85Iroc-Z

iTrader: (4)

I am planning on building a 383 Tuned Port for my car soon. The parts that I am planning on using are
383 Block from Summit Racing -
Eagle 383 Forged Stroker Kit http://www.summitracing.com/parts/ESP-B12111030/
AFR "1034" 195cc Cylinder Heads 65cc chamber, Comp Cams Roller Cam XFI268 218/224 (268/276) duration, .570"/.565" lift, 113 LSA
TPIS Bigmouth Intake, TPIS Big Tube Runners, Fully Ported Plenum,
30 lbs/hr injectors, and find someone to burn a prom for it.
My questions are is the cam I picked a good choice or should I go slightly bigger (XFI280?). What would my compression ratio be with this combination, 11:1? Is that too much compression? What kind of power numbers and 1/4 mile times should I expect? The car is going to be an around town summer driving car that may only see the track once or twice in its life. If there is anyone out there who has already done one of these builds, could you post your combo of parts and let me know how it worked out?

joeblue83

iTrader: (8)

for more top end I would recommend either the tpis mini ram or the holley stealth ram.

85Iroc-Z

iTrader: (4)

I was considering the mini-ram but I already have the entire TPIS set-up and it is not going to be at the track alot, just mostly driven around town.

Blackdog36

iTrader: (3)

Your combo looks pretty good. TPIS system will work great especially for the street. Check out this intake comparison on a 383 motor. TPIS motor made 460 hp and 534 ftlbs
http://www.compcams.com/Community/Ar...?ID=1737510521

Many people have had great success with XFI 268 on 350 or 383 TPI motors on this site. 383 could handle the more aggressive XFI280. Above article used a Comp Cam XR288HR cam, Trick Flow Specialties aluminum heads at 10:1 compression.

Modern aluminum heads like AFR's can take 11:1 compression no problem. It is preferred to run as much compression as possible since you will get max power. Check out compression chart on this site. Going from 10:1 to 11:1 will net you theoretically 2.5% more power. So on a 460 hp engine, you will loose 11.5 HP going down from 11:1 to 10:1. Not a big difference as you might initially think. You will want to figure out your static (scr) and dynamic (dcr) compression for engine build. Here is a good one, you will need to input cam specs.
http://www.empirenet.com/pkelley2/DynamicCR.html

I saw that you are looking at a forged 383 stroker kit. No need for forged parts unless you plan to make lots more power in future (nitrous, supercharger). For your use, you would be fine with typical stroker kits that are around $800. Something like this:
http://www.summitracing.com/parts/ESP-13055L030/

Using that kit with 7cc relief flat top pistons I get the following compression ratios for each cam:

XFI 268 - scr = 10.5, dcr = 8.5
XFI 280 - scr = 10.5, dcr = 8.1

Going with 5cc relief pistons I get:
XFI 280 - scr = 10.7, dcr = 8.3

Staying under 8.5 dcr is good with 91 octane.

3genpio

iTrader: (6)

I had 400 with Dart pro 1 fully ported, rollercam from 1996 LT1 , compresion 11,7 :1 and 2'' primary tube short headers, on top of it was sitting edelbrock Hi-Flow but completely ported, plenum as well, TB holley 2x58, and K&N RC 5000, 30# venom injectors, prom was just S_AUJP with few small changes.
Dyno showed 256 RWHP and 520 Nm @ 3150 rpm but the best was that 440 Nm @1400 Rpm
you have smaller displacement but beter cam and intake, so you should have more HP at higher rpm you should reach 320 RWHP with good prom and good porting job, the stock TB can be a bit to small at high rpm

85Iroc-Z

iTrader: (4)

I am also planning on installing a 52mm throttle body. I thought that the XFI268 was a good choice, but do you guys think I would be better off with the XFI280? Would it be too much for a 383 with TPI on top? I just wanted to put the fully forged set-up in as some extra insurance.

joeblue83

iTrader: (8)

it can't hurt going fully forged, just in case in the future you want to add a power adder

305sbc

iTrader: (3)

The XFI268 is plenty for your combination. Your biggest challenge will be having an exhaust system that will keep up with the engine.

joeblue83

iTrader: (8)

dyno dons shorty headers will work perfect for your combo, thats what I have

305sbc

iTrader: (3)

I've never tried those. Are they 1.75" primaries?
If so then they are good for a 383.

joeblue83

iTrader: (8)

yep 1.75 primaries and 2.5 collector

85Iroc-Z

iTrader: (4)

Right now I have a set of Hooker 2460's 1 5/8" primaries 3" collectors, Hooker Y pipe converted to 3 inch outlet, and a Flowmaster 3 in catback with an 80 series. Would switching over to Dyno Don's headers and Y Pipe really be worth the money? How much of a difference would they make? Also, what kind of power difference would there be between the XFI268 and the XFI280? I ran both of them on the comp cams cam quest and it says that the XFI268 makes more power? I know that it isn't exactly accurate but I don't understand why it would make less hp and torque.

305sbc

iTrader: (3)

On a 383 the smaller 1.5" primary exhaust normally costs 20 - 25 HP, in comparison to headers with 1.75" primaries & 2.5" collectors. A 3-chamber flowmaster will costs around 10 - 15 HP compared to a higher flowing unrestricted design. Running a hi-flow CAT can cost anywhere from 30 to 70+ HP.

Exhaust restriction usually isn't noticed as much at lower RPM and at part throttle, and can actually improve fuel mileage a bit by deadening cylinder scavenging.
However, peak power will suffer, and the extent depends on how much the camshaft depends on overlap to scavenge the cylinders. A cam with a narrow lobe-sep and more overlap will generally lose more peak power due to exhaust restriction. Exhaust restriction always causes high RPM power loss due to backpressure, no matter the cam specs.

You money and time would be much better spent on upgrading your exhaust system, rather than trying to run more camshaft.

85Iroc-Z

iTrader: (4)

OK, I just wasn't sure if going from 1 5/8" headers to 1 3/4" would be worth it or not. My car doesn't have a Hi-flow cat, just a stock one with a 3 inch pipe through it.

85Iroc-Z

iTrader: (4)

Anybody else have an opinion on the XFI268 vs. the XFI280?

1989GTATransAm

iTrader: (3)

With a 383 I would go with the XFI280. I have a 355 and another person also has a 355 both with the XFI268 and we just ran out of camshaft. The power just flat lines. With the 383 you are building it will flatline on power even sooner.

There are a couple of 355 cars in our club with the XFI280 and they just fine with a small lope at idle. With your 383 there may be minimal lope. I agree on the exhaust. Dyno Don makes a good set up with 1 3/4" headers. If your motor was only turning 5000rpm then I would look at 1 5/8" headers. But for the heads you have go 1 3/4".

As to the compression I agree not to go above 8.5:1 on the dynamic compression ratio. With my current 369" motor waiting to be installed I'm running 11.1:1 static compression, 8.45:1 dynamic and a .036" quench. The quench is important. This is on 91 octane. No detonation on the engine dyno and 535hp.

85Iroc-Z

iTrader: (4)

So thats 1 for the 268 and 1 for the 280. Like I said, when running the combo on Comp Cams Camquest, The XFI268 makes 413hp 521tq and the XFI280 makes 415hp and 489tq. Im sure these arent exact numbers, but why would the 280 only make 2 more hp and lose about 30ftlbs of torque? Is the 280 too much cam for a tuned port?

85Iroc-Z

iTrader: (4)

Who on here has done a 383 TPI build?

305sbc

iTrader: (3)

I have, and have had contact with three others. Why do you ask?
I eventually converted to carburetor, but kept the small camshaft - LPE216.

85Iroc-Z

iTrader: (4)

I was just curious what their combination was and what kind of power numbers they made.

305sbc

iTrader: (3)

Mine and one other was in the 350 RWHP range with the TPI. One was stock TPI intake, mine was Accel+ASM. Both were later switched to carburetor and then made 450 RWHP for mine, and the other was pretty close to that too.
We each made big gains by switching to 1.75" primary headers with a very open exhaust.

One other used a TPIS mini-ram, a larger camshaft, turned 7000+ RPM, and probably made close to 500 RWHP, but it was always having problems with parts breakage.

The fourth one (383 TPI) had every bolt-on imaginable with everything polished, but it never did run well. It was probably a lack of proper tuning.

I know a couple of people with 406 cid TPI cars. I don't know exact numbers but I'm sure one of them is in the between 400 and 500 RWHP range. I can't remember exactly what it has, but basically aftermarket TPI parts that have been ported, and I know it has a very good tune.

Every one of these, including the ones I don't know details of ran/runs the 730 ECM for speed-density operation, and at least a couple of them run a full time open-loop tune.
I ran an Accel stand-alone, but it's basically just like a 730 ECM and can run Open-Loop Speed-Density, OLSD mode.
I'm also pretty sure none of these cars ran/run any emissions equipment, and that definitely makes a difference on a 383.

The tune and ability to do so is just as important as getting the right combination of parts when it comes to making TPI work for you.
The DIYPROM section here is great if you haven't already been reading there.

TPI-Formula350-

I pick this 383 engine up tomorrow. Made 467HP@5500 RPMs and 517 TQ , those are crank/flywheel numbers.. I'll scan and post dyno sheet tomorrow after I pick it up

Viprklr

iTrader: (5)

Mine made 323hp and 383tq at the wheels when I was at the dyno.
Disappointing in my eyes.
Mods in the sig.

85Iroc-Z

iTrader: (4)

So is the tune of the car going to have that much of an effect on the power numbers. It seems that people on here haven't had much luck with their power numbers, but these two build I found on the internet have used the FAST XFI system and have had good results.

383 Extrude hone stock base, tpis runners and 52mm tb, Comp Cams 212/218 duration, .487/.495 lift, 110 LSA, L98 aluminum heads
made 458hp and 534tq. http://www.superchevy.com/technical/...t_results.html

383 TPIS Bigmouth Intake TPIS Runners and 52mm tb, TFS aluminum heads, Comp Cams XR288hr made 460hp and 534tq.
http://www.compcams.com/Community/Ar...?ID=1737510521

1989GTATransAm

iTrader: (3)

"So is the tune of the car going to have that much of an effect on the power numbers."

Yes, it can be significant. With a TPI on a 383 the longer the intake valve is open the more air that can be drawn in. This is within reason of course and another reason why I favor the 280XFI.

85Iroc-Z

iTrader: (4)

My build is pretty much all planned out for me now except for the cam choice still. Im not sure if I want to do the XFI268 or the XFI280. I get different answers from people and it makes the choice harder. Some people say the XFI280 is too much for a tpi and will be hard to tune, some people say it is better than the 268, and like I said the dyno simulator claims that the XFI268 will make more power than the 280 as I said above.

VincentZ28

iTrader: (2)

Go with the 280XFI. I'm using this cam in my 360cu in. Your manifold only flows about 240cfm. In needs to flow atleast 290cfm to make power above 5700rpms. Right now you manifold will drop off at 5200rpm. You are building a torque monster. Look at my sig.

VincentZ28

iTrader: (2)

After adding the transmission and accessorises, your wrhp will be down to 380-405.

Orr89RocZ

iTrader: (20)

LTR TPI wont go much over 5000 on a 383 tho. You need to shorten that runner to get anything much above that. Superam and 280xfi made peak in the 5500 range, and the 280xfi should be capable of a peak abit higher than that.

268 seems a touch small but better suited to the TPI powerband. a 224/230 xfi I think would be better choice but you would need to order it special from comp.

IF you overcam on TPI it will flatline the hp past where TPI wants to peak. IF it peaks near 5000 rpm, the power will flatline beyond that. The duration is there to breathe but runner length is too long to allow the air flow at higher rpms.

That popular comp cam article shows that. That 383 with that cam wanted the miniram/hsr to pull to 6000+ rpms. LTR TPI on those setups capped power significantly but you can see in the graphs power held on as rpms went up.

280 would work and allow performance down the road if you ever wanted to get a short runner intake. Make sure you get the 8019 springs upgrade from AFR!
Port the base/runners to get some good flow or else your bottlenecking those AFR heads.

88fastgta

iTrader: (9)

i think i have way too much torque right now with my tpi and its a 355... i have to lightly get on it from a start then go full throttle.. i just bought tires less than two years ago and i bout burn all the rubber off of them...... i think with a 383 tpi is going to be hard to hook from a stop....

Viprklr

iTrader: (5)

It is. It made it much easier to launch with drag radials on the street. My old regular ultra high performance tires didn't stand a chance. With street tires, I couldn't even punch it at 60mph without 'em screaming.

85Iroc-Z

iTrader: (4)

Viprklr do you have that custom ground cam from comp cams with the 224/230? How do you like it? Was it any extra money?

Viprklr

iTrader: (5)

Yep. It didn't cost anything extra.
I like it. It has a nice medium lope. However, it was a major pita to tune.

Orr89RocZ

iTrader: (20)

I have read/heard that comp doesnt charge anything extra for a custom grind if your just selecting lobes from their catalog. Those lobes are available you just need to select them.

85Iroc-Z

iTrader: (4)

Who did your tuning for you? How were the results of the tune after you were finished?

Viprklr

iTrader: (5)

I did the tuning to steady the idle and then I did the tuning with the car on the dyno.
The dyno shop I went to wasn't familiar with sbc's.

According to the dyno, by the time I was done, I had gained 50whp.

85Iroc-Z

iTrader: (4)

I would like to be able to tune my car myself by burning my own PROM but I just don't understand how to do it. So maybe that will be the cam that I will go with. Since I can't choose between the XFI268 and the XFI280 and everybody has said both choices, this one may fit my application better since it is more in the middle of the two. Anybody else agree with this choice?

85Iroc-Z

iTrader: (4)

Do you know what the rpm range would be with that custom 224/230 cam in a 383?

Orr89RocZ

iTrader: (20)

I would expect the 224 cam to peak near 5600-5800 in a 383 with a good short runner intake. The 280 would like to go to 6000+ with the right springs. Good heads and intake will help extend the rpm range. The 224 is probably better suited to TPI on a 383 but would work well with HSR or miniram as well. Seen a few 224-226 duration cams run well into the 11's with a short runner intake, thats why i feel the 280 is better for the miniram/hsr type builds with a 383

85Iroc-Z

iTrader: (4)

So the 224/230 grind would be better than the XFI268 and 280 for my set-up?

Orr89RocZ

iTrader: (20)

I think so

1989GTATransAm

iTrader: (3)

It is a step in the right direction for your set up. IMHO this is kind of like a racing class where you have to run a 2bbl carb. I'm basing this on the fact it does not look like you are doing anything to the intake system except bolting it on.

The recommendation in that type of situation is to run as high a compression ratio as you can and you are doing that. Another is to run the longest connecting rod you can like a 6". It is also the reason I favor the XFI280 camshaft. It will idle nicely with the high compression and your 383 cubic inches. It will also keep the intake valve open longer for the most cylinder filling.

Another solution is to look into a custom cam. Orr and myself have used Mike Jones and I have been very pleased with the results. They are not that expensive. Those AFR heads have excellent exhaust flow and it appears you have a decent exhaust system. For that reason you do not need a big split on your camshaft. The less split, the less overlap and the better the street manners.

Orr89RocZ

iTrader: (20)

312 bucks for Jones' cam isnt a bad investment. If you want the best, get a custom grind. 280 will work fine, i jsut think the potential of that cam is wasted with TPI so smaller duration will be easier to tune and fit the rpm range better, thus making more torque overall in the power band.

85Iroc-Z

iTrader: (4)

So now I think I will be going with the 224/230 cam and maybe just a tune from pcmforless. Could I possibly see similar power numbers as the builds in those magazine articles or do those numbers seem unrealistic?

305sbc

iTrader: (3)

That cam is really going to need some hands-on PROM tuning time.

VincentZ28

iTrader: (2)

Anytime you make a cam an or head change you will need prom tuning. It changes the idle, gas milege, drivability, wide open throttle and it leans the engine.

85Iroc-Z

iTrader: (4)

Do you think a place like pcm4less could handle a prom burn like that or should I go to somewhere local that can dyno tune the car for me? Also, what brand of injectors would you suggest I get?

3genpio

iTrader: (6)

you need to ask them, every time you change anythink,
they did a .bin for my friend but refuse to do to my car.....

Orr89RocZ

iTrader: (20)

PCMforless wont tune anything that doesnt use stock fuel pressures (Which I think is stupid, you can compensate for the difference). So tell them you are using stock fuel pressures and the injector size equivalent for the pressure you are actually running.

85Iroc-Z

iTrader: (4)

So I would just tell them I am running stock fuel pressure and 30lbs/hr injectors since that is the size injector im choosing? How well do you think a place like that will do on a tune like mine would need, anybody have any experience with them?