R16 Head

[70MTroadster]

Howdy folks,

I am getting ready to stroke my R16 to a 2L. I am finding tons of info on the 2L regarding porting, etc., etc., etc. but virtually nothing on the R16. Yeah, I know Joe Hauser has some stuff on his R16 adventures but it is all very general stuff.

Does anyone out there know of anywhere a fella can read up on what they did "specifically" to the R16 heads? Specifically.....combustion chamber volume stock versus modified? Bigger Chevy valves? If so, what size? I talked with Steve Allens head machinist regarding work done to Steve's cast iron R head, and he was of no help.....all he could say was he thought he'd used stainless steel valves...size unknown. He "thought" that the stock combustion chamber was 41cc. This is important to know when figuring final compression and piston selection. According to the Bob Sharp PDF info, the 2L combustion chambers are much bigger at 45.7cc's.

I am totally capable of getting this all done myself but as time has gone by, I've become more and more amazed at the lack of stuff on the R16 heads (at least that I can find) and the thought of ruining my smog port aluminum head by grinding in the wrong places ain't too nifty.

Lemme know

scott

[spl310]

I have a copy of the 1600 Bob Sharp manual on CD. It is a PDF file - I happened to have it here at work. There is some good information about the 1600 head modifications. I have sent a copy of it to be posted to the web, but I don't know how long it will take.

If you post to the main list, you may be able to find a hard copy. If you want the CD, send me a private message or e-mail.

Sid

[S Allen]

Scott,

Sorry to hear the machinist that did the work on my head was not more forthcoming with the info. I guess he does not want to look up the job sheet that tells exactly what was done. Unfortunately I do not have a copy of it. Short of pulling my head off and sending it to you I do not know what to tell you. Another fellow roadster enthusiast took an "R " head to them and asked them to give him an estimate on oversize valves, porting and polishing and he was quoted $1400.00. He politely said "See ya later!" I did not pay that much to have my head done even though it has been a few years. I will not be using them again because that is way too exspensive for an R motor. I would think you would be safe putting in H20 valves as they are bigger and using the competition valve springs. Try to port match the intake and exhaust so you have smooth flow in and out. Clean up any casting flaws you see and you should be in pretty good shape. You do not want your compression too high for a street motor anyway. Sorry for rambling.

Steve

[spl310]

Well I pulled up the CD, and here is the reader's digest version:

Exhaust ports - retain stock dimensions, except clean up the casting flash and roughness, gasket match the ports. (I think that blending the bowl above the valve head may be a good idea - caveat emptor!)

Intake ports - discard the locating rings and open the ports to 1 7/16 and one third down into the port, taper down 1/16 so that you don't grind down into the bolt hole.

Intake manifold - just match the port size, and smooth out any irregularities. - no serious porting needed.

exhaust manifold - again, gasket match.

Bob recommended stock valves. He does recommends a 45% angle, but that was before 3 angle jobs were in vogue. He does not recommend tuliping the valves due to possible weakening.

You may want to talk with the machinist for his suggestions about bigger valves. Some that are under cut on the stem and swirl polished would be good for flow. Tuliped valves would help with weight and helping keep the compression ratio down.

Rocker arms were suggested to be brass bushed for longevity and trimming/shaping and polishing them to reduce the weight by as much as 32 grams.

There are recommendations about modifying the pushrods and cam followers, rocker pedestals, milling the head and working over the chambers. There is also discussion about fly cutting the combustion chambers and milling the pistons to manage compression and provide valve clearance.

Although the information is likey way out of date for racing (heck this info is contemporary to the car...) it should be fine for a street engine in my opinion....

Best of luck!


Carb mods are listed in some detail. But I would suggest talking with someone like Steve that has done a stroker. He can probably tell you what works and what does not.

[70MTroadster]

Thanks everyone for trying to help. Steve, no worries mate, you are not rambling and I appreciate your trying to help out. The H20 valve idea is a great tip. Sid, I'm wondering if the PDF file I downloaded from Datsuns.org titled Datsun Competition Preparation Manual by Bob Sharp is the same thing you have? I guess not as my version only speaks to the U20 head and all the mods to do to it, not a word on the R16 head.

I pretty much figured that's the way they would do it, thank you for the info.

Scott

[spl310]

Scott,

The manual from Datsun.org is the 2000 manual. You are right, it ignores the earlier motors. I have a copy of each. Bob was pretty conservative in his engine preparations, but for a street car, I am sure that they are fine.

[Chris]

Here's my 2%, based on what I've done with my race car.

Valve diameters are 1.69" and 1.37". This is the max allowed by SCCA rules, but you physically can't go much bigger on intake without having clearance problems with the cylinder wall. Valve stem diameters are reduced, and valves are custom made Stainless. The A-series comp. valve springs work well, and I had some titanium valvespring retainers made. I also use titanium locks on the retainers, as well as titanium nuts on the valve last adjusting screws. Rockers have been lightened an polished. Rather than bronze bush the rockers, I have the rocker shaft coated with a low friction coating, and hone the rockers out slightly for correct clearances.

Combustion chamber volumes were matched, and worked out to be about 43-45 cc.

The rules only allow us to remove material from the head, not add. So that limits what you can do to improve air flow. A good job of port matching will go a long way. There's quite a bit of cleanup to be had on the intake manifold as well.

Pistons are custom made to match the combustion chamber. That's really the only way you can be sure you can get the combustion ratio you want, while still having a correct 'quench' area, and suficcient piston/valve clearance.

1.5" SU Carbs are heavily modified internally to flow more air.

A lot of what we do to the race motor is dictated by the rules. Col. Joe and Bob Sharp all had the same restrictions. With a stroked 1600, there's more flexibility in what you can do, since you don't have any rules you have to comply with.

As an aside, I remember hearing about an SCCA racer who would run a mild, but stroked, 1600 motor in practice, and switch to his full prep 1600 race motor for qualifying and races. Saved wear and tear on the race motor!

Chris Coker
http://www.risensonracing.com