Author Topic: Multi port EFI 496  (Read 1342 times)

Online jeremy.farlow

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Re: Multi port EFI 496
« Reply #15 on: May 21, 2020, 10:10:11 PM »
FINALLY!!! Heads have arrived!

Things of beauty.

Unfortunately, the GenVI Melling cam is proving too much. Itíll go back in the box and back to Summit. In its place Iíve got a COMP cams EFI friendly cam and lifters coming.
The GenVI replacement cam seemed a good idea at first, but it limited my options in timing set and in addition to needing the later style cam button and thrust plate I also would need to retrofit the GenVI method of aligning the lifters. While my block was machined for the thrust plate, I donít see any way to mount whatever aligns the lifters:

Something grabs those flats on the lifters. I assume it bolts to something else.
Where thereís a will and all... I have a lot of will, but the easiest WAY is to return some stuff and buy other stuff that better suits my needs.

Iíve built a handful of engines in my life. Even a couple of real hot-rods... but the hot rod engines were motorcycle engines and the other stuff was all factory replacement stuff. Nothing with the aftermarket support small and big block Chevyís have. I appreciate that Chevyís are EASY as well. One bellhousing pattern and minimal architectural changes beyond. But just enough in this case. The ďeasyĒ, factory roller cam swap was proving anything BUT EASY.

I got heads today and decided on another cam.

I hope to get the heads installed in the next couple days. I can loosely install the rocker studs, but Iím dead in the water until I get a cam. Comp says itís in the mail...

I put the studs in!!!:

Everyone wants to sell me an application specific ďthread sealantĒ but I have lots of this on hand and itís never let me down:

Speak now or forever hold your piece. I donít see why it wonít work. PTFE thread sealant, 250.C heat rating...

The AFR heads are gorgeous. They werenít CHEAP, not by any stretch, but at the price point Iím surprised to see fully CNC machined ports AND combustion chambers. That being said, there are a couple spots where there wasnít enough casting for the tool to hit. Despite being a cynic at heart Iím saying their castings are so tight the tool couldnít make a cut. In any case these heads are light years better than the Speedmaster parts. Thereís no thread inserts. I donít foresee ever needing to repair the threads in what appears to be a fantastic casting with well-conceived machining. If so, IíLL get to decide what sort of insert to repair them with. So be it if MY repair winds up being a helicoil set that I bought in the lawnmower repair section at Loweís.

Itís not a worthwhile expense to spare...

Anyhow... Iíve never had as much on the line as I have now. I made a budget pre-coronavirus and Iím HAPPY Iím still within that. Iíve paid upfront far less than a lot of guys in my position are willing to pay on a note for a driver. Iím gonna have a really nice, $25k, 30-year old truck after this. Everything is bought and paid for.

The engine is gonna be tight. I did build a Yamaha FJ1200 engine that was unbeatable in AHRMAís ďBattle of the TwinsĒ series. As ridiculous as I thought that FJ engine was at the time, I didnít have 1/3 the options I have on this thing. I had ONE crank option... ultimately based off a re-ground stock crank. Rods sized to fit. No option for throw. Pistons re-worked to fit a reworked factory head. The head was decked for improved squish... but there were no options for combustion chamber volume. No options for different sized pistons to address a different CC volume. There werenít cam styles to consider... or valve configuration... or springs with deference to either.
DOHC, spring under bucket configuration. No other option. Adjustable cam sprockets, sure... to work with ONE POSSIBLE valve-train.
I missed the two-stroke era... a fact I lament, because I like tinkering... and two-strokes=tinkering. Iím sunk if the virus lockdowns requires more than the suburban out of me, but this will be my next project:

For those who donít, thatís the last street-legal two stoke to American shores. Yamaha RZ 350. Enough displacement to require a tag in all 50 states. The picture above is my bike many moons ago. Itís been in long term storage for a while. As much as I love motorcycles, theyíre detrimental to sane life... with children and mortgages, etc. Building a square body GM was supposed to be easy...

Itís not a hot-rod...


Please lord, let me get 40k miles trouble free...

Stay healthy and safe


Online bd

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Re: Multi port EFI 496
« Reply #16 on: May 21, 2020, 10:34:55 PM »
Told ya you'd be pleased!   ;D

It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Online jeremy.farlow

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Re: Multi port EFI 496
« Reply #17 on: May 21, 2020, 10:49:26 PM »
Theyíre SO NICE

Offline Shifty

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Re: Multi port EFI 496
« Reply #18 on: May 22, 2020, 11:48:37 AM »
I've never been disappointed with AFR's heads!  (especially when Tony Mamo ports 'em)
87 V20 Standard Cab Longbed (current)

87 R30 3+3 Longbed (days of yore)

Online jeremy.farlow

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Multi port EFI 496
« Reply #19 on: May 26, 2020, 02:19:41 PM »
Iím not likely to port these heads any more than AFR sent them to me. Theyíre beautiful. Iíd hazard a guess that the machined finish they ship with is likely an awesome finish for a carbureted application. My guess is that the striations left by the tool will add turbulence and help fuel atomize better. Not so much a concern for my fuel-injected application, but an interesting aside.

Another aside: years back a European fellow published his findings regarding engine break-in and intake port design. His page has since vanished from the internet, but at one point this guy was purportedly the best non-factory, Super Sport motorcycle engine builder in that world.
He subscribed to the ďPopsĒ Yoshimura school that an engine should be broken in as quickly as possible. His theory was to verify the engine was oiling and then to make progressively faster and harder runs up a long hill. Start off in lower gears and lower revs and add RPM and gear with each successive pull. Always full throttle, always working the engine as hard as you can. Start in second gear, keeping RPMs low, 3000-4500 RPM (17000 RPM motorcycle engines, remember.) Kill the bike and coast back down the hill. Third gear, 4500-6000 RPM. Fourth, 6-8500, fifth 8500-12,000 or so and if you still had room for sixth, run it out.
The point was to develop as quickly as possible, as much cylinder pressure as he could to force the rings to really ďbiteĒ the freshly honed cylinders.

His other perspective was that modern 600cc motorcycle engines had intake ports FAR larger than what the engine actually needed. This builder had taken to reducing the size of the intakes with something like JBWeld and then reporting those openings. He published head-to-head comparisons of his reworked heads against the factory heads and showed monstrous improvements. He also showed that, according to a flow bench, his heads didnít perform nearly as well as the factory stuff did. The perspective he arrived at was that outright flow is only one component of intake port design. Equally important, especially in a carbureted application, was a degree of turbulence that allowed the fuel and air to mix better.

As Iím not building a 10/10ís racing engine and expect to ďleave a lot on the tableĒ Iím not gonna invest myself too thoroughly in making the AFR ports any better than they came to me. That being said, I am interested if anyone knows of concrete theory to prove or disprove that guys findings. Iíd also be interested to know if forced induction applications work differently. It seems to reason with any kind of turbocharging, the flow characteristics would become more important than the turbulence created. I have nothing to substantiate that theory on though.

Iíve swapped waiting on heads for waiting on a cam. I went ahead and installed the ďoddĒ head today. It has to come back off for the cam, so itís really just an exercise. It went smoothly. Studs torqued in four increments to ARPís recommended 80 foot-pounds. I used plenty of ARP fastener assembly lubricant.

This was a welcome tip some internet guru suggested... labeling the torque sequence on the head to prevent having to keep looking at the book.

Pushrod guide plates and rocker studs are loosely installed, with thread sealant as recommended. AFR uses two-piece guide plates of their own design. Their instructions got me to this stopping point.

Another trick I like is to mark each fastener with a paint pen once itís fully torqued. I spun the engine over to check the torque on the mains and rods and marked them as well.

Things are coming together. Not quite at the rate I really want, but enough so that I can feel it.

Safe and healthy and sane.

« Last Edit: May 26, 2020, 04:10:51 PM by jeremy.farlow »