What to do if Your Head or Block is Milled? (was "what to do with a decked head?") - Page 3

soybean · 06-28-2005

Originally Posted by jeff denton

The main thing is, you must not have any gasket material hanging over into the combustion chamber.
9-1/2 to 1 compression ratio should make for a nice peppy engine, will need 91 octane gas.

Jeff, that was what I was wondering about, "gasket material hanging over into the combustion chamber." That said, the 1.9 gasket being 2mm under, wouldn't it be prone to fail?

Originally Posted by nobody

, with the 2.0s you will be over 9:1 to start. I think around 9.4. I'd be watching the finished compression with that combination.

Too much compression with 91 octane gas with the 1.9 head? or should I step up to a 2.0l head with the 43mm intake valves and 36mm exhaust valves. I'd also looked at thread http://opelgt.com/forums/showthread....ht=S-10+clutch which discussed some of these questions here.Thanks, Jarrell

markandson · 06-28-2005

Well, Git Er Done!, I just took apart a stock 1.9 yesterday and I didn't throw out the old head gasket yet

. So here you go.... The crushed piston seal diameter runs between 3.736" (94.894mm) and 3.741" (95.021mm) and the crushed thickness at the piston seal area is .038" (.965mm). HTH

GTJIM · 06-28-2005

Originally Posted by nobody

Jarrell with the 2.0s you will be over 9:1 to start. I think around 9.4. I'd be watching the finished compression with that combination.

This is a perfect excuse to "unshroud" valves out to the edge of the new bore size as it helps in two ways - better air flow and slightly reduced static compression ratio.

kwilford · 06-29-2005

Originally Posted by soybean

Okay here comes a dumb question. Assuming you use the combo the Keith posted, in item 2 , he has 30 over flat top pistons (93mm). One uses the 2.0 l (95 mm) pistons, do you use the regular gasket set, or go with 2.0 l gasket set since you're over 02mm? or does it matter. Jarrell

Jarrell, I believe that you need to use the 2.0 head gasket for either the 2.0 pistons, or any similar size (such as the "economical" SBC 265, or stroked-crank with the 305 pistons). Call and ask Gil at OGTS, he will say for sure (or Bob or Dave could just chime in) and he also sells them of course. But as I recall, he was out of stock a few months ago...

greensmurf20 · 06-29-2005

about a month and a half ago i took the last felpro headgasket he had and said he was just about out of even the "normal" ones.

GTJIM · 06-29-2005

In a previous post Bob mentioned that the standard 1.9 head gasket can be used as the diameter of the holes is 94.8 - 95.0 mm in a compressed gasket.
So it looks like you can sneak by with a 1.9 head gasket on a 95mm - 2.0L bore.

nobody · 06-29-2005

The problem you get into using a 1.9 gasket on a 2.0 is that the inner edge of the metal to seal the combustion chamber is now in the combustion chamber. A stock head gasket is meant to be between the block and head and is actually above size for a standard bore. 2.0 0r 95mm is just over the working limit of stock so you run the risk of burning up a stock head gasket or piston hitting it if your pushing the compression limits. When I did the 2.0 I had gaskets galore and I found that the chances of one sealing and staying good were pretty slim. Use the right one and save the headache and worry.

azopelnut · 07-02-2005

[quote=RallyBob]When I used to build a lot of 2.0 litre circle track engines, I could get around 10.5-10.7:1 compression with flat-tops if I decked the block .010" and milled the head .085" with flat-tops and Chevy valves (1.85/1.50).
How did you correct the timing with that amount of milling? Did the profile of the cam make up for the milling?

soybean · 07-02-2005

[quote=azopelnut]

Originally Posted by RallyBob

When I used to build a lot of 2.0 litre circle track engines, I could get around 10.5-10.7:1 compression with flat-tops if I decked the block .010" and milled the head .085" with flat-tops and Chevy valves (1.85/1.50).
How did you correct the timing with that amount of milling? Did the profile of the cam make up for the milling?

Check out post 42 and a couple of earlier ones that Jeff posted, on how to change the cam timing. HTH, Jarrell

azopelnut · 07-02-2005

Right
I didn't think that that much milling could be compensated with the modified cam gear. Like Keith and Rallybob said 2 degrees retard for every .025 milled so if Rallybob milled a combination of .095 then that would be nearly 8 degrees retard and the modified gear would only be 6 advance leaving the engine at 2 degrees retard..right or am I missing something?

soybean · 07-02-2005

You are correct. Check out Bobs post 44 near the end, and from what I am able to gather that 2 degrees will give you some good low end torque. HTH, Jarrell

kwilford · 07-02-2005

Paul, the "6 degree" fix is just the modified cam gear. The vernier cam gears that Bob describes has much greater adjustment, and much more precise.

Travis · 07-02-2005

Don't be afraid to combine the 6 degree dowel pin trick with the offset bushing and even skipping teeth on the sprocket. You can get any adjustment you want this way.

For example, if you advance the cam one tooth(18 degrees if I remember correctly) and then retard the cam 6 degrees with the extra dowel hole, you'll end up with 12 advanced. You can then use the offset bushing to fine tune in either direction...

-Travis

RallyBob · 07-02-2005

Originally Posted by azopelnut

Right
I didn't think that that much milling could be compensated with the modified cam gear. Like Keith and Rallybob said 2 degrees retard for every .025 milled so if Rallybob milled a combination of .095 then that would be nearly 8 degrees retard and the modified gear would only be 6 advance leaving the engine at 2 degrees retard..right or am I missing something?

I also often have the cam ground with some advance in it too. So you can not only return the timing to zero but you can gain some cam advance as well.

jeff denton · 07-03-2005

There's way too much worry about all this. This is about doing all the decking and milling you want to get max compression and then just fix the timing problem. Forget timing marks. Degree in your cam according to the spec sheet that came with it and you're done. The nice expensive vernier sprocket is beautiful, the way to go, no doubt, but I'm talking about STOCK parts just kind of "messed with" for ULTIMATE performance. On a budget, may I add... I can drill two little holes in a gear pretty cheap... Was not surprised by Bob's finding that Opel racers had my trick figured out long ago. It's too simple to overlook once you get focused on it, just re-read my post about how I found it and do the experiment yourself. Trace the sprocket on paper, teeth, bolt holes, dowel hole, and all, then rotate it to the next bolt hole. Look at where the teeth land. Rotate it again to the next bolt hole, look at where the teeth landed this time. Do this and you will see the obvious simplicitity of the whole situation! If you are fretting about any of this topic you do not yet understand it, trust me, but keep looking, it will hit you eventually.

You could have the cam ground a bazillion degrees off and still fix it this easily, it is all about degreeing in your cam. When do you want the valve to open, make it happen. Skipping the chain a tooth on the sprocket changes timing nine degrees, as I recall from my first attempt at making an angle milled head degree in at all... that's all I did at first, and won a (trophy dash) race even, against 2.3 liter Mustangs

Washout · 12-09-2006

Guys, I've read this post a couple of times now and still need a little help. I've never had to degree a cam before but this engine I'm building now had been decked and I have no idea how much since there is no published factory height. All that said, I've installed a degree wheel after making a mounting hub out of an old pulley and I built a piston stop for insuring that I have absolute TDC set on the degree wheel. I set the cam using the old timing marks as a starting point and using the .050 reading provided with my ISKY cam spec sheet I started taking readings.
In my case the spec sheet says the intake should be open .050 at 4 degrees Before TDC and closed to .050 at 44 degrees ABDC. My measurements indicated the the cam was opened to .050 at 3 degrees After TDC and closed to .050 at 45 degrees ABDC. How can the ABDC reading be so close to correct (45 actual vs 44 planned) and yet the BTDC reading is off by 7 degrees(BTDC 4 planned vs ATDC 3 actual)? Is this attributable to timing chain stretch? I've only got the rocker arms installed on two cylinders to provide some tension on the cam, is that enough or do I need them all installed for a more accurate reading?

RallyBob · 12-09-2006

Originally Posted by Washout

In my case the spec sheet says the intake should be open .050 at 4 degrees Before TDC and closed to .050 at 44 degrees ABDC. My measurements indicated the the cam was opened to .050 at 3 degrees After TDC and closed to .050 at 45 degrees ABDC. How can the ABDC reading be so close to correct (45 actual vs 44 planned) and yet the BTDC reading is off by 7 degrees(BTDC 4 planned vs ATDC 3 actual)?

Quick question... Are you checking with zero valve lash, and at .050" lifter rise?

By my calculations, you are supposed to have a cam with 228* @ .050" and with 110* intake centerline. You are only measuring 222*@ .050" with a 114* intake centerline.

This shows two things:
One, the cam is 4* retarded.
And two, it has 6* less duration than what the cam card says it should have.

This is not entirely uncommon! Some cams are wayyy off from the cam cards, but sometimes it has to do with how you measure it. Some things that can affect it:
Is it truly at zero valve lash?
Is the dial indicator at the center of the lifter?
Is the dial indicator rididly attached, or does it move around?
Is the dial indicator perfectly perpendicular to the lifter?
Does the degree wheel spin when you rotate the engine?
Does the degree wheel pointer move around?
Did your 'positive stop' in fact move during the measuring process?

So it could just be a 'tolerance stack' of any one or all of these things. I am overly cautious when degreeing a cam, I will perform the same check 3-4 times until it's consistently the same, because I've had the same issues in the past!

HTH,
Bob

RallyBob · 12-09-2006

Originally Posted by Washout

I've never had to degree a cam before but this engine I'm building now had been decked and I have no idea how much since there is no published factory height.

Missed this before.
Factory deck height is A+T mm, this is measured from the top of the block to the crankshaft centerline.

Bob

Paul · 12-09-2006

Yea... what Bob said....

On the cams I've bought, I've found the lift and duration to be a little LESS than advertised. When dergeeing the cam, I did not try to get the @ lift numbers to match the cam card. I carefully measured and charted several lifts vs angles. I probably did more than a skilled tuner would have to do to understand the result, but sometimes the more information the better.

First, use Bob's guidelines above and be sure of your set-up. I found my dial indacator was moving slightly due to the tiny vibrations of the process. Next repeat 3 or 4 times, writing down the numbers each time and then check for variation. If you bought a big wheel then by all means record to the half degree.

I measured lifts on the lift side @: .005; .010"; .013", .025; .050"; .100"; .150"; .250 and then on the way back down again at each corresponding lift height.

Then, using the math I calculated Centerline at each lift: .005, .010" etc.

You may find the opening ramps and the closing ramps to NOT be symmetrical causing the C/L to be skewed. On one cam I found the numbers @.050" to be off slightly, so the numbers I took higher help to confirm the @.050 trend.

The numbers are still in a notebook, but it is in my desk at work. If you need, I can scan them in early next week and you can see exactly how I did it down to my calculations.

Washout · 12-09-2006

Bob,
The Piston stop is solid, I made it out of 1/2 inch thick by 1 3/4 wide 6061 aluminum, reamed the bolt holes for close fit and then threaded and installed a 3/8 bolt in the center. The 3/8 bolt is completely threaded into the stop all the way to the bolt head... it's solid, no flex. The Degree wheel is solid as well, I cut the pulley off of an old opel pulley then machined a face on it that the index wheel could fit over. Then I made a washer with a face to pinch the index wheel in place. The pointer on the block is simply a piece of welding rod but it too is solid.
I have the dial indicator directly on the lifter, perpendicular to the lifter (no rocker arm installed) and the magnetic base seems to be very solid. The results I've been getting are very consistant. I just don't quite understand them. You say the cam is 4* retarded, I thought it was 7 degrees retarded since it was suppose to be 4* BTDC and instead its 3* ATDC? The inaccuracy in the grind would explain the second reading though. Thanks for the information.

06-29-2005	#56 (permalink)
GTJIM 4246 Post Club Join Date: Jun 2003 Location: New Zealand Posts: 5,491 Classified Rating: 0% (0)	From "Search" In a previous post Bob mentioned that the standard 1.9 head gasket can be used as the diameter of the holes is 94.8 - 95.0 mm in a compressed gasket. So it looks like you can sneak by with a 1.9 head gasket on a 95mm - 2.0L bore. Last edited by GTJIM; 06-29-2005 at 04:54 PM..

07-03-2005	#65 (permalink)
jeff denton former opel racer Join Date: Nov 2002 Location: near some glaciers Posts: 2,745 Classified Rating: 0% (0)	There's way too much worry about all this. This is about doing all the decking and milling you want to get max compression and then just fix the timing problem. Forget timing marks. Degree in your cam according to the spec sheet that came with it and you're done. The nice expensive vernier sprocket is beautiful, the way to go, no doubt, but I'm talking about STOCK parts just kind of "messed with" for ULTIMATE performance. On a budget, may I add... I can drill two little holes in a gear pretty cheap... Was not surprised by Bob's finding that Opel racers had my trick figured out long ago. It's too simple to overlook once you get focused on it, just re-read my post about how I found it and do the experiment yourself. Trace the sprocket on paper, teeth, bolt holes, dowel hole, and all, then rotate it to the next bolt hole. Look at where the teeth land. Rotate it again to the next bolt hole, look at where the teeth landed this time. Do this and you will see the obvious simplicitity of the whole situation! If you are fretting about any of this topic you do not yet understand it, trust me, but keep looking, it will hit you eventually. You could have the cam ground a bazillion degrees off and still fix it this easily, it is all about degreeing in your cam. When do you want the valve to open, make it happen. Skipping the chain a tooth on the sprocket changes timing nine degrees, as I recall from my first attempt at making an angle milled head degree in at all... that's all I did at first, and won a (trophy dash) race even, against 2.3 liter Mustangs Last edited by jeff denton; 07-03-2005 at 03:49 AM..

12-09-2006	#69 (permalink)
Paul Member 1000 Post Club Join Date: Mar 2002 Location: Ft Smith, Arkansas Posts: 1,364 Classified Rating: 0% (0)	Yea... what Bob said.... On the cams I've bought, I've found the lift and duration to be a little LESS than advertised. When dergeeing the cam, I did not try to get the @ lift numbers to match the cam card. I carefully measured and charted several lifts vs angles. I probably did more than a skilled tuner would have to do to understand the result, but sometimes the more information the better. First, use Bob's guidelines above and be sure of your set-up. I found my dial indacator was moving slightly due to the tiny vibrations of the process. Next repeat 3 or 4 times, writing down the numbers each time and then check for variation. If you bought a big wheel then by all means record to the half degree. I measured lifts on the lift side @: .005; .010"; .013", .025; .050"; .100"; .150"; .250 and then on the way back down again at each corresponding lift height. Then, using the math I calculated Centerline at each lift: .005, .010" etc. You may find the opening ramps and the closing ramps to NOT be symmetrical causing the C/L to be skewed. On one cam I found the numbers @.050" to be off slightly, so the numbers I took higher help to confirm the @.050 trend. The numbers are still in a notebook, but it is in my desk at work. If you need, I can scan them in early next week and you can see exactly how I did it down to my calculations. Last edited by Paul; 12-09-2006 at 08:26 PM.. Reason: created spellin errors for Otto to find... LOL

06-28-2005	#52 (permalink)
markandson Senior Contributor Join Date: Oct 2002 Location: Kent Lakes, NY Posts: 1,388 Classified Rating: 0% (0)	Well, Git Er Done!, I just took apart a stock 1.9 yesterday and I didn't throw out the old head gasket yet . So here you go.... The crushed piston seal diameter runs between 3.736" (94.894mm) and 3.741" (95.021mm) and the crushed thickness at the piston seal area is .038" (.965mm). HTH

06-29-2005	#55 (permalink)
greensmurf20 OPEL-LESS!!! Join Date: Mar 2003 Location: Gobles michigan 49055 Posts: 2,110 Classified Rating: 0% (0)	about a month and a half ago i took the last felpro headgasket he had and said he was just about out of even the "normal" ones.

06-29-2005	#57 (permalink)
nobody No Access Join Date: Nov 2003 Location: in transit Posts: 3,873 Classified Rating: 0% (0)	The problem you get into using a 1.9 gasket on a 2.0 is that the inner edge of the metal to seal the combustion chamber is now in the combustion chamber. A stock head gasket is meant to be between the block and head and is actually above size for a standard bore. 2.0 0r 95mm is just over the working limit of stock so you run the risk of burning up a stock head gasket or piston hitting it if your pushing the compression limits. When I did the 2.0 I had gaskets galore and I found that the chances of one sealing and staying good were pretty slim. Use the right one and save the headache and worry.

07-02-2005	#58 (permalink)
azopelnut Member Join Date: Apr 2003 Location: Yuma Arizona Posts: 636 Classified Rating: 0% (0)	[quote=RallyBob]When I used to build a lot of 2.0 litre circle track engines, I could get around 10.5-10.7:1 compression with flat-tops if I decked the block .010" and milled the head .085" with flat-tops and Chevy valves (1.85/1.50). How did you correct the timing with that amount of milling? Did the profile of the cam make up for the milling?

07-02-2005	#60 (permalink)
azopelnut Member Join Date: Apr 2003 Location: Yuma Arizona Posts: 636 Classified Rating: 0% (0)	Right I didn't think that that much milling could be compensated with the modified cam gear. Like Keith and Rallybob said 2 degrees retard for every .025 milled so if Rallybob milled a combination of .095 then that would be nearly 8 degrees retard and the modified gear would only be 6 advance leaving the engine at 2 degrees retard..right or am I missing something?

07-02-2005	#61 (permalink)
soybean Moderator Join Date: Nov 2002 Location: Reidsville N.C. Posts: 2,160 Classified Rating: 0% (0)	You are correct. Check out Bobs post 44 near the end, and from what I am able to gather that 2 degrees will give you some good low end torque. HTH, Jarrell

07-02-2005	#62 (permalink)
kwilford Über OpelGT.com Moderator Join Date: Mar 2002 Location: Calgary, Alberta, Canada Posts: 3,720 Classified Rating: 0% (0)	Paul, the "6 degree" fix is just the modified cam gear. The vernier cam gears that Bob describes has much greater adjustment, and much more precise.

07-02-2005	#63 (permalink)
Travis Senior Contributor Join Date: Apr 2002 Location: Temple, NH Posts: 779 Classified Rating: 0% (0)	Don't be afraid to combine the 6 degree dowel pin trick with the offset bushing and even skipping teeth on the sprocket. You can get any adjustment you want this way. For example, if you advance the cam one tooth(18 degrees if I remember correctly) and then retard the cam 6 degrees with the extra dowel hole, you'll end up with 12 advanced. You can then use the offset bushing to fine tune in either direction... -Travis

12-09-2006	#66 (permalink)
Washout Member Join Date: Sep 2003 Location: Ohio for now, but Texas is Home Posts: 337 Classified Rating: 0% (0) Logbook Entries: 4	Guys, I've read this post a couple of times now and still need a little help. I've never had to degree a cam before but this engine I'm building now had been decked and I have no idea how much since there is no published factory height. All that said, I've installed a degree wheel after making a mounting hub out of an old pulley and I built a piston stop for insuring that I have absolute TDC set on the degree wheel. I set the cam using the old timing marks as a starting point and using the .050 reading provided with my ISKY cam spec sheet I started taking readings. In my case the spec sheet says the intake should be open .050 at 4 degrees Before TDC and closed to .050 at 44 degrees ABDC. My measurements indicated the the cam was opened to .050 at 3 degrees After TDC and closed to .050 at 45 degrees ABDC. How can the ABDC reading be so close to correct (45 actual vs 44 planned) and yet the BTDC reading is off by 7 degrees(BTDC 4 planned vs ATDC 3 actual)? Is this attributable to timing chain stretch? I've only got the rocker arms installed on two cylinders to provide some tension on the cam, is that enough or do I need them all installed for a more accurate reading?

12-09-2006	#70 (permalink)
Washout Member Join Date: Sep 2003 Location: Ohio for now, but Texas is Home Posts: 337 Classified Rating: 0% (0) Logbook Entries: 4	Bob, The Piston stop is solid, I made it out of 1/2 inch thick by 1 3/4 wide 6061 aluminum, reamed the bolt holes for close fit and then threaded and installed a 3/8 bolt in the center. The 3/8 bolt is completely threaded into the stop all the way to the bolt head... it's solid, no flex. The Degree wheel is solid as well, I cut the pulley off of an old opel pulley then machined a face on it that the index wheel could fit over. Then I made a washer with a face to pinch the index wheel in place. The pointer on the block is simply a piece of welding rod but it too is solid. I have the dial indicator directly on the lifter, perpendicular to the lifter (no rocker arm installed) and the magnetic base seems to be very solid. The results I've been getting are very consistant. I just don't quite understand them. You say the cam is 4* retarded, I thought it was 7 degrees retarded since it was suppose to be 4* BTDC and instead its 3* ATDC? The inaccuracy in the grind would explain the second reading though. Thanks for the information.