here is my new combo .040 over 400 block , splayed 4 bolt caps, gm steel 350 crank, steel h-beam 5.7 rods. dart pro1 230 heads 64 cc, flow 258cfm @.550 intake and 203cfm @.550 exhaust, comp cams xs290s solid lifter 252,260 duration@ 50 and .541,.559 lift 110 lobe seperation 106 centerline , and cam card shows .012 valve adj. and ground with a 4,7 swap, team g intake , 950 hp carb , pro race fogger 250 to 500 horse , 4sp , 4.11 gears 82 camaro . am planing on 11 or 11.5 comp. ross pistons(dont have yet) desk top dyno says 446 hp@5500 and 496 tq.@4000 but if i retard the timming 3* it picks up 20 horse . what do you guys think ? where should i run the cam? i live at 4800' elevation

mike

 

What does retarding the cam do to the powerband?Cant complian about 20 if thats all you have to do..The cam choice from what i underastand matches the heads pretty good..Crower says that if you get more by retarding or advancing more than 4* the cam is wrong..Im going through this with my current 406, we retarded the cam 7* and picked up 35 hp with the dart iron eagles and a smaller carb..

Why the choice for the intake? Have you bought it already?

 

intake is a weiland team g with the fogger in it. desk top dyno shows power peaking at 5500. the cam book shows the power band should b 2800 to 7200. last year i crossed the line at 6900 to 7000 rpm. now im worring that it might not turn that high with this cam. power band only losses a couple of horses at 2k but pick up 20 at 5500

mike

 

First, I think too much emphasis is put on Desk Top Dyno. This is not a professional tool, only a rough guideline & I emphasize rough.... I'd use it as a way to sort out a base combination, but would not spend my money on parts based on the programs recommendation. If that motor really makes only 450hp, you may as well lose 20 degrees of cam timing & 2 points compression, because thats what any decent builder can make with a 9.5:1 hydraulic cammed 400 with street heads on pump fuel at 5500 rpm.

I have never seen a 250-260 degree cam peak at 5500 on a small block unless the induction system was choking the motor. I'd expect this to peak around 6500-7000.

Are your 258 intake flow numbers correct? Im hoping they are more like 285 on that big of a head.

 

Is this a race only engine? or are you trying to build a street engine? If it is a street engine you will probably need to be at least 11.5 with that cam but I cant really see a cam like that in that small of an engine being even remotely useful in a street type aplication. If you are running only on race fuel then you should be looking for more like 12 to 12.5 :1 compression. Also if your numbers are correct for those heads then they flow very little for how big the ports are. Those heads should flow more like 300 cfm or more. Another question for you is this some kind of class engine with a displacement limit or is there some other reason you gave up 30 ci. by using a 350 crank? You should be able to make closer to 600 hp with a 377 like that with fairly high compression and decent heads but your heads and cam will deffinitely limit your power with that engine as well as giving up displacement.

 

What is the purpose of destroking an engine, doesn't it make less torque?

 

I agree with Lannie, no way would I buy parts based on what Desk Top Dyno has to say. I feel it is very in accurate and wouldn't really use it as a baseline for anything. In my old 383 I had a comp cams 242/248 hyd roller that went to 6300 and fell off, I feel sure your 252/260 and destroked motor will make power above 6500.

 

ok lets see if i can answer . yes that is the normalized flow # at 28" i was there, and it's a superflo flow bench . there is no port work done on the intake just some bowl blending and 3 angle, and ya they are low to what dart says they should be, the ex are blended and polished. this is a street/ strip motor hence the 11.5 compression. i use 2 gallons of race fuel to a tank ,and the cell for the nitrous is full of 114 race gas.reason for the 377 its what parts i have. last year when i bought the car it had 300miles on the motor the 350 was suposedly built for nitrous BUT it had CAST pistons , it did have the good h-beam rods steel crank. i ran a 250 shot for 8 weekends the first of summer then went to a 300 shot for at least 8 more weeks before blowing a head gasket. thats when i thew on the darts with no work done and put in the 350 jets but forgot that i advanced total timing it lasted 1 gear before breaking 7 pistons and cracking 6 cyld. walls. i had the 400 laying around and the crank and rods ck.ed straight and no cracks
i think i covered everything
last years cam was 252 @50 and .600 lift HR and this is my wifes street car that she lets me drive on the weekends

mike