Yeah, I don't have a Helm's. Someone want to crack their's open and let me know the specs? TIA

 

Just curious... are you decking it due to warpage or to gain a higher compression?

 

The block was packed poorly and it received some damage meaning that the deck will have to be spot welded in some places and then resurfaced. I was told that you can deck the block down to the small circles on the outer edge of the deck, but I am interested in numbers to give to the machine shop. I am not interested in gaining compression by doing this. Type S pistons and flat valves should do the trick nicely.

 

I don't have my manual in front of me right now, but if you can get away with 10 thou you will be fine. 10 thou on a 88mm is good for a .4 raise of compression. I believe even 20 will be ok since a buddy of mine has decked his block 10 though and his head 10 though on a h23a before. If you have to deck an insanely large amount then you might want to look into running a thicker headgasket... which I'm sure you already know.

 

Well that's a bit reassuring, but that's going to make for some big cimpression. Anyone have the max numbers so I can go play with the compression calculator?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by laughinxxx &raquo;</TD></TR><TR><TD CLASS="quote">The block was packed poorly and it received some damage meaning that the deck will have to be spot welded in some places and then resurfaced. I was told that you can deck the block down to the small circles on the outer edge of the deck, but I am interested in numbers to give to the machine shop. I am not interested in gaining compression by doing this. Type S pistons and flat valves should do the trick nicely. </TD></TR></TABLE>

I believe that is what those circular pads are for. As for giving your machine shop a number, that's easy to do. Take a straight edge, lay it across the block over the circular pad, then insert feeler gauges until you determine the clearance between the pad and the straight edge. That's the max you can deck. I'd use a set of calipers or a mic to double check the feeler gauge so that you have accurate measurements. A depth mic would also work in this case.

I looked at my block, and there's not much room. I didn't measure it, but I know the block has been decked before.

I did check my head the other day. I had 0.037 between the pad and the head surface. I just had the head milled 0.025 today.

Also, from what I have researched, those flat faced valves are worth much, compression-wise. I'd worry more about the additional weight on a high reving engine (that is, assuming you plan to rev the engine at or above the stock rev limit). You can gain much more compression by milling the head.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GudeH23a &raquo;</TD></TR><TR><TD CLASS="quote">I don't have my manual in front of me right now, but if you can get away with 10 thou you will be fine. 10 thou on a 88mm is good for a .4 raise of compression. I believe even 20 will be ok since a buddy of mine has decked his block 10 though and his head 10 though on a h23a before. If you have to deck an insanely large amount then you might want to look into running a thicker headgasket... which I'm sure you already know.</TD></TR></TABLE>

Can you tell me what numbers you used to get that result? My calcs show that to raise the CR by 0.4 you have to mill off 17 thousandths (assuming that the part you're milling has a diameter equal to the bore of the engine).

I milled off 0.025 from my H22 head, and my calcs show that this results in a 0.6 raise in CR. I milled my head for reasons other than raising CR, though.

 

I heard the same thing about the circles, but I wanted to make sure that that is what the Helm's says. When I took it to the machinist he thought that that was alot of material to be taken off of the deck. Obviously I wouldn't have all of it taken off, but it made me question whether or not the info about the circular pads was correct.

 

I do not have the calculations here with me at school, they are at home. I also had my machinest go over the calculations and check. Keep in mind I have an h23a.

 

Hrmmm, the only thing I'm finding in the Helm is the service limit for block deck warpage, which is .004 in. There is nothing in the specifications section nor the engine section regarding the limit on decking the block, or at least I can't find it.

 

Hmmm. Does it tell piston to deck clearance?

 

Strangely, no. Where's Satan, he'd have answers to this.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sharkcohen &raquo;</TD></TR><TR><TD CLASS="quote">Strangely, no. Where's Satan, he'd have answers to this.</TD></TR></TABLE>

He's busy looking at ****.

Send XES a PM, he is now running a lower compression headgasket due to piston-valve clearance and decking the head/block. He should be able to tell you how much you can go with safely.

 

Sounds good. PO.com mods get paid in pr0n so what else would you expect him to be doing?

 

Can someone tell me the stock head height? My 93 helm has a number in it, but it's 0.220" different than the head I just measured. There's no way the head was milled that much. I think the head has been milled before, but I don't know how to tell how much it was milled. There is about 0.030" between the pads and the head surface. Does anyone know the measurements for a stock head? Thanks...

 

146.95 - 147.05 (5.785 - 5.789)

 

Thanks for the info! Another source told me 5.788"