engine build help

[travisr1988]

Okay, I'll see if I can get my dad to measure the displacement if the heads as they are at his place and see how much was taken off then. Thank you Rich.

[454Man]

You just need a baby syringe with cc numbers on the side. And a Thick oil. With the heads upside down just fill the bowl or valve area with the oil from the syringe. Take note of how many cc used

What's under the hood??? If you have to ask maybe we shouldn't race...

[rich weyand]

Yup.  You only need to measure one, and you should have about 80 cc of oil on hand.

[travisr1988]

So, I talked to Comp Cams, Crower, Crane, Lunati,  Howards cams, and Isky. Waiting for isky to reply but the others have made their recommendations. Crower asked for the most info and gave the most input. Anyways: Comp cams rec. XE256H or XE262H. 212/218 @.050, .447/.454 lift on a 110LSA\ 218/224 @.050, .462/.469 lift on a 110LSA | Lunati rec. voodoo 10120702/60102 219/227 @ .050, .468/.489 lift on a 112LSA | Howards rec. 110991-08 221/221 @.050, .470/.470 lift on a 108LSA | Crane rec. 114122 204/214 @.050, .423/.446 lift on a 110LSA | Crower rec. 00904 torque beast 214/224 @.050, .444/.467 lift on a 112LSA. My father keeps talking about the Isky 270 MEGA saying it was the best cam he ever had, but I don't know what set up he had with that cam. specs for 270 MEGA are 221/221 @.050, .465/.465 lift on a 108LSA

On a side note, I may be able to pick up different heads like camel humps, someone I know wants to trade a few things for my 3/4 ton and I know they have several motors and heads, some are camel humps, so camel humps may be a possibility if any have accessory mounting holes.

[rich weyand]

I would choose the Comp XE256H (12-234-2) over the XE262H (12-238-2), for the torque to get that thing moving.  Torque is a better choice for street than horsepower.  Still, nlauffer picked the 12-238-2, and it is one of my four recommendations.  Actually, they both are, more or less: the 12-234-2 is so close to the 12-235-2 as to make little difference.  Hard to lose with either of those.  Don't know anything about the others, so I'm no help there other than to tell you to google the part numbers and read all the forums that hit.  Particularly the full-size car guys, Impalas and Bel Airs and such, because that's closest to the truck in weight.

Did you ever have those head volumes measured?  If they are stock 76cc heads, I would probably go 12-234-2.  If they have been shaved down, then you have the static compression to do better with the 12-238-2.  You gain about .1 in the static compression ratio per cc lost, so if they are down around 70-71cc, it makes a difference.

Either is an OK choice.  The 12-238-2 will start to give you mildly lopey idle, if that's what you like, at the cost of bottom-end torque, but with more horsepower.  Given the extra lift of the 12-238-2, you don't lose as much torque in the bottom as you would if the lifts were the same, and full-throttle passing will have more horsepower in the high rpms with the 12-238-2.

[travisr1988]

Measured the head volumes, turns out they are at 72cc. Multiple CR calculators put me at 9-9.3:1 CR with 72cc chambers depending on gasket and deck height, good for a street motor. I can't tell you the deck height for sure because I know very little about the flat top pistons, all I know is the valve reliefs add up to 2cc. I'm not sure how much that affects the equation. I talked with my dad today and showed him the cam specs on the recommended cams and he brought up the isky 270 mega again, it was his favorite cam and he says he used stock 882 heads on a 350 with factory dished 8.?:1 pistons and it was an excellent motor for street use and was pretty peppy. He says he also used it with reworked 882s (by someone else) and although the heads dropped a valve destroying the motor it was the best $150/hr he ever spent (cost of build divided by time before motor blew), then used it in a 327...loved it, and again in a 350 with 882s he ported and polished himself. That cam seemed to get around. Anyways he's a hard person to please and he swears he's never had a better cam so I'll honestly go with the isky, after all he has built more bad ass motors than anyone I've ever known.

[rich weyand]

76cc is nominally 8.5:1, probably actually closer to 8:1.  64cc heads get you about 9.4:1.  So 72cc should get you about a third of the way, or a compression ratio around 8.5:1.

If you use the nominal 8.5:1, it would be more like 9:1.

Here are the timing charts:
http://www.iskycams.com/Wcbeece7e23b6f.htm
http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=95&sb=2

Here is an article explaining cam selection:
http://www.crankshaftcoalition.com/wiki/How_to_choose_a_camshaft

Read the article and then work through the timing specs and see what makes most sense to you.  Note that your dad's experience with the smaller displacement 327, and with stock heads on a 350, may not be on point.  Bigger displacement and higher compression can both take more cam.  His experience with the reworked heads may be, depending on what "reworked" means.

[travisr1988]

The same pistons in his last rebuilt motor had the same pistons(2cc total valve reliefs) and 64cc heads ended up getting nearly 10:1. Which is why the new motor in his truck had different pistons(6cc valve reliefs) and thicker gaskets to bring it down to around 9.5:1 so he can use regular unleaded(prefers midgrade). Anyway, I ran the numbers through several CR calculators including the one in desktop dyno, one at csgnetwork, one at summit, one at Wallace racing, and checked the math using Lunati's helpful piston calculations page. All came back around 9.1:1 with 73cc heads and 9.2:1 with 72cc heads.