Pro Stock John

iTrader: (34)

Got a buddy with a 460 ci stroker:

• Ported LS3 heads
• 4.250 stroke engine
• 242/256 114 cam
• FAST 102 intake
• 1 7/8 headers, 3" exhaust
• stock DBW TB
• 3.5 air intake
• 4L80E
• pump gas

Made 488/610tq unlocked converter on Dynojet, HP flatlined at 5800-6000.

I'm thinking he should move to a 102 TB and a bigger air intake tube, 4" or maybe he can try doing something over the radiator, not sure what fits.

Any suggestions or comments? I also suggested he figure out compression in case it's up there and maybe he can do flex fuel E85 setup.

jasons69chevelle

compression ratio? What lifters? What valve train springs, retainers, rockers? Who measured the pushrods and are they all the same length?
What DBW TB is he using?

BigDaddy97

I have a HPR 468 stroker and make much higher numbers than your friend, and I flatline at about 6500rpm. I have a carbon PST intake, 105mm throttlebody, and a .675/.675 , 262/276, 114 +4 cam, Tony Mamo LS7 heads. I will be switching to a 4500 throttlebody and CID intake this winter. These 4.250 stroke motors need huge amounts of air.

ddnspider

iTrader: (26)

How I'm the world does a 460 make mild 408 numbers? I know it's unlocked but that's brutal. A log should show severe vacuum during the pull. It's probably starved for air, but thats still crazy low. Cam timing verified?

AgFormula02

iTrader: (13)

1 7/8 headers seems like an issue
do we need to look at 2 or even bigger?
what does the rest of the exhaust look like?

BigDaddy97

His numbers really don't surprise me given his parts: the fast intake is way small for this size motor, the air intake tube is small, his throttlebody is small, and even his cam is small (I ran a bigger cam than his in my old iron block 421). His torque is insane which is a good sign, so add as much air as you can and the hp will climb dramatically.

Che70velle

iTrader: (6)

460 cubes will need lots of air in/out. As said above, induction system is too small, cam is too small and needs at least 2” headers. I’d go 2 1/8” headers. Look at 260ish/272ish on a 114 cam…460 cubes will eat up duration. LS3 heads are not limiting this on my opinion, as they can adequately move enough air for the cubes, especially ported. Run as much intake as the vehicle will allow to physically fit. 102 or 103 Tb. Torque might drop a smidge, but it should pick up 125 hp easy, maybe 150. Thing will be a torque monster regardless with the cubes there.

BigDaddy97

Since he's using LS3 heads, I think a LOD intake with a 105 throttlebody would be pretty sweet on that setup

Che70velle

iTrader: (6)

I have no idea what vehicle is. Maybe a top mount 4500 tb on a CID? If it’s in a car, forget that remark.

BigDaddy97

Right. I got lucky as the overall height of the CID/4500 is the same as my carbon pst setup, so it will work on my S10 with no problem. Going on first thing as soon as race season is over.

Pro Stock John

iTrader: (34)

It's a very nice GTO street car.

Pro Stock John

iTrader: (34)

Full 3" exhaust with straight-through mufflers

Pro Stock John

iTrader: (34)

Logging KPH is showing a restriction yes.

I think your comments (I sent him the link) might push him to get a 102mm TB, and play with the air intake. Not sure if a carb intake with a 4500 is inline with his build plans but I'll mention it, I have 2-3 other friends running setups like that.

I'm not sure anyone makes 2" headers for his application but we can check around.

Keep them comments coming, thanks guys.

BigDaddy97

Hmmm.....given his hood restrictions, I'm now just thinking upgrade the air intake to 4", add a 102 throttlebody, port the fast 102 and put in the interchangeable short runners to bump up the powerband peak, and then change the cam up a few sizes. He will still have air restrictions but it will be tons better than what he has now. Very nice car btw!

Pro Stock John

iTrader: (34)

Thanks I'm sure he'll read the thread tomorrow.

ddnspider

iTrader: (26)

Seems hard to believe it would pick up 150whp from an intake swap, but I'm in for results.

Double06

iTrader: (1)

Something is not adding up. TQ = HP at 5252 so if 488 is best hp (at like 5800 rpm) lets say it was 450 hp at 5252 that means tq is also 450 ft pounds at 5252 or a drop of 160 ft pounds from peak which is horrible (even with cam being a little small there is no reason for a whole number delta (hp/tq) like this). Is this one of these annoying dyno graphs where the hp is on one side with a different scale and the tq is on other side with a different scale. Post a graph if you can. Also check for tire / converter slippage. For example they can run a mph instead of rpm. On a stick car with a 3.42 and a 26.5 inch tall tire it should be 115 mph at 5252 rpm. I know if you are an automatic but if you are 80 mph with 3.42 and a 27 inch tall tire there is your problem.

ddnspider

iTrader: (26)

That's why I asked about cam timing. Just doesn't seem right unless there was stupid converter flash.

SLOW SEDAN

iTrader: (13)

Replace mufflers with twin 88's, rest will sort itself out

Mavn

iTrader: (3)

Sounds like it's on 7 cyl. My 416 did this when I lost a coil pack. Made 460 wheel and a **** ton of torque. Found the dead hole on the dyno. Replaced the coil and bam 600 wheel next pull.