99 head swap and compression - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


Engine Performance This section is for discussion on all engine building related questions.
Sponsored by:
Sponsored by:

Reply
 
 
 
LinkBack Thread Tools Search this Thread
Old 02-18-2009, 12:42 PM   #1
Newb
Thread Starter
 
Join Date: Sep 2008
Location: UK
Posts: 39
Total Cats: 0
Default 99 head swap and compression

Hi all, I'm currently rebuilding a 99 head and intake to fit on my 1.8 mk1 (94) as I know that there are gains to be made from the head as it flows much freer than the stock head/intake. After this I will be making a choice as to whether I should stay NA or go turbo (for drift).

My question is, what does a 99 head swap do to the compression figures? Does it raise or lower compression of the engine? (assuming stock head gasket is used)

Also would like to hear from anyone whos turbo'd with a 99 head swap, was it worth while?
Seal is offline   Reply With Quote
Old 02-18-2009, 01:16 PM   #2
Elite Member
iTrader: (22)
 
Join Date: Dec 2006
Location: Sunny Spanish speaking Non US Caribbean
Posts: 3,257
Total Cats: 3
Default

Quote:
Originally Posted by Seal View Post
Hi all, I'm currently rebuilding a 99 head and intake to fit on my 1.8 mk1 (94) as I know that there are gains to be made from the head as it flows much freer than the stock head/intake. After this I will be making a choice as to whether I should stay NA or go turbo (for drift).

My question is, what does a 99 head swap do to the compression figures? Does it raise or lower compression of the engine? (assuming stock head gasket is used)

Also would like to hear from anyone whos turbo'd with a 99 head swap, was it worth while?
Welcome aboard seal. You should've taken the time to read the FAQs and do a search. You would've found the answers to all your questions.

FWIW, a 99 head swap is common and it sure means much better figures all around.

Now; please post your location below your avatar.
Rafa is offline   Reply With Quote
Old 02-18-2009, 01:39 PM   #3
Newb
Thread Starter
 
Join Date: Sep 2008
Location: UK
Posts: 39
Total Cats: 0
Default

Thanks Rafta. I've done a lot of searching on this on many different miata forums but have never found the answer, theres a lot of talk of 99 head swaps, and a lot of separate talk about compression ratios but I have never found a straighforward answer of the compression ratio of a 99 head on a 94, 1.8 engine. (which is what i'm hoping to find out)... unless my search skills are that bad!
Seal is offline   Reply With Quote
Old 02-18-2009, 07:18 PM   #4
Elite Member
iTrader: (5)
 
akaryrye's Avatar
 
Join Date: Jul 2006
Location: Central California
Posts: 2,526
Total Cats: 0
Default

true, i dunno if ive ever heard that either. Is the compression difference due to piston differences in the motor or less quench area due to head design? Is the head gasket the same thickness? The answer to these questions would help find the answer.
akaryrye is offline   Reply With Quote
Old 02-18-2009, 07:54 PM   #5
Junior Member
iTrader: (1)
 
Join Date: Oct 2007
Location: San Diego, Ca
Posts: 209
Total Cats: -1
Default

Its in the Pistons, they're slightly less concave than the earlier year models. if the gasket is any different, its probably only oil/water passages, doubt it matters even a minuscule amount if they changed the gasket size. I have a compression dropping head gasket for my Audi, but that bitch is like half an inch thick (not really) 2-3 mm iirc, so i dont think they would change compression with a gasket if they were already changing pistion, or, even if they weren't.
TeamPLUR is offline   Reply With Quote
Old 02-18-2009, 09:45 PM   #6
Tour de Franzia
iTrader: (6)
 
hustler's Avatar
 
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,114
Total Cats: 351
Default

its too bad you missed the part where he suggested you PUT YOUR MOTHERFUCKING LOCATION IN YOUR GOD DAMNED PROFILE. Follow the ******* rules...please.

As for compression ratio...it supposedly stays unchanged but only patsmx5 knows the truth since he measure that **** before headwork.
hustler is offline   Reply With Quote
Old 02-18-2009, 10:31 PM   #7
Moderator
iTrader: (11)
 
sixshooter's Avatar
 
Join Date: Nov 2008
Location: Tampa, Florida
Posts: 15,633
Total Cats: 1,559
Default

Quote:
Originally Posted by Seal View Post
Also would like to hear from anyone whos turbo'd with a 99 head swap, was it worth while?
Hustler did that swap just recently. Why don't you add your location details under your screen name, then ask him about it. He won't help you if you are in violation of standard protocol.
sixshooter is offline   Reply With Quote
Old 02-18-2009, 10:41 PM   #8
Elite Member
iTrader: (15)
 
patsmx5's Avatar
 
Join Date: Aug 2007
Location: Houston, TX
Posts: 8,793
Total Cats: 247
Default

Quote:
Originally Posted by hustler View Post
its too bad you missed the part where he suggested you PUT YOUR MOTHERFUCKING LOCATION IN YOUR GOD DAMNED PROFILE. Follow the ******* rules...please.

As for compression ratio...it supposedly stays unchanged but only patsmx5 knows the truth since he measure that **** before headwork.
I didn't cc the head and measure the volume before and after. But I know what dimensions I changed, and I did some quick math a while back and figured that it reduced the static compression ratio from 9.5:1 to at least 8.5:1, maybe as low as 8:1.

+1 on all the advice given. The 94 vs. 99' head should have the same volume combustion chambers. So compression should stay the same. The pistons were changed in 99' to increase the compression. Turbo FTW.
patsmx5 is offline   Reply With Quote
Old 02-18-2009, 10:45 PM   #9
Elite Member
iTrader: (46)
 
Stein's Avatar
 
Join Date: Dec 2007
Location: Nebraska
Posts: 4,812
Total Cats: 138
Default

Quote:
Originally Posted by Seal View Post
I've done a lot of searching on this on many different miata forums but have never found the answer, theres a lot of talk of 99 head swaps, and a lot of separate talk about compression ratios but I have never found a straighforward answer of the compression ratio of a 99 head on a 94, 1.8 engine. (which is what i'm hoping to find out)... unless my search skills are that bad!
I guess it is a valid question. Has someone ever cc'ed a 99 vs 94-97 to see if it alters compression, assuming the same bottom end? Me thinks it would be a negligible difference, if any, when strictly considering compression.
Stein is offline   Reply With Quote
Old 02-18-2009, 10:57 PM   #10
Tour de Franzia
iTrader: (6)
 
hustler's Avatar
 
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,114
Total Cats: 351
Default

Quote:
Originally Posted by Stein View Post
I guess it is a valid question. Has someone ever cc'ed a 99 vs 94-97 to see if it alters compression, assuming the same bottom end? Me thinks it would be a negligible difference, if any, when strictly considering compression.
well, considering the pistons are different ratios, we'd have to measure to really know. I wonder if I'm even lower than 8.5:1 with the addition of my head?
hustler is offline   Reply With Quote
Old 02-18-2009, 11:00 PM   #11
Elite Member
iTrader: (15)
 
patsmx5's Avatar
 
Join Date: Aug 2007
Location: Houston, TX
Posts: 8,793
Total Cats: 247
Default

Quote:
Originally Posted by hustler View Post
well, considering the pistons are different ratios, we'd have to measure to really know. I wonder if I'm even lower than 8.5:1 with the addition of my head?
I've seen both heads before, they "look" the same on the combustion chambers. 99' head has a slightly better angle of attack (not good, just less shitty). Diff spec cam w/ solid lifters on the 99', but other than that, they appear highly identical. If there is a difference, it's very small and largely insignificant.
patsmx5 is offline   Reply With Quote
Old 02-18-2009, 11:03 PM   #12
Elite Member
iTrader: (46)
 
Stein's Avatar
 
Join Date: Dec 2007
Location: Nebraska
Posts: 4,812
Total Cats: 138
Default

Quote:
Originally Posted by hustler View Post
well, considering the pistons are different ratios, we'd have to measure to really know. I wonder if I'm even lower than 8.5:1 with the addition of my head?
No, I'm talking about what he is talking about (I think) that if he takes off his 94-97 head and puts on a 99, will the compression ratio be any different on the same bottom end The only difference will be if the head itself is a higher or lower volume in each cylinder which will alter compression ratio. Thus, my question if anyone has actually cc'ed a 94-97 and a 99 head. I'm guessing negliglble difference unless someone works the cylinder side somewhat, which will lower compression or mill the head, which will increase it. But, stock-for-stock, are they the same cc's?

EDIT: Ahh, Pat ninja'ed ahead of me. I figured they would be close.
Stein is offline   Reply With Quote
Old 02-19-2009, 12:09 AM   #13
Elite Member
iTrader: (7)
 
Join Date: Jan 2008
Location: Knoxville, TN
Posts: 2,116
Total Cats: 43
Default

correct me if im wrong but didn't they jump to a hemispherical design on 99+? so i've got a hemi? haha

99-00 head swap does make a power difference. went and drove a 95 with similiar mods as mine and it just seemed to lag behind. and my VICs isnt even working! haha
flier129 is offline   Reply With Quote
Old 02-19-2009, 12:13 AM   #14
Elite Member
iTrader: (15)
 
patsmx5's Avatar
 
Join Date: Aug 2007
Location: Houston, TX
Posts: 8,793
Total Cats: 247
Default

Quote:
Originally Posted by flier129 View Post
correct me if im wrong but didn't they jump to a hemispherical design on 99+? so i've got a hemi? haha

99-00 head swap does make a power difference. went and drove a 95 with similiar mods as mine and it just seemed to lag behind. and my VICs isnt even working! haha
All miata heads are "hemi". VICS are normally open when not hooked up, so you won't see any more power hooking them up such that they stay closed until activated. Mine's unhooked so it just stays open all the time. Seems to work better on my setup with them open all the time.
patsmx5 is offline   Reply With Quote
Old 02-19-2009, 12:21 AM   #15
Elite Member
iTrader: (7)
 
Join Date: Jan 2008
Location: Knoxville, TN
Posts: 2,116
Total Cats: 43
Default

Quote:
Originally Posted by patsmx5 View Post
All miata heads are "hemi". VICS are normally open when not hooked up, so you won't see any more power hooking them up such that they stay closed until activated. Mine's unhooked so it just stays open all the time. Seems to work better on my setup with them open all the time.
Ah, i failed, i thought i was cool for a minute tho.

Stealth97 said he saw a 10ft-lb or so increase when he had VICS working, but he has a nice n/a build. What im stumped on is Artie's stock 99 manifold with butterflies in but not working and having more mid-range torque than the gutted 99 manifold. What caused it to have more tq if the butterflies were sitting wide-open vs not even there?
flier129 is offline   Reply With Quote
Old 02-19-2009, 12:28 AM   #16
Elite Member
iTrader: (15)
 
patsmx5's Avatar
 
Join Date: Aug 2007
Location: Houston, TX
Posts: 8,793
Total Cats: 247
Default

Quote:
Originally Posted by flier129 View Post
Ah, i failed, i thought i was cool for a minute tho.

Stealth97 said he saw a 10ft-lb or so increase when he had VICS working, but he has a nice n/a build. What im stumped on is Artie's stock 99 manifold with butterflies in but not working and having more mid-range torque than the gutted 99 manifold. What caused it to have more tq if the butterflies were sitting wide-open vs not even there?
Because they hacked the **** out of that manifold on the gutted on. Look at the pics. They got that american in 'em that says "if 3 is good, 10 is better!", so they cut all kinds of metal out. It gets technical, but long and skinny runners helps low end, short and fat runners help top end. But they took skinny and fat to the extreme. They basically tuned the intake for 14K RPMs. And lost some low end because of it.

My motor makes more power from 4k+ with the VICS open. Whether it makes a difference below 4k, dunno, but it's not noticeable.
patsmx5 is offline   Reply With Quote
Old 02-19-2009, 12:42 AM   #17
Elite Member
iTrader: (7)
 
Join Date: Jan 2008
Location: Knoxville, TN
Posts: 2,116
Total Cats: 43
Default

ah ok, gotcha. i figure ill just keep VICS in and maybe play with it post-boost. if i get all power happy ill just go for a BEGi style intake manifold.
flier129 is offline   Reply With Quote
Old 02-19-2009, 01:50 AM   #18
Tour de Franzia
iTrader: (6)
 
hustler's Avatar
 
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,114
Total Cats: 351
Default

I don't see the point in owning a miata if it doesn't have a 99 head.
hustler is offline   Reply With Quote
Old 02-19-2009, 04:23 AM   #19
Newb
Thread Starter
 
Join Date: Sep 2008
Location: UK
Posts: 39
Total Cats: 0
Default

Quote:
Originally Posted by Stein View Post
No, I'm talking about what he is talking about (I think) that if he takes off his 94-97 head and puts on a 99, will the compression ratio be any different on the same bottom end.
Yep, absolutely right, although the point you make about cc'ing should also be valid and tell us the answer right? I'm guessing many people have cc'd a 94 bottom end so we'd need someone to tell us what the cc value is of a 99 head and we should be able to calculate the compression ratio with that right? (assuming we use a standard head gasket).

Anyway, the reason why i wanted to know is, that i wanted to find out if the 99 head swap makes the engine better for NA (by increasing compression) or better for turbo (by decreasing compression).

and apologies for the location; now added
Seal is offline   Reply With Quote
Old 02-19-2009, 06:11 PM   #20
Elite Member
iTrader: (46)
 
Stein's Avatar
 
Join Date: Dec 2007
Location: Nebraska
Posts: 4,812
Total Cats: 138
Default

Quote:
Originally Posted by Seal View Post
Anyway, the reason why i wanted to know is, that i wanted to find out if the 99 head swap makes the engine better for NA (by increasing compression) or better for turbo (by decreasing compression).
Neither of the reasons above. It's better for both NA AND turbo applications because it FLOWS better. That's it in a nutshell.
Stein is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Project Gemini - Turbo Civic on the Cheap Full_Tilt_Boogie Build Threads 57 07-19-2017 05:11 PM
Another Cast Manifold Corky Bell Prefabbed Turbo Kits 18 11-22-2016 10:01 PM
Noob to Miataturbo from MA JxPhan Meet and Greet 3 10-02-2015 03:17 AM
Bad head gasket or ? shooterschmidty Engine Performance 8 09-30-2015 11:28 PM
Low oil pressure after 1.8 swap and new turbo setup JesseTheNoob DIY Turbo Discussion 15 09-30-2015 03:44 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 02:14 AM.