tell me what is wrong with this combo
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tell me what is wrong with this combo 
I am hoping someone can point me in a direction. Are my expectations too high or is there something wrong with this combo. I just built a 10-1 .040 over 4 bolt 350 with a balanced scat rotating assembly, kb flattops, new Brodix IK180 heads, compcams x4254H cam hyd. cam, gear drive, roller rockers, hei with 65k coil, Weiand xcelerator dual plane intake, edelbrock 600 cfm carb, and block hugger headers connected to new 2.5 inch exhaust with flowmaster 50 series mufflers, a new 350 built tranny a new converter with 2000 rpm stahl, 3.42 gears. Everything on the motor is brand new. Timing is set to 14 initial and about 36 total. I have adjusted the timing to where it seems to be best. My issue is I was expecting about 350 horse from this motor and it appears to only be making 280-300. Desktop dyno put it at closer to 375hp. The motor runs good and is responsive so I am confused as to why my power is so low. Any thoughts? the combo of parts are not right,you have a cam intake and carb that are made for low end torque and heads that are made for higher end hp,they dont work well together,you need a bigger cam intake and carb to make those heads work properly,i have built several 350's with those heads that have made 450 flywheel hp,just need to right combo of parts.
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cam x4 254H
duration at .050
210 intake
218 exhaust
.470 lift intake
.486 lift exhaust
with 1.6 roller rockers
111 lobe seperation
I chose this cam to get good vacuum and street manners and somewhat good gas mileage because this is a daily driver, I went with the heads because they had great flow numbers at low lift and just a couple steps up from stock with 180 cc intake ports so it wouldn't kill the low end torque.
duration at .050
210 intake
218 exhaust
.470 lift intake
.486 lift exhaust
with 1.6 roller rockers
111 lobe seperation
I chose this cam to get good vacuum and street manners and somewhat good gas mileage because this is a daily driver, I went with the heads because they had great flow numbers at low lift and just a couple steps up from stock with 180 cc intake ports so it wouldn't kill the low end torque.
the combo of parts are not right,you have a cam intake and carb that are made for low end torque and heads that are made for higher end hp,they dont work well together,you need a bigger cam intake and carb to make those heads work properly,i have built several 350's with those heads that have made 450 flywheel hp,just need to right combo of parts.
I would ditch the intake for a performer RPM, 750 cfm, 1 3/4" headers, and a XE274 would get you 400. If you use 1 5/8" may get you a bit more torque which is better for driving. The family of cams you picked is geared toward trucks for low rpm grunt.
IF you did want just a more power closer to your 375-390 Im sure that a just a cam change would be the most cost benificial. If you dont have to farm out your work then for the $150 or so, swap the cam and keep your top end. You will be happier with the 600 if its a daily driver. XE268 ive seen this on a create 350HO with vortec head make 375 with a RPM, and 750, 1 5/8"headers. The XE274 was at 405 with a RPM, 750cfm, and 13/4"headers.
Last edited by jester1; Jan 22, 2008 at 09:37 PM.
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The motor pulls hard from 1500-5500 like it should. According to the cubic inches and the VE the carb should be more than enough. I built this motor to make peak horsepower at about 5200 rpm. This is a street car and therefore will never see 6000 rpm. I had a drag car before that was running low 11's with 1 5/8 headers and a 750 carb. This motor is not even close to that one in horsepower and shouldnt require that much of a carb or exhaust. The block hugger headers are 1 5/8 tubes into 2.5 inch exhaust. I dont think breathing or fuel is an issue because the motor pulls hard throughout the rpm range. I am making my comparison on how much horsepower it has based on running this motor in a 78 vette against my 91 vette. My 91 vette is bone stock except for a K&N and aftermarket mufflers. The two cars are dead even across the rpm range. I am estimating the 91's horsepower at around 260.
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Low end torque and horsepower is what I was after for a daily driver. Desktop dyno put the hp and torque at 360/375 with my combo. I chose it so it would have as much low end torque as possible. I looked at various different cams before going with this one. I think there was only a difference of 15 horse going with the larger cam.
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I would ditch the xcelerator (2000-6500 rpm) intake for a Action +, Edlebrock EPS performer, or a Cyclone intake to match your rpm requirements. I haven't heard of too many people that actually liked the results of the xcelerator. Your carb is another problem, you have the right size of carb on there, but I would get a better carb like a Road Demon 625 cfm carb.
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I keep thinking about the cam being the issue as well. I was leaning more towards an issue of it being installed incorrectly but the fact that it runs so good makes me think that is installed correctly. I did not degree the cam in as I should have and used a negative 2 degree bushing in the gear drive. What cam would work well with this combination that will still give me strong low end torque and good power below 5500 rpm while having good vacuum for the brakes and headlights and getting decent gas mileage?
The XE274 which I mention above is the 12-246-3, it will wake up you engine!
RPM intake and a 750holley. That will get your 82' into the low 12's if everything is in order.
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From: Atl. ga
Hey Jester1 who makes the cams you talk about, the XE274 - 405 HP. I'm in the process of building a 383 Vortec headed stroker engine, and I'm still debating what cam to use. Are these hydraulic flat tappet, solid flat tappet, or hydraulic roller? Getting back to the question of this post, I would change cams and bolt on an Edelbrock Performer Rpm Air Gap intake.
I think if you swap out the cam and go with a different carb you're gonna see a lot more difference than you think. I've built a few engines and compared the dyno numbers with desktop dyno and they weren't even close.
