bandit dot head

[vmax]

Hi Guys ...New to the group but come here often to read posts I drag race a bandit well its sorta a bandit. Im installing a dot head on 1216 piston when I dial my cams in  (750 cams slotted bandit sprockets) Ive only got about .040 to .050 thou piston to valve clearance on ex at 15 to 20 degrees before top dead center everything ive known  recommends 80 to 100 thou clearance . I could mill the piston pocket I suppose but I keep reading this mod can be done . I'm also running 40 mm lectrons msd ignition  lock up clutch stuff like that degree  105 106 thanks in advance any help would be great I have to be missing something

[Oilyspanner]

Welcome to the site Vmax -  the dot head chamber shape is smaller and  the 1216 pistons are designed for the larger 1052/1127/1157  combustion chamber - low compression pistons are less of a problem. It's likely that the edge of the squish on the head is very close to the crown of the 1216 pistons, not just the valve pockets. Measure the clearance around the piston, chances are you'll need to have the pistons milled for clearance. You could fit a thicker base/head gasket for clearance, but the squish will grow accordingly, losing a little power - depends what you want/expect  Bud.

[Gixer1460]

I've always tried to maintain minimum 1mm piston to head squish clearance ie. 0.040". If you are chasing max power you could squeeze that to 0.8mm / 0.065".

For valves, due to the chance of valve float, I try to keep 2mm or 0.080" and change.

Anyone quoting 80 - 100 thou. squish is losing power but very safe...............racing isn't about safe LOL!

Edited January 22, 2018 by Gixer1460
Inch figures corrected / amended!

[Fula28]

You can pocket std pistons upto 1mm been there done that, ran fine for 1000,s miles ,Even turbod  was still ok.

[dupersunc]

2 hours ago, Gixer1460 said:

I've always tried to maintain minimum 1mm piston to head squish clearance ie. 0.255". If you are chasing max power you could squeeze that to 0.8mm.

For valves, due to the chance of valve float, I try to keep 2mm or 0.050" and change.

Anyone quoting 80 - 100 thou is loosing power but very safe...............racing isn't about safe LOL!

You need to check your zues book. ;D

1mm = 0.040"

As has been said. Dot head has a small chamber and more critically the valves are approx 3mm or 0.120" longer than bandit valves so the head of the valve starts closer to the piston even when it's closed.

Edited January 22, 2018 by dupersunc

[vmax]

just might go a bit smaller on lift with cam to gain a bit of clearance I believe the longer valve may be the issue (never thought of that) thanks for all the replys  its all helpful the 80 to 100 is safe and 40 to 50 gives more power lol but when the piston touches the valve it makes no difference u have no power thanks again

[vmax]

3 hours ago, Gixer1460 said:

I've always tried to maintain minimum 1mm piston to head squish clearance ie. 0.255". If you are chasing max power you could squeeze that to 0.8mm.

For valves, due to the chance of valve float, I try to keep 2mm or 0.050" and change.

Anyone quoting 80 - 100 thou is loosing power but very safe...............racing isn't about safe LOL!

got lots of room for the piston going in the head chamber  but only 0.050 piston to valve around 15 deg btdc ex valve I already did the bandit head in valve looks like the letter s   and your right racing isn't about safe but it gets expensive lol I'm a proud owner of 12 oil cooled motors thanks again lol

[Gixer1460]

2 hours ago, dupersunc said:

You need to check your zues book. ;D

1mm = 0.040"

I fackin' hate inch conversions ! ! ! Wood comes in both 2.4m of 4x2" and we build houses with mm!

[wraith]

2 hours ago, Gixer1460 said:

I fackin' hate inch conversions ! ! ! Wood comes in both 2.4m of 4x2" and we build houses with mm!

Me too, mm evey day there is oldskool and then oilsteem 

[vmax]

got the clearance I wanted had to dump the gsxr 750 ex cam once I installed the bandit ex cam I have a little more wiggle room thanks again for the info..... In my mind lol bolting a dot head straight on a bandit with 1216 pistons theres things to consider  not just a straight swap  I also do believe the longer valves is the main issue  thanks guys

[dupersunc]

What CR did you end up with?

[Dezza]

14 hours ago, Gixer1460 said:

I fackin' hate inch conversions ! ! ! Wood comes in both 2.4m of 4x2" and we build houses with mm!

Anything in non-SI units sucks, except maybe tyres. The diameters are in imperial but the widths are in metric on the SAME tyre but wierdly this does not cause confusion

[Ted M]

@vmaxCould I ask you the make of your pistons. I have just had my B12 bored out to 1216 and I'm using Wiseco pistons and planning on using a DOT head with them.

[370steve]

2 hours ago, Ted M said:

@vmaxCould I ask you the make of your pistons. I have just had my B12 bored out to 1216 and I'm using Wiseco pistons and planning on using a DOT head with them.

Snap 

[vmax]

7 hours ago, Ted M said:

@vmaxCould I ask you the make of your pistons. I have just had my B12 bored out to 1216 and I'm using Wiseco pistons and planning on using a DOT head with them.

Wiseco is what I have  106 in and 109 ex degree .... Has 70 thou clearance 15 degree btdc  intake cam from dot head    ex has 90 thou clearance but had to use bandit cam lower profile... ive tried running tighter clearance but for drag racing if u miss a shift booooooooooom in my case  If I was to do over I would mill deeper pockets in piston for the valves or if u want to go cheaper double up cylinder base gasket everthing ive read on the net is the dot head and cams will bolt straight on a bandit with 1216 pistons I just did not like the clearances

[Ted M]

 Many thanks for this, I have three cam profiles to try B12, GSXF 750 and GSXR 750 Slingshot I will post the results on here when I've done.

[dupersunc]

If you guys are looking at running Dot heads and 81mm Wisecos, check your compression ratios. I think they'll be very high. 

 

It's one thing running a drag bike like the OP's running 120 octane at 13.5:1. Quite another thing on a road bike though.

 

[Ted M]

Will do  @dupersuncthanks for pointing this out. This was one of my reasons for choosing Wiseco as they are advertised at 11:1. Having read the posts etc some reckon that a DOT head would take the CR up by one point which would have given me 12:1 ish which would be ok for street fuel.. JE have got 2 types to select from 11:1 and 13:1 this was why I asked the original question of what make was being used. If the Cr is too high it gives me an excuse to get another engine and use the DOT head on that one. Of course I will need to get another frame to go with the engine

[vmax]

14 hours ago, dupersunc said:

If you guys are looking at running Dot heads and 81mm Wisecos, check your compression ratios. I think they'll be very high. 

 

It's one thing running a drag bike like the OP's running 120 octane at 13.5:1. Quite another thing on a road bike though.

 

you bet race fuel all the way  more like 13: 1  and I'm running  under a min a pass in total  compared to the street... I don't think I would do this mod for a road bike but everyone has a choice  but if you make the wrong choice look at the 3rd pic

[vmax]

Also I done this mode because I like the way the port is  haven't flowed the head but it looks a lot better than the bandit head

[markfoggy]

On 25/01/2018 at 2:46 AM, vmax said:

 

Is that a side stand or am I missing something?

Edited January 28, 2018 by markfoggy
all photos.

[Ted M]

I was doing some maths last night (my head hurt this morning) and I have  calculated the compression ratios of the DOT head with 1216 Wiseco pistons and Cometic head gasket as 14.8:1. This was without calculating the volume of the valve cutouts. so it may be a little lower but not much. I double checked my figures and calculations against the B12 head and I arrived at 10.9:1 which is as near as damit the advertised figure. The volumes of individual combustion chambers are: DOT head 21.5 ml and B12 is 29 ml. I was quite surprised at the difference.

 

 

 

Edited January 30, 2018 by Ted M
Accuracy of description

[370steve]

Question for all the Knowledgeable people on here,

If i still wanted to use a Dot head with 1216 Wiseco pistons for street application,  could i use a bigger base gasket to lower the compression ratio, and if so how do you calculate the thickness required, and most importantly, where would i get one? 

[dupersunc]

28 minutes ago, 370steve said:

Question for all the Knowledgeable people on here,

If i still wanted to use a Dot head with 1216 Wiseco pistons for street application,  could i use a bigger base gasket to lower the compression ratio, and if so how do you calculate the thickness required, and most importantly, where would i get one? 

Base gasket is the least suitable way, as you increase the squish gap, tighter the squish the more compression you can get away with. 

I've got a dot head, that I've just fitted to a stock bandit bottom end, I've opened up the combustion chamber a little around the valves, as the valves in the dot head are quite heavily shrouded, so there are gains to be had by in shrouding the valves with the bigger bandit bore, this will have drop the compression a tad, I regained most of that by skimming  0.5 mm of the head, but you wouldn't need to the skimming.

Even opening out the combustion chambers you would still need to drop it more, I would look at machining the very top of the piston, and probably the valve pockets too, to get the desired compression, and valve to piston clearance.

If this sounds like a lot of work, it is. You'd be better off fettling the Bandit head, and fitting the dot head cams.

 

[370steve]

Cheers for that dunc :),  but not looking for "all out" top end power,  I was going to fit the Bandit cams to keep the mid range so dont think i will have valve clearance probs.