408 build
Thread Starter
Teching In
Joined: Feb 2025
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408 build Hello. This is my first post and I'm new to the LS builds. I have a lot of questions so hopefully you guys can point me in the right direction.
I'm building a 408 stroker from a Gen 3 Escalade block 'N' casting 2002.
I've used the summit compression calculator and these are the numbers.
Bore - 4.030
Stroke - 4
Cyl volume - 65
Dome volume - 8
Deck - .005 in the hole (avg from 8 cyl(.002-.009)
Gasket compressed - .040
= 11.14 roughly
Parts for the short block are the summit pro LS kit.
SUM-R24400308
Camshaft - btr stage 2 ls7 230/25x 650 lift 116 lobe
Heads - 245 afr ls1
F.A.S.T intake
I'm trying to get to 12:1 compression. Is this too much compression for the cam? I'm possibly going to put a bigger cam in it later. I just want the torque down low.
Will I have any fitment issues with the intake if I mill the heads down to 58 cc?
I'm going to use cometic gasket c15517-40.
Is there any gasket thinner than this for better quench?
Arp calls for a bore of 2.100 gasket. I've found a cometic gasket that is 1.190 but is thinner c5319-036. Would I run into any issues using the smaller bore gasket? Not many options on the 2.100..
Like I said this is my first LS build and I'm okay with constructive criticism. My numbers and thought process could be completely wrong but that's why I'm here. Thanks
I'm building a 408 stroker from a Gen 3 Escalade block 'N' casting 2002.
I've used the summit compression calculator and these are the numbers.
Bore - 4.030
Stroke - 4
Cyl volume - 65
Dome volume - 8
Deck - .005 in the hole (avg from 8 cyl(.002-.009)
Gasket compressed - .040
= 11.14 roughly
Parts for the short block are the summit pro LS kit.
SUM-R24400308
Camshaft - btr stage 2 ls7 230/25x 650 lift 116 lobe
Heads - 245 afr ls1
F.A.S.T intake
I'm trying to get to 12:1 compression. Is this too much compression for the cam? I'm possibly going to put a bigger cam in it later. I just want the torque down low.
Will I have any fitment issues with the intake if I mill the heads down to 58 cc?
I'm going to use cometic gasket c15517-40.
Is there any gasket thinner than this for better quench?
Arp calls for a bore of 2.100 gasket. I've found a cometic gasket that is 1.190 but is thinner c5319-036. Would I run into any issues using the smaller bore gasket? Not many options on the 2.100..
Like I said this is my first LS build and I'm okay with constructive criticism. My numbers and thought process could be completely wrong but that's why I'm here. Thanks
TECH Fanatic
Joined: Aug 2009
Posts: 1,845
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From: Coast of San Mateo County Between Pacifica & HMB
#1. ABSOLUTELY the WRONG Cam for those cylinder heads!
The AFR 245 Cathedral heads will work best with between +4*-+8* extra exhaust duration vs
intake duration for the majority of street applications with a good exhaust system.
A good "low end torque" spec for a 408" with AFR 245 heads would be something
~ like 235*/243* 114*+2* .621"/.604".
Look at Cam Motion Cams for Cathedral Head Stroker applications for a general idea
and remember that the AFR Cathedrals have exceptional exhaust port flows and
need even less split, let alone compared to Rectangle port heads.
What is the application, weight, transmission and rear gears also.
Just my .02
The AFR 245 Cathedral heads will work best with between +4*-+8* extra exhaust duration vs
intake duration for the majority of street applications with a good exhaust system.
A good "low end torque" spec for a 408" with AFR 245 heads would be something
~ like 235*/243* 114*+2* .621"/.604".
Look at Cam Motion Cams for Cathedral Head Stroker applications for a general idea
and remember that the AFR Cathedrals have exceptional exhaust port flows and
need even less split, let alone compared to Rectangle port heads.
What is the application, weight, transmission and rear gears also.
Just my .02
Thread Starter
Teching In
Joined: Feb 2025
Posts: 15
Likes: 1
#1. ABSOLUTELY the WRONG Cam for those cylinder heads!
The AFR 245 Cathedral heads will work best with between +4*-+8* extra exhaust duration vs
intake duration for the majority of street applications with a good exhaust system.
A good "low end torque" spec for a 408" with AFR 245 heads would be something
~ like 235*/243* 114*+2* .621"/.604".
Look at Cam Motion Cams for Cathedral Head Stroker applications for a general idea
and remember that the AFR Cathedrals have exceptional exhaust port flows and
need even less split, let alone compared to Rectangle port heads.
What is the application, weight, transmission and rear gears also.
Just my .02
The AFR 245 Cathedral heads will work best with between +4*-+8* extra exhaust duration vs
intake duration for the majority of street applications with a good exhaust system.
A good "low end torque" spec for a 408" with AFR 245 heads would be something
~ like 235*/243* 114*+2* .621"/.604".
Look at Cam Motion Cams for Cathedral Head Stroker applications for a general idea
and remember that the AFR Cathedrals have exceptional exhaust port flows and
need even less split, let alone compared to Rectangle port heads.
What is the application, weight, transmission and rear gears also.
Just my .02
Torquey stroker LS cam (235/242-114+4) cathedral port
Oddly enough I saw this cam and considered it but went with the BTR.
This will be an LS swap for a '71 Cutlass convertible.
Trans - 4L80e
Weight - Google search shows 3600
Gears - this is tricky, 411+ I am going to put 24 or 26-in rims on the car. (Yes, I'm one of those guys) So that will add to the weight of the car. I'm thinking 3900, shrug.
This of course is why I wanted the torque down low to get the car moving.
NAVYBLUE, do you have any experience with this torquey stroker cam? I will sell the BTR cam and cut my loss, but yes I don't want to go into this build without doing it correctly. Thanks
Thread Starter
Teching In
Joined: Feb 2025
Posts: 15
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So the 4.190 is a tad smaller but some gasket will be in the combustion chamber. not much but some. Didn't know if that would create an issue.. Hope that made sense..lol
TECH Fanatic
Joined: Aug 2009
Posts: 1,845
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From: Coast of San Mateo County Between Pacifica & HMB
I have no experience with that specific cam, however I did have a custom cam done by Cam Motion and their product and service was/is
exceptional. I would target 11.5:1 compression max on a street car with 91/93. Even with 24/26" rims for a convertible cruiser street car
I would go 3.73, 3.90s max with a 2800 stall converter you will have a hard time hooking up with the torquey stroker cam with those heads, but still
have a brutally fast cruiser, hopefully upgrading the brakes and suspension as well.
exceptional. I would target 11.5:1 compression max on a street car with 91/93. Even with 24/26" rims for a convertible cruiser street car
I would go 3.73, 3.90s max with a 2800 stall converter you will have a hard time hooking up with the torquey stroker cam with those heads, but still
have a brutally fast cruiser, hopefully upgrading the brakes and suspension as well.
Thread Starter
Teching In
Joined: Feb 2025
Posts: 15
Likes: 1
I have no experience with that specific cam, however I did have a custom cam done by Cam Motion and their product and service was/is
exceptional. I would target 11.5:1 compression max on a street car with 91/93. Even with 24/26" rims for a convertible cruiser street car
I would go 3.73, 3.90s max with a 2800 stall converter you will have a hard time hooking up with the torquey stroker cam with those heads, but still
have a brutally fast cruiser, hopefully upgrading the brakes and suspension as well.
exceptional. I would target 11.5:1 compression max on a street car with 91/93. Even with 24/26" rims for a convertible cruiser street car
I would go 3.73, 3.90s max with a 2800 stall converter you will have a hard time hooking up with the torquey stroker cam with those heads, but still
have a brutally fast cruiser, hopefully upgrading the brakes and suspension as well.
11:5 is probably the better approach too. I'll have to mill the heads to 62 cc's to achieve it but that should keep the intake lined up. which is great.
Brakes and suspension are a must.This is a 6 year project and I'm finally starting to see the light on getting it done! Appreciate the input..
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Thread Starter
Teching In
Joined: Feb 2025
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I accidentally bought the 4.060 gasket. I am going to use what you recommended. The c5319. I don't feel like it will be a problem. Thanks
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@02EBC5Z06 brings up a good point
Since the heads are designed for larger displacement LSX motors it might be good to do a quick check of the worst case dimension cross-section on the chambers. That being said, a 454LSX is 4.185", so they probably wanted to have safety margin to accommodate that bore size, not that the chamber required it.
AFR states the smallest bore allowed to clear the valves, is only 4.0", so doubtful the chamber cross-section is significantly bigger than that. Therefore unlikely the .01" smaller diameter is an issue, but never hurts to confirm. To put it in perspective, you're talking 0.5mm radial difference (just slightly thicker than a fingernail).
Since the heads are designed for larger displacement LSX motors it might be good to do a quick check of the worst case dimension cross-section on the chambers. That being said, a 454LSX is 4.185", so they probably wanted to have safety margin to accommodate that bore size, not that the chamber required it.
AFR states the smallest bore allowed to clear the valves, is only 4.0", so doubtful the chamber cross-section is significantly bigger than that. Therefore unlikely the .01" smaller diameter is an issue, but never hurts to confirm. To put it in perspective, you're talking 0.5mm radial difference (just slightly thicker than a fingernail).
Thread Starter
Teching In
Joined: Feb 2025
Posts: 15
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Okay so I just got my heads back and they were milled down to 62 cc's and am looking forward to continuing with this build.
I'm still stuck on camshafts and will probably go with the cam motion torquey stroker but I have other options and wanted some opinions. I'm going to lay out a few here and whatever one you'd pick I'd like to know why. Or you can pick it just because..
Tick Performance Cathedral Port Stroker Stage 1 Camshaft
236/245 | .625”/.610” | LSA112+3
Tick Performance Cathedral Port Stroker Stage 2 Camshaft
242/249 | .630”/.610” | LSA112+2
cam motion Torquey Stroker LS Camshaft (235/242-114+4) for Cathedral Port
TSP Tsunami Stage 4 Cam Specs: 235/240 .629"/.615" 111 LSA
TSP Magic Stick 4 Cam Specs: 239/242 .649"/.600" 111.5 LSA
As previously stated I want power all around but mostly low end, snappy
I'm still stuck on camshafts and will probably go with the cam motion torquey stroker but I have other options and wanted some opinions. I'm going to lay out a few here and whatever one you'd pick I'd like to know why. Or you can pick it just because..
Tick Performance Cathedral Port Stroker Stage 1 Camshaft
236/245 | .625”/.610” | LSA112+3
Tick Performance Cathedral Port Stroker Stage 2 Camshaft
242/249 | .630”/.610” | LSA112+2
cam motion Torquey Stroker LS Camshaft (235/242-114+4) for Cathedral Port
TSP Tsunami Stage 4 Cam Specs: 235/240 .629"/.615" 111 LSA
TSP Magic Stick 4 Cam Specs: 239/242 .649"/.600" 111.5 LSA
As previously stated I want power all around but mostly low end, snappy
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- Header type, primary size
- Exhaust size, dual, dual crossover, single, muffler type, open headers, cats
- Vehicle weight
- Rear gear ratio
- Manual or automatic, 1st gear trans ratio, torque converter stall
- Peak shift rpm
- Typical cruise rpm
- Use: Daily driver, towing, offroad, 1/8 mile, 1/4 mile, autocross, road course
- Driveability: Idle roughness, low rpm part throttle response, or mostly mid-upper full throttle
Thread Starter
Teching In
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- Header type, primary size - 1 7/8
- Exhaust size, dual, dual crossover, single, muffler type, open headers, cats - 3 inch dual exhaust x pipe
- Vehicle weight - 3600 / 3800
- Rear gear ratio - 3.91 or 4.11
- Manual or automatic, 1st gear trans ratio, torque converter stall - 3200 to 3800 stall 4L80E
- Peak shift rpm - no idea
- Typical cruise rpm - no idea
- Use: Daily driver, towing, offroad, 1/8 mile, 1/4 mile, autocross, road course - weekend driver, cruiser, with attitude
- Driveability: Idle roughness, low rpm part throttle response, or mostly mid-upper full throttle - smooth or rough idle is okay, snappy throttle response, fun to drive.
TECH Resident
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Higher ratio rockers means more stress on the valvetrain including pushrods, camshaft and seat of the valves and heads. Definitely check with the camshaft manufacturer if they recommend that ratio, and have your head info with the valve spring details. Doubt the power difference is going to be worth the extra strain on the valvetrain and noise.
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Also, the rubber band tires are going to be like trying to take off on ice with a 408. Strongly suggest at least dropping down to 24" if not 22" with that tire diameter. It will make a significant difference.
Thread Starter
Teching In
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Not to sound like a smart-*** but have you ever used 1.8 rockers for anything? Were you able to smooth out the valve train, or make it quiet and did it make any more power? If you did what was the application might I ask..