418 cid heads question !!!
Thread Starter
Staging Lane
Joined: Oct 2009
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418 cid heads question !!! Hi
My mods are ls3 418 cid stock milled ls3 heads cam 239/255 fast intake and tb 102 mm 1 7/8 headers am looking for switch the heads to prc 250 ? Do u think its better or u prefer 255 or 260 or 265 prc ? Or tfs ? My goals is max rwhp on motor
My mods are ls3 418 cid stock milled ls3 heads cam 239/255 fast intake and tb 102 mm 1 7/8 headers am looking for switch the heads to prc 250 ? Do u think its better or u prefer 255 or 260 or 265 prc ? Or tfs ? My goals is max rwhp on motor
If you're looking for max rwhp on motor, the FAST is only going get you so far with said camshaft. You could try a different cam to get some more ponies and also get your stock heads ported. Switching to the PRC's or TFS will only probably net a few more horses than the stock heads and that to me doesn't justify the expense. If you want to keep the FAST, then I say port your heads and intake and get a cam ground to support those things. It will increase your power across the board and pick up some peak ponies. If you can do away with the FAST, then I say get a carb style intake and a cam to match it and your powerband should move up nicely and your peak hp will jump, but at the expense of lower end torque. You do have a 418 so I dont see torque dropping too far down the graph
Thread Starter
Staging Lane
Joined: Oct 2009
Posts: 81
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If you're looking for max rwhp on motor, the FAST is only going get you so far with said camshaft. You could try a different cam to get some more ponies and also get your stock heads ported. Switching to the PRC's or TFS will only probably net a few more horses than the stock heads and that to me doesn't justify the expense. If you want to keep the FAST, then I say port your heads and intake and get a cam ground to support those things. It will increase your power across the board and pick up some peak ponies. If you can do away with the FAST, then I say get a carb style intake and a cam to match it and your powerband should move up nicely and your peak hp will jump, but at the expense of lower end torque. You do have a 418 so I dont see torque dropping too far down the graph
Porting in my city is not much better because we dont have a good hands so that i cant play with them a stupid game and i should looking for prc or tfs .
Porting in my city is not much better because we dont have a good hands so that i cant play with them a stupid game and i should looking for prc or tfs .
If you're all about power, take a look at the new LS3 TFS aftermarket casting.
Thread Starter
Staging Lane
Joined: Oct 2009
Posts: 81
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No am from middle east and it too much difficult way to send it so that i decied to change it better and cheaper !! Lol
If you're looking for max rwhp on motor, the FAST is only going get you so far with said camshaft. You could try a different cam to get some more ponies and also get your stock heads ported. Switching to the PRC's or TFS will only probably net a few more horses than the stock heads and that to me doesn't justify the expense. If you want to keep the FAST, then I say port your heads and intake and get a cam ground to support those things. It will increase your power across the board and pick up some peak ponies. If you can do away with the FAST, then I say get a carb style intake and a cam to match it and your powerband should move up nicely and your peak hp will jump, but at the expense of lower end torque. You do have a 418 so I dont see torque dropping too far down the graph
100% agree.
Thread Starter
Staging Lane
Joined: Oct 2009
Posts: 81
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Actually i planning for better heads and cam on the FAST102mm because maybe in the future i will go with bigger cubes . So switching to the prc or tfs its not worth ? And now we still with a cam !! Do u think with the cam ONLY i can get my goal ??!!!! 500+ rwhp
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Verdad Gallardo What did it dyno with the setup you have now? A 418 with that cam should have dyno'd 500+ with a manual transmission in the car. Something is wrong with the combo. You have a restriction of some sort. You have a catback on there or what does the exhaust consist of with those 1 7/8 headers? Where did you get that cam from?
Here is a little reading for you. The right cam and combo will work wonders.
https://ls1tech.com/forums/dynamomet...o-results.html
Here is a little reading for you. The right cam and combo will work wonders.
https://ls1tech.com/forums/dynamomet...o-results.html
Thread Starter
Staging Lane
Joined: Oct 2009
Posts: 81
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I already dynoed it an got 485 rwhp 461 rwtq actually i bought the motor used from someone and he already assembled it before 2 months ago and his goal was 150 shot (keep in mind pressure ring clearance) , when i asked him about the cam specs he said i dont know 
so that i decied to change the cam and already i oredered it and got prc 250 heads to improve the CR to get a good rwhp , about my exhaust setup its 1 7/8 headers 3" ory with borla catback fully opened e-cutout , btw i already read that forum u sent it .
so that i decied to change the cam and already i oredered it and got prc 250 heads to improve the CR to get a good rwhp , about my exhaust setup its 1 7/8 headers 3" ory with borla catback fully opened e-cutout , btw i already read that forum u sent it . That is awfully low for a 418. Stock cube ls3's make that much hp on the dyno. Something is definitely causing a major issue. What rpm does that cam peak to? Do you have a dyno graph. A 418 should make 530+ hp all day long with a medium sized cam and a manual trans.
Thread Starter
Staging Lane
Joined: Oct 2009
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I know about that bad number and my cam until now not installed yet ! Because i want to install both heads and cam at the same time so that i asked about the good heads will fit with my cam and untill now i found prc 250 68cc if theres better i will change my head ! And i dont have a grap
and my cam until now not installed yet ! Because i want to install both heads and cam at the same time so that i asked about the good heads will fit with my cam and untill now i found prc 250 68cc if theres better i will change my head ! And i dont have a grap Wait.....stop...I'm confused. What cam is in the car now? So the 239/255 cam is not in the car? Plus you don't know what cam is in the car or the compression of the motor?
You need to find out what you are working with now before you just waste money and throw parts at it. That's the bad part about buying a motor off somebody and not knowing exactly what's in it.
You need to find out every detail about that motor first and foremost. That motor might have a dished piston for boost and the compression might be low for boost and you're trying to make naturally aspirated horsepower. You also need to see what cam is in it. It might be better than the one you have.
You also keep wanting to change the heads. Leave that alone right now. Stock LS3 head flow really well in stock form so that can be put aside right now.
John Lingenfelter had an old saying back in the day "Put the worst heads on top of the best cam in the world and the engine will make no power, put the best heads on top of the worst cam and the motor will still make decent power".
We need to know alot of details about the motor so we can get you the best head and cam combo to compliment the bottom half you have. There should be an L92/LS3 piston with a -3 or 4cc dish from the valve relief in there to accommodate the big valve that's in the LS3/L92 heads. You said they milled the heads, how much? If you can get the cam out of the motor. See what numbers are engraved on the cam so we can see what kind of cam is in the motor. Take some pics and post them on here when you start to take the motor apart so we can see what parts you have and what can be improved upon.
You need to find out what you are working with now before you just waste money and throw parts at it. That's the bad part about buying a motor off somebody and not knowing exactly what's in it.
You need to find out every detail about that motor first and foremost. That motor might have a dished piston for boost and the compression might be low for boost and you're trying to make naturally aspirated horsepower. You also need to see what cam is in it. It might be better than the one you have.
You also keep wanting to change the heads. Leave that alone right now. Stock LS3 head flow really well in stock form so that can be put aside right now.
John Lingenfelter had an old saying back in the day "Put the worst heads on top of the best cam in the world and the engine will make no power, put the best heads on top of the worst cam and the motor will still make decent power".
We need to know alot of details about the motor so we can get you the best head and cam combo to compliment the bottom half you have. There should be an L92/LS3 piston with a -3 or 4cc dish from the valve relief in there to accommodate the big valve that's in the LS3/L92 heads. You said they milled the heads, how much? If you can get the cam out of the motor. See what numbers are engraved on the cam so we can see what kind of cam is in the motor. Take some pics and post them on here when you start to take the motor apart so we can see what parts you have and what can be improved upon.
On The Tree
Joined: Jul 2010
Posts: 188
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That is awfully low for a 418. Stock cube ls3's make that much hp on the dyno. Something is definitely causing a major issue. What rpm does that cam peak to? Do you have a dyno graph. A 418 should make 530+ hp all day long with a medium sized cam and a manual trans.
Thread Starter
Staging Lane
Joined: Oct 2009
Posts: 81
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Ok i bought the motor from my friend and i know its 4" with 6.125 with 4.080 -3 valve reliefs !!
And his goal was 150 shot not forced induction !
About the cam that one inside the motor ( me and he dont know the specs ) so that i already orderd 239/255 and until now iam not install it ! I know the bottom end is very good and nothing wrong i think the wrong with heads and my cam also with CR ! Sothat i wanna but best head and 239/255 cam and best head gasket to get good CR and best na rwhp !!
And his goal was 150 shot not forced induction !
About the cam that one inside the motor ( me and he dont know the specs ) so that i already orderd 239/255 and until now iam not install it ! I know the bottom end is very good and nothing wrong i think the wrong with heads and my cam also with CR ! Sothat i wanna but best head and 239/255 cam and best head gasket to get good CR and best na rwhp !!
Last edited by al3flangy; Oct 16, 2013 at 03:11 AM.
I am currently running a 418 (4" stroke 4.083 bore). It has PRC 237 heads milled to 58cc (13-1cr) and a 254/260 cam. Through a power glide with 4, 500 converter it makes 516rwhp on a dyno jet. It has made 546rwhp on a dyno dynamics.
My point, dynos are great for comparing changes to your own combo not someone else's halfway around the world. Take it to the track.
That being said, even with new heads, I am not sure that cam is a grea grind. If you are trying to get max rwhp from it, you are going to want mid 250 to low 260.
If you do go with new heads, be sure to get a light weight intake valve as it will be easier to control.
My point, dynos are great for comparing changes to your own combo not someone else's halfway around the world. Take it to the track.
That being said, even with new heads, I am not sure that cam is a grea grind. If you are trying to get max rwhp from it, you are going to want mid 250 to low 260.
If you do go with new heads, be sure to get a light weight intake valve as it will be easier to control.
There's no helping you. You are determined to put a set of heads on this motor no matter what and use that cam that you have. Good luck and hope you get what you are looking for.