VR5 or VR6?
need 20 characters
6 in my case, matches the engine block in my avatar…add a another bank and you have a W 12 for Bentleys, add couple for cylinders and another bank and you have a W 16 for a Bugatti Veyron.
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I’d suggest like (Photomancer did above) have a good machine shop vat, measure, hone, surface and start with a clean bare bock then use the facilities of the Space for assembly.
Some procedures and or processes are better left to those that have to tooling set up for specific tasks.
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Forgot that they will vat it for you. Comes back looking new plus the scale on the water jacket is removed so more efficient for cooling and oil galleys are clean.
Not the first rodeo. As a member I am interested in promoting the space and doing the work myself as much as possible. Bridgeport is a class I have yet to take, but good to hear we have the equipment. The block is perfectly fine; considering re-ringing but do not have expensive tools to measure for sizing purposes.
Would anyone be around this weekend to help milling the head? The head is stock height and straight. Just need to skim the top to remove old gasket and slightly increase compression rate.
Photomancer would be your guy for decking the head and giving a tutorial on checking the bore on the cylinders.
The lesson is easy: I find a friend that has had it done locally, ask if they would recommend them, if so, have them do the work. Here’s why
It’s not that our tools couldn’t machine the head, but when done it will be a custom one off design: variable compression (as in each cylinder would be slightly different). The trick to milling a head FLAT and SQUARE is getting fixtured up flat and parallel to the bed of the mill. Assuming the head 24" long, and you can get it to within 1/4 of a degree of parallel, the difference would be 0.100" different end to end, if it’s 10" wide it would be off 0.040" side to side.
They have fixtures and that will align it to less than that. I’m not sure how much difference a 0.100" of would make in compression because I don’t know the chamber size, but I’d guess probably half a point of compression so the engine wouldn’t be balanced from a compression standpoint.
We have no tools capable of boring the cylinders.
Surely the Bridgeport table is flatter than that…
The table is flatter that. But the surface you want to machine won’t be resting on the table. It has to be positioned so that surface is parallel to the table.
Now if you believe the head is not flat or true now, what do yo use as reference points to determine it’s parallel? The top of the head, where the cams, etc. are will be the side facing the table, so you fixtures will have to support the head so they are not in contact with surface of the table.
Cam bearing bolt holes? (that surface). Those (presumably) should be flat when the head is mounted to the block.
First, know nothing about car engines. This is just a question.
Could you not use the cylinder surfaces as your reference surface? Run a dti on their vertical surface and adjust until you have all grouped cylinders vertical. Averaging out any error among them?
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You could perhaps for the engine block… Unfortunately, the cylinder head and engine block are two separate components and the heads don’t contain any portion of the cylinders, so you can’t reference one to the other. Not a bad idea though if he were trying to machine the engine block.
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This seems like a perfectly valid idea, but I would probably use general points along the gasket surface, rather than trying to use the cylinder caps (combustion chamber tops, squish areas, call 'em what you wills) for a few reasons:
- unlike the pictured VR6 cylinder head, most heads have angles/slopes/other oddities in this area, as they’re built to promote combustion (here’s an example of a (Cosworth modified) Miata combustion chamber)
- the gasket surface is actually the important part
- you can select, say, 4-6 points spread along edges of the sealing surface (think “in line with the head bolt holes”) and, using the described technique, “average the error”. Depending on your (and the equipment’s) ability to do this well, you should end up with a reasonably planar surface, which is (mostly) the goal.
(added this image of cylinder head, Mitsubishi in the pic, but that’s not terribly relevant) with marks in red for the places I think I would measure to ensure planularity, using at least the 4 corners, and increasing in number as desired to reduce error. The green dots might also be useful, but redundant, in my opinion.)
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Interesting, thank you for the explanation.
Given that information, my suggestion would be to place a straight edge (precision) on the gasket surface in at least an x and y direction and run the dti on the underside of the straighedge that projects past the surface. This would automatically ‘average’ the surface and provide a clean, defect free surface to run the DTI against. Use machinist jacks to support the surface and provide fine control in adjusting the plane.
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I’ll prove what an ignorant slob I am, ask what a “DTI” is. I assume something like “digital table index”, but you know what they say about assuming…
The “clean, defect free surface” is the hard part, since you’re looking to make it so, rather than already having it. I did fail to mention that in any cylinder head resurfacing technique, it would NOT be used to clean up the remaining gasket material. That should be done before attempting machining. Assuming you’ve removed all old gasket material, your technique with the straight edge should be just fine, I think. Do we have such a straight edge at DMS?
A DTI is a dial test indicator. This is the kind that has a short range (< 0.030") and provides readouts of 0,0005" or 0.0001".
This is as opposed to a DI (dial indicator), the most common version reads to 0.001" and has a range of 0-1"
Here is an image of a DTI
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I’m not saying it can’t be done. You are welcome to try doing it. If the cost savings and experience of doing it yourself out weights the potential loss of the head, go for it. I personally just think if I’m working on my car the cost of having it professionally done is worth it. Clearances and other associated items are too critical.
I assume you have already determined the head is no longer flat (beyond manufacturer’s specifications) such that it requires machining or you are doing it for a specific performance issue.
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Very true, though grabbing a junk head from a otherwise trashed car, could be an interesting group project. Also, even if you aren’t going to do the work, it can be a useful exercise to think about how you would fixture something like this. It can help learn the process for when you do have something to do.
I don’t know how similar this engine is, but it sounds like it would be a great one to practice things like the above with.
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I could NOT agree more. I was approaching from the hypothetical.
Asking @Brandon_Green how he fixtured when he did the 240 might be helpful from the non-hypthetical…
It looks like he just bolted it to the table…
LOL.
very similar, except MUCH smaller.
1800cc/4cyl=450cc/cyl
So @72cc the Honda engine is about 6 times smaller than a single cylinder on the Miata. 