Well, I am sort of confused on how to figure what length pushrods I will need or whether stock will work.

I am planning on getting an comp cams xtreem energy cam. I was thinking about the xe274 or xe284. The 274 specs are as follows:

Specifications:
* Advertised duration: 274 intake/286 exhaust
* Duration at .050 in. cam lift: 230 intake/236 exhaust
* Gross valve lift: .487 in. intake/.490 in. exhaust
* Lobe separation: 110 degrees
* RPM range: 1,800 to 6,000
* Very strong mid-range torque and throttle response, 2200+ torque converter

and the 284:

Specifications:
* Advertised duration: 284 intake/296 exhaust
* Duration at .050 in. cam lift: 240 intake/246 exhaust
* Gross valve lift: .507 in. intake/.510 in. exhaust
* Lobe separation: 110 degrees
* RPM range: 2,300 to 6,500
* Rough idle

I have a 78 350 with stock replacement pistons and heads that were origionally off of an 85 lg4(I know, I know) but they have been ported and gasket matched and have 1.94 and 1.5 valves. I have a higher stall converter already that actually matches the second one better, but I wondered will these cams provide enough vacume to operate everything? I will have hooker lt headers, a quadrajet w/ dr rods and b hanger, and temporarily a gasket matched stock alum intake. I have a 3.45 rear w/ 700r4 w/ shift kit and an alum drive shaft. Back to my origional question. How do I know what length pushrods I will need. I want to put roller rockers but should I use 1.5 or 1.6? Will any macining need to be done to the heads other than srew in studs for a cam this size? Sorry about the length and thanks in advance for the help.

Ben

 

With either of those cams, you'll need to get your valve spring pockets machined for larger springs in order to use 1.6 rockers. I would not waste any further money on a set of 305 heads if it was my engine, IMHO you should consider cutting your losses on those heads, and get some decent castings to sink your $$$$ into. Porting, gasket matching and bigger valves don't make much difference in those heads; that's about like putting 1" fittings on the end of a ½" garden hose, they will have very little effect on the total flow capacity of the system.

The 274 will probably be OK on vacuum. The 284 would probably not. Either one will benefit dramatically from a higher-stall taorque converter. The 284 especially will be a total dog around town with a stock one.

I had a XE 274 in my 400 for a while, it ran great.

You should probably use 7.500" pushrods with either of those cams. Stock ones will almost certainly be too short, get an adjustable push rod to make sure.

 

Well, I did the porting with the help of my cousin so I didnt really loose any money there, the only thing I am putting money into is the valves and screw in studs. I know the heads are not good, but my car has not run for months and I dont want to wait much longer. I would like to get better heads, but I dont have the money to do that with all of this other crap. Why would I need to have the spring pockets machined? Are the springs that comp sells to match the cam different than the stock size or somthing? The whole insides of the heads were ported, and I was planning on putting the 1.94 and 1.5 valves in so I would think that would free them up at least some? I have heard of vortecs that came pre machined for higher lift with screw in studs and soforth, but do you know how much or where I would get these? What do you think would be my best bet as far as heads for cheap, because I dont know that I have the time to port another set right now. I am trying to get my car going at least by the end of the summer.

Thanks for the help,

Ben

 

Your heads (or any other ones in stock trim for that matter) have 1.25" diameter spring pockets. The lift limit for even the best (not stock) springs with that outer diameter is around .500". To exceed that lift safely, you need to step up to larger springs.

305 heads with the most porting you can do will almost equal the flow of a set of unported 350 heads.

A set of quality valves is about $140; machine work to install them is probably somewhere around $150. Studs plus machine work to install them will run you around $120 more. So, by the time you're done, you'll have around $400 more in those heads than whatever you have now.

Why spend that kind of money on heads that don't flow?

Vortec heads have that problem, plus their valve guides are too tall. The retainers hit the guides at around .450"-.480" in various samples. They would require as much or more machine work as the 305 heads to use either of those cams. At that point, you have lost their economic benefit, and it makes more sense to do something else. That is, if their performance as they come, with their limits, is adequate, they're a great deal; the minute you do machine work to them, you're getting less head for more dollars than you could get some other way.

What pistons do you actually have? specifically, are they flat-top, or dished; and if dished, how much? "Stock" covers alot of ground when it comes to things like that. If they're flat-tops, a set of 58cc 305 heads will give you a compression ratio of about 11.2:1, which won't run on pump gas.

For a budget build, you could go with a set of Vortecs out of the box with the matching Performaer RPM for Q-Jet, and a Comp XE262 with 1.5 rockers. That combo will smoke anything you can possibly do with a set of 416 castings regardless of how much money you spend on them.

 

I dont know exactly what they are, the short block was put together before I got it, but I matched them up at one point with the replacements that (I think) silvolite sells, and it said that with 58 cc heads it would have just over 10:1. What, heads would your suggest then? If I were to use a rev kit I heard somewhere that you are supposed to use lighter springs(dont know if its true) but if it was I thought that maybe I could get away with a smaller diameter spring. I already have a pretty high torque converter so I would like to make the motor rev a little so I really dont want to smother it, I just want to get it done. Is there a head that you would suggest that wouldnt cost me a fortune. Im not sure, but the pistons may not even be replacements. All I know is that there is no lip on the block and it has new rings and bearings and seals and stuff like that.

Ben

 

ttt, anyone have a suggestion on heads that arent too expensive? I might be able to get a set of 327 camel hump heads, but dont know if they are the ones that are new enough to have the mounting for my accessories or not.

Ben

 

Take the advice that RB83L69 gave you. I have put together two 350cid engines using the XE262 cam and unmodified vortec heads. They make sweet engines that have good vacuum and great power. As mentioned before, the money you spend on the machine work for the 305 heads will come close to the price of a set of vortecs.

Lonnie

 

How are the dart sportsman IIs? I found some that are supposed to be ported, and support up to like 650 lift, and flow like 270/210. I am still waiting for a reply from the guy to see if he still has them and some more specifics on them. I plan on using hooker lt headers and was wondering if I could use straight or angled plugs or if they have to be a specific way? Its not that I dont aggree with you its just that it sucks not being able to drive my car yet. Well I guess I will save up and get something better but what do you think of these heads? Oh, and what do the vortec heads flow by the way does anyone know?

Ben

 

ttt