Im building a high compression 84mm B18C1. I would like to know what is a good deck height to watch out for? Im using a cometic .03" Head gasket, and Blox type B cams. In order to achieve my desired compression (11.5:1) Im going to need to remove some material from the block, and need to know when to stop. How far is too far?

Edit: forgot to mention it's an 84x89 build using eagle b20 rods.

 

i don't have a direct answer, however here's what you need to know for a ballpark:

(compression height)+(rod length)+(stroke/2) ≤ (deck height)

claying the final assembly to check for valve to piston clearance (and piston to head clearance) is not a bad idea.

 

what pistons are you using...go with higher dome pistons...if u shave the block u cant get that back...pistons can be changed...

 

I usually set them up for .035-.040". With a .030" gasket, you may want to keep the piston at least .005" in the hole.

 

Well, using the formula Hondamark35 gave me, I should have .02" Piston-to-deck height, that's after decking the block .015" or .39mm (for a total 212mm deck height) and then with the headgasket I should have .05" from piston to head (which is milled .007" also)


Im using Wiseco K567M84 Pistons (+2cc, 30mm Comp Height)


My whole thing behind this question is:

GSR Deck Height: 212.39mm
B20 Deck Height: 211.84mm

If these pistons were meant to be used in the shorter B20 Block (Which would yield a .013" Piston-to-deck), then taking some material from the taller GSR block should present no problem at all. What does HT think?

Of course, I'd be claying the motor when its time to check for clearances, but, as cibao2ner mentioned:

So I need to make sure, I'm not making a NEWB mistake, and building a motor for impending doom.

 

The B20 block has different length rods and crank.

Keep in mind that at very high speeds, the rods will actually stretch a tiny bit, and a lot of people don't check for piston to valve clearance with the valves down as far as they'll be while in vtec. IDK what's acceptable...

 

Right, I'll be using a b20 crank, eagle rods (137mm [standard b20 length]) and arp "2000" rodbolts. Everything will be torqued down to specs. And I will still have .02" room left, which is .007" more than a standard b20 build is anyway. I know it must be impossible to know, but how much can I expect the rods to stretch?

 

Forgot to mention this in my first post

 

use whatever gets you 0.030-0.040 piston to head clearance.

 

Thank you. I'd imagine this is just a general measurement because p2v contact also may play a factor in piston to head clearance.

But what I'm seeing is that as long as the pistons is inside the block, and the p2v clears, then I'm good?

 

you generally want 1mm of space between the piston at TDC and the quench pads on the cylinder head.

so do some math.

if you are using a GSR head, and a .030 gasket, and your pistons are flush with the deck, you only have .030 clearance. thats .75mm. pretty tight but it should work. lets just hope your bearings dont get tired.

 

Does anybody know what the stock B18c piston to deck height is? .030 or .040" ? Im just trying to compare and finding it difficult to measure overall deck height accurately.

 

The deck height of a block only changes if you have the block decked/milled.

If it is a completely stock B18C with;
212.4mm Deck height
87.2mm Stroke
30.25mm Piston Compression height
137.9mm Connecting rod

You are looking at a piston to deck height of 0.838mm (0.033").

 

Thank you very much.

 

i was just wondering, does this general rule apply to stock or aftermarket cams? i know that you need to clay the motor for p2v clearance, but i just want to get a range of what p2d height to aim for when using bigger cams so that i can try to figure out how much to mill and what thickness gasket to buy. any input will help. thanks.

 

one more try. any ideas at all?

 

Depending on what you are using for internals. ie, the amount of stretch, thermal expansion of the parts. Also the RPM you plan to run your engine all play a part in what clearance you can run. But to answer your question in a general matter of speaking, yes, 0.040mm is a safe clearance to maintain for larger lift cams.

 

GhostAccord I want to clarify 0.040mm or 0.0015" is minimum clearance for piston to deck or piston to head? 1 and a half thou is very small which is why I was surprised.

I am currently running .035" p2h with a .026" OEM head gasket.

 

Shyte, sorry! That should be inches not mm.... shoot for 0.06"-0.08" 0.040 would be a tad on the tight side....... must have been having a few

 

was reading this thread again and again.
whats the conclusion.

piston to deck clearance
piston to head clearance

which one is you all referring to?

 

Piston to head is what matters. But the easiest way to calculate piston to head (p2h) is by measuring piston to deck clearance (p2d) then adding the head gasket crush thickness (~.028" for OEM).

 

what I mean this thread is confusing

which measurements are people referring to usually?

is the .030-.040 clearance refered to as minimum. is that the piston to deck clearance or piston to head. that's what I wanted to clarify.

and is it in mm or inches

 

that zeal autowerks calculator also throws you off. half of it is in metric other half is in inches...

 

.030 ~.040" piston to HEAD. Inches

 

Nice that means i have exactly enough with 30 or 35" headgasket