Match port and pollish intake, exh & head on N/A 616, 617 - PeachParts Mercedes-Benz Forum

sedecrem · #1 10-19-2007, 09:58 PM

Has anyone done this or know of someone who has? It would seem, with N/A engines at higher engine speeds and air flow rates match port and polishing, especially on the intake side would give some increase in performance. Anything that creates turbulance and interfeares with air flow is going to reduce pressure, therefor air density and correspondingly effective compression ratio. Would not help much off the line at lower engine speeds, but even a small increase in top end power would help hill climbing and highway performance.

cchkaiban · #2 10-19-2007, 11:10 PM

I have.

Matt L · #3 10-19-2007, 11:13 PM

Of course, there will be no increase in performance without additional fuel. If you're smoking black under full power now, more air will help.

sedecrem · #4 10-20-2007, 12:16 AM

Have you gotten it put back together yet. If so, how is the performance?

#5 10-20-2007, 05:28 AM

Quote:

Originally Posted by cchkaiban

I have.

images

Didn't you have cracking issues afterwards?

Porting is NOT something to be done at home. It should be done by a pro that that specializes in porting/polishing heads. A little too much metal and you'll enter the waterjacket or weaken the structure and cause cracks.

rwthomas1 · #6 10-20-2007, 11:12 AM

The terms should be defined first:

Gasket matching: This simply means checking to see if the gaskets between two mating surfaces protrude into the port and also making sure, by using the gasket as a template, that the ports line up to each other as perfectly as possible. This can be done easily at home by anyone with a brain. If you can remove a head and reinstall it you should have the skills to understand the process. It is unlikely that much material will need to be removed and there is virtually no chance of penetrating a waterjacket unless the part was a very poor design from the beginning.

Polishing: This goes hand-in-hand with gasket matching. The idea is to smooth the ports, remove casting lines and flashing if there are any, break any sharp edges, etc. The port shape, volume, etc. should NOT be altered in this process.

Porting: This is the part that is best left to the professionals. Generally a flowbench is used to verify that the cuts made to a port are actually increasing flow. It is very easy to go hogging out a port and actually hurt the flow. As mentioned by FI, it is also quite easy to cut into the waterjacket, oil galleys, headbolt bores, etc. and ruin a head if you don't know what you are doing. On popular racing engines there are templates available that allow the home porting mechanic to duplicate a successful port job without a flowbench. I can guarantee you 100% that these templates don't exist for our engines.

Saying that performing these modifications without increasing fuel will NOT increase power is wrong. IIRC, its been years since I read this stuff so its a bit fuzzy, is thus: The easier it is for the engine to ingest and exhaust air the more power it will produce. The reason is pumping losses. If there is resistance in the intake tract then not all the air that can enter the engine during the intake stroke will enter. The same goes for the exhaust. If the energy is lost from pushing the exhaust out due to restrictions then that energy is not used for producing power. Things get a bit more complex with a forced induction setup however it should be obvious that if a turbocharger is pushing air through a restrictive passage then more power will be required to drive the turbo. This is a vicious cycle as more backpressure develops from pushing the turbo harder, etc.

Now I am not saying that huge power increases can be had on a diesel simply from porting/polishing/etc. The gains without fuel would likely be fairly small, maybe just 3-4hp on a 617. Is that worth it? Well I suppose that is the decision of the engine builder. I would guess that a good port/polish job on an MB would result in a smoother running engine that has a flatter torque curve, build boost at lower RPM's, and maybe achieves 1+mpg better than a stock engine. I would hate to discourage the home engine builder that spends a little time polishing and gasket matching. Its a worthwhile effort and should be thought of as "polishing" our beloved MB's, making them shine even more if only on the inside.

RT

cchkaiban · #7 10-20-2007, 11:50 AM

Well said rwthomas1. My first head, in the above image did have a hair-line crack in it. My mechanic at the time, who did the porting/polishing did not believe it was a result of porting, just a coincidence. The new head he put on after was also ported and polished. My car does have strong pick-up and is quite fast, however it does smoke. (believe the smoking is another issue) I don't have enough experience with 123s to determine how much is a result of the porting / alda adjustments / engine rebuild...but like you said, maybe just psychological, my wagon sure seems to look and run a lot better with all the love I have put into it's restoration. (kinda like herbie...)

t walgamuth · #8 10-20-2007, 12:15 PM

I would not think that porting would improve the flow. I bet they match really well from the factory.

Balancing is done very well at the factory too.

Tom W

sedecrem · #9 10-20-2007, 04:43 PM

The reason I posted this ? is that I have a spare 616 engine with a blown head gasket that I was going to overhaul. I read an article on basic cylinder head porting by Standard Abrasives. It describes a process, for which they provide an abrasive kit, that involves matching the manifold/gasket/head interface and smoothing/polishing out the existing ports to eliminate any marks or sharp edges. The point is of course to improve flow in and out of the cylinders to increase fuel/air mixture to the cylinders on intake and reduce back pressure on the exhaust cycle. They point out that it does not involve any design changes in the intake/exhaust system which they warn requires professional help. It was oriented towards gassers but I don't see how it would not help a diesel.

It would be interesting to see if there was any resulting increas in power or effiency.

sixto · #10 10-20-2007, 08:06 PM

Quote:

Originally Posted by t walgamuth

I would not think that porting would improve the flow. I bet they match really well from the factory.

What Tom said. If the ports don't match the gasket, get a better quality gasket.

If kicking up the boost doesn't improve performance appreciably, neither will porting and polishing. The 61x engines are used in trucks. Lots of breathing ability inherent in the design. Port and polish because you enjoy it, but I don't think you're going to get your money back in mpg.

Sixto
87 300D

RUN-EM · #11 10-21-2007, 08:29 AM

Back in the day, before extrude hone, we used to clean up the ports via sandblasting. Coated the valve seats with duct tape and blasted away. Leaves a baby bottom smooth surface, removes casting dingle-berries, and promotes air flow as factory intended. Easier than porting via grinders and much less labor intensive. Just don't get carried away and try and use a dump truck load of sand to run thru the ports. Just smooth up what is there.

Regards

Run-Em