Best Heads for a 408 ci
09-08-2011, 02:56 PM
#21
The exhaust is definitely capable of supporting more hp so that is not your problem even though like in my case bigger would probably squeeze out a few more ponies.... I would be willing to bet a GOOD tune is most of your issue and will give you a nice bump.
I also thought about whether you had enough injector. IIRC LS3's are 42lbs. so if you are running a set of those you are ok. Still may want to check the pump to make sure you are ok there.... I just went ahead with a Wahlbro to be on the safe side but I honestly do not know what a healthy stock pump will support...
If you can post the dyno sheet that may be of help....
EDIT:Clarification.... LS3 injectors are 42lbs. @ our 58psi
I also thought about whether you had enough injector. IIRC LS3's are 42lbs. so if you are running a set of those you are ok. Still may want to check the pump to make sure you are ok there.... I just went ahead with a Wahlbro to be on the safe side but I honestly do not know what a healthy stock pump will support...
If you can post the dyno sheet that may be of help....
EDIT:Clarification.... LS3 injectors are 42lbs. @ our 58psi
09-08-2011, 06:36 PM
#23
The exhaust is definitely capable of supporting more hp so that is not your problem even though like in my case bigger would probably squeeze out a few more ponies.... I would be willing to bet a GOOD tune is most of your issue and will give you a nice bump.
I also thought about whether you had enough injector. IIRC LS3's are 42lbs. so if you are running a set of those you are ok. Still may want to check the pump to make sure you are ok there.... I just went ahead with a Wahlbro to be on the safe side but I honestly do not know what a healthy stock pump will support...
If you can post the dyno sheet that may be of help....
EDIT:Clarification.... LS3 injectors are 42lbs. @ our 58psi
I also thought about whether you had enough injector. IIRC LS3's are 42lbs. so if you are running a set of those you are ok. Still may want to check the pump to make sure you are ok there.... I just went ahead with a Wahlbro to be on the safe side but I honestly do not know what a healthy stock pump will support...
If you can post the dyno sheet that may be of help....
EDIT:Clarification.... LS3 injectors are 42lbs. @ our 58psi
I will work on the tune within the next few weeks. I do have LS3 42lb injectors in there. The tuner didn't even change the injector data for the LS3 top end. He left them stock 36lb in the tune when I got it back. I'm sure there are lots of hiccups like that in the tune i'm running.
09-08-2011, 09:30 PM
#25
Sounds like theres more in the tune but @ 265 cc of runner volume, the 300
plus cfm those heads flow has less than ideal port-speed for the weight of a
truck. If small runner AFRs or TrickFlows aren't in the budget then maybe
some AI 317s w/FAST would help create a flatter torque band.
plus cfm those heads flow has less than ideal port-speed for the weight of a
truck. If small runner AFRs or TrickFlows aren't in the budget then maybe
some AI 317s w/FAST would help create a flatter torque band.
09-08-2011, 10:31 PM
#26
Sounds like theres more in the tune but @ 265 cc of runner volume, the 300
plus cfm those heads flow has less than ideal port-speed for the weight of a
truck. If small runner AFRs or TrickFlows aren't in the budget then maybe
some AI 317s w/FAST would help create a flatter torque band.
plus cfm those heads flow has less than ideal port-speed for the weight of a
truck. If small runner AFRs or TrickFlows aren't in the budget then maybe
some AI 317s w/FAST would help create a flatter torque band.
09-11-2011, 09:27 AM
#30
09-11-2011, 02:11 PM
#34
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Putting 215's on a 400+ CID engine is a good way to create a turd with no top end. AFR 230 or TFS 235's will have just as much low end and a hell of a lot more upper RPM power.
Having a small intake runner doesn't magically make gobs of torque come out your engines ***.
Having a small intake runner doesn't magically make gobs of torque come out your engines ***.
Last edited by JS01; 09-11-2011 at 02:17 PM.
09-12-2011, 09:52 AM
#35
Keep in mind this is a truck...not a 3000 pound car.
I know what builds torque...especially at altitude. But take it straight to the horse's mouth. Call AFR. Give them the vehicle, weight, gearing, intake hardware, exhaust, cam specs, rockers, etc. See what they recommend. They would know best.
I know what builds torque...especially at altitude. But take it straight to the horse's mouth. Call AFR. Give them the vehicle, weight, gearing, intake hardware, exhaust, cam specs, rockers, etc. See what they recommend. They would know best.
09-12-2011, 01:42 PM
#36
Something is wrong with your combo; a cammed 408ci with LS3 H/I should be at 450rwhp/450rwtq or more, even on a mild auto setup..unless that dyno is wayyyy stingy. Track numbers?
I would keep the LS3 heads and get em ported along with a FAST 102..
I would keep the LS3 heads and get em ported along with a FAST 102..
Last edited by Johnnystock; 09-12-2011 at 01:55 PM.
09-14-2011, 01:04 AM
#40
You need to use the best flowing heads that you can afford............period.
408 cubic inches will eat up just about any head available. Then your plastic intake will be the restriction. Which is good.....then you can upgrade the intake later when you have more cash, but get the best flowing heads possible that $$$ allows.
Don't just get what everyone else has that has a 408ci...........
.
408 cubic inches will eat up just about any head available. Then your plastic intake will be the restriction. Which is good.....then you can upgrade the intake later when you have more cash, but get the best flowing heads possible that $$$ allows.
Don't just get what everyone else has that has a 408ci...........
.