I've searched the boards and didn't find a clear answer on this topic so I figured I'd ask. I bought these headers and made small improvements to my motor along the way...now I'm worried that they may be too small. I'm looking for 500 RWHP.

longrod HT383, blueprinted and forged, 11.5:1 compression, AFR 190 heads, cc306 cam, LT1 intake, 58MM TB. Engine built for nitrous use with cam change.

Another thing is ground clearance...how bad is it? This car is for road racing so I'm concerned about that since there are a few rough spots around here, and i have a 1" drop. Also have a T-56 so I'm worried about clearancing the slave cylinder. Maybe I should get 1 3/4 shorties?

 

500 rwhp is almost 600 hp at the flywheel, which is quite a bit. 1 5/8" headers will support it, but 1 3/4" would be better. Hooker 2210's (LT's) are 1 3/4" and they fit with no problems with a T56. Ground clearance is acceptable and should be just fine for road racing (flat roads, not bumpy gravel roads and such). You're probably looking at 3.5-4" ground clearance, my guess. With 600hp I would definitely shy away from shorties, longtubes are much better, even if they were 1 5/8". With that much power you might also think about getting a Tremec TKO and a Spec clutch. Stock T56's are only rated to 450 tq whereas the TKO is rated at 550 tq, but thay have been known to live behind 800hp drag cars...

 

600 HP engine.. id put 1 7/8

 

Only bad thing about 1 7/8" is that it will have to be custom, and it will run around a grand for them at a shop. Just a heads up...

 

yep. 1 3/4's would be your best bet, but even that might not be big enuff. 1 7/8's would be best... and yes when you get to that point of hp, your gunna endup spending money on special equipment.

 

You need 1 3/4". Your car will run with the 1 5/8" but will be holding you out of some top end power potential. The CC 306 is a serious cam especially matched with AFR heads of any kind. Is this an LT1 motor by chance. Not may people choose aftermarket LT1 cams for thier cars unless they have it.

 

1 5/8" LTs become a liability around 475-500 HP. 1 3/4" should be fine for your combo, RPM has greater affect on primary size then HP #s, kind sorta.

Say you have 2 500hp motors. One making 500hp at 5600rpm and the other making 500hp at 6200rpm. The 5600 motor would be fine with 1 5/8s while the 6200 motor will demand the 1 3/4s.

It sounds like you plan to spin, go with the 1 3/4s.

 

Yeah. I expect power peak over 6000. No, this is not an LT1, it's just a standard Gen I SBC crate HT383 that was modified with 4340 rods and forged pistons with all the little goodies. I sometimes regret not going to an LT1, but there shouldn't be anything that an LT1 can do than an L98 can't, right?

 

No you are better off because you have more head choices, have the great flowing intake (I would go with an LT4 intake with your combo, the stock LT1 vmay actually hold you back a bit) and you do not have to worry about that stupid opti spark.

 

Also, you will have to consider the size of the exhaust ports for your heads. 1 5/8s may be to small and overlap the port.

 

The 1 5/8's may create more torque overall but will definatly hurt your 6000+ rpm peak hp some, 1 7/8 i think would be overkill and may get the best peak #'s but overall hp wouild suffer and for roadracing might create a problem. Refresh my mind whats the 306 specs? I'll bet you'll be over or around 500hp so the 1 5/8 would start hurting you a bit, and the 1 3/4 would be the best bet. I would not go any higher unless your building the moter exclusivly for the nitrous. As for ground clearance the headmens would offer excellent clearance as long as your running open headers, its whatever y-pipe or other piping you put in after that that hurts the ground clearance as you must run underneath the tranny x-member. As for clearing the slave cylinder i know that the hedmans will not clear t5's or so i've heard, i have no personal experience there. good luck!