Pro's please analyze my dyno graph.

[Dbeck002]

What I suspect.

By looking at my dyno graph I suspect that my intake manifold is inhibiting my engines ability to make torque after 4000 RPM. Its an explorer manifold with light porting and the lower-to-head ports are much smaller than the head ports themselves. When i layed the manifold on the heads, i felt the manifold ports step into the bigger head ports, this is the choke point i say.

Here is the graph.

Notice that as soon as the engine hits 4000 RPM torque starts to drop. It builds fast which is great but then it just shoots down.

Here are my major mods.

That explorer manifold
70mm TB
AFR165s
TFS1 cam
Long tube headers and 2.5" catless H with some unknown catback.
73mm C/L
AFPR
24 lb injectors
255 pump
etc...



the cam, heads and exhaust are built for higher RPM power, but my shop tells me my manifold is killing me. Please help me verify.

 

[DMAN302]

Numbers look good for your parts...I tend to agree a larger intake might very well open up the band a bit. My only thoughts were that the explorer intake was identical to the GT40..and the GT40 untouched has been shown to put up good numbers against other big name intakes in testing. If it were me I'd be inclined to get summit to ship me an RPM...I'm sure nothing but good things would be the result in the upper RPM's. May also want to contact Ed to see if he has any info..he seems to have put together a cam that work really quite well in the low mid range..perhaps this was the intention of the cam?.

 

[Dbeck002]

The cam i use is the trickflow stage 1. I think its a great cam and i love its 'personality'. But i feel the engine being choked above 4k RPM. I suspect its this manifold, i want a holley systemax.

I think its also my cat back, its 2.25" not 2.5".



EDIT: i dont know, everytime i look at the RPM manifold i dread seeing those 180 degree turns the air has to make on the 2 inner runners in the plenum. maybe im just over critical.

Also, i am very happy with the numbers it makes but i know that this torque curve is not normal. I want it flatter and im 90% sure my manifold is causing the drop in torque at the higher RPM.

 

[1SLO306]

hey i got a TFS street heat intake sittin in my garage.$275 shipped. pm me if interested.

 

[Dbeck002]

I was leaning towards something a little more higher RPM than the street heat. I'll consider it though...

 

[DMAN302]

opps sorry miss read your post..I thought I read FTI cam not TFS..too early and not enough coffee I guess.

 

[Michael Yount]

I'd work on the exhaust side and have tmoss port your gt40 lower -- I believe you'll find that will be more than up to the task of the other parts you have and will be MUCH less expensive than replacing the whole intake.

 

[Dbeck002]

How much will it cost for him to port my lower? Where is he located? I am in south florida and im interested. But what about the upper, shouldnt that be ported too?

 

[Michael Yount]

Search tmoss on this site or Corral.net. Ask him for HIS pricing. I believe you'll find it's gonna be in the range of 1/4 the price of a new Holley set up. He's in the St. Louis area.

The bottleneck to flow on the GT40 family of intakes (Cobra, gt40, Explorer) is the lower, not the upper. With the lower ported, the upper/lower combo should support your combo nicely. You'll likely pick up a few more HP up top with a Holley set up, but it's probably going to be at the expense of some power/torque lower in the range. The question is are you willing to pay 4 times the price for gains that likely occur only above 5500 rpm? Especially when that cam is likely to make peak HP around that rpm anyway.....just my thinking though.

 

[Grn92LX]

That tfs 1 cam is far from a higher rpm piece. You can play with the ICL to have it go higher w/o hurting low end torque. A guy on here and corral was talking with buddy rawls for a custom cam and buddy ended up recommended a tfs 1 cam installed on a 108* ICL. He had ported edelbrock heads with an rpm manifold. He made 315rwhp and the cam did seem to work very well with the combo at that ICL. I had a tfs 1 cam installed dot to dot and it did not perform as good as the set up I mentioned.

Properly ported, your manifold can perform pretty decent. I'd suggest degreeing the cam like I said and either porting the lower or using an rpm manifold. Or run it at the track a few times and see how it does, then make some changes. How about an rpm manifold and a fairly aggressive custom cam with a 6500 rpm shift? You can even port the rpm lower too. Sorry, i'm getting out of hand spending your money

 

[Paul Perreca]

those HP numbers are awesome!! You are now in the 300 club lol I wish I could be - i need to have my car tuned - Did you get your car dyno TUNED or just Dynoed??

 

[Dbeck002]

Thanks paul. It was dyno tuned with just AFPR and timing.



Grn92LX i know its not a HIGH rpm cam like yours but its HIGHER than stock, its just relative to stock.

What im trying to say is, i want my torque curve to be horizontal like everyone elses. And i know my manifold is whats killing me. I am definately going to consider TMOSS i hear he is the man with porting, my budget is fairly low these days. thanks everyone.

 

[-=Red5.0GT=-]

http://www.tmossporting.com/ <--- that's his site if you need it.

 

[Dbeck002]

thanks everyone.


I checked where he is located and its pretty far. The down time will be weeks and this is my daily driver. Im not sure if i can afford that much time without a car. I saw his work and it looks amazing, i wish he cold port my lower but i dont think he can due to distance.


I might just go ahead and buy an edelbrock RPM, more suggestions are welcome.

 

[Michael Yount]

dbeck - have you talked with him? He often is able to send you one that is already ported, and you return yours after you swap them to get your deposit back.

Alternatively, buy a used lower -- send it to him to have the work done; keep driving yours in the mean time; install it, and then sell your stock lower.

 

[tmoss]

It never takes weeks. I can turn one around in 1-2 days if you coordinate shipping with me. Total time would be ~5 days. An option lots of guys take (as I do not stock the GT40 style lower) is to buy a core off ebay or somewhere else, have it shipped to your name @ my address "care of" my name so I know who the intake is for. I then work it up and you can sell your lower after the swap.

Edit: those numbers are respectable for your combo. And you need to take a look at some dyno graphs - most turn down around 4,000 rpm. Look at the Jan 06 5.0 magazine test of a 347 with several intakes on AFR185 heads and a XE282 cam - all but one had torque peaks at 4,000-4,200 rpm.

 

[Dbeck002]

It never takes weeks. I can turn one around in 1-2 days if you coordinate shipping with me. Total time would be ~5 days. An option lots of guys take (as I do not stock the GT40 style lower) is to buy a core off ebay or somewhere else, have it shipped to your name @ my address "care of" my name so I know who the intake is for. I then work it up and you can sell your lower after the swap.

Edit: those numbers are respectable for your combo. And you need to take a look at some dyno graphs - most turn down around 4,000 rpm. Look at the Jan 06 5.0 magazine test of a 347 with several intakes on AFR185 heads and a XE282 cam - all but one had torque peaks at 4,000-4,200 rpm.

Cool... I always thought that my torque curve should be flatter instead of dipping down like that. I bet i could pick up a good 7 rwhp from just the porting job. My lower intake is insanely small compared to the AFR heads (i saw the pic on your site of the scribed AFR/GT40 lower port pattern, there is about 15-20% of material to be removed!!)

Anyway, Tmoss i will get in touch with you soon hopefully. When winter break starts i'll have more time to work on the car. Thanks guys.