Head gasket layers question
12-05-2015, 05:41 PM
#1
Senior Member
Thread Starter
iTrader: (3)
Join Date: Oct 2008
Location: Indianapolis
Posts: 610
Total Cats: 12
Head gasket layers question
I picked up a Felpro 9717 PT MLS head gasket for 94-00 Miatas to use on my VVT engine with coolant reroute at rockauto for $22. The box says Made in Japan and "replaces BP05-10-271, what is this? It seems thick, my caliper broke so I cant measure it. Do the stock oem gaskets have 3 layers or 4?
Thanks
Thanks
Reply
0
0
12-06-2015, 04:26 PM
#5
Boost Pope
iTrader: (8)
Join Date: Sep 2005
Location: Chicago. (The less-murder part.)
Posts: 33,015
Total Cats: 6,587
A few basic truths:
The head gasket in the '90-'00 engines was of a very ordinary design.
The cooling system design in those engines, however, was pretty awful. The thermostat being located at the front of the head meant that the back of the engine didn't get much cooling when it was open.
In '01, coincident with the switch to VVT, Mazda changed the design of the head gasket. The blocked off most of the cooling ports around the #1 cylinder, and around the forward half of #2.
This improved the coolant flow through the engine somewhat, but it still wasn't as good as the original (FWD) design, which is what a rear-thermostat reroute restores. Worse, doing a reroute on an engine with the '01-'05 style head gasket will cause more harm than good, by completely stagnating the coolant around #1.
That said, btabor is on target wanting to install a '94-'00 gasket on his VVT engine and do a reroute. This is the best solution.
To directly answer the original question, I have no idea WTF BP05-10-271 is. Rosenthal doesn't recognize it, and I can't find it in any of the catalogs. The p/n for the '94-'00 HG is BP26-10-271, and the stock '01+ gasket is BP6D-10-217. It's possible that BP05-10-271 might have been used in the MSM engine, but that's only a wild guess.
Visually compare your gasket to the picture I posted above.
The head gasket in the '90-'00 engines was of a very ordinary design.
The cooling system design in those engines, however, was pretty awful. The thermostat being located at the front of the head meant that the back of the engine didn't get much cooling when it was open.
In '01, coincident with the switch to VVT, Mazda changed the design of the head gasket. The blocked off most of the cooling ports around the #1 cylinder, and around the forward half of #2.
This improved the coolant flow through the engine somewhat, but it still wasn't as good as the original (FWD) design, which is what a rear-thermostat reroute restores. Worse, doing a reroute on an engine with the '01-'05 style head gasket will cause more harm than good, by completely stagnating the coolant around #1.
That said, btabor is on target wanting to install a '94-'00 gasket on his VVT engine and do a reroute. This is the best solution.
To directly answer the original question, I have no idea WTF BP05-10-271 is. Rosenthal doesn't recognize it, and I can't find it in any of the catalogs. The p/n for the '94-'00 HG is BP26-10-271, and the stock '01+ gasket is BP6D-10-217. It's possible that BP05-10-271 might have been used in the MSM engine, but that's only a wild guess.
Visually compare your gasket to the picture I posted above.
Last edited by Joe Perez; 12-06-2015 at 06:15 PM.
Reply
0
0
12-06-2015, 04:37 PM
#6
SADFab Destructive Testing Engineer
iTrader: (5)
Join Date: Apr 2014
Location: Beaverton, USA
Posts: 18,642
Total Cats: 1,866
A few basic truths:
The head gasket in the '90-'00 engines was of a very ordinary design.
The cooling system design in those engines, however, was pretty awful. The thermostat being located at the front of the head meant that the back of the engine didn't get much cooling when it was open.
In '01, coincident with the switch to VVT, Mazda changed the design of the head gasket. The blocked off most of the cooling ports around the #1 cylinder, and around the forward half of #2.
This improved the coolant flow through the engine somewhat, but it still wasn't as good as the original (FWD) design, which is what a rear-thermostat reroute restores. Worse, doing a reroute on an engine with the '01-'05 style head gasket will cause more harm than good, by completely stagnating the coolant around #1.
That said, btabor is on target wanting to install a '94-'00 gasket on his VVT engine and do a reroute. This is the best solution.
To directly answer the original question, I have no idea WTF BP05-10-271 is. Rosenthal doesn't recognize it, and I can't find it in any of the catalogs. The p/n for the '94-'00 HG is BP26-10-271, and the stock '01+ gasket is BP6D-10-217. It's possible that BP05-10-271 might have been used in the MSM engine, but that's only a wild guess.
Visually compare your gasket to the picture I posted above.
The head gasket in the '90-'00 engines was of a very ordinary design.
The cooling system design in those engines, however, was pretty awful. The thermostat being located at the front of the head meant that the back of the engine didn't get much cooling when it was open.
In '01, coincident with the switch to VVT, Mazda changed the design of the head gasket. The blocked off most of the cooling ports around the #1 cylinder, and around the forward half of #2.
This improved the coolant flow through the engine somewhat, but it still wasn't as good as the original (FWD) design, which is what a rear-thermostat reroute restores. Worse, doing a reroute on an engine with the '01-'05 style head gasket will cause more harm than good, by completely stagnating the coolant around #1.
That said, btabor is on target wanting to install a '94-'00 gasket on his VVT engine and do a reroute. This is the best solution.
To directly answer the original question, I have no idea WTF BP05-10-271 is. Rosenthal doesn't recognize it, and I can't find it in any of the catalogs. The p/n for the '94-'00 HG is BP26-10-271, and the stock '01+ gasket is BP6D-10-217. It's possible that BP05-10-271 might have been used in the MSM engine, but that's only a wild guess.
Visually compare your gasket to the picture I posted above.
That's what I meant in my other post
Reply
0
0
12-06-2015, 05:35 PM
#7
Senior Member
Thread Starter
iTrader: (3)
Join Date: Oct 2008
Location: Indianapolis
Posts: 610
Total Cats: 12
Thanks for all the info. I plugged that part number on the mazda competititon website and it came up with a gasket that is $48. The 99 head gasket is $49 or so. The felpro one looks exactly like the 99 oem gasket. I measured the felpro and even though it has 4 layers instead of the oem 3 layers it measures 0.032". I belive the oem is 0.040". I also shaved my head 0.030" so I think I will achieve a cr of around 10.8:1 which is exactly what I wanted since I will run 93 octane and tune with my MS3.
I'm hoping I'll make around 150whp with that compression, flat top and racing beat header.
I'm hoping I'll make around 150whp with that compression, flat top and racing beat header.
Reply
0
0
12-06-2015, 07:53 PM
#9
Senior Member
Thread Starter
iTrader: (3)
Join Date: Oct 2008
Location: Indianapolis
Posts: 610
Total Cats: 12
Joe Perez. I have been researching how many degrees of timing a 0.030" head shave will cause. I have read anything from 0.5 to 2 degrees. I'm thinking on getting an adjustable cam gear and set it at 1.5 degrees advances on the exhaust side and start dyno tuning from there. Does that sound like a decent plan?
Reply
0
0
12-07-2015, 11:59 AM
#10
Boost Pope
iTrader: (8)
Join Date: Sep 2005
Location: Chicago. (The less-murder part.)
Posts: 33,015
Total Cats: 6,587
Joe Perez. I have been researching how many degrees of timing a 0.030" head shave will cause. I have read anything from 0.5 to 2 degrees. I'm thinking on getting an adjustable cam gear and set it at 1.5 degrees advances on the exhaust side and start dyno tuning from there. Does that sound like a decent plan?
I believe what you are asking is whether shaving the head by 0.030" will cause the camshaft timing to become retarded, and thus, require compensation by the use of adjustable cam gears. Correct?
The answer is no.
Well, in theory, decreasing the distance between the camshafts and the crankshaft will alter the valve timing. But compare the change being made (three one-hundredths of an inch) to the nominal distance between the crankshaft and the camshafts (a foot and a half, maybe?) and then try to get a sense of proportion as to the magnitude of the change here. I'm going to do the math, but we're talking about a change on the order of maybe a few tenths of a degree, if not a few hundredths? Whatever it is, it's going to be so small that you'll never be able to measure it, as the slop inherent in the cam belt will outweigh it by several orders of magnitude.
Trying to correct for such a minute change is like trying to improve the fuel economy of the vehicle by removing that one dead mosquito that's stuck to the front bumper. Theoretically plausible, but utterly impractical in the real world.
Reply
0
0
12-07-2015, 12:45 PM
#11
Former Vendor
iTrader: (31)
Join Date: Nov 2006
Location: Sunnyvale, CA
Posts: 15,442
Total Cats: 2,099
Well, in theory, decreasing the distance between the camshafts and the crankshaft will alter the valve timing. But compare the change being made (three one-hundredths of an inch) to the nominal distance between the crankshaft and the camshafts (a foot and a half, maybe?) and then try to get a sense of proportion as to the magnitude of the change here. I'm going to do the math, but we're talking about a change on the order of maybe a few tenths of a degree, if not a few hundredths?
Reply
0
0
12-07-2015, 12:57 PM
#12
Boost Pope
iTrader: (8)
Join Date: Sep 2005
Location: Chicago. (The less-murder part.)
Posts: 33,015
Total Cats: 6,587
Unless you happen to have a variable-diameter exhaust cam pulley.
Reply
0
0
12-07-2015, 01:15 PM
#14
Senior Member
Thread Starter
iTrader: (3)
Join Date: Oct 2008
Location: Indianapolis
Posts: 610
Total Cats: 12
I honestly think 13 degrees is not true. I calculated it on my Honda Crx when I was in high school, back in the days and it came up to 3 degrees with a 0.040" shave.
It would be nice to get results from someone who actually measured with a timing wheel.
It would be nice to get results from someone who actually measured with a timing wheel.
Reply
0
0
12-07-2015, 01:17 PM
#15
Senior Member
Thread Starter
iTrader: (3)
Join Date: Oct 2008
Location: Indianapolis
Posts: 610
Total Cats: 12
Another thing, most people in this forum states the oem gasket is 0.040", I read from Quinn at clubroadster.net that it is 0.020" and then read from Emilio that it is 0.031" (which is the same as my felpro).
Reply
0
0
12-07-2015, 01:44 PM
#18
Senior Member
Thread Starter
iTrader: (3)
Join Date: Oct 2008
Location: Indianapolis
Posts: 610
Total Cats: 12
I'm pretty sure each tooth is 12 degrees not 2.5. So much misleading information, one person says one thing the next one says something completely different
Reply
0
0
