Max bore size

[lamchop77]

Just a quick one guys.

Does anyone know what size the bores can be taken out to safely. I have seen that Hiro/Vagos were planning to go to 98mm and that 97mm pistons are available. Are there certain blocks which are thicker than others?

I could do with knowing as i'm about to order a set of custom pistons from JE.

Also for race motors is it ok to have them linered (is it preferential?). I have heard that they can drop through and hit the crank (that was on a 16v red top vauxhall motor!). I have got 2.0, 2.2 and 2.4 blocks to go at.

Thanks

Chris

[Hiro]

Just a quick one guys.

Does anyone know what size the bores can be taken out to safely. I have seen that Hiro/Vagos were planning to go to 98mm and that 97mm pistons are available. Are there certain blocks which are thicker than others?

I could do with knowing as i'm about to order a set of custom pistons from JE.

Also for race motors is it ok to have them linered (is it preferential?). I have heard that they can drop through and hit the crank (that was on a 16v red top vauxhall motor!). I have got 2.0, 2.2 and 2.4 blocks to go at.

Thanks

Chris

Hi Chris,
With the 2.0 block 97mm is safe & 98mm is possible but looks borderline,
For this reason I've limited my overbores to 97mm.
The other issue with overbore is about the headgasket:
For a 97mm bore you will need a "98mm hole" headgasket,
This one is available from Risse Motorsport but quality is questionable.
But for a 98mm bore you will need a "99mm hole" headgasket,
IMO this one is not available off-the-shelf so you need to go for a custom one.
Just another info that might be usefull for you:
If you stay with a 96mm bore this allows to use the famous "Zackenringe" headgasket from Elring.
To my knowledge this one is the tougher currently available for relatively low £,
But its "hole" are only 96.5mm so you can't use it with 97mm pistons.
HTH,
Hiro

[lamchop77]

Thanks Hiro

If 97mm is safe then thats what it will be. I'll try and compare the thickness of the 2.0 blocks with the others. I'm going for a cometic head gasket (the MLS one) big bucks but pretty well bomb proof by all accounts.

Just out of interest what comp ratio will a std head gasket (Payen) cope with?

Thanks again

Chris

[RallyBob]

Just out of interest what comp ratio will a std head gasket (Payen) cope with?

I've run the Payen gaskets at 11.5 to 11.8:1 compression with zero issues. As long as you see no detonation, you should be fine. Detonation will kill any gasket, no matter how good it is!

[SantaClaw]

The C20XE, 16v red top is a COMPLETELY different engine from the 2.2 - 2.4

Problem starts when you forget to order pistons with lowered wrist pin holes...

[SantaClaw]

I've run the Payen gaskets at 11.5 to 11.8:1 compression with zero issues. As long as you see no detonation, you should be fine. Detonation will kill any gasket, no matter how good it is!

To eliminate detonation, on any engine, install water\ethanol injection.. It will cost you around 400$ but guarantees NO detonation(156 octane)... And all you need is wiper fluid, with more than 50% ethanol...

Also, depending on the engine, you get 10-15% more power...

[jeff denton]

This 96 to 97mm bore max, does this apply to the 1.9 blocks, too? If not, can we discuss max bore for the 1.9 while we're at it? Chris and I may be building similar engines here. But all I have is 1.9 blocks. Aplenty! Still want a 2.2 crank...

[Hiro]

Just out of interest what comp ratio will a std head gasket (Payen) cope with?

as Bob said it's pretty tough,
but I don't use it on my 85mm stroke race CIH because it's a tad thin.
with forged pistons the piston rock @ TDC is substantial,
I'm always afraid to bang on the head during warm-up,
so just to be on the safe side I prefer not to take this risk.
Hiro

[Hiro]

To eliminate detonation, on any engine, install water\ethanol injection.. It will cost you around 400$ but guarantees NO detonation(156 octane)... And all you need is wiper fluid, with more than 50% ethanol...

Also, depending on the engine, you get 10-15% more power...

sure but this is not allowed by my vintage race regulation,
although I could always argue I made a mistake when plumbing my wiper tank!

[jeff denton]

although I could always argue I made a mistake when plumbing my wiper tank!

I love it! Why didn't I think of that? Oh, yeah, wipers aren't allowed. Dang.

[Hiro]

The C20XE, 16v red top is a COMPLETELY different engine from the 2.2 - 2.4

Problem starts when you forget to order pistons with lowered wrist pin holes...

you probably mean lower cd piston?
the C20XE rod ratio is only 1.66 so if you lower the pin,
the rod will be even shorter & ratio will drop below 1.66?
please explain,
Hiro

[Hiro]

This 96 to 97mm bore max, does this apply to the 1.9 blocks, too? If not, can we discuss max bore for the 1.9 while we're at it? Chris and I may be building similar engines here. But all I have is 1.9 blocks. Aplenty! Still want a 2.2 crank...

looks like this depends upon the 1.9 block quality:
here in Europe some 1.9 blocks overbored to 97mm start showing cast-porosity problems,
whereas IIRC Bob overbored it more than that & it was OK.
Bob I don't remember your overbore value, help!
(hum... 98.43mm?)

[Hiro]

I love it! Why didn't I think of that? Oh, yeah, wipers aren't allowed. Dang.

hum...
what about saying it's a drink-tank for cooling the pilot?
OK I see your point: no alcohol allowed during racing!

[ggl]

Hi Chris,
With the 2.0 block 97mm is safe & 98mm is possible but looks borderline,
For this reason I've limited my overbores to 97mm.
The other issue with overbore is about the headgasket:
For a 97mm bore you will need a "98mm hole" headgasket,
This one is available from Risse Motorsport but quality is questionable.
But for a 98mm bore you will need a "99mm hole" headgasket,
IMO this one is not available off-the-shelf so you need to go for a custom one.
Just another info that might be usefull for you:
If you stay with a 96mm bore this allows to use the famous "Zackenringe" headgasket from Elring.
To my knowledge this one is the tougher currently available for relatively low £,
But its "hole" are only 96.5mm so you can't use it with 97mm pistons.
HTH,
Hiro

Interesting, never thought of that, I assume the "Zackenringe" is what ENEM in Sweden has been selling all these years or is that something different again ?

I'm just curious because I had to replace the headgasket on the 2.7, as Rob pointed out, detonation killed it, and I purchased a "steel reinforced" headgasket that was supposedly the same as the ENEM one, has these steel rings that's not supposed to compress but rather "cut" into the cast iron mating surfaces when you torque it down ....?

Anyways, it was doing fine when I last ran the engine, which is some 7 years ago now, despite not asking for an overbore gasket, it just never dawned on me to do so because I called Mantzel and they said any head gasket would do as long it wasn't *smaller* than the bore, I didn't measure it but did a test fit....are you saying I'm looking at some potential problem here because if I remember correctly the 2.7 is a 97 mm bore right ?

[lamchop77]

Cheers guys for the replys

Jeff, i have a 1.9 block engine which is bored out to 95.5. That had don 30000 miles no probs at all. I'll see if i can get a measurement of the wall thickness for you.

As for the detonation problem, i will be having the car rolling roaded to get it sorted. I have to run std pump fuel plus we can use an additive so absolute max octane rating is 101/102 The engines i'm building are both around the 11/11.5-1 ratio. Am i likely to run into problems with this set up? Haven't built any real high comp engines before so i haven't run into this problem.... yet.

Thanks

Chris

[Hiro]

Interesting, never thought of that, I assume the "Zackenringe" is what ENEM in Sweden has been selling all these years or is that something different again ?

I'm just curious because I had to replace the headgasket on the 2.7, as Rob pointed out, detonation killed it, and I purchased a "steel reinforced" headgasket that was supposedly the same as the ENEM one, has these steel rings that's not supposed to compress but rather "cut" into the cast iron mating surfaces when you torque it down ....?

Anyways, it was doing fine when I last ran the engine, which is some 7 years ago now, despite not asking for an overbore gasket, it just never dawned on me to do so because I called Mantzel and they said any head gasket would do as long it wasn't *smaller* than the bore, I didn't measure it but did a test fit....are you saying I'm looking at some potential problem here because if I remember correctly the 2.7 is a 97 mm bore right ?

it's this same headgasket,
Elring is making this one since the 70's for most of the Opel motorist,
Irmscher was using it on his groupA 2.0 CIH & nowadays Gerent is still using it.

as you say this headgasket has steel circles in each bore,
the inner diameter of these circles is 96.5mm
and the pressed thickness is 1.2mm

I've test-fitted this headgasket on my 96mm or 97mm overbored blocks:
it's OK with the 96mm bore but not with the 97mm bore,
you can clearly feel with your hand that the steel circles protrudes a tad inside the bore,
so I did not take the risk with my 97mm block.

I asked Elring's custom service (Adrian Blessing) if they could make a custom gasket with 98.5mm bore,
they said it was possible but they would remove this steel circle,
so this was a no-go for me of course!
Hiro

http://rroc.net/forum/ForumPics/Elring1.jpg
http://rroc.net/forum/ForumPics/Elring2.jpg
http://rroc.net/forum/ForumPics/Elring3.jpg

[ggl]

it's this same headgasket,
Elring is making this one since the 70's for most of the Opel motorist,
Irmscher was using it on his groupA 2.0 CIH & nowadays Gerent is still using it.

as you say this headgasket has steel circles in each bore,
the inner diameter of these circles is 96.5mm
and the pressed thickness is 1.2mm

I've test-fitted this headgasket on my 96mm or 97mm overbored blocks:
it's OK with the 96mm bore but not with the 97mm bore,
you can clearly feel with your hand that the steel circles protrudes a tad inside the bore,
so I did not take the risk with my 97mm block.

I asked Elring's custom service (Adrian Blessing) if they could make a custom gasket with 98.5mm bore,
they said it was possible but they would remove this steel circle,
so this was a no-go for me of course!
Hiro

http://rroc.net/forum/ForumPics/Elring1.jpg
http://rroc.net/forum/ForumPics/Elring2.jpg
http://rroc.net/forum/ForumPics/Elring3.jpg

Dang, sounds like I ought to open my engine before putting it back in then, I was hoping to avoind that, especially since that head gasket is expensive as .... or was when I bought it at least

Now you actually have me worried about having done damage to my bores or something, all the M2.7's were 97mm bore right ?

Sorry for going OT

[jeff denton]

have to run std pump fuel plus we can use an additive so absolute max octane rating is 101/102 The engines i'm building are both around the 11/11.5-1 ratio. Am i likely to run into problems with this set up? Haven't built any real high comp engines before so i haven't run into this problem.... yet.

I'm not sure but I've heard there is an octane booster that will get you up to 110. Our track considers 115 racing fuel to be what the rules call "automotive fuel only" but forbids ANY additive. So I've never had any reason to play with booster.
Remember that compression ratio and ignition timing go hand in hand; so go easy on the total advance when you're not sure your octane is up to the compression. Surely you'd be safe at 32 degrees total? Then carefully try 34? See why I want one of those electronic knock detectors?
What are you planning to use for head bolts?

[Hiro]

Dang, sounds like I ought to open my engine before putting it back in then, I was hoping to avoind that, especially since that head gasket is expensive as .... or was when I bought it at least

Now you actually have me worried about having done damage to my bores or something, all the M2.7's were 97mm bore right ?

Sorry for going OT

remember there were two versions of the 2.7:
one version for sure is a 97mm bore,
about the other version I have no clue.
the only way to check would be to lift the head,
but clearly the headgasket will not like it!
Hiro

[wrench459]

Remember that compression ratio and ignition timing go hand in hand; so go easy on the total advance when you're not sure your octane is up to the compression. Surely you'd be safe at 32 degrees total? Then carefully try 34?

Jeff you crack me up.
I can see myself before the judge.. on your behalf..
"""Your racing Honor
Jeff has never bent the rules. I can say without a doubt he's never advanced/retarded a cam trying to increase cylinder pressure for a given track"""
Second thought I'd better stay out of the court room.
The underlined might be the third part in the mixture.