I have been milling over engine combos for some time, and think I have my combo picked out. Let me know what you guys think. It is a late model 355 with unmolested bowtie heads (screw in 3/8 studs, guideplates), an LT4 hot cam; 218, 228 @.050 with .525 lift with 1.6 roller rockers, hyper pistons (9.0 to one with 64 cc heads), x-rods, stock crank, cast rings, clevite bearings, a street avenger 670, performer RPM or weiand stealth intake, proform HEI, 4.55 gears in a ~3400lb corvette with a T-56 6 speed tranny. Some stuff I have, some I am not sure on. The shortblock is done, as is the tranny and rear end. Any more info needed, let me know. Thanks, guys.

 

Sounds like your intended application is mostly street. Stock bow tie heads aren't the greatest compared to what is offered today. Vortec's flow better than unported iron bowties. I would go with a better head (say AFR 190), and more compression (although you say your shortblock is finished). You must be running a dished piston to have only 9:1 compression on a 64cc head. With that much gear and a standard tranny, you could go more aggressive camwise, but might lose some streetability.

 

Yes, mostly street use, with a trip or two to the track. Do you know what the bowties flow, anybody, I had heard that they flow better than the vortecs. The number I heard was 250cfm intake. And, yes, I do know that there is more to a head than max intake cfm, just that was the only number I had heard. Thanks.

 

These guys have some bowtie head data http://users.erols.com/srweiss/tablehdc.htm
The bowties were really meant for custom porting. If you use the bowties or the vortecs, be sure to do at least a minimal pocket port on the exhaust. The vortecs can be brought to 239I/175E (73%) without much effort. Don't use as much exhaust lobe on this ported head as you would with the unported exhaust port (Vortec exhaust usually flows like 147CFM or a poor 62%).


[Modified by HeaderDesign.com, 5:38 AM 10/29/2002]

 

Go to http://www.chevyhiperformance.com to see all the info on just about every smallblock head.

 

My 2 cents
OK the 355 is a good choice, the LT4 hot cam is a good street cam. Trash the 1.6 roller rockers, if you want more lift then get a cam that has it. With the cam you are using the extra lift won't amount to much more than money out of you pocket. 9:1 compression seems a tad low for the cam, a little more would put it in the ball park. Forget the X-rods, old school. Eagle has some that for a tad more than resizing are brand new and will take more. Upgrade the rings at least to moly, not much more in price. Stock crank will survive, bearings are personal. 4.55 is way to much for the engine/cam combo. 4.55 is something for pulling stumps or heavy drag racing. Your engine is not setup to use the 4.55, a 3.48 or lower would do the trick. Since you said the tranny and rear and engine are done then you need to concentrate on some RPMs. Run what you have but keep your eye on higher RPMs or go with a rear gear that allows the engine to work correctly. And for this the heads will have to go.

 

Sounds like a good streetable combo. I personally like living on the ragged edge of streetability. But, I'm slightly insane. :jester

 

Be it right or wrong, some of my decisions are already made. I will try to justify them, but I may be wacky, too. The gears were selected to go with the tranny, since it has two overdrives, I figure I could get away with very steep gears (2000 rpm in 6th at 70mph) And still shred my tires at will. The roller rockers were never in the picture before now, except the LT4 cam was designed to for 1.6 rockers like the LT4 engine has (I like that cam because it can come to my door brand new for $200.) I figured I would also get rollers, because they are easier on the valve train, especially with a roller cam, and they are now in my price range (I sold a couple sets of heads for way too much money). The x-rods were an antiquated idea of mine. At first, I had intended to build barely more than stock, now that is not the case. I did get a good deal ($100) on some prowler 5140 with 180,000psi bolts, but decided against them in this motor, as it was already balanced and assembled. I would also like to have run more compression, but the 9:1 decision was made with the goal of 87 or 89 max. octane, while I save some dollars for the AFR 400 in the future. So, some things I am stuck with, and hopefully will not have to learn my lesson the costly way, others I am not yet decided on, but either way, I do appreciate your imput everybody. :cheers: