At the time we attributed it to carb and/or timing issues. Note the big 39mm chokes. Compared to the Isky cam dyno runs in 2019 (more modified engine, 11.7 compression, bigger valves, crank fired ignition, Dellorto carbs with 37mm chokes, unfortunately it ran too rich on the dyno) at 3000 rpms it only had 105lbs, but by 3500 it's at 125 and hits 130-134 at 4000rpm and carries on 4700. At 5500 it's still making 128, but the engine was drowning in fuel, like 10.5 to 1 and it was struggling to rev and choked off at 6200rpm... I need EFI! And that started THAT adventure :lol: .

Today, with EFI controlling the fuel mix, we know it's not a fuel ratio issue. It might be a result of the size of the intake (39mm venturis in the carbs back in 2004, and the now I run 40mm throttle bodies) but I kinda doubt it. I do wonder about ignition timing, so I may try a bit more advance under load than I ran with the Isky. Maybe the change has created a condition where it wants more timing? It's my understanding that reduced timing can make the engine response "lazy" but she must not knock! If that doesn't work, well... somehow I will have to figure out how to run the Isky. The car's not horrible or anything with the RB, but there was a response I could count on that I really liked, and it's different enough that I notice it. As many know, I have had this car a very long time (my third car ever owned). This summer I kept noting how often I felt like I was in 4th gear only to see I was in 5th because the car was just more responsive. I attributed that to the EFI, but the cam seems to be a big part of it. I may have to have Delta cut a smidgen off the lift to say .520 lift and not run the lash so tight (6 and 8 cold, could go stock 8 and 12) and maybe that will give me the clearance I need.

So there's the story... thanks for reading my dribble. Of course I'll keep you posted... I can't help myself :roll: :smt005
Greg Burrows
'67 2000 #588
Tacoma, WA
User avatar
spyder
Roadster Fanatic-Site Supporter
Posts: 2162
Joined: Tue Apr 12, 2005 1:43 am
Location: Live Oak, TX.
Model: 2000
Year: High Windshield-68-70

Re: Cams cams cams...

Post by spyder »

My Z-196 has the same lift but more duration however, I have stock valves. Are you sure that the wipe pattern is in the center of the follower. I ground off a bit of the two areas that protrude above the hardened wipe surface to gain additional clearance because when I first installed the cam it wasn't exactly centered over the all the followers and it ticked when the cam would hit that surface. As far as the valve striking the relief in the cylinder wall, would that be inspectable with a bore-scope. Perhaps put weak test springs on a couple of valves and check for interference.
User avatar
SLOroadster
Roadsteraholic
Posts: 5323
Joined: Sun Dec 08, 2002 2:53 am
Location: Napa Ca

Re: Cams cams cams...

Post by SLOroadster »

I noticed when I put my race head and big cam back on my engine that it now had tons of valve noise that wasn't there when it was build. I don't know what changed, but the head wasn't skimmed, and its exactly the same cam and rockers. The valves were replaced (I had 8 different length valves :roll: ) so now everything is the same length, but this version is super noisy. I ran it by my machinist who thought it was an exhaust valve cooling issue, and he suggested I tighten up the clearances from 8 and 10 to 7 on both to help transfer heat from the valve and valve stem to the head/oil better. It helped some, but its still loud. The heat theory seems to fit as its quiet when the engine and oil are cold, and gets louder as things warm up.

Will
Sorry, I find modern engine swaps revolting. Keep your G, R, or U series in your Roadster!
User avatar
Gregs672000
Roadster Fanatic-Site Supporter
Posts: 8324
Joined: Fri Aug 07, 2009 11:47 pm
Location: Tacoma, WA

Re: Cams cams cams...

Post by Gregs672000 »

Thanks gents, I was hoping you two would chime in. Pat (Unklpat) has a scope and has offered to come by or get together, and I expect we'll do that soon. Ya, the 48mm intake valves are likely overkill and unneeded but what's done is done. Clearance would probably be fine with stock 46mm valves.

I took it out and played with timing some, but it didn't really make enough difference for me to not want to go back. It revs smoothly and feels linear, but I do feel it's down 5-10lbs. I think it feels smoother because it's less responsive. Strangely I feel safer stomping on it. For whatever reason, my engine seems to like more lift. Sure wish I had been able to get on the dyno and actually see numbers.

Anyway, the tapping has gone away for the most part. It gets more tapping above 2000 rpms, but still more quiet than before. And a rattle that was very prominent especially at lower rpm light load (like motoring through your neighborhood in 2nd gear, 2000-2500 rpm) is completely gone... that was the one that worried me most. The car is fine and has plenty of power, but I know better. It will be fine for now... the primary driving season is ending soon around here so I'll do some more poking about and likely talk to Delta. I will consider your suggestion Spyder and see if I can test clearance with a light spring. I'll have to see what I have tool wise.

One thing I did notice when I took the rockers for surfacing is that all the intake valve rocker pads showed signs of "chatter". That may have made them more noisy.
Greg Burrows
'67 2000 #588
Tacoma, WA
User avatar
Gregs672000
Roadster Fanatic-Site Supporter
Posts: 8324
Joined: Fri Aug 07, 2009 11:47 pm
Location: Tacoma, WA

Re: Cams cams cams...

Post by Gregs672000 »

I guess I could also try adjusting the cam timing, as I do have an adjustable gear. It revs to 7000rpm easy enough, but I don't regularly go there that often. I could try advancing the cam a few degrees and see if it likes that better. Spyder, where does your cam come on? I know you're running 50mm carbs and have retarded the cam some as I recall. What's the duration of the 196? What's your final drive ratio... I'm 3.9.
Greg Burrows
'67 2000 #588
Tacoma, WA
User avatar
spyder
Roadster Fanatic-Site Supporter
Posts: 2162
Joined: Tue Apr 12, 2005 1:43 am
Location: Live Oak, TX.
Model: 2000
Year: High Windshield-68-70

Re: Cams cams cams...

Post by spyder »

Being the rear is a 4.89 and an aluminum flywheel it takes off rather quickly. A real world number is it starts to pull hard around 4K rpm's. The cam shows 264 deg at .050. Recently I decided to advance the cam about 2 deg because I was unable to dial in any knock with my base timing knob in the glove box and now I can cause it to knock if I lug it in a low rpm. So I back it off a bit and it seems much peppier in the low range.

SLO- "he suggested I tighten up the clearances from 8 and 10 to 7 on both to help transfer heat from the valve and valve stem to the head/oil better."

If you lessen the clearance the valve spends less time in the seat therefore less heat is transferred. Mine says to set them at .010 for both intake and exhaust cold. I think in the end it is how violently the valve is pushed around. all things being equal. I posted a video on youtube a few years ago which shows the valve train noise at idle. Anything past that it is smothered. I know this dosen't apply to a U20 engine but I rebuilt a J13 in a pickup and it called for the rockers to be set at .014 hot. There was one valve that ticked rather loudly. The only way I was able to stop it was to set it to .007. Screaming 67 HP engine :shock:
unklpat
Roadster Fanatic
Posts: 351
Joined: Fri Feb 15, 2019 8:43 pm

Re: Cams cams cams...

Post by unklpat »

In the interest of clarity, if you lessen the clearance, the valve spends more time in the seat. This helps transfer heat,and was a popular tuning method in the past. I'm interested to know otherwise... Pat
User avatar
Gregs672000
Roadster Fanatic-Site Supporter
Posts: 8324
Joined: Fri Aug 07, 2009 11:47 pm
Location: Tacoma, WA

Re: Cams cams cams...

Post by Gregs672000 »

Regarding lash and heat transfer, more time was my understanding as well. The way to burn a valve was to keep it from seating and transferring heat. Maybe Will is experiencing what you did Spyder with the cam riding the rocker. BTW, my pads were all wiping perfect with the Isky other than the chatter. My guy at Delta was saying it was more how they were surfaced, but I think he was under the impression that they had not seen many miles, and this cam had run several thousand (and all the exhaust were great. Every intake showed chatter). I think it had to do with the valves and clearance but that's just a guess.

It's surprising how much visual difference there is between .478 and .531 on your caliper. I don't know how well we be able to see with the bore scope, but I look forward to trying and seeing how close the valve comes now. Hope the valves and seats are OK, but it will be hard to tell. It seals great with 210lbs of compression and no leak down past the valves, but neither of these tests caught the broken piston ring before...

Spyder, your cam makes more sense with the high final drive but for me I want the duration and power band down lower. Regarding lash, the cam card said 10in 15ex cold, but I ignored that and ran them tighter (6 in 8ex). It quieted up some when I went 8 and 10, which lead me to believe it was the valves hitting the block, then after reading the "15%" rule I made the change. In hindsight I could have loosened the lash more. Depending on what our investigation finds, I'm leaning toward grinding a slight reduction in lift and being careful with lash.
Greg Burrows
'67 2000 #588
Tacoma, WA
User avatar
spyder
Roadster Fanatic-Site Supporter
Posts: 2162
Joined: Tue Apr 12, 2005 1:43 am
Location: Live Oak, TX.
Model: 2000
Year: High Windshield-68-70

Re: Cams cams cams...

Post by spyder »

unklpat wrote: Wed Sep 28, 2022 12:22 am In the interest of clarity, if you lessen the clearance, the valve spends more time in the seat. This helps transfer heat,and was a popular tuning method in the past. I'm interested to know otherwise... Pat
Think about it this way, the less lash you have the more surface on the cam the follower contacts. Purpose of contact with the cam, to open the valve. If you adjust the lash to less than .000, when does the valve close?
User avatar
spyder
Roadster Fanatic-Site Supporter
Posts: 2162
Joined: Tue Apr 12, 2005 1:43 am
Location: Live Oak, TX.
Model: 2000
Year: High Windshield-68-70

Re: Cams cams cams...

Post by spyder »

Memory tickler alert. April 2012 I had a Z-196 cam that deveolped a ticking noise. The cam had a odd wear pattern on the opening side of the last valve. The follower looked fine. Isky reground it and am currently using it. ???

Image
User avatar
Gregs672000
Roadster Fanatic-Site Supporter
Posts: 8324
Joined: Fri Aug 07, 2009 11:47 pm
Location: Tacoma, WA

Re: Cams cams cams...

Post by Gregs672000 »

Ya, that's a weird spot to wear. I had some small pitting on a couple rockers before the last build that had me thinking about running a spray bar, but like you, Delta cleaned it up and it's been great since. I now use 20/50 Valvoline Racing oil with a Hyper-lube additive (not a thickener) that works differently from zinc, and it's been really good. I also decided to add Motorkote recently but can't say it made any difference.

I'm just gonna take my time, do my clearance testing and see what's what. In my mind, it's significant that only the intake rockers showed chatter and I suspect it's telling me something.
Greg Burrows
'67 2000 #588
Tacoma, WA
User avatar
Gregs672000
Roadster Fanatic-Site Supporter
Posts: 8324
Joined: Fri Aug 07, 2009 11:47 pm
Location: Tacoma, WA

Re: Cams cams cams...

Post by Gregs672000 »

Interesting... I just watched a Garage 4A-GE YouTube video where he compared two different "big" cams with different lift and duration. Granted, this is a very different engine than a single cam U20 (twin cam 4 valve, 8500 redline), but the cam with more lift and duration made the same or more torque across the board and more peak HP with no apparent change in where it made power (the higher duration didn't hurt it down low). There was only. 020 more lift (.413 to .433, 258 duration at 50 thousands vs 272 respectively) and it was better in torque below 5000rpm and never gave that up.
Greg Burrows
'67 2000 #588
Tacoma, WA
User avatar
rwmann
Roadster Fanatic-Site Supporter
Posts: 559
Joined: Wed Aug 20, 2008 6:11 am
Location: Port Washington, NY
Model: 2000
Year: High Windshield-68-70

Re: Cams cams cams...

Post by rwmann »

I suspect the U20 limitation is its valve springs.
User avatar
spyder
Roadster Fanatic-Site Supporter
Posts: 2162
Joined: Tue Apr 12, 2005 1:43 am
Location: Live Oak, TX.
Model: 2000
Year: High Windshield-68-70

Re: Cams cams cams...

Post by spyder »

Years ago I had a chance to talk to Ed Isky and in this conversation he said the U20 valve springs should be good to 8K rpm. I suspect ones in good condition. I have a set of Isky valve springs but they are much stiffer than stock. I tosssed around the idea of just replacing the small internal springs. Perhaps one day..........
User avatar
Gregs672000
Roadster Fanatic-Site Supporter
Posts: 8324
Joined: Fri Aug 07, 2009 11:47 pm
Location: Tacoma, WA

Re: Cams cams cams...

Post by Gregs672000 »

rwmann wrote: Wed Sep 28, 2022 3:39 pm I suspect the U20 limitation is its valve springs.
My valve train is not completely stock... I use L-series retainers and lash caps, and lighter 8mm stemmed valves (I just weighed them vs stock the other day actually). The .531 lift is most definitely near the max of the stock U20 spring... any more and you're just about guaranteed to coil bind. I was very careful with this!
Greg Burrows
'67 2000 #588
Tacoma, WA