V2Rocket

not like you have anything better to do

and bring some of mel's meth

86 951 Driver

How can you port the whole manifold? Meaning how do you get down in the runner?

ZR8ED

Flexible shaft die grinder/micro die grinder. If it is too tight/curvy, then unless you have very specialized tools (read expensive) then you extrude hone the passages. That is a process where they pump a pressurized abrasive paste like mixture and force it through the passageways to smooth out the surface. I found a couple of somewhat local shops where I can get this done, but I have no idea the price. The modification here as others have pointed out are not big hp generators so the "bang for the buck" is extremely limited. If you can do some of these things yourself, the cost is only your effort. I have limited equipment, so I am going to use my time/ability/experience to have some fun for some mild improvement. Anything I can easily do to improve VE will have some effect, on hp, throttle response, fuel mileage etc etc.. Hopefully all for the better!

86 951 Driver

I watched Horsepower TV where they did a little do it yourself portjob. It seemed like you need to get some junk heads first then practice. I would like to do that on my 951, but if you don't get much in return(a little shocked by this) then whats the point. I guess if you polished the chambers, and gasket matched the ports you should see a decent bump in power. Thats just me thinking out loud.

ZR8ED

Only minor bumps in power from cyl head jobs seems to be the norm with these cars. My experience with Datsun 240z's have proven to me to not take these internet asssumptions as absolute facts. Head work alone won't make huge improvements, but if one improves the entire system, then cyl head modifications can be maximized. Problem is this kind of work takes experience, and that doesn't come cheap if you have to pay someone else, and no one wants to spend huge sums of money for relatively small gains. You can have a v8 or turbo for the same kind of money it would take to pay someone to do all this to an 8 valve n/a motor.

I've heard lots of stories of "mild gains" from some of the stuff we are talking about in this thread, but what needs to be kept in mind is that even a 20hp bump in power CAN be felt. Even 10hp all across the power band can be noticed, so there is nothing wrong with modest gains. These aren't big torquey v8,s, so if someone expects that kind of result is in for disapointment. Some of this stuff is also not race legal depending on the type of racing you are involved with, so that leaves lots of modifications off the table except street cars, and "unlimited" class racing. Not many street only car guys are willing to do this kind of work. Whoops I hope I didn't get too much off into a rant, I want to keep this thread on topic.

BTW I've been reading for hours here in the forum, and there are quite a few VERY old threads talking about head work, manifolds etc. It would be great if some of these "old timers" chimed in with their results/experience. Most of these discussions end with "its cheaper to buy a turbo" yea..so what.

V2Rocket

the reason porting doesnt do much for the 944 is the ports are already so freakin big for the displacement of the engine and rpm range that making them much bigger just knocks down the air velocity

ZR8ED

Its true, these cars are seriously low in compression..turbo motor low. Increasing compression to 10:1 (can still run pump gas with no worries) would wake these cars up quite a bit, match it with the intake and a nice cam, and freeflow exhaust, and you would be in "s" car territory.

As an update, I need to get some more grinding wheel attachments, so I stopped working on the inside, and began cleaning up the outside. Looks WAAAAY better now. I'll take some more pics of the progress this weekend. Would anyone be interested in this intake? I'm still looking for the n/a manifold. I looked over the car last night, and it is just not worth the effort to convert over to the turbo intake only to switch back to the n/a one just for a trial.

V2Rocket

the euro cars came with 10.6:1 compression and made 163hp, but they also generally had no cats on them.

the US 944s aren't that low, they are middle of the road compression at 9.5:1. the only turbo motors coming with that even nowadays are the DI engines (VW 2.0 etc)

a cam and different intake (with euro pistons) would likely be able to bring you up a little more, MAYBE 170...but then again for the cost of a cam and those euro pistons you can just buy an S head and pistons and have 190...

Paulyy

Hi Comp + Hi Octane (e85 or race fuel) + more timing = more power
okay it's not that simple.

V2Rocket

yea, back of my mind is thinking about building a 13.5:1 944S solid-lifter E85 motor to 7500rpm to blow past 200hp...screamer

but for the cost of the cams alone i could have half a v8 swap done...or just finish my damn supercharger 3 years into it...

bad_monkey

Right idea about the air velocity - ITB's and velocity stacks seem to be a good idea for that reason. I have read about people actually decreasing port size for more power - and flattening out the floor radius of (16v ports especially) to help make the air turn toward the back of the valve through adhesion to the port wall. This can be done with epoxy.

Anecdotally the 2.5 valvetrain will handle up to 8000rpm before starting to have issues.

A combo of bike throttles / short velocity stacks / cam timing / skimmed head / bumped rev limiter might make more power but would be difficult to tune, and perhaps lacking in street manners.

I've had a couple of discussions with RogueAnt about an SD/Alpha-n blend for ITB's - my initial experiments with 4x43mm bike throttles and a cut NA manifold seemed interesting, despite still pulling through the stock AFM. Could just be the illusion given by the faster throttle opening, however. Project is on hold for now.

ZR8ED

Well I think I'm pretty much finished with the turbo intake and TB. It is all port matched, smoothed out some of the roughness, and cleaned up the exterior, and mating surfaces. It may not make hp on its own, but it should improve the throttle response. I found a source for a manifold, so I hope to have an n/a manifold in a few days.

ZR8ED

Ok. So I may be able to pick up the n/a intake in a couple of days. I have to take a detour and work on my Z for a day or two, pick up the new intake, and then I'll be back at it. I'll measure the two intakes, and report back. I will begin porting work right away, but I will not likely install any of this stuff until the car comes off the road for winter.

As a side note, I was tinkering in the garage, and decided the pull off the afm and have a look. It didn't take me long to pull out the die grinder, and clean up the inlet and outlet, as well as reshaped the outlet side. It sure had some funky angles and casting marks. I stuffed a rag in the afm to protect it from the filings, and once I was finished I spent a considerable amount of time cleaning it out to ensure there were zero filings left behind. I already have it back in the car, and I will take it out for a drive, more to make sure It all still works. I seriously doubt I will notice any improvement, but it sure looks a lot smoother, and I got the guts of it all cleaned out, and did some engine bay detailing while it was all apart. I was suprised how much "gunk" was on the inside walls of the afm. Maybe it will make a difference!!! hehehe

Paulyy

how are you measuring the airflow to know if they're port matched?

ZR8ED

I think you are thinking of "port tuning".
Port matching refers to matching the mating surfaces to help the air transition smoothly from one "part" to another. We can't change the basic design of the system (without serious r&d and custom fabrication) be we can make the parts fit together better than they did from the factory. These are mass produced parts, and there is enough variation in the mfg process, that there are small gains to be made by ensuring the parts that YOU have match and fit as best as possible.