Custom Rusch Motorsports P-90a head

[BRAAP]

Here is a custom P-90a head that we are working over for a customer in the UK. We acquired this head here in the US, the casting number is P90A, yet the rocker pivots are the traditional solid adjustables and there are no oil galley ports in the bottom of the rocker pivot bosses, i.e. mechanically this head was cast and machined at the factory as a mechanical cam L-series head yet the casting number is P90A?!?!? Could this be a JDM head?

 

Any how, the head is progressing along nicely, destined for a 3.1 stroker. These pics are of the completed ports and chambers just prior to installing the new valve guides. Guides will be shorted a little bit to keep as much of the guide itself out of the air stream. We will then cut the seats, CC the chambers, then after CCing the chambers, give the chambers a final finish, assemble the head with the Rebello cam, set the cam wiping pattern, order the appropriate lash pads, and ship the head to its owner in the UK.

 

Depending on our schedule, we will post follow up pics of the progress on this head. We are also working on a Z-N-47 destined for another 3.1 stroker on the right coast, pics of that to follow as well.

 

 

 

 

 

[Workinprogress]

Nice

[JMortensen]

Yeah, the Japanese used the P90a with solid lifters, so when you see one it's usually a used Jap engine.

 

Nice work!

[rztmartini]

jesus that looks sweet. what kinda use is this engine being built for?...that is if the owner/customer is willing to disclose...

[slownrusty]

Absolutely stunning!!! That baby is going to flow!

 

Yasin

[1 fast z]

Nope, LOTS of P90-a's stateside have solid lifters. I own three myself, and One I personally pulled off of a zxt. Late 82 zxt's have P90-a's with solid lifters. My 12 second NA 280z uses a solid lifter P90 a. Looks good though Braap.

[olie05]

Looks awesome.

 

One day i hope to get some headwork done by Rusch Motorsports.

 

On a side note... last night I had a dream that i was given a p90(no "a")

 

anyone care to make my dream come true? lol

[BRAAP]

The seats have been cut. Next step is to blend in the chamber wall cut and the bowl hog to the ports, then surface the head, CC the chambers, pre assemble for valve train set up, etc. etc. etc.

In the past, I have tried to get pictures capturing the different angles that are cut with the seat cutters but none of the previous pics really represented what was going on, very well. This time, I think I was able to take a decent shot of the seat work we perform using the Sunnen VSC seat cutters. I just LOVE these seat cutters for their precision, repeatability, finish quality of the seat face itself, etc.

 

This first picture shows the cylinder head set up on the mill table with the cutting pilot installed in an intake guide. I then use the finger dial indicator and run it up and down the full length of the pilot in two directions to square the “head of the mill” to within .0001” of the pilot which is true in the guide. This keeps the “mill head” true to the valve guide so that the valve seat will be cut “square” to the valve stem, not tilted or canted. I then spin the finger indicator around the pilot to center up the cylinder head perfectly under the mill head, within .0001”. This allows me to cut the valve seat itself to within .0005” concentricity to the valve guide, (not offset to one side). Now I lock the mill table down tight, then double check all of my runouts in “X”, “Y” and “Z” just to make that tightening the table down didn’t disturb the settings, which it sometimes does when you are trying to keep such tight tolerances. This procedure is done for each and every valve seat that I cut.

 

You may have seen or heard about a “seat & guide machine”. Serdi and DCM both make quality sat and guide machines. The seat and guide machine itself replaces the Bridgeport style mill that I use for performing seat and guide work, even though it uses the same cutting systems that we use here on the mill. A seat and guide machine is much quicker as its sets up much faster, but uses a bubble level and you are trusting that the table is plumb to mother earth, (or you should be double checking it once in while at least). I’ve used a DCM in the past. They are very convenient and are typically accurate enough for even high end production shops, as long as the operating is keeping tabs on the table/bed being level. This approach of using the knee mill is more precise even though it takes a little longer. With the mill, I know for darn sure that on each and every seat that I cut, that I am dead nuts on.

 

 

 

 

 

This next picture shows one of the chambers with an Intake and an Exhaust valve. The valves themselves have purple lines on the seat faces to help identify the face and back cuts. The face is ground at roughly 44-44.5 degrees and the 30 back cut is 30 degrees to aid the air flow transition from the back side of the valve to the seat at low valve lifts, less than .100” lift.

 

On the valve seats in the head, I marked the angles in green, with the offset green mark being the actual 45 degree valve seat face itself. The intake on this head has 5 angles, the exhaust has 4 angles. I try and get 5 angles as often as I can, but several factors dictate if I am even able to or not, such as new seats, valve head size, etc. With every head that we do, we are able to open the throat of the valve seat itself at least .040” sometimes as much as .060” over OE. This is like going to a larger valve without actually installing the larger valve itself. This modification is really only good for really high valve lift flow, at low valve lift, it doesn’t help. Of course actually installing a larger valve allows me to open the throat of the seat even further, but for most mild to moderate street L-series, this is not needed. For the Intake seat, the top angle in the chamber is 15 degree, then 30, then the 45 degree seat itself, then 60, then 70, then the bowl hog cutter which is the Blue marks, (the bowl hog is either 75 or 80 degrees, I forget which, forgive my poor memory), and then the port walls themselves. For the Exhaust seat, the top angle is 30 degree, then the 45 seat itself, the 60 degree, then the 70 degree and then the bowl hog. The green circle just left of the intake seat is the chamber wall relief cut which radiuses the 15 degree cut into the chamber wall and roof, (the 15 degree and chamber radius is actually on one cutter, as well as the 30, 45, and 60 degree cutter).

 

On pretty much all of the valve seats we cut for N/A applications, whether it be Briggs and Stratton’s, Datsun L-series, or Little Block Chevy, we cut the Intake seats at .040” in width, and all the exhaust seats at .060” in width. Also, all of the Intake and Exhaust seats are exactly the same diameter as one another respectively and they are also cut to within .002”-.003” depth of each other respectively. On some boosted applications, we will cut the exhaust seats at .080” in width, this is application dependant. Of course, if the customer has specific seat geometry he/she needs to meet, we try to accommodate the best we can.

 

 

Whew, back to work…

[RIP260Z]

Hi Paul,

Things are looking great. Are you having that "warm fuzzy feeling" about this head Paul?

I am the chap in the UK who Paul is building this head for. I feel very lucky and honoured that Paul is doing this for me. I would not hesitate in recommending him.

 

Rtzmartini, this is going to be a street engine. If you're interested, the set up runs like this;

Cam spec, I quote, " The cam specks are quite deceiving as the duration at .50 is about 226 deg but the cam makes power like one of our bigger cams due to a unique lobe design. The lift is .487".

Triple 48 Dellortos, Nismo header, properly tuned exhaust, flat top pistons, 1mm gasket, LD28 crank from a Maxima (brought from the US), balanced/shot peened L24 con rods, BHJ front damper, Tilton 11lb flywheel, rotating assembly balanced, ARP bolts where possible.

 

But I have to finish restoring the rest of the car before building the engine.

 

Cheers

Ian

[flames_187]

i always wonder about the air flow differences b4 and after a process like this...i know its a huge difference...just wondered if there are any numbers on it...espically b/w diff wall finishes...

[1 fast z]

Yea Paul, Im curious about the percentage difference between before and after. Do you have any Percentage difference numbers on some of your heads paul?

[BRAAP]

Ian,

Ah yes, we do have that warm fuzzy feeling with this head. The other head that we didn’t get that feeling from is destined to be used for further L-series head development, possibly sectioned up, mapped, etc…

 

 

 

As for numbers, no guys, sorry I do not have any numbers, “yet”. We will be running some of the more popular chamber and port configs soon and most likely will post those, but only to satisfy the numbers/math geeks among us.

 

 

In regards to port flow figures. It is in my opinion, and the opinion of many other professional engine builders, that quoted Flow Bench flow numbers as given to customers, are only given for the purpose of their records, just as the bearing clearances, torque values, etc. quoted on an engine build sheet are given. The flow numbers are not numbers that should be used to compare one heads theoretical possibility to produce any sort of power to another head. A lot of guys like to compare flow numbers of heads and most people automatically assume that bigger numbers are better and mean more power. Generally speaking, that thought holds some truth, but not all of the time. The flow numbers derived from a flow bench are just static flow numbers only and do not reflect how much power an engine will produce, or how it will produce power within its intended rev range, i.e. torque under the curve. If you are comparing flow numbers while bench racing with your buddy, you may as well be comparing torque values for your Rod Bolts while your at it. Then when you want to compare something tangible, compare dyno sheets or ¼ mile time slips.

You can take two identical cylinder heads that are ported differently, but flow pretty much the same CFM on a flow bench at the various valve lifts. Put these heads on identical short blocks and one engine could very easily make considerably more peak power than the other, and they will both have distinctly differing power curves as well. A flow bench can NOT measure all the variables taking place on a running engine such as the rapid opening and closing of the valves and the pressures that build from this surging air flow, (I just wrote an article about this very thing in this thread towards the bottom of the page http://forums.hybridz.org/showthread.php?t=108398&page=3 ). A flow bench does not take into account the fluid dynamics and pressures of the spent hot exhaust gasses. A flow bench does not take into account the cylinder scavenging during valve overlap. Material removed during porting from different areas of the ports and chambers will have differing affects under running conditions that a flow bench just can’t measure or tell you about. A flow bench is a valuable tool that when used by competent experienced engine builders, can help shorten the learning curve to producing maximum effort engines. The Flow Bench is a tool to be used by the engine builder himself, to get an idea of what port/chamber mods made a change, and he should also not assume that all changes that allowed for more air flow will allow that engine to produce more power, or better yet, more “useable power” for its intended application. The info derived from the flow bench should only be used by the engine builder, and as a very rough guide, not gospel. One head that flows more than another could actually produce less power due to the variables that a Flow bench can’t measure. In short, either a dyno sheet or a ¼ mile time slip coupled with the vehicles weight, are the real tests of what an engine can or can not do, not the flow numbers from a flow bench. The Flow bench is just another valuable “tool” in the engine builders tool box.

[1 fast z]

Agreed, everyone knows you cant tell everything from flow numbers, as it is a static system. BUT it does give an idea, and some flow benches tell velocity as well, which is key in engine dynamics. Percentage difference of before and after figures is important though. It may not tell the whole story but it sure tells alot. So do you not flow test your heads at all? Im just curious. I do NOT just use flow numbers in my head building either but it is something to tell you and give you an idea of whats going on, and to let the customer know the same information. I use the Track to do My testing as well.

[1 fast z]

And if you notice that I say PERCENTAGE DIFFERENCE, not flow numbers, Im just curious about the percentage increase. I respect your work a BUNCH braap, so dont get me wrong im just curious. As we are basicly the only two head builders that talk about this stuff online, im just curious thats all, but work LOOKS GREAT. Im actually in the process of using our new CNC to re-face all valve seats, Im in the process of building a jig to do the work now, and I think it will work great.

[flames_187]

thats for the info braap...i dont mean to side track the conversation since im new with engine flow i thought id put a question out there...how useful is Helmholtz equation...id been playing around with it sometime for my school's FSAE program but neva got around to testing it...plus there are so many different variations of it that makes me wonder how does one get good information out of it?...also i was just wondering how much better the air flow with a process like the one your going through. i understand that there are other variables that will give different hp/tq readings i was thinking more as a nondimensional number not anything standard...i was just thinking it the engine flows better maybe it can handle more rpm...given that the engine has the correct equpiment...please do comment back if u have the time.

 

fyi, im just a geek that likes to look at numbers...i blame it on school :-/

i posted the question in the other link too just in case u dont wanna answer it here.

[BRAAP]

Brian,

I agree that it is the difference made, as measured on the flow bench, and how it is interpreted that really counts. As I mentioned, we will post our gains in the near future.

You mentioned CNC for cutting seats? That would be very cool. Are you incorporating CNC port work into that as well?

 

BTW, I sent you an E-mail..

 

 

 

 

 

Flames187,

If you are going to school and involved in an F-SAE project, then you would have, or should have, access to the SAE books that should have the most in-depth info in print regarding Helmoltz tuning.

As you mentioned, there are so many variations of formulas for calculating ideal intake runner length and diameter for a given displacement and within a given RPM range that it really muddies the waters. I haven’t the foggiest which to use or why.

 

Ah. I have an idea. IF you have a report for school that you have to do, maybe you could research that and post your findings? The SAE books would be great place to start. I’m sure I am not the only one here that would love learn more about this.

[flames_187]

good idea...i will look into that...the hard part would be coming up wit a test method for it...i once played with the idea of making the runners out of pcv piping just to test different runner lenghts and plenium cambers to see with derivation of the equation worked the best...

[naviathan]

Some newer cars have plastic intakes. It's feasable that you could make an intake out of pvc.

[flames_187]

it would just be for trail purposes anyway...gotta wait till school starts to work this out..

[Silent]

right coast?

midwest!

 

 

i'll call ya tonight man