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Old 11-26-2009, 06:54 PM
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355 vortec heads comp xe268 build questions

I am new to this site and there is some really good info from what I have read. I just started my first project on my 92 ext cab 2wd silverado. I am going .30 over, hyper flat tops, vortec heads with comp xe268 cam, i found a edel air gap intake on CL for a good price. I have been searching for 350 recipes for a while and most seem to be happy with this setup. I am still looking for info on lifters rods etc. I do have the stock rods, lifters and rockers that came with the heads but not sure if they will work. machine shop said they will have the short block and reconditioned heads that will be good for about a .550 lift back to me in about 2 wks. they are doing a valve job and new springs.

A few questions I have are
1. what size carb do yall recommend?
2. which lifters and what size push rods should i go with?
3. I read something one time about drilling larger holes for the push rods?
4. anyone running this setup, should i be aware of anything?


thanks in advance

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Old 11-26-2009, 07:12 PM
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a 650 to 700 carb will work fine. As for push rods your way over shooting the importance. A set of comp cams stock lenth heat treated push rods are all you need. A set of federal mogul lifters will suit you fine. Make sure the intake you have will bolt on to Vortec heads. The old style intakes have a 12 bolt pattern or 6 on each side. Vortec heads have a 8 bolt pattern or 4 on each side.
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Old 11-26-2009, 10:28 PM
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I ran a similar set up in a SWB chevy. The RPM was a bit too much at low RPMS for my liking but I also had 3:23 gears. I changed it 3:55 in it's later years and it seemed to appreciate that a bit more. I think you will be happier with a Eddie high rise Z28 style. Advance the cam 4 degree's.
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Old 11-27-2009, 09:50 AM
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ok, so i'm good on the rods and lifters then. will the lifters and rods that came with vortecs work. as far as intake it is for vortec heads, time to start collecting my coins for the carb. thanks
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Old 11-27-2009, 10:51 AM
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Quote:
Originally Posted by TX512
ok, so i'm good on the rods and lifters then. will the lifters and rods that came with vortecs work. as far as intake it is for vortec heads, time to start collecting my coins for the carb. thanks
This a roller or flat tappet cam? Unless they are roller lifters, throw them away (or keep them IN ORDER and store them away with the cam they wore into)- flat tappet-type lifters cannot be reused on a new cam!

The rockers need to be self aligning- this is what came on the Vortec heads, but could have been changed along the way.

If they're not SA, you'll need guide plates. Regarding your question #3, what you may have heard is that the push rod hole in the head that guides the p-rod on non-SA equipped heads needs to be enlarged if using guide plates, a high lift cam or if larger diameter p-rods are to be used.

In your case, I would reuse (or buy roller fulcrum) SA rockers and like DV said, use a good set of hardened p-rods in the stock diameter, but a thicker wall.

There are p-rod legnth checking tools that don't cost too much, or have the machinist check for p-rod length before ordering them. If you are handy, you can easily make your own adjustable p-rod to save some $$$ (see image below- nothing more than a halved p-rod threaded for a 1/4" stud)- the machinist doing it will prolly be the most expensive alternative.

Getting the geometry correct is important. In the process of rebuilding the engine, the the right p-rod length can change from stock. Decking the block/heads, head gasket thickness, machining of the valve tips and seats when the heads are rebuilt, different rockers (if used) can all alter the p-rod length needed.

Good luck!
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Old 11-30-2009, 09:55 AM
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Thanks for the info, I guess I thought I had the lifters but I dont. I'll check out summit.
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Old 11-30-2009, 10:07 AM
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on a 268XE lobe you have to use the springs spec'd by Comp, or you will be buying another cam after that one fails. Spring choice is CRITICAL with these agressive cams.
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