Not really cleared up IMO.

From my personal observation, AFRs that are lower seem to create more torque. W/O jumping around the net trying to find a reliable source to confirm/deny the 13.2 number, I'm going to assume that's for 100% gasoline. And, since most areas are running E10 now, I bet the more relevant target to shoot for would be around 12.5:1.

In my own tune, that's where I found the sweet-spot for TQ.

 

The 2 shops I linked you to, are porting shops. They are very well known within their circle and very good at what they do. In the past I have owned or built engines that used cyl heads and intakes ported by both shops. No disapointments in their work and that is why I recomended them. I do not think either do general repair/labor type work..... I'm positive neither do computer work for LTX.

I don't think you'll find a shop that can do everything very well. Your talking about 3 very different displines. Porting, assembly and tune. When you want the best work you have to get 3 experts to do that work.

I would recommend you take the car to your local shop and have them pull the heads and intake. Measure the pistons to deck at TDC (I need that measurement so I can tell you what head gasket and what cc to cut the heads to). Then take the heads and intake to one of the shops I recomended. Once the heads and intake are done have the local shop re-assemble and meaure the pushrods to correct the rocker/valve train geometry.

As for an estimate on cost.
Labor to tear down/install/measure pushrods - $1000.00
Port intake - $200-300
Deck cyl heads - $150
Gaskets/antifreeze/sealer/oil - $150
retune - $300-$600
Will

 

Thanks Billy,

To summarize; Ball-parking $2K will port the LT1 intake, purchase and install pushrods, Shave heads to acheive a 12/1 compression ratio (to accomodate ethanol) properly size a head gasket, and tune to.

I have posted here before and I have to say that I am extremely happy with the quality of the information and the helpfulness I have gotten in relpy. You guys are great! I will begin saving for my "horsepower fund" and contact the shops to get appointments for the work.

Please go out on a limb and guestimate the reasonable gains (torque and hp) I can hope for. I am desperately seeking a competent tuner in my area. Any leads would be appreciated.

I have heard of a LTX guy out of New Smyrna Beach that will tune in Orlando at Next Level's facility.

Thanks again for the helpful advice. I look forward to a strong stroker.

Mark

 

It sounds like your car runs pretty well as it sits. Is it really worth $2,000 for a 20-30 hp/tq gain?

 

When it's all done the increased compression is going to add a lot to your midrange TQ/HP and a little on the top end.

Your combo with the intake and compression fixed (11.5 SCR) should be a 420-430RWHP car and 385-390RWTQ (Dyno Jet).

Now all dyno's read a little different and those are just general numbers. I built an LT4 engine for a friend here using a very similar Reed Cam and only 10.8SCR (8.4DCR) - thats what it made. Most everyone with the 280XFI or similar cam is in that HP/TQ range.

I'd expect HP to peak at 6000RPM and TQ to go over 350RW@3500RPM and carry over 350 till about 5200-5500RPM.

While you save your $$$, drive the car and enjoy it. Your current 400RWHP should make a pretty good running car.

Of course you have a really good point.... but everybody has a different idea of what's worth what. I just supply the technical information around here.

Will

 

Your numbers are fine and exactly in line for what a short runner intake will make with that combination of parts. If you wanted more torque, you need longer runners and match the cam to that. Going to 11 to 1 or so compression will not yeild significant gains, likely 20-25 hp/tq IMO. Its a good gain, but certainly not going to get you near 450wtq

 

Maybe this is where somebody (me) should remind LTx owners that FIRST FI does make a long-tube setup for the LTx platform. Seems like it was this spring where one/two LT guys thought they might give one a try. Too many people ignore that intake IMO.

Of course, the 300cfm let's you keep the top-end too.

 

Gentlemen Thanks to all of you for participating in this thread. Ya'll provided exactly what I was looking for. Cold hard facts AND opinion. I appreciate it all!

I think it makes sense to sit tight with my 412rwhp and 388rwtq (dynojet) and enjoy the vette. I love the C4 Corvette and get a lot of compliments from people that prefer the classic styling (I came back).

Thanks again guys!

 

my only concern is does it fit under the stock hood? I guess for vettes it would but for fbodies, i am not so sure. The LT1 intake is a good design, runners are alittle short of being optimal but still work well enough to create good power, and broad torque curves.

 

 

Cool pics!!!

 

As long as it gets you around the track fast enough, I 100% agree. With the higher torque of a long-runner under my hood, I have to admit it's best suited to sub-highway speeds. It'll get you to 60-70mph as fast as a bat, but once you get the pony running, having more ponies can be just as fun. And, judging by your pics, you got yourself a pony!

 

Thanks Greg,

It is a very fun (easy) car to drive and it appears that I've gotten most of what I can for a motor that will see mostly roadcourse service.

 

If you needed a broader hp power curve up top, a different cam could help with that. What rpm does it peak at now and how much power do you lose at 500 rpms past peak? Widen the duration split alittle, like a 230/242 cam and it will hang on alot longer after peak so you can stay in gear longer. May come in handy on a road course.

 

Talked with a C4 guy at Daytona during the PBOE weekend. He was running the LT1 383 with a TPIS long runner intake. Claimed torque numbers around 450. Seemed to fit under the hood pretty well.