Freddie

Hi

I'm thinking of replacing the 929 camshaft in my 406" SB (8,5:1 compression, 882 heads) to an Xtreme Energy 256 camshaft.

But do I need to change valvesprings as well?

According to Dyno 2000 this seems to be an excellent choice, especially if I install the camshaft at 110 degrees ATDC on the intake lobe centerline.

Suggestions?

Thanks in advance

/Freddie

Freddie

Camshafts specifications.

Comp Cams XE256H-10
-------------------------------
212 degrees intake duration @ .050"
218 degrees exhaust @ .050"

.447" intake valve lift
.454" exhaust valve lift

Lobe center: 110 degrees



G.M. 3896929
------------------------------
195 degrees intake duration @ .050"
202 degrees exhaust @ .050"

.390" intake valve lift
.410" exhaust valve lift

Lobe center: 112 degrees

BAD-HABIT

I Run the CompCams XM270HR in my 358SBC. Mine is the roller I think the hydraulic version is the 270H. It idles @700 yet still has a nice lope to it. Runs up to 5300rps and has a real nice mid-top end to it. I would go a lot bigger than the 256 anyway you go though......Especially for a 406. Get Deniss Moores book it has a listing of several very good cams hydraulic and roller. If you have a SBC and don't have this book that should be the FIRST thing you do. You might want to leave a message on the board here for Deniss Moore he checks in from time to time and can give you the info you want.....Good Luck

Bad-Habit

Freddie

Thanks for the reply.

I've got the book by Dennis Moore now. He recommends the XE256 camshaft for SBC 406" with less than 9,0:1 compression.

I've used Dyno 2000, and tested many camshafts for example XE262, XE268, XE274. But the low-rpm power seem to fall very quickly as I increase duration and the top-end increases just a little if any at all. So this seems to be a good compromise.

The best would be to get a hydraulic roller camshaft, but that's much more expensive. And I probably have to change valve springs and machine the valve spring pockets to accept the larger springs.

I can't find anything in the book saying that I have to change valve springs if I install the XE256 camshaft, so I guess I don't have to.

/Freddie

BAD-HABIT

Many Compines make springs that will fit in the stock spring seats......I got mine from Crane. I don't remember the # but they are good for up to .550 lift I think...Also if your gonna change the cam why not have the heads milled to get ya to 9-1? Just my .02cents......

Bad-Habit

olysan

I'm running the XM 262 in my 406 with vortec heads and 9.1-1 comp. The engine idles at 650-700 with very little lope. At the very least I would go to the XM262. My engine is just begging me to go bigger.

Freddie

XE256 (Intake centerline: 106 degrees) "advanced 4 degrees"
2000 153
2500 194
3000 235
3500 263
4000 276
4500 277
5000 285

XE256 (Intake centerline: 110 degrees)
--------------
2000 152
2500 190
3000 232
3500 262
4000 282
4500 288
5000 276


XM262 (Intake centerline: 110 degrees) "advanced 2 degrees"
--------------
2000 149
2500 189
3000 231
3500 262
4000 279
4500 282
5000 265

XE256 (Intake centerline: 106 degrees) "advanced 4 degrees"
2000 153
2500 194
3000 235
3500 263
4000 276
4500 277
5000 285

XE256 (Intake centerline: 110 degrees)
--------------
2000 152
2500 190
3000 232
3500 262
4000 282
4500 288
5000 276


XE262 (Intake centerline: 106 degrees) "advanced 4 degrees"
--------------
2000 150
2500 190
3000 233
3500 263
4000 280
4500 283
5000 266

XE262 (Intake centerline: 110 degrees)
--------------
2000 148
2500 187
3000 230
3500 261
4000 284
4500 292
5000 285

XE268 (Intake centerline: 106 degrees) "advanced 4 degrees"
---------------
2000 142
2500 183
3000 227
3500 261
4000 283
4500 295
5000 290



Comp Cams recommended the XM262 cam, and Dennis Moore recommended the XE256 camshaft in the book.

It seems to me that the XE256 cam at 110 degrees intake centerline is a pretty good choice. And this camshaft only got a 0.454" maximum lift so I should be able to use "stock" valvesprings.

/Freddie

olysan

Those numbers all look very low compared to what my 406 does, and what dyno said it should do. Once again...the 262 cam is very tame in my engine. It has a nice low end, and a very strong midrange, but my 406 could definitely handle more. Max lift on the 262 is .477, so I'm also running stock springs.

220BR

I ran the XE256H-12 in my mostly stock 350 Merc. Gained about 700 rpm and idle was still smooth. I'd go a little taller if I were you. XM262H or one of the XM roller cams.

I'm putting the XM270HR in the 383 I'm builidng.

Freddie

OK.

Thanks for all answers.

/Freddie