I bought a Comp cams High energy 268 K-kit among other things recently and I'm going to install them all at once pretty soon. I will be getting AFR 190 street heads too, and I just realized that they both come with valve springs, valvle seals, spring retainers, and locks. Which ones should I use if I will be putting both the cam and heads in at the same time? This motor will be putting out about 365hp @ 5500rpm and 400ft-lbs tq @ 4000rpm according to dyno2000. Also, since I will be changing the rocker ratio to 1.6, would it be worth it to change to roller rockers and if so what would I need to convert from the stock ones? Plus, AFR recommends Fel-pro head gasket #1010 which is .039" compressed thickness, pre-flattened copper with a 4.166" bore. I read in CHP that they used Fel-pro #1094 (.015" compressed thickness, 4.100" bore) to bump the compression ratio up a bit. Can I use this gasket with the AFR heads? My motors compression ratio is patheticly low right now. (somewhere in the 7.8:1 - 8.5:1 range) Also, AFR recommends hardened 5/16" pushrods but they didn't specify a length. Anyone know which ones to use? Thanks guys, and sorry for writing a book I just want it done right the first time!!
John

------------------

• 84 Firebird w/ T/A gfx
• 350 4bbl (LM1)
• Automatic
• Non-leaking T-Tops (new rubber all around)
• Working headlights (new parts)

Mods: K&N, 180* stat, ram-air hood, flowmaster muffler (ugh), Accel cap & rotor, MSD Super Conductor Wires, 24mm solid rear & 36mm hollow front sway bar w/ PST polygraphite bushings and endlinks.

Mods Coming Soon: new gray interior, Spohn SFCs, more PST bushings, front WS6 springs and an entire exhaust.

http://www.homepagez.com/350thirdgen/

 

John,

SPRINGS
Use the spring sets provided with the cam kit. The AFR-provided spring sets might be adequate, but the Comp springs were selected to be used with that specific cam profile.

ROCKERS
Roller rockers are generally better than the stock rockers, if for no other reason than the reduced friction and heat. They generally operate at a lot more accurate ratio as well, so valve timing and lift are as correct as possible.

COMPRESSION
Since you are replacing the heads, the compression ratio changes should all be done with chamber size if possible. Avoid trying to bump compression with a thinner head gasket, since it only invites potential problems later. Size the chambers of the new heads to provide your desired compression ratio.

PUSH RODS
Use the hardened push rods as directed. Since you are changing the entire valve train and heads at the same time, no one can tell you exactly what push rod length tho use (which is why they didn't specify). You will have to assemble the heads and mount one on the engine to measure the proper length. There are adjustable check rods used for this purpose. The improved cam with stock heads would almost certainly require longer push rods, but the AFR heads will change all of that. The key items to check are push rod binding in the heads, binding at either end of the rocker stud, clearance for the valve spring retainers at the closed position, and proper height of the lifter pintle in the bore (lash point). A good guide is to have the rocker perpendicular to the axis of the rocker stud at 1/3 of the valve lift:



------------------
Later,
Vader
------------------
"Let the bodies hit the floor!"
Adobe Acrobat Reader

 

since you're buying the cam kit i'd try to buy the heads bare, but then you'd need valves. guess you'll have to do compare prices and see which would be best for you. if you do get the heads bare consider the manely pro flow stainless valves, about 10 dollars each.

------------------
ICON Motorsports
1st & 3rd
MM Black Diamond 538 F&AM

 

Thanks! The only reason I am considering the thinner gasket is because the smallest combustion chamber size for these heads is 68cc. The stock irons I have right now are 72cc so that won't change much. CHP said they got another .3 point increase with this gasket. Does this mean I'll have to look into new pistons? I'm assuming a thinner head gasket is more prone to leaks? As for the roller rockers, if I just buy them, will they fit directly on without any other conversion parts? and one more thing: do I need stud girdles?

[This message has been edited by johns84bird (edited June 24, 2001).]

 

The thinner gasket is not merely "prone to leaks"; with aluminum heads, I would describe a shim-stock gasket like that one as "guaranteed to leak withn 10 heat-cool-cycles". Don't do it, you'll regret it. The 1010 is the gasket of choice for your combo. Always remember, the guys in CHP aren't going to be depending on that engine to be theirt daily driver. All they have to do is get it to run and do a few dyno passes or strip runs or whatever, which isn't the same thing as building it to last 100,000 miles.

You may find that your heads would come with 1.45" springs, while the ones in that particular K-kit are 1.25", in which case you'd want to use the AFR ones. If AFR equips them with 1.25" springs, then ede's suggestion is the best way to go. Check to see what price AFR will charge if they sell the heads bare and add the valves in a box or something.

Your CR right now should be about 8.5:1. With those heads, it will be about 9:1. It's not as bad as you might think to have a slightly lower CR, especially with a real mild cam like that one.

1.6 rockers are an extremely good idea. It doesn't make any sense at all to have heads whose ports will flow like a fire hose, only to set the engine up with valve action that just barely cracks open the valves. You effectively waste every dime you spend on heads that way. With those heads, you won't have to change anything at all to use roller rockers, except the rockers themselves. If you want full roller ones I'd recommend going with Comp 1302s; steel is better than aluminum for long-term survival on the street.

You absolutely must dump the stock exhaust to realize the gains from those heads as well. You won't get any 365 HP out of that with the stock exhaust; you'll be lucky to get 280. Like the valves, it doesn't make sense to spend cubic mega$$$ on fire-hose heads, only to hook them up to garden-hose exhaust. You still get garden-hose performance. Flow, flow, flow....

------------------
"So many Mustangs, so little time..."
ICON Motorsports

 

RB,

DOH! Brain fart! I'm busted again!

I'm glad you caught that one, though. I wasn't considering the part matching that Comp does for replacement kits in a non-stock head application. DU-UH!

- - - - - - - - - - - - - - - - - - - -

John,

RB is correct (as usual). Ask Comp if you can exchange the "981" springs from their K-kit for the "989" or "990" springs. They will provide the same closed seat pressure and allow a lot more lift and service life.

Or better yet, exchange the cam kit for a different one. Make all the lift you want with the lobe profile and not the rockers, then change the rockers if you feel it is appropriate. You really don't want to do this twice (like I did - should have listened ot GhoSSt first). Since you're already pushing the limits of a stock torque converter with this 268 cam, you might want to improve the cam and plan on a converter swap. A 274 or 284 might work well with those heads at higher RPMs, and since you are carbed you might get away with more overlap.

I also read the post a little more carefully and realized that you probably have the non-HO engine in your car. You might well have dished pistons in the "LaMe1". The choice is yours. Keep the lower compression ratio or bump it now. The bottom end will change the price tag significantly, but you don't have to do it all at once, either.

------------------
Later,
Vader
------------------
"Let the bodies hit the floor!"
Adobe Acrobat Reader

 

It's OK, Vader. You've protected me from myself a time or 2, it's good we're all here to keep each other honest.

------------------
"So many Mustangs, so little time..."
ICON Motorsports

 

Thanks RB, yeah I guess I should mention I have a pair of SLP 1 3/4" headers jet-hot coated, a hooker cat-back, catco hiflow cat, weiand 8000 egr dual plane intake, and the other previously mentioned parts waiting to go on a carbed 350. All emmisions equipment and computer will still be working, so do you think that 365 hp level is a bit overrated? The thing about this program is that they only have one dual-plane intake setting and I'm sure they are many variations in real-life. Also, the probably don't take into account the emmisions equipment. Well, I picked the largest high energy (emmisions legal) cam they had and decided on 1.6 rockers giving about .484" lift on both exhaust and intake. This creates a very nice "theoretical" power curve on the program. So, with the aluminum heads and about 9.1:1 compression, I should be able to run 87 octane correct? Oh and if I run a 50 shot of nitrous every once in a while, the stock bottom end of that 1200 dollar (non-HO) motor should be able to handle it don't ya think!? Thank so much everyone!
John

[This message has been edited by johns84bird (edited June 24, 2001).]