BBC dome fitting

richie 2 · 04-01-2014, 07:04 AM

big old sealedpower dome piston fitting into the chamber of a #781 oval port/open chamber head. quite a job..the main area by the exh. valve.... any tips or other spots to check? tks.

Keith 944 · 04-01-2014, 08:44 AM

check the sides of the domes for barely hitting the head. had this happen on some closed chamber heads....as you prob. know, use clay and check without head gasket. too much clearance is better than not enough, lol

richie 2 · 04-01-2014, 09:01 AM

10 o'clock area looking into the exh. port is the major interference spot. ill play/doe the sparkplug to get that clearance. usual .005'' deck and .041'' gasket. im laying back both the dome and & chamber a touch at a time. I agree, better enough room than too close...just call me the human milling machine.

Adger Smith · 04-02-2014, 09:48 AM

Put the head on the empty block and scribe the head in the area of the ex. Lay the head back to the cylinder wall and then scoop the quench area out on that side to direct the flow toward the ex port/valve. The spark plug tip needs to be at least .100 away from the piston when it is positioned @ approx 36-40 degrees before TDC. .035-.040 @ TDC. I've done this on a couple of SS engines as well as shifted the heads with offset dowels (intake toward the center of the cylinder) and seen over .010 in ET & some MPH improvement .

richie 2 · 04-03-2014, 10:58 AM

lots of room everywhere else after testing. going to file a slight angle of the chambers edge at the exh. valve/dome area to be sure theres enough room at its radius. that will give us more room there being the closest and hard to measure.

Tim H · 04-03-2014, 01:00 PM

Are you working with a 4.250 or larger bore ? I have done a couple 454 based motrs w/049 heads and big old Speed Pro open chamber pistons with good results.

richie 2 · 04-03-2014, 01:56 PM

tks everyone. tim yes it's a 4.310'' bore x 454ci stroke w/781 head. so you had relieving to do?

Tim H · 04-03-2014, 08:16 PM

Yup, in the exh valve area, I had switched to 1.88 " valves as well. A bit off dome and a bit of chamfering on chamber as I recall.

richie 2 · 04-05-2014, 10:07 AM

tim this is parkers bbc/monty stuff. solid cam now... vast improvement over previous combo. hope your ready to go, wont be long ...sp.

04-01-2014, 07:04 AM	#1
richie 2 Senior Member Join Date: Feb 2009 Posts: 918 Likes: 321 Liked 157 Times in 73 Posts	BBC dome fitting big old sealedpower dome piston fitting into the chamber of a #781 oval port/open chamber head. quite a job..the main area by the exh. valve.... any tips or other spots to check? tks. Last edited by richie 2; 04-01-2014 at 09:03 AM.

04-01-2014, 08:44 AM	#2
Keith 944 VIP Member Join Date: Feb 2006 Location: Dela-where? Posts: 2,116 Likes: 1,004 Liked 1,649 Times in 521 Posts	Re: BBC dome fitting check the sides of the domes for barely hitting the head. had this happen on some closed chamber heads....as you prob. know, use clay and check without head gasket. too much clearance is better than not enough, lol __________________ KEITH MAYERS 2 X somebody many X nobody Last edited by Keith 944; 04-01-2014 at 08:53 AM.

04-01-2014, 09:01 AM	#3
richie 2 Senior Member Join Date: Feb 2009 Posts: 918 Likes: 321 Liked 157 Times in 73 Posts	Re: BBC dome fitting 10 o'clock area looking into the exh. port is the major interference spot. ill play/doe the sparkplug to get that clearance. usual .005'' deck and .041'' gasket. im laying back both the dome and & chamber a touch at a time. I agree, better enough room than too close...just call me the human milling machine. Last edited by richie 2; 04-01-2014 at 11:08 AM.

04-02-2014, 09:48 AM	#4
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,349 Likes: 435 Liked 678 Times in 262 Posts	Re: BBC dome fitting Put the head on the empty block and scribe the head in the area of the ex. Lay the head back to the cylinder wall and then scoop the quench area out on that side to direct the flow toward the ex port/valve. The spark plug tip needs to be at least .100 away from the piston when it is positioned @ approx 36-40 degrees before TDC. .035-.040 @ TDC. I've done this on a couple of SS engines as well as shifted the heads with offset dowels (intake toward the center of the cylinder) and seen over .010 in ET & some MPH improvement . __________________ Adger Smith (Former SS) Last edited by Adger Smith; 04-02-2014 at 09:52 AM. Reason: sp

04-03-2014, 10:58 AM	#5
richie 2 Senior Member Join Date: Feb 2009 Posts: 918 Likes: 321 Liked 157 Times in 73 Posts	Re: BBC dome fitting lots of room everywhere else after testing. going to file a slight angle of the chambers edge at the exh. valve/dome area to be sure theres enough room at its radius. that will give us more room there being the closest and hard to measure. Last edited by richie 2; 04-03-2014 at 01:54 PM.

04-03-2014, 01:00 PM	#6
Tim H VIP Member Join Date: Jan 2007 Posts: 1,010 Likes: 898 Liked 430 Times in 142 Posts	Re: BBC dome fitting Are you working with a 4.250 or larger bore ? I have done a couple 454 based motrs w/049 heads and big old Speed Pro open chamber pistons with good results.

04-03-2014, 01:56 PM	#7
richie 2 Senior Member Join Date: Feb 2009 Posts: 918 Likes: 321 Liked 157 Times in 73 Posts	Re: BBC dome fitting tks everyone. tim yes it's a 4.310'' bore x 454ci stroke w/781 head. so you had relieving to do?

04-03-2014, 08:16 PM	#8
Tim H VIP Member Join Date: Jan 2007 Posts: 1,010 Likes: 898 Liked 430 Times in 142 Posts	Re: BBC dome fitting Yup, in the exh valve area, I had switched to 1.88 " valves as well. A bit off dome and a bit of chamfering on chamber as I recall.

04-05-2014, 10:07 AM	#9
richie 2 Senior Member Join Date: Feb 2009 Posts: 918 Likes: 321 Liked 157 Times in 73 Posts	Re: BBC dome fitting tim this is parkers bbc/monty stuff. solid cam now... vast improvement over previous combo. hope your ready to go, wont be long ...sp. Last edited by richie 2; 04-05-2014 at 11:03 AM.