377Z

iTrader: (1)

These are World Products stock replacement iron heads, advertised 170cc intake ports, advertised 67cc chambers, 1.94/1.50 valves (finally got them apart). My plans are to do the best I can for these heads without a flowbench—i.e. smooth the casting & ridges, trim the valve guide, polish the chamber, unshroud the valves, and maybe make sure the roof by the common wall is as flat and straight as I can get it.

It doesn’t look like there’s much to do—I guess I expected more than this (I am a beginner here so I won’t be surprised if I’m missing something). One thing’s for sure, I’m not a photographer; the casting is much smoother than it appears in the picture and the ridge isn’s as pronounced as it looks but I can’t seem to get the pictures to look like the part does in real life. The longside radius is smooth with no harsh transitions (see second pic, still hard to see I may need to try to take some additional pictures). Looks like the bulk of the metal removal work will be trimming the valve guides; smoothing the ridge won’t take long at all.
Also, I’m not sure if its because I’m used to seeing 305 heads, but as far as the laying back the chamber by the spark plug mod for the intake flow, there’s not much to work with (the darn thing is pretty open already—see the end of the carbon buildup. I’ll eventually verify the chamber cc’s (after I polish them up a bit), I wonder if it isn’t actually closer to 76 cc’s (it’ll be nice to know what the real volume is anyway). I’ll be sure and post pics of progress when I get started; can you guys point out anything I may be missing before I get started?

Finally, can spark plugs be had with different thread lengths? The recommended plugs when installed have like 2-3 threads exposed—this can’t be good. I’ll be looking up how the delco p/n’s work to see what I can do about this; I’d like the end of the thread to be more or less flush with the chamber when installed. Is this paranoid?

Thanks in advance.

377Z

iTrader: (1)

pic #2

five7kid

iTrader: (14)

That guide protrusion is huge. I don't know why they cast them like that. Reducing and shaping them will make a significant difference in flow. Your ridge at the bowl is a lot smaller than mine were. The radius also needed some clean-up.

However, compared the the 081 factory casting that I used for practice, they cleaned up a lot easier than the factory head. Doing what you've got planned should improve them nicely.

I didn't do a plug fit check while the heads were off. I just installed Accel 276S after the engine was together. The plug threads don't seem to have significant carbon on them (although removing them from the head may be scraping it off).

377Z

iTrader: (1)

Yeah, the guide boss I figure will consume the most time.

Curious--has anyone completely removed the guide boss on a SBC head? IIRC, the Pontiac SD 455 heads had no cast in boss, just a pressed in guide. From cross sections I've observed, it seems there would still plenty of guide left in the areas most critical for support. I'm guessing its just because a significant gain would not be seen with no guide versus a substantially trimmed/shaped one. No, I am not going to try it, nor am I thinking about trying it, especially not on the exhaust side.

MrDude_1

just to answer your picture problem for later... you need good lighting and no flash... because the flash comes from the camera, it reflects points back, making it look rough.

for the spark plug things, yea, a few threads is ok, it wont harm anything.. 98% of all SBCs are like that... very few people index their plugs.. thoes that do are in the upper levels of racing... motors that arnt tweeked to the max like theres will show no improvement.

good luck on your porting

377Z

iTrader: (1)

Thanks, hopefully it will go smoothly. I'm itching to get started; it may take a while because the whole project is moving pretty slow. Currently all I have are 2 carbide cutters--one flame shape and one cylinder with a round tip--so I'll still need to get other bits to complete the job. I figure you use a stone to finish the intake, not sure what the best tips are for polishing the chamber/exhaust--I'll have to run a few searches.


As far as the plug issue, my concern is to do everything in my power to avoid detonation. If the heads really are 67cc (which I will check) I should be around ~9.7:1. It seems like the thread peaks would be prime 'hotspots,' but if its not a big deal I'll just note the length of the threads in the head and go from there if I have an issue later. The motor likely will have quench clearance of around 0.070" which was another concern. I don't have experience with at what compression neighborhood the theoretical ideal quench clearance becomes important, but I've been told its not worth pursuing with my situation. The shortblock is actually at the machine shop right now so I could get it zero decked but I'm not a fan of cutting metal when its not necessary.

gmgod

I would not put it together with a .07 quench area if you are trying to avoid detonation at all costs. Have the machine shop mill .01 off of the decks ( if its a virgin ) and use the gm .026 head gasket. Also make sure that your pistons don't have a compression height of an additional .025 in the hole..... or any amount for that matter. If your pistons do sit an additional .025 in the hole have them cut off .02 to .025 and use the .015 steel shim head gasket.

83ho86tpi

CRITICAL!!!! Cover your valve seat with strips of duct-tape that fit over them. I took this precaution and still got a minor scratch or two from porting.

377Z

iTrader: (1)

I was finally able to get started on the porting. One question: I cut into the valve guide a tiny bit on the left side of the pic--I figure its not a big deal as long as the valve or is there a reason it needs to not be 'knife-edged' in this area? I plan on making the rest look more like the right side. The only way I could see of 'undoing' this would be to have the guides milled down a tad, forcing me to go back in there to clean it up and risk the same result.

Also, if I understand correctly, the area of primary concern is the common wall side of the guide boss--how much should I concentrate on the other side?

Finally, can anyone see anything I've overlooked?

377Z

iTrader: (1)

These are just rough cuts with the carbide by the way--I know the intake is to be left slightly rough, but what is the final step? looks a little too-rough where I've gone with the carbide, and in areas where significant material removal is not the goal, what (if anything should I use? A rough stone? Nothing?

Do you leave the port floors completely untouched or is there anything to be gained from cleaning up the surface? I figure on the exhaust the entire thing needs to be polished, just not sure on the intake side.

If I am just going mild, is there gains to be had by opening the pushrod pinch a little? I've heard both yes and no before.

377Z

iTrader: (1)

One last thing--for a 383 that won't see much past 5000RPM or 0.550" lift, whats a good (valve throat)/(valve dia.) ratio that will work good for street use?

RB83L69

Use 85%.

I usually take a valve of a size just slightly smaller than my target diameter, and work the bowl until it just slips in, then continue (with a 1" roll sander or something like that) to rbing it to the exact diameter I want. For example, if I'm working the bowl for a 1.94" valve, I might use a 1.6" exhaust valve as my gauge, and make it just fit; then carefully enlarge the whole bowl about .050" more, to get to the target diameter.

377Z

iTrader: (1)

Excellent, thank you.

I appreciate the tool and technique recommendation, it can get spendy if you're forced to buy stuff just to try it, and the carbide cutter cuts awfully fast for small details.

I'll need to check whether the area isn't already larger than this; they looked pretty large untouched, and all I did was a slight smoothing to the ridge. Of course my eyeballs don't make good measurements. Heck, it may be a good excuse to get bigger valves (I'll need to buy new valves anyway).

Hopefully this work will make a XE276HR suitable--played around a bit with some calcs and DCR comes out to ~7.7.

Vader

That's either a typo, or we now have a new term to use for massage parts to size - "RB-ing, it".

RB83L69

377Z

iTrader: (1)

Updates & a couple questions:

How much effort (if any) do you guys recommend put into making each port the same?

Obviously a head with smoothed edges/slimmed guides should flow better than its as-cast former self, but I noticed dissimilarities between ports on the exhaust side of the intake bowls. As viewed from the chamber, some walls slant slightly towards the valveguide, while others are more vertical. I first noticed it when slimming the guides on that side of the bowl--on some the 1/2" round tip cylinder would almost reach to floor on that side (once the guide was trimmed), and on others it won't fit as deep (so I used the flame shape to finish cleaning up in that spot). From previous reading I gather this isn't a high flow area; am I making a mountain out of a molehill worrying about this?

My other concern is that the intake bowl diameter kind of “necks down” and there is enough metal to bring it to the 85% diameter, but going deeper in the bowl it opens up again—is this okay or will this slow the intake mixture down hurting flow?

I’m guessing that this may be a result of these being a ‘jack of all trades’ casting World uses for several heads including S/R torquers which come with 2.02/1.60’s. I’m considering getting the heads cut for the larger valves as I will need a valve job and valves anyway but I’m not that far along yet. I figure after blending the bowls for the larger valves this feature would be minimized.


The common-wall sides all look pretty uniform which I'm happy with (especially because some of the areas on this wall & the bowl you can still see some casting marks which I plan to massage out with the cartridge rolls). I made a rudimentary template that goes along this area and all ports are pretty close with a straight (albeit low, and still as cast) roof. I will try to make some measurements of the ports in various locations to see that I’m not gaining cross sectional area going deeper into the port (from the intake face).
Inputs?

377Z

iTrader: (1)

In case anyone was following this thread, I decided to even the port dimensions up as much as I could with templates and hit water in an exhaust bowl.

Started a new thread, here's a link:

https://www.thirdgen.org/techbb2/sho...hreadid=249218