While I know not to live by desktop dyno I've always been told its 'in the ball-park' if the inputs are all pretty accurate. If I plug everything in as is now I get about 310-320HP from my 355, which I believe is pretty accurate(figuring that the accessories knock off 30Hp or so) considering my 98.2mpg trap speed. The entire combo is;
355 Ported World S/r 1.94/1.5 valved heads,
Dart Sportsman II Dual Plane intake, 650 Holley DP, 1.5 Roller Rockers, 8.9 Compression, 203/212@.050 hydraulic 50-state legal cam(246/262 adv. .429/.435), 1.5 cheapo headers with 2 1/2 straight pipe(with H) into flowtech mufflers dumped at the rearend. Msd Distributor with 35 total timing in at 2900rpms. also a taurus electric fan.

I had flow numbers for my heads stock at around 200/145 @.500 Lift and after porting with back to back(no other changes-weather identical) dragstip runs I saw a 2mph increase with nearly .3 drop so I'm guessing now they flow around 225/165@.500 Lift with moderatly strong low lift #s. If I plug this all in and then switch the cam to a xs268 solid cam(230/236@.050, .488/.501 Lift, 268/274 adv.) with a .5 increase in compression, I get a nearly 50hp gain with no other changes.

Does this seem accurate? In the real world what gains would i see(both in hp and at the track?)? If anyone could run this through EA and see what increases the cam change causes I would be very appreciative. Thanks for the replies and sorry for the length of this post!

 

I can't guess at how much hp you will gain but it will be a lot! The cam you have now is really tiny. You should see gains everywhere in the powerband because the SR has a much more radical lobe profile, that will hold the valve open more for longer. You will definitely be happy with the change if you also change to the recommend valve springs.

 

I would say that is possible. up-ing the comp, along with a way bigger cam should give some good HP numbers. As for torque? It might need a bit more rpm to get it going.

 

I believe that is a mechanical flat tappet cam, not roller. But either way, you should see a nice gain over what you have now.

 

OOPs sorry i saw XS and thought solid roller. Never mind you will not see the gains that i said you would. You will gain a little peak hp, but will lose lots down low. With those heads there is no reason to run a solid cam, a hydraulic flat-tappet cam will be better. With a low compression ratio of 8.9 i would not go with a very big cam, it will be very easy to over cam it, and it will be a dog. Try something like a XE262 or XE268 if your feeling lucky.

Also what is the purpose of this vehicle, street/strip, drag, street? What tranny do you have? What gears? What stall converter?

 

Wow those S/R heads dont flow very well out of the box. Isnt that close to what a stock 416 head flows? Either way I could defenetly say that you would gain about 30hp with more compression and a bigger cam assuming the cam matches your compression and you heads. theres no sense in getting a bigger cam when your heads are already flowing to the max with the one youve got. I say just just have your heads milled for about 9:5:1 compression and add 1.6 roller rockers it will raise your lift about .30 then youll need a little more stall but I think youll be happy. Good Luck.

 

The Compression is going to be upped to 9.5 with a head gasket change. The xs268 is just Competition Cams solid version of the popular hydraulic xe268...the #s are a little bigger but solids 'act' 6-8 degress smaller as I understand things. I wanted to go solid cause from all the info I hear and dyno's I've seen solids give a little more torque down low then comparable hydraulics which would be good for me cause the big cam change would prolly make the bottem end a little soggy(not to mention I know of someone running this cam in a 355 with 186 heads and is running low 13s in a 4200lb truck!).

As for purpose- its 75% street/ 25% strip. Runs 14 flats now at around 98mph. Would like to see mid/low 13s. Tranny is a Tremec TKO 5-speed manual with 3.42s(in 1st gear its like having a th350 with 4.56s so gearing is no problem!). Has Nitto Drag Radials on it also.

 

Just like some of the more unsavory body parts, everyone has an opinion. So take mine for what it is worth.

You listed "75% street / 25% strip" as the intended vehicle usage. Unless you flip=flop that description, and increase it to about 95% strip / 5% street. you might eventually be dissatisfied with a solid roller cam. Modern hydraulics and decent rockers are more than adequate to meet your goals with a very high degree of reliability and streetability. Why would you sacrifice that?

 

Its a solid flat tappet cam, not roller(I have non-roller block). I like the way they sound(l love the sound of the 11:1 CR solid cam LT-1 70 Camaro engines) and it seems they offer a tad more torque down low and slightly more hp to a comparable hydraulic flat tappet.

Thanks for the comments guys, keep em coming!I really appreciate it.

 

Get the standard XE268 and call it done, you don't want the solid lifter cam for a 75% street car... But it's not my car...

I bet you'll get on up over 30-35hp from the cam swap, who knows it could get near the 50hp number spit out by DD...

 

Solid is fine for the street, but can create a bit of a problem with detonation sensors if your engine has one. They will also require periodic adjustment. If you get it right, you may only have to check adjustment every year or so, depending on your use and mileage.

There were a lot of solid lifter engiens on the road years ago, and many people never adjusted valves. Chrysler crooked sixes are a prime example, as well as some current imports, like Mitsubishi. They typically don't have as aggressive a profile as what you may be planning, however.

 

You can get retro fit roller cams (roller cams designed to fit pre-roller blocks) that are obviously roller designs, but have the flat sprocket mounting face to accept non-factory roller cam gears. Furthermore, any solid roller cam you would get would be of the retro-fit nature as there never was a factory roller design.

however, retro-solid rollers cost a pretty penny.

 

Your telling me. The kit with everything you need to convert is upwards of 800-1000 dollars and it still doesn't include new pushrods I would probably need!