Next you need to pick up and replace the bushings valves. To do this, use the bronze bushings from Honda. Bronze better heat dissipation than cast iron.

To the left of the Honda, right stock.

 

Since I do not plan to greatly increase the engine rpm (maximum 7200 rpm), I leave the springs stock. For exhaust valves decreased the thickness of the valve stem. Therefore we must find new retainers. I also use Honda.

Stock

Honda

 

In the area of the 4th cylinder there is a channel of exhaust gases for the EGR. I disconnected this valve software. This channel should be mute. It will not heat the cylinder head. This will allow you to use a plastic intake manifold. It will also give a more even flow of gases from the 4th cylinder.
This is undercut in the body of the channel.

 

Next is plugged.


In the future, all the projecting parts are ground down.

 

After replacing valve seats and bushings, it is possible to broaden the channels for intake and exhaust.

 

However, it is impossible to mindlessly increase the channels. The intake channel has just such a form

If you just increase (expand) the input. The fall in the rate of air flow. Therefore, the form should remain as shown above.

 

Now the Assembly can start.


Tomorrow I will finish the story

 

Bravo! This is one of the coolest things Ive seen in the 4g69 world for a while!

Off topic, but Im curious since you mentioned it. What do you think would be involved in making a 4g69 have a higher redline? Less rotating mass? Less stroke? Better valvetrain? All of the above?

 

I'm not exactly understand your questions. You mean how much HP you can get from the 4G69?
I will say this, for (N/A) street version 280-300 HP
The racing version of 380-390 HP

 

Good to know.

My question was about the RPM limit. How do you think you could spin the engine up to 8000 or 9000 safely? How would you go about doing that?

 

I get it now. The RPM depends on the average velocity of the piston. Safe speed 23 m/s.
This is the formula:

V = (C x g) / 30

V - velocity of the piston
С - the piston stroke in meters
g - RPM
30 - a constant value. (this is half a minute. You can specify a 60, but it is necessary to increase in 2 times the piston stroke, for 1 revolution, the piston makes 2 movements)
For example. 4G69 piston stroke of 100 mm. (0.1m). in addition, for 6000 rpm the piston speed is 20 m/s.

Accordingly, we can deduce another formula.

g = V x 30 / C

g - RPM
V - velocity of the piston (we took a maximum of 23m/s)
С - the piston stroke (m)
30 - a constant value

For 4G69 23 х 30 / 0.1 = 6900

You can calculate any motor. For example, several Mitsubishi engines and critical turns:
4g63 piston stroke 88 mm (2l) 4 cyl — 7840 rpm
4g69 piston stroke 100 mm (2.4 l) 4 cyl — 6900 rpm
6a13 piston stroke is 80.8 mm (2.5 l) 6 cyl — 8540 rpm
6g75 stroke 90 mm (3.8 l) 6 cyl — 7666 rpm
8а80 stroke 96.8 (4.5 l) 8 cyl — 7128 rpm

A further increase in speed leads to increased wear and destruction. The sharp decline of the resource.

 

continue
In General, everything seen in the photos

 

 

Now it is necessary to conduct a air flow test. Reinstall the head on the purge stand.

 

So, the result of the flow test. 298 CFM Intake, 214 CFM Exhaust



I did a test before the valve lift of 13 mm (.512) Further lifting does not make sense. There is simply no camshaft with the same lift. But if I do as is customary in the US to 15mm (.590) It will be well over 300 CFM.