I've seen vehicles that run 9psi and get 450whp, then I see Z's that run 14psi and get the same whp #'s. Now I now there are more things to do to a car to get better numbers.

My question is what can I do on an engine build if I have a fresh engine that is getting a complete overhual. What would I need to make this car make efficient power.

 

bump

 

Cams, larger valves, Major head work, bigger exhaust, larger TB. Over all your trying to make the whole system efficient not just the engine. Internal Combustion Engines like a pump using compustion to move the air through. Make the whole system more efficient the more power you get out of it. Make just the engine efficient you have restrictions on the intake and exhaust side it chokes out your potential.

Basicly a balance of intake, combustion, and exhaust flows will net the optimal gains. The wierd thing you look at is the oddities that you spoke of. My original engine was like that, I was at 450whp at 9psi.

With the new one I'm going the route you are asking about. I had all that I listed in the first peragraph and will be hunting down a 3" dual to replace my Injen SES Dual set up this spring. But with the wastegate dumps that bypasses the exhaust pressure in at full boost. Thus eliminating the restrictive pipe and length of the Injen setup.

But yeah I tend to ramble alot so this is my .02

 

Appreciate it. I'm going to be putting in a built engine that I am buying off annother member here and then doing a complete build myself on the original. This will be my first engine build but am looking for a project to do for the next 6 months. So just looking for info. By major head work do you mean port and polish the heads.

1. cams
2. larger valves
3. larger TB
4. larger exhaust

 

port & polish intake and exhaust, knife edge the dividers, bowl work, larger valves, 5 angel job (3 on head 2 on valve) smooth out the valve seats. One thing I forgot to add you want to keep the engine cool, heat robs power.

This is what Im talking about head work

Left OEM right is worked on


Close up of bowl work and big valves


OE intake


Worked on Intake


OE exhaust


Worked on Exhaust

 

Wow thats alot. can something like that be done by me with the right tools. I'm guessing just the right drill. I can probably take it somewhere and have it flow tested. What about the valve retainers.

 

Bronze guides, Stainless retainers (under the valve spring), Titanium locators (On top of the valve spring). Stainless high angle stay like 50 deg's when stock is like 35 I think. The springs are the HD 155lb Ferrea springs. Should handle well over 7500 RPM with the ARP rod studs and 1/2" head studs.

the fat @$$ head studs.



For High RMP and head lift. This pertains to your question in that you raise the Rev limit you can potential flow more air, with apropriate mods, at the top end of your power band.

 

I dont think u can port and polish it ur self let a pro or atleast some 1 who had done this b 4.

 

air flow is nearly the same as liquid flow at high velocity. when i ported my heads, i left about 3# of alum. on the table, but never changed the port design. most of your work happens in the bowl area. follow with me- the valve opens and closes, now think about this at 6000rpm. flow gets stopped abrubtly by the valve closing, what happens to the airflow at velocity when the valve closes? milli-seconds later the valve opens again. overlap on the cam tries to restart this flow. if your bowl area is designed correctly, the charge will swirl in the bowl ready for the next valve opening. in other words, look to the bowl for your hp gains.
n/a has trade offs for high hp, forced induction over-rides alot of these, but port volume and flow will never change with the heads no matter if the charge is forced in or not. they just happen at different rpms.
there is so many variables to what i just said, but i will wait for opinions to elaborate.

 

Yeah definately a no-no. Well unless you have that money to throw arround. Than if you do I can use some my way.

 

btw- on the exhaust side, does not matter f/i or n/a, port volume is not as much of an issue, you just want the stuff out! stopping my self now before i get into cam/flow/dymanics and especially how f/i relates topic.

if you port the heads on your own, do not over think it. the factory spent alot of money figuring the correct flow patterns. do not change them!

 

Yeah fluid flow and hydrodynamics are always the same flow reguardless of pressure. Thats the beauty of volume.

Yes most of your hp comes from bowl work keeping the air moving and ready to leave. It is always easier to evacuate dynamic air than static air. Thats why I went with the extra bowl work more optimal HP gains.

 

Well I don't really have the money to be throwing away, I have the money to send it to a shop, but would really like to do the work myself. I think I'll try it. It is an extra engine so I don't have to depend on it.

 

I'm not telling you not to try it but at the very least practice on some junk yard heads first.
Porting isn't that hard if you know the how and why side of it
but you will ruin a set of heads really quick if not.

A few really quick things to help.
1. Buy the right tools or sell me the heads before you ruin them
Bits for aluminum a die grinder sand rollers a scribe etc
2 Study pictures and go slow don't go hog it out all crazy hitting a water jacket.
3 Realize it more about shape then size.(search for info on the "short turn radius" ) Curves that flow well
4 Let someone else do the valve job not trying to offend you but just leave it to a pro with the right tools
5 Texture. Search words "boundry layer" & "laminar flow" if your a golfer think about why those dimples are there;-)
6 Don't let anyone here talk you out of it but please don't use your VQ heads as your first set. As long as you treat this as a learning tool and not a way to save money you'll enjoy it. On the other side of things you can always send them to me $$$$$.

 

Match porting and polishing are pretty easy with the right tools and some practice. Along with what everyone else has posted another aspect of porting to be considered is the size of the ports. Exhaust side *IDEALY* should be around 80-85% of the valve diameter and intake should be around 90-92%. You can take some junk valves and grind them down to the right diameter and use them as guides. As far as valve seats I've heard 3-5 angle on intake and full radius on exhaust.

 

Thanks for the info. A friend of mine actually has a head from a civic motor. I'm gonna be playing with that first. The heads on my Z won't come off until late Feb. I'm just here trying to get info on where to look for info, tools, specs, and just advice. I don't plan on making my Z heads the experiment but they will be second on my list. Unless I royally screw up the civic motor.

 

Correct me if I am wrong, but the mearsuring positive manifold pressure only gives you a clue into how much air DID NOT get into the motor. Making the rest of the engine more efficient in flowing more air, will result in same cfm at less psi...
Or something...

 

Yes, or rather the more accurate way since we wont dial down the boost is more CFM at the same PSI. Which equates to more power. More Air + More FUEL (in the form of a good tune) = more power.

 

Better exhuast, a head and cam upgrade with keeping your stock compresion tuned.