Heads and head gasket combo question
Thread Starter
Instructor
Joined: Aug 2021
Posts: 102
Likes: 7
From: Alabama
Heads and head gasket combo question
I’ll make this short, I have a 1988 L98 motor with a FIRST TPI and long tube headers leading to h-pipe exaust. I want new heads and the two options I see are AFR 195cc eliminators (or whatever the CNC ones are) which I can get milled down by them to 58cc chambers and use a felpro 1003 (.043) gasket to get a static ratio of 9.5:1 or so, they also correct geometry for the grind. The other option is promaxx maxx 190cc which they said they can mill to 62cc chamber and if I do a felpro 1094(?) (.015) it’ll have a static compression of 9.74:1. I’ll save money with the promaxx but I don’t wanna cheap out and decrease reliability. I haven’t chosen a cam yet as my choice here will influence cam choice. What do y’all think?
Burning Brakes
Joined: Nov 2012
Posts: 788
Likes: 100
From: Indianapolis IN
You should shoot for a finished quench distance of .039 to .044 or very close with the head gasket, do not attempt to adjust compression without staying within this parameter.
Big price and high quality flow difference btw these 2 choices, one is arguably the best off the shelf without any additional porting and with quality hardware. All I know about the Promaxx is that they may be the better of the least expensive castings but IDK about their hardware.
Likely it would be best to buy the Promaxx bare and have them assembled and tuned-up locally with your own hardware, buy your springs with the cam too.
I went for the AFR for a few reasons.
Edit : I wouldn't worry about 10.0 -1 or 10.50 -1 compression with AL heads.
Big price and high quality flow difference btw these 2 choices, one is arguably the best off the shelf without any additional porting and with quality hardware. All I know about the Promaxx is that they may be the better of the least expensive castings but IDK about their hardware.
Likely it would be best to buy the Promaxx bare and have them assembled and tuned-up locally with your own hardware, buy your springs with the cam too.
I went for the AFR for a few reasons.
Edit : I wouldn't worry about 10.0 -1 or 10.50 -1 compression with AL heads.
Thread Starter
Instructor
Joined: Aug 2021
Posts: 102
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From: Alabama
I talked to a guy I work with who’s built SBC engines in the past and he said about the same thing, so I think I’ll go with the AFR’s. Replacing heads is just entirely new to me so I don’t wanna over spend unnecessarily or cheap out if it’s something I should save up for, and it’s sounding like something I should save up for. AFR recommended the 1003 which are .043 compressed so that should be good right?
Instructor
Joined: Sep 2020
Posts: 121
Likes: 47
From: Sullivan, MO
I talked to a guy I work with who’s built SBC engines in the past and he said about the same thing, so I think I’ll go with the AFR’s. Replacing heads is just entirely new to me so I don’t wanna over spend unnecessarily or cheap out if it’s something I should save up for, and it’s sounding like something I should save up for. AFR recommended the 1003 which are .043 compressed so that should be good right?
Another option, which I will likely do, is have TPIS CNC port your stock heads. They get around 260cfm of flow and keep you stock chamber size for compression.
Safety Car
Joined: Sep 2001
Posts: 4,160
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From: Glenbeulah Wi
Burning Brakes
Joined: Sep 2017
Posts: 941
Likes: 170
I’ll make this short, I have a 1988 L98 motor with a FIRST TPI and long tube headers leading to h-pipe exaust. I want new heads and the two options I see are AFR 195cc eliminators (or whatever the CNC ones are) which I can get milled down by them to 58cc chambers and use a felpro 1003 (.043) gasket to get a static ratio of 9.5:1 or so, they also correct geometry for the grind. The other option is promaxx maxx 190cc which they said they can mill to 62cc chamber and if I do a felpro 1094(?) (.015) it’ll have a static compression of 9.74:1. I’ll save money with the promaxx but I don’t wanna cheap out and decrease reliability. I haven’t chosen a cam yet as my choice here will influence cam choice. What do y’all think?
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Thread Starter
Instructor
Joined: Aug 2021
Posts: 102
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From: Alabama
I called AFR and they said the felpro 1093 gasket should be fine for their 180cc eliminator heads. That should make my total quench .045 max .035 min. I’ll need to change my chamber to compensate for the thinner gasket though, with the cam I’m getting I’m already at max dynamic compression for pump gas.
Thread Starter
Instructor
Joined: Aug 2021
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From: Alabama
So the current build data is this just in case anyone is looking to do something similar.
AFR 180cc SBC Street Cylinder Head - Angled Plug custom called 60cc chamber.
Fel-pro 1094 Shim Headgasket 0.015” compressed
Comp Cams XR276HR 224/230 110LSA .502/.51 lift
1.5 Roller Rockers (unpicked for band or style)
ARP 134-3701 Head Bolt Kit
What’s already on the Vehicle
FIRST TPI intake
27lb Bosch D3 Injectors @ 43.5psi 25lb @ 39.15psi
adjustable fuel pressure regulator
high flow fuel pump (45gph max 40gph min, 123.25psi max 79.8psi min) turbine style
Long tube Headers to H-pipe exhaust
160° Thermostat
all other mods won’t effect engine peak performance
With this configuration compression is 9.91, dynamic compression is 8.37, quench is about .040. Roughly estimated horse power using some random calculator is 437 @ 6036rpm but that’s not accounting for the FIRST system or the exact cam so it’ll likely be 380-420 @ 53-5800 rpm
AFR 180cc SBC Street Cylinder Head - Angled Plug custom called 60cc chamber.
Fel-pro 1094 Shim Headgasket 0.015” compressed
Comp Cams XR276HR 224/230 110LSA .502/.51 lift
1.5 Roller Rockers (unpicked for band or style)
ARP 134-3701 Head Bolt Kit
What’s already on the Vehicle
FIRST TPI intake
27lb Bosch D3 Injectors @ 43.5psi 25lb @ 39.15psi
adjustable fuel pressure regulator
high flow fuel pump (45gph max 40gph min, 123.25psi max 79.8psi min) turbine style
Long tube Headers to H-pipe exhaust
160° Thermostat
all other mods won’t effect engine peak performance
With this configuration compression is 9.91, dynamic compression is 8.37, quench is about .040. Roughly estimated horse power using some random calculator is 437 @ 6036rpm but that’s not accounting for the FIRST system or the exact cam so it’ll likely be 380-420 @ 53-5800 rpm