Max Compression ratio 2F and bolt length (1 Viewer)

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I got the data back from my machinist on what happened with my rebuild - they said that the head was already trimmed to the max and so they decked the block and head by 0.003" only .

It is a late 2F that has the combustion chambers that has the kidney shape like in the 3F.
The cylinders has also been over bored to 0.060"

According to them the compression ratio is now 9,5:1 . (I asked them to aim for 8,8:1 but it seems they had no option .)


Mark W states in various threads the CR of 9,5 in a 2F is acceptable. I will have to rum premium gas but the gas here is 95 so it may work OK.
The cam I am placing is the Delta Cam KC859-250s - so I need to find out what effect that will have on Dymanic compression .

The one problem is that the cylinder head bolts appear to be too long .
Could that be due to the fact that the head had been trimmed to the max ?

What do I do now - Just trim the bolt shorter ?
 

Spike Strip

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I think you can just use an appropriate washer with the bolt. May have to order the right thickness.
 

GLTHFJ60

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I would trim the bolts. Have you measured down the bolt holes to see if you're actually bottoming the bolt out? My head bolts took a LOT of effort to get them to thread in due to the rust in the bolt holes.
 

Wile E Coyote

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My head bolts took a LOT of effort to get them to thread in due to the rust in the bolt holes.
Hence the common recommendation to run a bottoming tap (non-tapered is preferred) down each hole before assembly. It allows for a truer torque value.
 

GLTHFJ60

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Hence the common recommendation to run a bottoming tap (non-tapered is preferred) down each hole before assembly. It allows for a truer torque value.

Makes sense. I just kept threading the bolt in and out with a bit of lube on it to pick up the rust. Worked pretty well.:meh:
 

Spike Strip

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Incidentally, Yspen, the two bolt holes where the rear hoist hook goes are shallower that the rest by just the thickness of the hook.
 
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I just used .100 grade 8 washers on the head bolts, you can find them at any hardware store. you may need something a little thicker. been in there for 3-4 years now with no problems.

And I just took a head bolt from a box of 2f junk and made some cuts in it with a cut off wheel, I used it to chase the threads like a tap. finding a tap to fit our blocks can be pretty difficult and not cheap.

13X1.5?
 
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I have never had a problem with the bolts being too long after cutting the head. My bet is that you need to chase the threads.

That cam will be happy with that CR. Although personally O would have gone with the KC859 262... which would be a better match for the higher CR ;) But you will not be disappointed I do not think.


Mark...
 
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I went back and found the old bolts - they are shorter my about 7mm and has a washer . ( I see that the order number for the bolts are the same 2F and 3F - so it cannot be that I ordered the wrong part )
I will chase the tread and see if there are any gunk built up at the bottom of the hole .

Re the cam : From the thread " 2F performance camshaft" I got the impression that the inlet valve ( of the 250s cam )closes at 58* - that would give a lower dynamic compression . I now see that the cam actually has the inlet closing at 53* ( same as stock ) .
Considering the high CR is will be better to fit a 262* cam with the inlet closing later at 58* and the longer overlap to bleed off the gas.

It took me a lot of $ and about a month to get the cam here in South Africa from Delta in Tacoma - so I will stick to the KC859-250s cam and hope that it works OK .
 

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