GREGGPENN

Where did you get that idea? Unless you swap your intake, heads, cam and drive in upper rpms way more often, you made the right choice!

Tom chose the larger size because he was planning a supercharger (IIRC).

Steven chose the larger size because he has an LT1 motor. Now that I've seen L98/LT1 heads side-by-side, in addition to both sizes of Tri-Y headers side-by-side, I can say the smaller set would partially block the top of the LT1 exhaust port. That means the larger set is necessary for LTx cars (or Brian would need to offer more combinations of headers).

Brian sent me the larger set after I asked which size is the best for a fully-ported 350 with a HSR and 220ish cam. To be honest, I still think the 1 5/8" size would have worked as well/better -- if the port config was correct for higher exhaust ports (like LTx or AFR heads) -- and particularly for someone who doesn't race.

I could provide some links to further confirm your selection if you like.



BTW: What happened with your gas lines? Since your posting, I've seen issues with flexible gas lines breaking down. Has that gotten your attention?

corvette_bob

I went with EARL'S lines/fittings. From the filter to the rail. BTW, thanks Gregg, now I have that to look forward to.
JK, I think I'll be OK, EARL'S is a pretty good name and the Perform-o-Flex line has been around awhile.

STEVEN13

Now for the Dyno numbers! All are SAE.

Last dyno run was May, 2006 HP 266.1 TQ 297.7

Dyno run today Oct. 23, 2008 HP 289.7 TQ 316.53

To be clear in 2006 the motor was completely stock. Now it has a tune, 1.6 Rockers, and the Tri-Y headers.

IMHO these bolt-ons are worth it. With future up-grades the headers and exhaust are complete. One less thing to do when building a new engine.

While I had some issues with these headers, Brian did build a great header I am happy with them!

Steve

GREGGPENN

Nice improvement! It sounds like you're happy.

As stated, your tune/rockers/headers can't individually be given credit for you gains. I've heard of a tune by itself giving nearly as much improvement as you saw. But, I think all together had some effect. How much for each???? We don't know.

At sale-time, Brian said Tri-Y's would provide 30hp MORE than Hooker Super Comps. But that could be at a certain rpm on a 700hp motor going downhill (vs uphill) on a cold day!

Have any comment on conditions for your 2-yr apart run?

gp

TJM

Good numbers. Give the heads more air they will be able to us it, know.

A good set of ported runners and 40 PSI fuel should double your improvements.

What [ and at what RPM ] was peak torque made ???

TJM

GREGGPENN

I'm not sure porting a stock LT1 intake would improve his results that much... maybe with heads?

I thought stock fuel rail PSI was already between 44-45 PSI?

gp

STEVEN13

GP,

I can't find the original sheet for the May 2006 pull-I have it saved as a jpeg file. When I scanned it,it does not show the bottom of the page. From what I remember it was in the mid 60s.

The conditions from today were 59.9 degrees and 30.78 humidity.

TJM,

peak torque was at about 3,800-4,400 rpm. At about 2,500 rpm its about 300ftlbs. Very flat curve.

Also remember, that both are SAE corrected.

Steve

TJM

I think stock was 38 Lbs. ? Need to check the book to be sure.

I have 48 Lbs, now.

As far as air, the debate rages what restricts more, the heads of the runners.

Bench racers share the opinion the L98 stock heads can breath a little better with large [or shorter] runners.

The advantage is questionable. Header scavenging has an affect, but if the Runners are the issue, the the heads can not pass iwhat they don't get.

If it's heads runners would, logically not help?

Don't have any science to back that up, just bench BS.

TJM

Enuzio

Hi guys...

Just to share some performance results from some bolt-ons...
My car is an '86 roadster; running with following mods:
Bassani Stepped Tri Y 1-5/8 step to 1/ 3/4 to parallel "X" dual stainless 2-1/2 pipes back to Corsas, SLP Cold Ram, powercoupler, K&N filter, descreened MAF, Air foil, Hypertech 160 deg chip, underdrive pulleys, 2:73 rear with a 700R4 tranny:

2.27 sec 60 ft. (did not hook-up well...right foot too heavy)
9.0 1/8th
13.88 1/4 @ 102.98

I went with the Tri Y to help back road passing...it can be felt in the "buttometer"

Ear plugs are necessary for a cruise, but then I am also of retirement age.

Cheers,

Enuzio

Enuzio

HI TMJ...

In checking with Doug Rippie Motorsports and the guys at TPIS...if one really wants to get some serious power out of an L98 you have to do heads, cam, baseplate and runners and customer chip.

The base plate alone with nothing else will give about 4 hp. The large tube runners alone maybe 10 hp. Going to a 52 mm throttle body by itself from the 48 mm and all else stock --nothing--stock runners won't enjoy the benefit of the 52mm throttle body. Going with new heads without the rest of the goodies will be equally disappointing, unless you already know that and have plan forward to upgade as your budget permits.

Also the plenum needs to be ported...an easy thingy with a dremel tool.

TPIS publishes a great little book called Insider Hints...well worth the money.
Anyone considering mods to their car really have to consider carefully how they will use it.

Having said that...very streetable 375 hp and 400 ft lbs torque out of an L98 is quite doable. (But is it still a L98 without the small long tube runners anymore?)

TTFN (ta ta for now)

Enuzio

TJM

I agree, I have ported and siamesed SLP runners [ I think I posted a picture back in July?] , and an enlarged plenum and base plate. Chip and ADJ fuel pressure.

The issue of heads I argue some. Hard to believe old 1966 327 heads flowed better that the L98 units? But L98's issue is the runners not the heads so much [ within reason , now ], it's the runners [mostly].

I have not put mine on the dino yet, fiddling with Borla mufflers, right now, but I expect a peak torque in the 380 Ft Lbs range at close to 4,600 rpm. 330hp? Nothing better will happen at higher RPM [ but I could get a surprise!!!]

So......Ta DA!!!!!!!!!!!!!!! I made LT4 level performance, with lower shift points & more grunt than an LT4

Not an unreasonable expectation.

No science just my guess.

TJM

TJM

My "butt agrees"

Get a factory Dana 3:07 gear and visit the low 13 'S

Gears and grunt matter. Fire you like a bullet.



TJM

GREGGPENN

DRM/TPiS are correct. All components need to be done for serious gains. And, 350+hp is possible.

For those wondering which part is the biggest restriction:

From this link:
http://www.thirdgen.org/techboard/po...39-post30.html

Head Intake flow at stock cam lift: 176cfm
Head Exhaust flow at stock cam lift: 156cfm
Stock intake w stock runner: 198 cfm
Ideal exhaust pipe size for 156cfm: 1.45"-1.55"
Actual L98 manifold size (necks down to): 1.25"

Ideal exhaust size chart:
http://www.popularhotrodding.com/eng.../photo_04.html

Ideal exhaust size was derived via Vizzard's chart (link above). The 1.25" observation about L98 manifold size has been made by multiple forum members. Besides the smaller-than-expected 1.25" measurement, air tubes create additional obstruction by protruding into the exhaust manifolds.

From my perspective, the ongoing/outspoken philosophy that the L98's exhaust being the biggest restriction is true. The numbers support it -- as do improvements measured after improvement of the exhaust system. Of course, poor CATS and stock manifold flow/shape compound exhaust problems. Overall replacement of the exhaust system on an L98 has led to improvements exceeding 30hp. With the possible exception of the heads, no other single improvement can effect L98 performance this much.

Often, alternative intakes are reported to create some improvement, but the numbers don't support an intake "restriction". But, that doesn't mean you can't change the character of the motor by focusing where it makes power. Some have even claimed as much as 50HP improvement (all of which is above 5k rpms). The question in my mind is how to measure the overall change. To gain high-rpm power, mid-range power is sacrificed and visa-versa.

Assuming the attached head flow measurements are accurate, an aftermarket cam (alone) might add 20hp (10cfm). I've seen 25hp gain reported. But, I've also seen some flow charts on the 113 heads slightly better (by about 10cfm).

Next to exhaust though, the heads are the next biggest restriction. That's the way I see it anyway. That's what the numbers I've seen tell me. You may see it differently. But, as DRM/TPiS state, you really need the intake, heads, cam, and exhaust working together as a unit to have maximum performance with minimum waste/loss.

gp

BTW: The insider hints book contains some suggestions which have been widely disclaimed in this forum. Investigate any improvement carefully before proceeding -- even those you find in the "Insider Hints" book.

JeepCycle

I have to revive this thread as I am in the primary stages of an engine build.

I am building a Gen I 383 to get maximum low to mid-range torque for my 85...I don't expect the RPMs to get eny higher than 5500, these seem to generate power in that range...that said, is the install for 1 5/8" tubes fairly seamless, ie not a lot of fabrication?

GREGGPENN

If you read what you revived, you'd know the answer. Both sizes are covered here and the choice of tube size (1 5/8 vs 1 3/4) didn't seem to alter installation issues. Look for Corvette Bob's posts in this thread -- since he installed the smaller size.

Since the x-long length of the secondaries, combined with the 2-stage design of these headers are as much responsible for lower rpm "boost" as the use of a smaller tubing size (1 5/8), selecting the smaller size wouldn't necessarily be the direction I'd go for a "built" 383. OTOH, I don't know what your heads will flow.

Also, this company recommends the larger size even for stock LTx cars. You should be making more power than that.

corvette_bob

Personally, I recommend you go with a set of either Hooker or TPIS headers. The reason is 1)an easier install, and 2) 383's are notorius
torque monsters. Unless you're pulling stumps, you're gonna have more torque than you can deal with. For the little bit of extra torque the tri-y's offer, I'd go with the Hooker or TPIS product. Further details of my recommendations can be found throughout this thread.

TJM

Is this a drag cars?

If yes Get Hookers or another 4-1 set of tuned headers

Road race? The tri-y's will do a better job for you.

TJM

JeepCycle

Thanks for the replies...there is so much going on in this thread it is a little hard to pull out all the useful info...I'm afraid I lack the patience of many of you guys to mess with this for an extended period of time....my real question should have been:

Did anyone figure out how to streamline this install?


I am setting the car up to do some SCCA Solo Hillclimbs(roadrace)....but it is mostly to be street driven...only to be raced about 5 times per year....against the clock...

I figure the heads I select will be in the 190 range to keep velocity high at low to mid rpms....

GREGGPENN

Best summary I can give....

Make sure you ask for the #2 tube "correction". When they arrive, test fit. If they're going to hit anywhere, bang on headers with hammer/socket until they fit. Fabricate heat sheilding where appropriate. Fabricate/modify rear brackets for A/C and/or alternator.

BTW: In addition to the #2 tube correction, you might want to ask them to shorten the secondaries 1" for an easier fit too. I had mine shortened 4" but that raises rpm peak. It sounds like you want it as low as possible. These headers are way longer than most. There will be no room for pre-cats -- unless you go at least as short as I did.

I assume you mean 190cc vs 190cfm (since the later is stock)?