Ok, i've decided its time for me to start playing with my car again. About 1.5 years ago i built a non roller 357 with forged flat top pistons, stock crank, pro topline 220/64cc heads, and an modified LT1 intake. (Eventually i'll want to swap this intake with something better.) I didnt have the block decked or the heads milled so i estimate somewhere around 9.6:1 compression. I stuck the xfi292 flat tappet cam in there with the required beehive springs, and the pro magnum roller rockers. I have since put a fast bank to bank efi system in and the car starts and runs but not worth a crap. I can get some decent top end out of the car but not like i should. Idle is pig rich and vacuum is non-existent which i think is why i cant get my timing right. I have had probably 10 different people help me try to tune this thing and its just not happening. I've had all kinds of trouble. So, i think i want to go with a smaller cam. At first i was thinking of going back to roller but dont want to spend the money on all the retro stuff right now, as i'd rather spend the money on the paint and body. So, what do you guys thing about going one or maybe two steps smaller on the cam? I was thinking of the 268xfi or 280xfi. I forgot to mention i have a 3000 stall converter infront of a very strong newly built 700 turning 4:10's I really want to get this car going and painted. I'd like to get at least 400hp out this engine. I've always been told to pick a cam and go one step smaller. I guess i should've done that in the first place.

 

Not a big time engine builder but IMO:
1. Heads are to big for your application. 220cc heads on a 350 are a high RPM deal. They also like a lot of lift.
2. Cam is too big. The compression is too low for that big cam. What is the duration at .050". ~242deg.? It kills you bottom end and in an LT1 set-up(Stock top-end) power should be made <6000rpm. Use the torque to accelerate the car.

I'd do three things depending on your pocketbook.
First, pick a cam that has less than 230deg of duration. If you have a roller block the 268XFI Hyd.Roller would be a good choice. You cold use stock hyd.roller lifters and spider to save cost. For a Hyd. FT use the XE268H w/1.6RR. Even a GM hot cam set-up wold be better that what you have now.

Second, change heads. The new GM Vortecs would work well or anything that flows good in the 180-195cc port volume(RHS, etc.). TFS and Patriot heads are also good, inexpensive Aluminum heads. Really good head would be small AFR's but they cost a lot.

Third, raise the compression. I don't know what pistons are in your motor but I'll bet their not Flatops. Therefore you may have less than 9.5 to 1 compression. If haven't already, I'd put steel shim .015" head gaskets on it and get a little more compression. You'll get more quench effect as well.

I'm sure others may have better advice than I.

 

1) I bought these heads because i was after a high RPM motor. The engine runs great between 5,000-7,500 rpm. It pulls very strong. I dont want to give up the heads. As far as i know RHS heads are the same as the ProToplines, just a new name since C.C. bought them out.

2) The came is 292xfi which is advertised. Duration -- 248 int./253 exh. and .584/.579 lift. I went to an LT1 intake because i was after a high revving combo. I dont like loads of torque off the line. I hate having traction issues. I dont want to modify the suspension at all.

The block isn't a roller block. It is an early 70s 4 bolt. I built the engine right here in my garage and I assure you they are forged flat top pistons. BTW i had the engine balanced and according to the machine shop said its good for 8k rpm. How much compression would those head gaskets add?

Thanks for your input.

 

well if you have TRUE flat tops with 64 CC heads your CR would be higher than 9.6:1...

I dont understand what you are looking for out of this Engine... you built a screamer to live above 5K and now what? want it more streetable? want better times?

the .015 gaskets wont add that much maybe .12-.18 CR but decking the block to run them safely with all the extra compression will add a pretty good amount...

Now cams we need to know what you plan on doing with this thing to help... i mean getting your compression up a few steps might make the cam your already running okay for your purpose... but if you want to go smaller cam you might not want to play with your CR...
but just going to a small cam wont solve all your problems those heads will need a bigger cam... i mean some say 210CC is to big for a decent 383


So we need more info like what you plan on doing with the Car, what you want it to do

 

Basically i am not making enough vaccumm to be efi friendly. I cant get the timing synced and keep the car running at the same time. It takes lots of fuel and lots of timing to keep it idling. Ive had this ongoing problem with the timing sync process and have determined that its just not going to work with this cam even though comp cams says it will. I only make about 5" of vacuum at about 1000rpm and even at 1000rpm with an advance light set to 60 degrees my mark is not anywhere near the balancer. But thats another issue that i dont want to get into. I know the engine is together properly and everything is lined up. I took it apart once already just to verify and have checked everything else countless times. I can make it run alright but i have no idea where my timing is. I just advance the crap out of it, basically all of the way to make it run. But the computer says one thing and the mark says another. when it is set like this it still runs really rich. If i start it in the garage the gas fumes will burn your eyes within 15 seconds, and that is with the door open. As far as what i want to do with the car, i want it to run properply and be able to drive it everyday (with my timing synced) and be able to go more than 80-90 miles on a tank and still make some decent power.

 

Seems to me like you want it all. If you built the engine to be a "High RPM Screamer" then you are going to have to give up something. Namely streetability. You are not going to get great vacuum and a nice idle out of a High RPM cam. Its just not the nature of the beast.

Your post is too conflicting though, why get the gears and stall, if you dont want to leave the line quick? Why run an automatic period? If you dont like traction problems, then the first thing you should be addressing is the stock suspension, not the engine.

You have entirely too much intake volume, for the induction and purpose. A set of heads with a 200cc intake ports would make just as much HP, more TQ, and operate in the same powerband as your cam. As posted a million times before, your cam and valvetrain dictate your RPM, not your forged rotating assembly or intake port volume. Those dictate potential, not actual. Match a cam to heads, and your car will be miles ahead.

 

Didnt say i wanted it all. I said i didnt want alot of torque because i dont like having bad traction problems out of the hole which is why i got away from the tpi and low end torque. This car was all over the road before i built this combo. This cam that i currently have requires 3000 stall which is why i have it. Streetability and being tuned properly have nothing to do with each other. I dont care about the idle, i just dont want it dump fuel while its doing it. And i know that my cam and heads dictate my rpm. I was mentioning pistons in a previous post to give an idea of my CR. I posted this thread for help on a selecting a cam that will work with the rest of my combo, not to find out whats wrong with what i got now.

 

Streetabilty and being tuned properly have everthing to do with each other, actually. The purpose of your 3000 stall is to allow the engine into its proper power band upon launch, which defies the purpose of building a low torque bottom end engine. The point is, no cam will really serve the purpose any better than what you have. If you go with less cam, it wont gain any power, obviously, maybe a little more low end grunt which is the opposite of what you want. If you go with more cam, you get more top end, less driveabilty, worse idle, and something harder to tune.

 

What i meant was that i dont care how the car idles, sounds, feels at low rpm or around town. I just want the dang thing to be more efi friendly. I know that if i yank all of that stuff off and a single plane intake with a carb it will run perfect but i want to keep it fuel injected. I guesss i should have just ran a higher CR and/or bigger displacement. Basically i want to run decent without having to ditch all my stuff. I am not saying i dont want to change anything, i just want to do it on a budget. Between what i spent on parts, machine work, more parts, transmission, and EFI system i've already spent a fortune.