CNC Head Surprise
Thread Starter
Staging Lane
Joined: Aug 2009
Posts: 75
Likes: 0
From: everett, wa
CNC Head Surprise Check out the welcomed surprise i got when i pulled my heads off:
I bought the car from a dealer a few years ago thinking it was a bolt on car. I slowly found more things as time went on. 12 bolt, suspension mods, the front sway bar was disconnected and the forged 383 rotating assembly when i dropped the pan to replace the gasket. Anyone have any info on these heads like who it might be(hopefully AI) or on the valve springs? I know there are there are only a few companies that cnc these heads. The car drove pretty damn stock but that's about to change after i get my new cam and button up the 24x conversion
I bought the car from a dealer a few years ago thinking it was a bolt on car. I slowly found more things as time went on. 12 bolt, suspension mods, the front sway bar was disconnected and the forged 383 rotating assembly when i dropped the pan to replace the gasket. Anyone have any info on these heads like who it might be(hopefully AI) or on the valve springs? I know there are there are only a few companies that cnc these heads. The car drove pretty damn stock but that's about to change after i get my new cam and button up the 24x conversion
Thread Starter
Staging Lane
Joined: Aug 2009
Posts: 75
Likes: 0
From: everett, wa
I paid 5k at the dealer for a pretty low mile 6 speed car which at the time were very scarce around here. Car has Callies forged crank, splayed 4 bolt mains, SRP pistons, full bolt ons, Strange 12 bolt, ported heads, the 6 speed has a rebuild tag on it so I'm guessing its been gone thru, full stereo and I'm sure there's a bunch i forgot. The car drove so mellow i figured it was just bolt ons. The funny thing is with all that's done when i got a mail order from Solomon he said the tune was stock and I think it was the VE tables cranked up. The exhaust ports are BLACK and covered in carbon is that normal? As well as the different amount of build up on the pistons i would assume it should be uniform.
I would think a 383 with ported heads would be a strong runner. Does it have a mild cam? I'm no piston expert but with dished pistons I'd think the compression would be lower despite the increased displacement. Seeing how its all forged and reduced CR, I'm thinking this engine was boosted before you bought the car.
Looks like they started a boosted build but bailed on it. Good quality parts...but low compression, mild cam, and a stock tune. That is quite a thick layer of carbon on everything.
I would clean and CC the heads first, and find a part number on those pistons. You may be good to slap on a procharger, get a dyno tune, and make some very respectable numbers.
I would clean and CC the heads first, and find a part number on those pistons. You may be good to slap on a procharger, get a dyno tune, and make some very respectable numbers.
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I kind of doubt Lingenfelter would use SRP. Then again it has a Callie crank..........
There was also a company out of FL that did some mediocre CNC LT1 heads. Friend had them and his heads/cam car ran cam only numbers.
There was also a company out of FL that did some mediocre CNC LT1 heads. Friend had them and his heads/cam car ran cam only numbers.
Last edited by 96capricemgr; Mar 9, 2012 at 10:52 AM.
Thread Starter
Staging Lane
Joined: Aug 2009
Posts: 75
Likes: 0
From: everett, wa
Thanks for the responses. I'll check the heads when i get home from what i remember tho they do have a serial number punched into them. Sooooooo anyone have a used procharger they wanna let go cheap? haha. I was planning on cleaning the heads, dropping in a new cam and calling it a day. I would like this car to be my daily so I'm a little iffy on a boosted build but since its set up for it maybe that's the way I'll go. How much am i leaving on the table by just tossing a new cam in there with the low compression?
Probably not intended as a boost build.
Probably has dished pistons because someone ignorant spec'd the build and did not understand proper compression for an NA LT1.
I know it is a stretch to make that guess from what little info we have BUT you would be shocked to seen how many "built" LT1s endup at way too low a compression. Guys have actually gotten back engines with lower than stock compression for NA setups. Just in the last week or two someone was defending 10.0 compression on an NA setup because it was "safe". That was the compression for the 87 octane iron head Caprice engine. Even the stock aluminum head LT1 was 10.4 and the LT4 was 10.8.
Loose rule for a boost LT1 would be to probably keep it mid 9s, for NA or nitrous I would go at the very least 11.5.
Figure out where it is at now before deciding on much else.
Probably has dished pistons because someone ignorant spec'd the build and did not understand proper compression for an NA LT1.
I know it is a stretch to make that guess from what little info we have BUT you would be shocked to seen how many "built" LT1s endup at way too low a compression. Guys have actually gotten back engines with lower than stock compression for NA setups. Just in the last week or two someone was defending 10.0 compression on an NA setup because it was "safe". That was the compression for the 87 octane iron head Caprice engine. Even the stock aluminum head LT1 was 10.4 and the LT4 was 10.8.
Loose rule for a boost LT1 would be to probably keep it mid 9s, for NA or nitrous I would go at the very least 11.5.
Figure out where it is at now before deciding on much else.
Thread Starter
Staging Lane
Joined: Aug 2009
Posts: 75
Likes: 0
From: everett, wa
The bottom of the piston was marked with an SRP logo and 40D from what the great big google machine brings back it could be a few different sizes but another build identical to mine had these pistons and stated they were -16cc. I'll probably use this as an excuse to tear the motor down swap pistons and freshen up the bearings. Funny how these things always snowball....
The bottom of the piston was marked with an SRP logo and 40D from what the great big google machine brings back it could be a few different sizes but another build identical to mine had these pistons and stated they were -16cc. I'll probably use this as an excuse to tear the motor down swap pistons and freshen up the bearings. Funny how these things always snowball....
I was thinking the same thing. The CNC steps on the intake ports look pretty close to what I have. If that's the case the chambers will probably be around 60cc's for a stock compression ratio with those pistons.
Thread Starter
Staging Lane
Joined: Aug 2009
Posts: 75
Likes: 0
From: everett, wa
