posted on January 05, 2014 13:31
The Heart of a Record Breaker III: Completing the VVL Head Swap and Engine Assembly
In part one of our engine build series, we did a quick overview on the anatomy of our record breaking engine dubbed the SR15VET 20V. Next, we introduced you to the "23 doctor," Nick Hunter of 5523 Motorsports and then dove into his assembly of the SR15VET 20V’s bottom end. If you’re not up to speed yet, be sure to go back and read up on the Heart of a Record Breaker Series. In this installment, we’ll follow Nick Hunter in the assembly of the coveted "20V" cylinder head and also cover the SR20VE head swap.
Originally, our resident HNIC (head nerd in charge), Mike Kojima, graciously offered up a SR20VE 20V head that he had stashed away in the far reaches of his toy box. Mike’s 20V head was fully ported and had 1 MM larger Super Tech valves installed.
After a record breaking run, Nick inspects our original 20V head to understand the root cause of the failure.
Unfortunately, after our record El Mirage run we’d find out this head’s valve job was questionably performed, which resulted in 40% leak down across three cylinders. We had crushed a land speed record by 30 MPH but now only had a month before Speed Week to resolve our head issues. It was truly bitter sweet.
Marked with "8H6", the SR20VE 20V head is a rare and pricey piece of hardware. With only a few weeks until Speed Week 2013, we were in a real bad position.
Without enough time or money to source the parts to repair Mike’s 20V head, Nick and I scoured the earth for another super rare 20V head. Fortunately, Clark Steppler at Jim Wolf Technology always has a good stash of hard to find Nissan and Datsun goodies around. After bartering my first born daughter over some rolled tacos at Sombrero’s, we had ourselves an unmolested SR20VE 20V cylinder head. Thanks Clark.
With only a handful of weeks until Speed Week, Nick Hunter did what he does best and tapped into his Captain Zombie Vampire super powers to repair our head. Forgoing sleep and living on nutrition void fast food, Nick Hunter was able to perform a miracle in record time, barely. How the Captain does this, I’m not sure. It’s just what zombie vampires do I guess.
Monday, January 06, 2014 7:24 AM
I have used that valve spring retainer tool on my 4A-GE when I was installing valve stem seals. It is worth its weight in gold.
It cost $80 but if you do this for a living its a huge time saver. ( I borrowed mine from a friend (^_^;)
Monday, January 06, 2014 11:36 AM
Maybe this was answered, but does this block/head combo have the ability to be reverted back to a 2.0 if you ever desired? Obviously you would be switching the crank, rods and pistons but is there anything preventing a similar setup on a 2.0 to pursue another LSR?
Monday, January 06, 2014 11:54 AM
@protodad there's nothing really preventing us from going back to 2.0L. As you mentioned, it would just be a matter of crank, rods, and pistons. Currently, we don't have any plans of swapping back to a 2.0L This probably wont be considered until after we set a record over 200 MPH though.
Monday, January 06, 2014 2:54 PM
Lots of overlap on Turbo. Ughh . Really high EGTs ???
Monday, January 06, 2014 5:30 PM
How much extra flow do you actually see from knife-edging the port divider? I have my doubts that it isn't significant enough to go creating stress-risers in your cylinder head (you even talk about engineers going to such trouble to reduce them with your fancy valve springs on the next page)... Also, how come only /near/-flush for the valve guides? Does grinding them completely flush cause damage or something?
Also, you wrote "crank angle sensor", but it looks like you mean "cam angle sensor".
Monday, January 06, 2014 5:35 PM
Ummm Crank Angle can be had from the CAM ... Theres inner 180deg marks "Crank Sensor" Outer 1deg marks are cam sensor... So a Crank sensor can be on the cam but Cam not on the crank .. This is why its taken at the Cam and Crank only sensors don't support sequential injection as theres no way to know TDC Compression or Exhaust stroke.
Monday, January 06, 2014 5:39 PM
Alright sparky, no need to take a tone...
Monday, January 06, 2014 5:58 PM
Monday, January 06, 2014 7:05 PM
In a lot of 4 valve heads, besides the obvious valve seat and bowl work, narrowing the port splitter is one of the areas where you can get big gains.
Monday, January 06, 2014 7:30 PM
I would think that they wanted to retain some length on the valve guide so that it can still do what it does (guide the valve) effectively. The shorter the guide, the greater the angle within the guide the valve can have (form perfectly parallel to the guides bore), causing premature wear which could lead to binding and really fast wear.
That said, it is a race engine that is not built to see a lot of running time between refreshes, so you can be more aggressive than a street car of course.
"Back in the days of NASA SE-R cup, if we ever threw our rocker arms, we’d just find which ever ones we could and toss them back into the engine. In other words, no thought was given to shim size or clearances."
^that is unreal.
Thursday, January 09, 2014 12:26 AM
Remember Chuck is talking about plain ol' SR20s with hydraulic lash adjusters. The shims in those engines aren't used for adjusting clearance, but can have some teeny tiny impact on getting the two intake valves to open at exactly the same time. Hard to imagine that mattering on a dirty old SE-R cup engine. Hell, I'm not really even sure how you could check this on an SR with HLAs...
Thursday, January 09, 2014 12:34 PM
@ Dave Coleman- Nick Hunter has some fancy pants Nissan tool for doing this.
Thursday, January 09, 2014 12:39 PM
Just a simple dial gauge it all that should be needed to set rocker angle .. Also I think with HLAs you do need to set the correct hight as the HLA can over or under lift giving in correct rocker ratio???
Saturday, January 11, 2014 1:39 AM
Monkius, knife edging the port divider does indeed create a stress riser, but it's not in the combustion chamber and not an issue. As kojima stated above, this is 1 of 3 major gains to be had from this head. I'll get into the other two in a minute
SM_clay - you are absolutely correct! This is not something that I would typically do for a street car. As you said above, its a race engine, and it is thoroughly checked before each event to prevent issue. Also, on the 8H6 head, the port roof (specifically on the intake side, it's there on exh also, but not as bad) has a very strange (and big pain in the ass to port!!!!) trench cast into it. To flush cut the guide to the roof would mean cutting approx another 1/4" towards the water jackets to eliminate this. Since that's insane, and would lead to water going where it shouldn't, I only cut them down to match the roof.
Shaggy is absolutely correct.... CAS does cam and crank. Same trigger wheel as a Silvia, and very similar to a FWD distributor except for the position windows are not symmetrical as they would be with a single coil
Coleman and shaggy again - we are ALL of us guilty of the old pitch the rockers and do what has to be done at the track trick! It is, however, really bad for the valve train. In a hydraulic head, the guide shim (with the widdle footies) is 3.0mm thick. Only available in one size. The goal is to level the rocker arm when assembled between cam and properly bled HLA. If the rocker is not leveled, you get into weird taper wearing of cam live and rocker, uneven (even if only a tiny bit) valve flow, and also weird side loading of valve/spring/retainer stack up. Remember that a properly setup HLA head should have ZERO LASH! SR HLA's WILL NOT SELF BLEED CONTRARY TO WHAT ALOT OF PEOPLE THINK!! This is the one engine nissan built with this feature, all the rest of the production HLA's will self bleed! On a mechanic head, specifically a VE, the guide shims to away and we are actually setting valve lash measured at the valve stem (NOT THE ROCKER LIKE THE STUPID BOOK SAYS). On kojimas dog car with the converted de head, I made dummy lifters and then set lash. Converted HLA head still require the guide shim as it still has the floating rocker. Don't ever do this.... Its a big pain in the ass to setup and is tough to get right!
The other two big gains to be bad in these heads is valve bowl blending.... Nissan apparently has never believed in doing this! Removing the low spot in the bowl just beyond the seat. The third gain (specifically with 8H6 head) is deshrouding the valves in the combustion chamber. They did this to promote swirl as they were chasing the great white emissions rabbit.... Helped them, but it sucks for making power! I (and a lot of very diligent cam designers) strongly follow what I call the "punch clock rule". Simply put..... When you go to work and punch the time clock, your boss doesn't want you sitting around shooting the shit for 20 minutes before doing any work.... They want you working straight away! I want maximum flow AS SOON AS POSSIBLE! This particular head wasted a ton of valve lift before there is any real flow around the valve face.... So I de shroud the valve seats big time. You have to be careful here as you can easily wrech the combustion chamber design. In chucks defense, I asked him not to show a couple of these porting photos as I am greedy and don't like to share.
Saturday, January 11, 2014 1:41 AM
And I typed that all on an iphone, so please excuse my spelling.