Datsun R 16 head porting advice?

[Daryl S.]

A previous head which had some welding done on the combustion chamber turned porous, leaking into the water jacket, so I'm working on a new to me head. The intake ports seem to be pretty good, but the exhaust ports look to need work?

20181125_140304.jpg

20181125_140248.jpg

Stock Valve sizes are 42mm Intake and 32mm exhaust (8.7mm stem, dual springs), I am considering 44mm and 34mm with 7mm stems, beehives.
Flow on the head just removed was 190 cfm @ 28" on the intake and ~125 cfm exhaust.
I'd like to at least match the intake, but get the exhaust higher, 130 - 135 if possible.

2065 cc 4 cyl pushrod engine, trying for 165+ HP, basically sunny weather street sportscar. 7000 rpm max.

Thanks
Pictures below are from the previously worked 'leaky' head....

[Daryl S.]

Intake Port Cropped Resized.jpg

Intake Port Side Cropped Resized .jpg

[Daryl S.]

Exhaust Port Top Ruler Resized.jpg

Exhaust Port Side Resized.jpg

Exhaust Port Angle Resize.jpg

[Carnut1]

https://www.speed-talk.com/forum/viewtopic.php?f=1&t=51342
Take a look at my VW thread. They have similar prts but the VW ports are straighter. I would think about keeping the port volume as low as possible to stock to keep torque in a usable range. Thanks, Charlie

[hoffman900]

It’s a L20, but close enough:

http://performanceforums.com/forums/sho ... atsun-head

I’m sure Tony will be along.

Also, those heads are similar to the Triumph / Volvo heads, which Erland has experience in, especially the exhaust ports.

[Carnut1]

It’s a L20, but close enough:

http://performanceforums.com/forums/sho ... atsun-head

I’m sure Tony will be along.

Also, those heads are similar to the Triumph / Volvo heads, which Erland has experience in, especially the exhaust ports.

Bob, thanks for that link, Tony's work is top notch!

[mag2555]

You realize what your saying here?
Out of a 126 cid motor your looking to make 1.3 hp per cid to attain 165 hp!?

It's funny the way the numbers work out on this one as Intake cfm wise @28" you need to average 165 cfm per cylinder by my math to hit the target HP number.

[hoffman900]

You realize what your saying here?
Out of a 126 cid motor your looking to make 1.3 hp per cid to attain 165 hp!?

It's funny the way the numbers work out on this one as Intake cfm wise @28" you need to average 165 cfm per cylinder by my math to hit the target HP number.

A L16 is capable of nearly 200bhp in race trim. A L20 can be north of 230bhp.

Hell the little 5 port BMC A-Series can make nearly 2hp/ci in race trim.

[induction apprentice]

I have ported a few L 16 and L 20 heads.
I also tried welding in chambers and roof of port around spring perch. I was devistated after many attepts at welding went bad. i weld lots of aluminum heads. But those are funny buggers? They love to fracture and off gas like no other. So avoid welding if possible I would say. They dont look anything like a volvo b20b head or ports. But I do agree Erland is one guy that could help you. They are very good heads. But thin casting as the cutaway shows. So stay conservitive. The exhaust is mostly bowl work. Grind out the guid bos and slope the exh bowl roof the way it naturally wants. Youll see.

[mag2555]

Where did I post / say that level of power could not be done my friend?
Also please note that the OP has stated he is talking about a "fun street car" , NOT a 2 hp per cid full out race motor as you are talking about!

[Daryl S.]

Thanks for the links. Read through them and found this one too...

Very similar to the Volvo...
https://www.speed-talk.com/forum/viewtopic.ph ... 8&start=30

And the Triumph TR4...
http://www.tr3a.info/FAQ_heads.htm (bottom of page)

Though I'm not sure the Datsun exhaust is as bad....?

The stock head/stock 42 mm intake valve flows about 165 cfm @28", 32 mm exhaust flows right around 100 cfm, both at .500"

Question.... If the intake already flows the required air for the power target, what advantage is there to making it flow 190 - 200 cfm?
Guessing since there is a minimal port size increase, it has to be increased velocity, and therefore increased cylinder filling...

The port walls seem to be pretty consistent around .250" thick, thinking I should be good removing up to .125"? (parts of exhaust port...)

Will clean up head and get some more pictures up this weekend.

[Xnke]

R16 and L16 are two different engines-Not the same head/ports/anything.

Look at U20 heads if you are looking for similar ports and how they're ported, the R16 and U20 use very similar cylinder heads, although they're not the same either.

[Daryl S.]

5 plus years, a couple of heads and I'm having another go at this.....fresh start after finding what looks like a leaking crack inside the exhaust port of an iron head.

Crack in Exhaust Port resize.jpg

Also, guess I really should have seen this before, it has been pointed out that the combustion chamber extends about 4mm over the block on the intake side as can be seen in the photo. Would it be worth cutting some of the block away to match the combustion chamber.... good for a few cfm? Would this require taking it back to the bare block?
Tried an internet search on 'relieving the block for intake valve' and came up with nothing.....

Combustion Chamber Over Block resized.jpg

Thanks...

[mag2555]

That exh port looks pretty poor.
If your able I would raise the roof .060” and then weld up the short turn and the runner floe out to the flange that same amount.

With a head like this you need to first concentrate on the exh 5 cycle where the exh starts the next intake cycle and any pressure wave assist intake flow you can work out.

[Daryl S.]

Thanks mag2555,
Have an aluminum head I'm working on now. Had a head welded (someone reccomended by machine shop) a while back (combustion chamber) and it got rather leaky, so I'm not in a hurry to try that again. Exhaust port is pretty small (~1.1" x 1.25"), so not sure how someone would be able to get at all of it.....
Tried this on the exhaust....? No way to test/compare it yet, but working on it.....Is that the general idea to work toward?

First Exhaust Porting resize.jpg

Looking at oversize valves for the exhaust, possibility of a 35mm, maybe cut down to 34.....

So...the combustion chamber overhanging the block is not an issue? or is the exhaust so bad that cutting the block there wouldn't help?
Also have a custom 4-2-1 header to help with the exhaust. Considering a 2" AR chamber right after the header.