Help with building ls7
Thread Starter
Joined: Aug 2013
Posts: 116
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From: carroll county, md
Help with building ls7 So I got a ls7 long block planning on swapping into my 98 trans am with 01 computer and harness. shooting for 600whp but will take what I get since I know my intake will hold me back some but have a few questions on which parts to run. Tring to do this build on a budget not going cheap but I camt afford high end top of the line stuff either. Planning on running 93 pump gas till we get a few more stations around the have E then swap over to flex fuel sensor
First the heads I'm gonna have the guides replaced and dont know which exhaust valves would be better Ferra hollow stem ss valves or solid ss valves keeping stock intake valves. Im Doing che trinnion on stock rockers. How much should I have milled. .20 or .30 gonna run stock gaskets. Arp head bolts
Valve springs I'm looking at using pac 1207x but from what I've been reading they dont recomend using stock lifter so which lifters should I run?
Cam is Texas speed ls7 4.2 cam
Cam Specs: 248/260, .657"/.655", 111 LSA, 108 ICL
intake is a ported ls7 stock fuel rails
nick William's 92
Fic 850cc injectors
bottom end is all stock
which oil pump would be best going wet sump
Timing chain which would be best?
before anyone says anything about drivability issues. The car is driven 2-3 thousand miles a year. Already used to driving with a over sized cam.
First the heads I'm gonna have the guides replaced and dont know which exhaust valves would be better Ferra hollow stem ss valves or solid ss valves keeping stock intake valves. Im Doing che trinnion on stock rockers. How much should I have milled. .20 or .30 gonna run stock gaskets. Arp head bolts
Valve springs I'm looking at using pac 1207x but from what I've been reading they dont recomend using stock lifter so which lifters should I run?
Cam is Texas speed ls7 4.2 cam
Cam Specs: 248/260, .657"/.655", 111 LSA, 108 ICL
intake is a ported ls7 stock fuel rails
nick William's 92
Fic 850cc injectors
bottom end is all stock
which oil pump would be best going wet sump
Timing chain which would be best?
before anyone says anything about drivability issues. The car is driven 2-3 thousand miles a year. Already used to driving with a over sized cam.
600 rwhp is a tall order on stock heads. While heads are off, you are doing valve guides. I recommend moldstar guides. Cut out your valve seats and recut them. That should fix any eccentricity issue. Point of reference, I made 564 rwhp with a 248 cam on a humid day in SC, 428ci bottom end, Lingenfelter heads, stock ls7 intake, EWP, dual 3" exhaust.
Thread Starter
Joined: Aug 2013
Posts: 116
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From: carroll county, md
600 rwhp is a tall order on stock heads. While heads are off, you are doing valve guides. I recommend moldstar guides. Cut out your valve seats and recut them. That should fix any eccentricity issue. Point of reference, I made 564 rwhp with a 248 cam on a humid day in SC, 428ci bottom end, Lingenfelter heads, stock ls7 intake, EWP, dual 3" exhaust.
Someone like KCS might chime in and correct me where I have not been technically correct. I do know when you do a valve job, you use the guide to center the tool, so a proper valve job with a new guide fixes the issue typically.
TECH Addict
Joined: Sep 2010
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The camshaft specification has optimum valve events however the 30 degrees of overlap is really going to affect driveability and you will lose some low end torque and hp.
I would definitely mill the heads to get the compression up and also do a CNC job for optimum flow if you want to reach your goal.
With stock heads, you won't get there.
I would definitely mill the heads to get the compression up and also do a CNC job for optimum flow if you want to reach your goal.
With stock heads, you won't get there.
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Thread Starter
Joined: Aug 2013
Posts: 116
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From: carroll county, md
OK, let's say you take the stock heads, do new guides and lap in the valves on the seats. The seats are not always concentric (perfectly aligned on center with each other) with the valve guides on stock LS7 heads. That issue was their downfall on what was otherwise the best factory head GM ever made. That's where you get guys who say to just replace the valve guides every year or so on LS7 heads. But, if you do a whole valve job -- new guides, recut the seats, etc -- you fix the concentricity issue. Sometimes, it can be fixed just cutting the existing seats, other times you put new seats in and re-do them. The shops that know how to fix this will not steer you wrong. One reason I'm a fan of aftermarket LS7 heads is that the AM castings have truly fixed the issue by correcting the misalignment in the casting.
Someone like KCS might chime in and correct me where I have not been technically correct. I do know when you do a valve job, you use the guide to center the tool, so a proper valve job with a new guide fixes the issue typically.
Someone like KCS might chime in and correct me where I have not been technically correct. I do know when you do a valve job, you use the guide to center the tool, so a proper valve job with a new guide fixes the issue typically.
I can confirm that cam takes a bit of learning how to drive it around town to keep from looking like you're driving stick for the first time. It doesn't like being under 2k much, that's for sure.
That cam needs to breathe so I'd say if you want 600 on a 427 you probably need better than an LS7 intake, in hindsight I regret not getting my MSD ported by Tony. Also 2" headers and true duels would pay dividends. That cam on my bigger motor peaks at only ~6300 so it's choked off on my setup but if you can support the airflow to get it to peak near 7k then I'd think 600 on a 427 should be doable.
That cam needs to breathe so I'd say if you want 600 on a 427 you probably need better than an LS7 intake, in hindsight I regret not getting my MSD ported by Tony. Also 2" headers and true duels would pay dividends. That cam on my bigger motor peaks at only ~6300 so it's choked off on my setup but if you can support the airflow to get it to peak near 7k then I'd think 600 on a 427 should be doable.
Thread Starter
Joined: Aug 2013
Posts: 116
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From: carroll county, md
I can confirm that cam takes a bit of learning how to drive it around town to keep from looking like you're driving stick for the first time. It doesn't like being under 2k much, that's for sure.
That cam needs to breathe so I'd say if you want 600 on a 427 you probably need better than an LS7 intake, in hindsight I regret not getting my MSD ported by Tony. Also 2" headers and true duels would pay dividends. That cam on my bigger motor peaks at only ~6300 so it's choked off on my setup but if you can support the airflow to get it to peak near 7k then I'd think 600 on a 427 should be doable.
That cam needs to breathe so I'd say if you want 600 on a 427 you probably need better than an LS7 intake, in hindsight I regret not getting my MSD ported by Tony. Also 2" headers and true duels would pay dividends. That cam on my bigger motor peaks at only ~6300 so it's choked off on my setup but if you can support the airflow to get it to peak near 7k then I'd think 600 on a 427 should be doable.
Does anyone have any suggestions on which oil pump, lifters, timing chain setup to run along with valve springs with solid ss exhaust valves
For the heads, I'd recommend West Coast Cylinder Heads (WCCH) hands down. He has a great program to replace the guides, re-cut the valve job, deck the surface etc. Very good quality work, excellent price for the quality, great technical support and an honest guy that will steer you in the right direction. He also has a reasonably priced CNC option for the stock LS7 heads to get them around 400cfm. http://www.proheads.com/WCCH_LS7.html
For exhaust valves in my LS7 heads I used SI Valves solid stainless valves (part number SL-1137) with BTR Platinum springs and Ti Retainers. It's been good to 7200 RPM so far. WCCH can get you the valves. They are pretty inexpensive. I wouldn't put an Inconel valve in a N/A engine though. No need to add all that weight unless you need the temperature resistance of Inconel for a forced induction application.
Oil Pump, ported LS2 or Melling 10296. Don't forget to convert to wet sump, you will have to machine the front of the crankshaft snout shorter.
Timing Set - Stock LS2 chain and Damper. If you're feeling worried, put a IWIS chain in it.
Also, you'll need to change the reluctor wheel on the crank to a 24x.
Overall, I'd say your combo looks pretty good and the LS7 intake may hold you back some on the top end and may not allow you to get to the peak number you're after, but it will be fun to drive on the street that's for sure.
Cole
For exhaust valves in my LS7 heads I used SI Valves solid stainless valves (part number SL-1137) with BTR Platinum springs and Ti Retainers. It's been good to 7200 RPM so far. WCCH can get you the valves. They are pretty inexpensive. I wouldn't put an Inconel valve in a N/A engine though. No need to add all that weight unless you need the temperature resistance of Inconel for a forced induction application.
Oil Pump, ported LS2 or Melling 10296. Don't forget to convert to wet sump, you will have to machine the front of the crankshaft snout shorter.
Timing Set - Stock LS2 chain and Damper. If you're feeling worried, put a IWIS chain in it.
Also, you'll need to change the reluctor wheel on the crank to a 24x.
Overall, I'd say your combo looks pretty good and the LS7 intake may hold you back some on the top end and may not allow you to get to the peak number you're after, but it will be fun to drive on the street that's for sure.
Cole
Thread Starter
Joined: Aug 2013
Posts: 116
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From: carroll county, md
I really appreciate everyone's help here. For the reluctor wheel I got the lingenfelter 58x to 24x conversion box. And for the dry to wet I got the scoggin dicky crank spacer. The swap side of it seems for the most part pretty simple. Like I said I figured the intake would hold me back. What are these stock bottom ends good for rpm wise for shift points
TECH Addict
Joined: Sep 2010
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Brian Tooley has a great reputation when it comes to camshafts.
Please explain what was wrong and the combination it was on.
Thank you
i just got done going through this, not done yet but at the end of the home stretch. i went with big name heads, but i can basically guarantee that with your exhaust, and even a really really really good valve job and port work on the stock ls7 heads, you will be very lucky to get 575 rwhp with the ls7 intake and the rest, assuming you are an M6 car. like you said the the msd can be done later but you will NEED 2 inch headers someday.
and to repeat a fan favorite quote thrown around on here, "whoever is doing the heads should spec your cam"
TECH Senior Member
Joined: Jun 2016
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From: Central Cal.
Blaming the cam for a car being a turd is silly, especially a cam from one of the bigger ls guys. simply put, something is wrong unrelated to the cam, unless it isn't degreed proper.
…….and to repeat a fan favorite quote thrown around on here, "whoever is doing the heads should spec your cam"
…….and to repeat a fan favorite quote thrown around on here, "whoever is doing the heads should spec your cam"