3.4L drysump build

This is the other 3.4 Im doing along with the CIS version. It was brought to me in pieces, not even a bearing in the block but the heads were still assembled and the 360 crank was provided.

I had pistons and cams made, upgraded the rod bolts with ARP parts, springs suited to these cams, new valves, guides and bearings etc. The crank remains standard but has been polished. Liners machined using my torque plate. One main was a little tight so we made a quick pass to even everything out, a light pass on the decks then set liner protrusion which was inconsistent and had to be corrected. Ring end gaps checked and adjusted. Pistons go in next. Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login

 

And light! Interesting to see the change in direction where they want a larger second ring gap than the top which is the opposite to what was gospel not too long ago and is directly tied to the reason behind the accumulator groove.

 

Original dry sump application.

 

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Measured actual compression ratio is 10.2:1 which was chosen to work with our ethanol free 91 octane fuel.

Stock 9.2:1 512 boxers are really 8.75:1 when actually measured and the 8.8:1 308's actually measure out at 8.5:1

 

Also to relieve pressure buildup between the rings. It made sense to me that the upper ring would run hotter requiring a larger gap to make up for that and were gapped accordingly. We’re not talking a huge difference now but the second gap depending on bore can be the same or a thou larger than the top gap.

You have to wonder if you would ever notice the difference. I’ll say no but maybe on John forces car you would.

 

I’ll think about it lol

 

Here's how much the timing mark moves when the bolts are installed but left loose allowing it to rotate left and right taking up the clearance between the bolts and flywheel bolt holes. So when I tighten it how do I know where to put it to have true TDC?

A boxer /Testarossa for example has a locating dowel between two boltholes to prevent this.


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With true TDC established using a piston stop and a degree wheel Ill know where to put the flywheel to have an accurate pm 1-4 mark, problem is it might shift because it wants to be rotated counter clock-wise to line up and crank rotation / load will encourage it to shift back. At least cam timing will be correct and I can set base timing assuming the mark is right and play with ignition timing on the road tests.

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No I didn’t because ignition timing is all it’s effecting which I’ll just play with. It just proves more than anything that setting cam timing with the flywheel is a mistake. Using the factory marks on the flywheel and cams could mean you’re cam timing is 6 degrees off (or more) because the cam marks are a starting point not dead on and the flywheel mark is a moving target. Takes time to do things correctly rather than good enough and you can’t know unless you check.

 

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Cams degreed in which lead to my next step.....Checked valve to piston clearance the harder way but the better way as well. In the last pic you can see how much the play dough is pinched at the far right indicating how close the valve edge is to hitting the piston. The depth of the relief is great, side clearance not so great. I wouldn't have known that clearance if I just pushed down on the bucket throughout the valve event as a quick check rather than re and re the head to do this test. Not every one is this way and I expect the CIS version to not be an issue here due to the less aggressive cams but every time I find something like this it reinforces the fact you can't skip steps. Exhaust valve clearance is great, didn't even touch the play dough. So Ill push the pistons out and open up the relief just a bit and back together it goes.

Just to clarify the last pic, I took a cross-section of the play dough with a razor blade to get a clear look at how close the valve is getting to the piston.

 

Agreed but there are a lot of factors, valve timing being one of them.