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-   -   GM 188 head question (https://www.offshoreonly.com/forums/general-q/352934-gm-188-head-question.html)

veloc410 03-23-2018 01:43 PM

https://photos.app.goo.gl/0okJzL26xsm0sndA2

still have these heads.

veloc410 03-23-2018 01:52 PM

It does look like that head was shifted somehow during machining operation on that chamber?? Are all the Chambers on 5hat head like that or just the one chamber only. The intake side also looks shifted over. That chamber might be bigger than the rest,by the looks of it

convincor 03-23-2018 01:54 PM

They all are.
Almost looks like there were to close to the plug side of the head and didn't want to go any deeper.
I'll clean them up and CC them and compare to the other head.

veloc410 03-23-2018 01:59 PM

Might flow different. Also if all Chambers are bigger on one side of engine it might vibrate or run unbalanced, more compression on one side. Have the heads cc'd for comparison. Somehow got a reject head. Or someone worked on it. Twins or single engine boat.

convincor 03-23-2018 02:03 PM

Single.
Yep, out of all the chances I got the reject. LOL
Nothing is ever easy.

veloc410 03-23-2018 02:16 PM

If s__t hits the fan and you decide to buy new heads. I just bought Brodix DS320 Dragonslayer heads. They are awsome. They digitzed the bb2 plus cnc then cast it as new. It out flows the cnc version at half the price. All the seats are right on and have almost no core shift at all. Look at my posts I put up under Velocity forums. I posted out of box pics. These are a new castings you will only see pics in there 2018 catalog. they sent me flow numbers by email before I purchased. I'm bumping compression up to 10:1

mcollinstn 03-23-2018 05:47 PM

Valves appear to be about the same height both heads.
The head (with no blue pen) were spotfaced with a larger diameter cutter than the head with the blue pen. This could either be a physically different tool with different cutter geometry OR it could be the same tool, but the "blue pen" head's tool had worn or damaged cutting inserts in it. Those inserted cutters usually sound different when they get worn or chipped, and the machine spindle load definitely changes, but if it was close to the end of shift the operator may have ignored it and let it fly. This would have been during a machining cell operation, not with a person doing the work on a manual machine. Then, in inspection they may actually not hold that feature very tight on its tolerance. Adjusting and blending all of that sort of stuff is just par for the course when you start blueprinting and touching things up.

MC

veloc410 03-23-2018 06:28 PM

Off location check the intake side closely on right

veloc410 03-23-2018 07:50 PM

They used multi spindle machining heads . The heads move in, in a straight line, cut a number of features at the same time ,pull back then part transfers to next station and cut a different feature and so on. That's the way they used do when the bbc were made and any other engine back then. They didn't change the tools /cutters until they were worn out or broken for thousands of cuts. Part probably located wrong in fixture ,clamped up and all 4 chambers got cut wrong. Now everything is CNC machined and cutters get interchanged in same spindle.Thing is, who was the bone head that let that head get out. There were gages to check all features at different intervals of cutting stages and visual checks also. We ran the big blocks here in tonawanda. **** happens I guess.


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