I'd like to know who runs one? How much vacuum do you have at idle? I need to know b/c I think this is the cam I want to go with and I'll need to know if I need a vac. secondary carb or a mech. secondary carb. Thanks.

What are you going to be putting it in? I am running the XE284 in my 410" BBC. I get 7" at 750 idle. Not really enough the get best out of power brakes.

Regards,

I use one in a low comp 350 w/factory heads. I have 6-7" of vac at idle. I have a manual trans, and a check valve on the booster vacuum line for the brakes, so I don't have an issue with brake function. Any rpm above idle, I have 25+" vacuum (as long as it's not floored)

FWIW, I use a 650dp carb, but I have a 4 speed and 4.66 rear gear. A vac sec carb may work better w/ auto trans and lower number rear gear.

Chris

I've got one in a 385 stroker smallblock. The engine hasn't been run yet as it is waiting for its home to be completed.
Do you guys have any suggestions on this combo:
4 bolt main 350 block, bored .040" over.

Scat 9000 series cast steel crank

Scat forged 5.7" I beam rods w/ ARP hardware, bronze bushed for full floating pistons

KB hypereutectic pistons, approx 10.2 compression ratio.

Comp cams XE284H hydraulic cam & lifter set.

1.6 ratio aluminum roller rockers on top of 2.02/ 1.60 valves in 74cc iron heads with "stage 1" porting (bowl blend, slightly unshrouded valves, light porting on the intake side).

Edelbrock Performer 750 carb on a Performer RPM intake.

Probably will run a converter with a stall of around 2,800-3,000 using a GM 4L60 tranny and a 3.73 rear end.

All of this is for a '72 Chevelle Malibu.

I started collecting parts for the engine before I even had a car to put it in. I also wasn't experienced in matching parts when I started buying them either.

What would you guys change?

Thanx fellas for the replies.

It's going into a stock 350, but when installed the 350 will be getting 64 cc Iron eagle heads and a new intake. I've already ordered a 750 cfm vac secondary Holley but wasn't sure if it would work in this combo or if I need to go double pumper with mech. secondaries.

The car it's going into is a '71 Chevelle. The tranny is a TH350 and the current rear is a 12 bolt with 4.10 gears. I may change to 3.73 in the future....not sure yet.

I also have power brakes so I'm wondering how well trying to power my brake booster as well as have vacuum for the trans. modulator is gonna work. BTW It's going to stay a foward valve body as a manual valve body is out of the question.

i've got the XE284 in my 406 and my best friend has one in his 383 neither carries more than about 7" of vacuum at idle. love the performance, but i think it might be a tad too big for a 350 in a heavy car. i'd recommend the XE274 if you haven't already purchased the 284. i know of a few guys running the 274 in 355's and they seem to work really well. IMO, the 274 is as well suited to a 355 as the 284 is to a 383 or 406.
three85stroker, sounds like a pretty decent combo to me. personally i would run a 3310 Holley if you are mostly street, or a 750dp if you are worried about getting every last tenth at the track. i don't like Edlebrock carbs, but that's just me. graemlins/thumbsup.gif

I had almost the same engine as you have planned except with the XE274. I had 4.11 gears and ran a 3310 carb in my s-10 blazer. I had about 12" of vacuum at idle. It made about 390hp on the "stock" bottom end and worked pretty well until I cracked the block.

I'm with m71 on this.
If you plan on going to a 3.73 gear you should step the cam down.
The XE274 cam will make more torque at a lower range that will compliment the 3.73 gears in a 350.
If you were building a 383 or 400 you could do it and get away with it since they make more low end torque and the cams duration doesn't effect it quite as much.

That XE284 with 3.73's is a bit too much, especially in a heavy 71Chevelle.
Also if those cams only make 7inches of vacuum in a 383 or 406, they are going to make even less in a 350, you are going to have a hard time with your breaks unless you run something that creates more vacuum.
There are electric pumps that you can run but to me it sounds like your best bet is to step the cam down.

Originally posted by three85stroker:

Edelbrock Performer 750 carb on a Performer RPM intake.

What would you guys change? Edelbrocks carbs are fine for a cruser.
For serious perfornamce Holley or BG is the way.

I have the XE284 cam in my new motor but it's not in the car yet. IF you can wait 1,2 or 3wks I'll tell ya that I too probably have 7" of vacuum at idle tongue.gif For a stock 350 it's way too big IMO and if you plan on street driving I'd chose the XE274 or one of UDHarolds grinds instead. For a 350 the XE284 is really a borderline street cam(even with Iron eagles). It's pretty hard on the train as well if yer car see's any milage. Even now I still have second thoughts about my choice and wonder if the XE274 would have been better for what I use the car for currently(street/autox/rr). Guess I'll find out smile.gif

Well, to be honest with you I planned on eventually stroking this engine but I guess by that time while I had the block apart perhaps then would be the best time to step up the cam to an XE284? And for now just run the XE274?

So now as a rule does a specific cam give a bigger engine more vacuum as opppsed to a smaller engine with the same cam?

Also how much vacuum is required to operate the vacuum module on the transmission?

Oh, how much lope does the XE274 have? Summit lists the XE284 as having a "rough idle" which to me sounds like the regular "blompita blompita blompita" that you hear. I'm wondering how the XE274 will sound.

You will be much happier using the correct cam in this engine rather than suffering untill you stroke it.

Humm..That just doesn't sound right for some reason tongue.gif

Using the exact same components on two engines, one being a 350 and the other a 383, the 383 will have more vacuum.

I think CompCams has a sound bite of the XE274 on their site somewhere.

Eh the only ones I found were the 282, 292 and one other cam, not the XE 274.

Originally posted by Junkyard Dawg:
Eh the only ones I found were the 282, 292 and one other cam, not the XE 274. They're all under the XE line of hydraulic cams. Otherwise theres a 282H magnum cam and a solid 282 as well I believe. Same thing for the 292.

Here's a XE274 (http://www.compcams.com/Technical/Search/CamDetails.asp?PartNumber=12-246-3)

I was hoping for a sound clip of the XE274...unless there's a link on that page and I'm blind as a bat....

I got your back Dawg! tongue.gif

http://www.c3sharktank.com/sound/sound1.html