U20 Rebuild project

[timurf]

Starting on a U20 home rebuild. De-rusted the block before dropping back off at the machine shop.

20220320_181940.jpg

20220320_163504.jpg

[Gregs672000]

Let the fun begin! Get that good ol rope seal right... follow the directions (soak in oil for 24hrs as I recall) like I didn't or pay the price! Not sure if that's the reason but mine leaks, but it does first time in 3 or 4 rebuilds. I also really like the Permatex equivalent to the Toyota sealer for gaskets, used sparingly. Great on the front cover, tensioner cover and oil pan etc.

[timurf]

Yessir! I can't remember what seals I used on the last rebuild but it hasn't leaked since.

Okay *fine* it leaks from the front cover a little but that's a different story.

BTW we had a good exchange a few years ago on the subject and, as a direct result, I plan to unapologetically copy your cam spec. on this build. ✌

[timurf]

Cleanest cylinder head ever to grace a dining room table!

Uncut, uncensored.

IMG_0875.JPG

[Gregs672000]

BTW we had a good exchange a few years ago on the subject and, as a direct result, I plan to unapologetically copy your cam spec. on this build. ✌

Ah ha, the Isky grind? I looked for it on their site awhile ago and it didn't come up... you may have to call them. Z-197. 246 duration at 50 thousands (B cam ish powerband) but a fair amount of lift (cam lift .384, valve lift with a Roadster rocker ratio of 1.4 which give a valve lift of .537). Be sure to check valve springs and watch for coil bind cause it's tight! I'm very happy with this cam, but I want to wait for the final dyno tune/run this spring to see how the profile works and where (I've since added EFI to the mix and dropped compression down to a more "reasonable" 11 to 1 or so). The previous dyno runs before the EFI showed a good torque curve from 2800rpm (104 ft-lbs), peaking at 4800rpms (134 ft-lbs) and dropping progressively down to 120lbs at about 6200rpms. The engine made peak HP a bit lower than I expected (142 at 6200rpms), but I had some significant fuel and timing issues that I'm expecting will be solved with the EFI and a better timing map.

Since we talked long ago, I have to say this... I have since learned that there can be some losses with too much valve lift. It used to be that there was no such thing, just diminishing returns. That may not be fully accurate. I'm not saying this cam has too much (I don't know) but I have read some about it. And since you're kinda "taking my advice" I would also encourage a discussion with the folks at Isky about their thoughts on that. It's been awhile since I talked to them, but they were always super nice to me and took the time to discuss such things. Anyway, I like it, it's not peaky at all and can launch no problem on a hill even with a light flywheel. Keep us posted on your progress!

[timurf]

Hi Greg,

Thanks for your stoic advice as usual! My only concern with excess lift is that it opens up a can of worms; harder on the valvetrain and more friction acting against the power gains.

I may go with the RB cam, or see if I can find a cam grinder to basically make the Isky spec. but reduce the lift by 'a little.'

Did you or your builder try different button heights in your build? This can yield extra lift, but of course your potential gains are limited.

[timurf]

Speaking of Isky, my old roommate was telling me about getting to meet Ed himself a few years ago at a trade show. (A show like SEMA, but not SEMA.)

Talk about characters. Ed's hobby-turned-business literally spans the history of hot rodding in it's entirety. He started messing with cars in the late 30's!

[Gregs672000]

Hi Tim, agreed on the extra stress from the higher lift. If the spring can't control the valve then it can "ski-jump" on the rocker and hit it harder. My valve train may be a little lighter than stock with smaller diameter stems (but larger size, 48mm and 38mm) and using L-series collets and lash caps. Earlier I had a couple lobes and rockers show some wear, however Delta Cam polished them up and I re-broke in the cam and it's been fine since. I was concerned enough that I considered adding a spray bar. However, I've become very careful with the oil and additives I choose. I'm running Valvoline VR1 Racing in a 20/50 weight (summer driving mainly) and added a product called Hy-per Lube Zinc replacement that DOES NOT contain any zinc so it doesn't mess with the the oil additive package the oil is designed to have. Per my research on sites like "Bob the oil guy" adding zinc/ZDDP etc can actually reduce the effectiveness of the anti-wear elements by throwing off the formula. This Hy-per Lube product doesn't do any of that and works differently. It uses a "polymer ester" that I did some research on but it got more technical than I could understand. I'd like to see it tested on one of those YouTube channels to see how it performs, but so far what I'm doing is working so I'm not going to mess with it. I just ordered another off Amazon, but I am concerned that it is not listed on the Hyperlube.com website. It seems that Rislone has merged (?) with Hyperlube.com and now offers a ZDDP product that is not the same, made by Rislone. You can still buy the zinc free stuff on Amazon, and the manufacturer is listed as Hy-per Lube (and not "Hy-per Lube by Rislone" like the other product), but I sure hope it doesn't get replaced.

I have what I believe is a "Racer Brown grind" cam I ran for years that I really liked, used before the bigger valve experiment. As I recall it too has a near B cam duration with a little more lift (found it: 248 degrees duration at 50 thousands and .478 total lift WITH the rocker). Delta Cam has it listed as a 341R grind. There's a formula out there for estimating max lift, but for now I'm running the ISKY. A little more A/F ratio tuning this spring and I'll run it on the dyno to finalize the timing map, then I'll post a pull. Right now the cam is set stock or what I call "straight up", but if the dyno graph suggests some change then I may advance or retard it. But honestly, I'm more focused on reliability now than max power.

Hope this helps... I know I write a lot...

[timurf]

Admiring the NOS Arias pistons before they end up disappearing within the engine block. Such works of art!

Did you ever measure the dome CC on yours? I plan to CC mine with clay but was wondering if you might have already done this.

I am going to save and fully digest your lube advice, this is something very easy to overlook!

At this point I think I have (finally) made up my mind on cams, the choice being 1. the lazy route: buy an RB. 2. find a shop that will custom grind a stock cam to my spec. And my specs. will be duration similar to your Isky but with the lift backed off by an amount TBD.


[img2][/img2]

[Gregs672000]

Those pistons look familiar! I have the same set, machined down quite a bit. Unfortunately I lost all the pics I had on my pad when it needed repair or I'd post what they look like now. Really bummed about that as it would help you some now. Compression ratio was calculated by my machinist. I think he used clay to fill the void, figured out how much the clay displaced water in a beaker, and using the results calculated compression ratio. He seemed pretty confident in that, telling me it was 11.7 to 1 once done (my head is cut some too). That was too much for the street and 92 pump gas as I found, even with a lot more control over ignition timing (prior to EFI and Microsquirt controlling timing, I used a Megajolt crank fired set up). So, I recently had them machined further to what I/we think is about 11 to 1 now (different shop). I've been very happy to be able to run Total Seal rings, just give them a call with your piston specs. Watch your ring gaps... pretty sure I broke the top compression ring in #4 in the previous build due to too tight a gap (still had over 200lbs of compression!). As I recall, you're building primarily a race engine, but I've certainly learned that while more compression can improve output it really depends a lot on the fuel you plan to run and what control you have over timing. I think other more experienced folks like JT68 would agree based on his comments. I would base your compression ratio on the octane fuel you plan to run and the ignition curve (if you want to talk crank-fired systems I have a working knowledge of the Megajolt using a Ford EDIS system. A more plug and play would be the 123 distributor, with a lot less effort).

I got a return email from Rislone/Hy-per Lube and they indicated that basically once stock is gone they don't plan on continuing it... I think that's a real shame as it appears to be fairly unique and effective. It's twice as expensive now as their other ZDDP containing product and I think marketing sees that people respond to ZDDP and want that vs a "zinc replacement" even if it works better (IMHO, and Bob's).

Contact Delta Cam in Tacoma... they can grind whatever you want on an A cam, and can resurface your two piece rockers too. They have all the specs for the A, B, C, Racer Brown and my Isky cam, maybe others too. They profile every cam that comes in. JT, Dean, Ross at Sports Imports and maybe other vendors have thicker lash caps as needed for the U20 collets. The taller collets that use L-series pads may not be a bad idea with the thicker caps, but I have not had a problem with losing one so far. Onward!

[timurf]

Thanks for the cam tip! Now I just need to figure out what lift I want and how much they will have to grind off of the base circle to get there, i.e. see if it seems do-able.

This head is un-cut, 1st one I have encountered in all the years of messing with U20's. I'll let you know what I come up with for CC's!

I may end up going high compression after all. I don't street drive them nearly as much (and never long distances like I used to...)

[JohnnyB66311]

Great stuff guy's

Very interesting and in formative, as well as great read.

I will follow just because the reading is cool and lots of conspiring knowledge being passed

[Gregs672000]

Found some pics on my phone of the Pistons before I pulled them out and cleaned them up. You can see that a fair amount has been machined off, and that took me to 11.7 to 1 compression. They are cut a little bit more now to be at what I think is about 11 to 1. Sorry I lost all the other pics, a side shot would have shown more.

[timurf]

Oh cool - thanks!! It looks like they were turned/chamfered rather than planed down? Or perhaps both. When I get home I'll grab one of mine for more calibrated comparison eyeballing.

Questions questions - do you know the thickness of your head?

I'll have to slip the piston into the bore at TDC height to do a clay negative, since the CC kit needs a flat surface to keep the fluid from leaking and messing up the measurement.

What springs did you go with on your setup? Not seeing any options for stiffer springs (although I could also try looking harder.)

[timurf]

@ Johnnyb66311

Thanks for the compliments and glad to see others taking an interest in the technical stuff. Doesn't seem to be as much content in this area lately on the forum!

It seems that with some subjects you get too little or no advice and with other subjects you get too much...