R16 Modification Questions

[peter]

Ooh, and and whats more important that the bore size is larger.

[Daryl Smith]

Well, If I could have got the gasket, I would have gone with , maybe 89.5 mm bore....that would have given a total of 127.4 Cubic inch displacement, or 6.45 Cu. In. over the stock engine. On a well built engine that would be worth 1.2 to 1.4 times those inches in horsepower and torque. so at the low end 1.2x6.45= 7.74 more horsies. At 1.4x6.45= 9 more horsies.
Those little horsies, and the added torque, will push your car along just a little bit faster than the cars that don't have the extra little horsies, and the advantage is at all rpm ranges, unless your head doesn't supply the breathing necessary for the larger displacement.....

[peter]

My bore size is also 88.9 mm now and the gasket is 91mm
Daryl, I can arrange a gasket here for yo and send it to Canada, it cost about 30 dollar to ship till 2kg.
But I have to order them in the Republic of Lithuania for about 20 dollar a piece, how many gaskets do you want.

[Daryl Smith]

Thanks Peter, but the machine shop is already on the bore, so it will have to wait for the next engine...

Ford Y block lifters are about 1" diameter, .200" taller, and 7.5 grams heavier than the stock Datsun lifters. This means there is about an extra .050" diameter over stock. IF there is any worthwhile advantage in that .050", it may be in increasing the acceleration rate on the lobe, lifting the valve a little quicker to increase the air intake. BUT, the cam would have to be specially ground to take advantage of it. Putting Y block lifters with a cam ground for Datsun lifters will give you no advantage at all.
At least this is the way it has been explained to me.....

[Daryl Smith]

Re: R16 and U20 connecting rod "big end thickness" - both use the same bearings.
I measured an R16 rod @ 1.133" and a U20 rod @ 1.127"
The Clymer manual lists the R16 rod thickness @ 1.1319" - 1.1339"
I cannot find a spec for the U20 rod.......

Is the R16 rod skimmed slightly on the big end thickness for the U20 crank?
Is there a minimum big end thickness? Does it matter? Is the rod kept in position by the piston?
Could a modern rod that is narrower (1.0 - 1.1") be bolted in place and work long term?

Thanks,
Daryl

[Daryl Smith]

Just spoke to Micky at "Cometic Gaskets".
They have files on hand and can make up gaskets for the R16/H20 with a turn around time of approx. 4 days.
Available with either a 89 or 90 mm bore and either .043" or .059" thick.
Says the .043" gasket should compress to about .038", which to me is just about right for a flat top or dish piston!

Their price as of today is $82.99 ea.

[Daryl Smith]

Anyone try different shapes on the back of the intake and exhaust valves?
The stock valves have a bit of a tulip shape to them. It has been recommended to me to use a 'penny on a stick' shaped valve for more flow.
Trouble is, from what I've read, there is no way to be sure what's best without trying it, usually on a flowbench.

So....has anyone experimented with this on the R head and care to share their experience??

Cheers,
Daryl

[hearing]

I would say .3130 stem diameter undercut for the bowl maybe even a 7mm stem. I am planning on a .100 long 3130 with 1.5 " ex and I am still trying to figure out how big of an intake I can run with that exhaust. So, any help in that area would be great. Thanks!! Dave

[Daryl Smith]

Hmm....From that answer Dave I can't tell if your talking over my head, or are a newby with a bigger is better attitude, which would be the wrong way to go unless you're planning to spend some big bucks all around on your engine.

So....tulip or penny on a stick?

[Daryl Smith]

With .500" valve lift, is it necessary to cut valve pockets into the pistons? Flat top pistons?

[jake7140]

Some people have beveled the top edge of the Y-block Tappet to reduce weight.

[Daryl Smith]

No one using .500" Valve lift has had to cut valve reliefs into their Pistons??

Haven't been able to find any info on this. Competition manual doesn't mention it, but mentions using .480" valve lift ..and cutting the head .125" ....???
Piston manufacturer doesn't seem to have info either.....

Thanks

[spl310]

I think that it's not that simple as the valve timing would play into it as well. Some clay and time are in your future...

[jake7140]

Well put. You can get initial ideas by measuring (see various places that custom make Pistons) but clay and a degree wheel will serve you well. There are many variables.

[Daryl Smith]

Several variables - piston shape, rod length, lift, duration, valve head diameter (when non-stock), thickness of head, thickness of gasket......That being said, not many using a .500" valve lift other than in racing which typically would have a much longer duration - on Dean's site, 306* - logically, it should open sooner, and stay open longer, than what I am looking for - about 280* advertised - therefore, by my thinking , if someone using this 306*, or a similar cam, had to cut valve reliefs, it is likely I will have to also. IF it was not necessary, with a flat top piston, then I won't either, I think.....

Please feel free to poke holes in my logic!

I am building an R stroker, and most of these questions are going to get answered one way or another, and the answers will be posted in this thread. I'm pretty sure I'm not the first to try any of this stuff, so the answers are out there. It's just a matter of poking the right person

I have some 1600 pieces around here I might be able to cobble something together to test. Higher rod ratio, flat top pistons, should get me close enough.....