CDH Power DIO reed cylinder. Is this port timing normal???

Joined
Sep 26, 2018
Messages
96
Likes
4
#1
Hello everyone,
I blew my engine a while ago so I tore it down and I'm rebuilding it. So I got a DIO reed cylinder.
I placed the cylinder on the block and the piston created a huge overhang on the transfers and exhaust. I ground out the casting blemishes and it took 3 base gaskets (about 5mm) to raise the ports almost to the top edge of the cylinder at BDC (ran out of base gaskets and can't grind much more off the top of the head). Port timing after grinding the top down to the top fin and raising the port a little, I'm getting 160 degrees of exhaust and 115 degrees of intake and 20 degrees of boost. Stroke is 38. FM-80 Crank.

My question is, is stock port timing usually this awful without modification?? Is this cylinder meant for the 40mm stroke?
I have no clue what my original timing was because the cylinder was casted to the head.
 


Street Ryderz

Well-Known Member
Joined
Oct 14, 2016
Messages
2,752
Likes
574
#2
Hello everyone,
I blew my engine a while ago so I tore it down and I'm rebuilding it. So I got a DIO reed cylinder.
I placed the cylinder on the block and the piston created a huge overhang on the transfers and exhaust. I ground out the casting blemishes and it took 3 base gaskets (about 5mm) to raise the ports almost to the top edge of the cylinder at BDC (ran out of base gaskets and can't grind much more off the top of the head). Port timing after grinding the top down to the top fin and raising the port a little, I'm getting 160 degrees of exhaust and 115 degrees of intake and 20 degrees of boost. Stroke is 38. FM-80 Crank.

My question is, is stock port timing usually this awful without modification?? Is this cylinder meant for the 40mm stroke?
I have no clue what my original timing was because the cylinder was casted to the head.
What cylinder is cast to the head? The ports are not flush with crown at bdc and is quite normal they have allready done their work when piston is at bdc and it's time over area that determines their effect, not being flush.
 
Joined
Sep 26, 2018
Messages
96
Likes
4
#3
What cylinder is cast to the head? The ports are not flush with crown at bdc and is quite normal they have allready done their work when piston is at bdc and it's time over area that determines their effect not being flush.
My old cylinder setup. The chinese revised the cylinder for 2018 and decided to cast it as 1 piece. That cylinder is history now because it caused detonation and blew the piston to bits which got caught in the cylinder.

As for the ports not being flush with the crown, that's not my issue. I was worried that when I raised the cylinder that much i would have too much intake timing. But now that I calculate it to be 115 degrees, is the original timing around 70 degrees and the stock exhaust about 120 degrees? Im just confused I needed to raise the cylinder so much.
 

Street Ryderz

Well-Known Member
Joined
Oct 14, 2016
Messages
2,752
Likes
574
#4
My old cylinder setup. The chinese revised the cylinder for 2018 and decided to cast it as 1 piece. That cylinder is history now because it caused detonation and blew the piston to bits which got caught in the cylinder.

As for the ports not being flush with the crown, that's not my issue. I was worried that when I raised the cylinder that much i would have too much intake timing. But now that I calculate it to be 115 degrees, is the original timing around 70 degrees and the stock exhaust about 120 degrees? Im just confused I needed to raise the cylinder so much.
The Chinese did not revise the cylinder for 2018,there is only the BT cyclinder that is cast as one peice! Stock port durations are commenly 146-8 exhaust,108-110 intake,125 transfers.but these are durations not the points of open and close for that you need to use a degree wheel,your raising the cylinder is changing the timming and not in your favor.
 

Street Ryderz

Well-Known Member
Joined
Oct 14, 2016
Messages
2,752
Likes
574
#5
Also there is no such thing as too much intake timing,your using a reed that controls the intake duration over 172 degrees of crank rotation.
 
Joined
Sep 26, 2018
Messages
96
Likes
4
#6
Also there is no such thing as too much intake timing,your using a reed that controls the intake duration over 172 degrees of crank rotation.
My bad, I meant transfer timing.

The Chinese did not revise the cylinder for 2018,there is only the BT cyclinder that is cast as one peice! Stock port durations are commenly 146-8 exhaust,108-110 intake,125 transfers.but these are durations not the points of open and close for that you need to use a degree wheel,your raising the cylinder is changing the timming and not in your favor.
I didn't get a BT engine and I got a solid cylinder and head. Remember?
IMG_20181029_150633.jpg

Anyhow. The timing I stated before is what I have right now with the raised cylinder. They aren't perfect but close enough to where I have an idea where I'm at. Jag recommended exhaust timing to be at least 160 degrees and most people I've seen have said 120 degrees is okay for transfer.

What should I do then?
 

Street Ryderz

Well-Known Member
Joined
Oct 14, 2016
Messages
2,752
Likes
574
#7
My bad, I meant transfer timing.


I didn't get a BT engine and I got a solid cylinder and head. Remember? View attachment 84475
Anyhow. The timing I stated before is what I have right now with the raised cylinder. They aren't perfect but close enough to where I have an idea where I'm at. Jag recommended exhaust timing to be at least 160 degrees and most people I've seen have said 120 degrees is okay for transfer.

What should I do then?
Jag's figure are a little whacky at times,160 degrees of exhaust duration means that the port has to be 24mm from the deck to the top of port on a 38mm long rod stroke measured linearly(depth).Stock transfers for a 38mm stroke,long rod are all ready 125 degrees of duration and raising the jug should have no varience in that,only altering the window diamentions or the stroke would change this,raising it shifted the open/closed degrees (timing)not the duration.
 
Joined
Sep 26, 2018
Messages
96
Likes
4
#8
Jag's figure are a little whacky at times,160 degrees of exhaust duration means that the port has to be 24mm from the deck to the top of port on a 38mm long rod stroke measured linearly(depth).Stock transfers for a 38mm stroke,long rod are all ready 125 degrees of duration and raising the jug should have no varience in that,only altering the window diamentions or the stroke would change this,raising it shifted the open/closed degrees (timing)not the duration.
You are right about the transfer duration due to it's size, but since it isn't fully uncovered in the 38mm of stroke, the 13mm of the transfer become 7-8mm in my case because the piston doesn't uncover them fully. So I raised the piston just enough so it wouldn't interfere with duration. Any more and I'll only be messing with timing like you said.
 

Spare_Parts

Active Member
Joined
Nov 29, 2017
Messages
709
Likes
238
#9
The Chinese did not revise the cylinder for 2018,there is only the BT cyclinder that is cast as one peice! Stock port durations are commenly 146-8 exhaust,108-110 intake,125 transfers.but these are durations not the points of open and close for that you need to use a degree wheel,your raising the cylinder is changing the timming and not in your favor.
Someone else is making a 1 piece cylinder/ head. Looks like the slant head.
 

junglepig

Active Member
Joined
Oct 30, 2018
Messages
213
Likes
60
#12
Someone else is making a 1 piece cylinder/ head. Looks like the slant head.
I bought my engine off eBay from China and that's how I got that cylinder. The post showed a normal slant head and cylinder but that's not what I got
I think I'd hit the "return request" on that one, and they'll likely send you the engine they advertised without asking for the odd one back.
 
Joined
Sep 26, 2018
Messages
96
Likes
4
#13
I think I'd hit the "return request" on that one, and they'll likely send you the engine they advertised without asking for the odd one back.
They only accepted returns if shipment is DOA. No longer an issue, it grenaded and I'm rebuilding the engine. But that cylinder was alot better at clearing the ports than what I have right now
 

gary55

Well-Known Member
Joined
Nov 27, 2012
Messages
2,917
Likes
813
#15
They only accepted returns if shipment is DOA. No longer an issue, it grenaded and I'm rebuilding the engine. But that cylinder was alot better at clearing the ports than what I have right now
CDH is using a 40mm stroke long rod with B type piston and 2 base gaskets. So with the longer stroke and 2 bases the top of the piston opens the transfers almost if not completely. Your 38mm stroke with a single base won't work well with a cdh jug.
 
Joined
Sep 26, 2018
Messages
96
Likes
4
#16
CDH is using a 40mm stroke long rod with B type piston and 2 base gaskets. So with the longer stroke and 2 bases the top of the piston opens the transfers almost if not completely. Your 38mm stroke with a single base won't work well with a cdh jug.
Note taken, I compensated with 3 base gaskets and sanded alot off the top of the cylinder. What you say makes sense for how it's set up stock.

Edit: Does anyone know where I could find a cylinder base plate to raise the cylinder without as many paper base gaskets.
 

Top