Guest Anonymous Posted August 16, 2003 Share Posted August 16, 2003 I'm looking into this engine instead of the pervious LT1 engine.. Could I get high HP/TQ rating out of the 350TPI engine with some moding? Or would the LT1 be better (Ocorse the LT1, but is it worth the difference in price).. Something came up and the money is getting tight thats why i'm changing. I want either engine to become turbocharged sometime in the near future but not to sure, mainly bepends on my budget. So should I stick with the LT1 idea or go with the TPI? I could get the TPI a whole lot cheaper and faster but I just want some input. If the LT1 is the best investment to acheive I'll save up longer to do so. P.S If I get the TPI it's going to have forged insides and Aluminum heads.. Thanks Kenneth Quote Link to comment Share on other sites More sharing options...
Mike C Posted August 17, 2003 Share Posted August 17, 2003 If a max output motor is your goal, the LT1 is the way to go. If you want a fast V8 Z with fuel injection, the TPI motor will be fine. In order to get big power from the TPI, you need a new base, and new runners, and possbily even a new plenum. Add a bigger throttle body and injectors, and the LT1 would have easily have been paid for. A Caprice LT1 can be had for around $800 from a wrecking yard. At a later date you can add AFR heads or the LT4 kit from GM. There are some advantages to the older TPI setup in your choices of ignition systems, aftermarket heads, etc. The TPI motor can run an engine driven fan (so can the LT1, but the HD engine driven cooling fan is EXTREMELY hard to find.) It all boils down to your preference IMO as they can each make big power if you throw big bucks at it. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted August 17, 2003 Share Posted August 17, 2003 I dunno where you are, but I can get running LT1's for about $400 bucks... I actually may know someone in Upstate NY who has a great running LT1 all palleted up and ready to ship, if you like. But by far... LT1 all the way! With just a mild cam and new springs and roller rockers, you'll have plenty of power in a light Z! Another bonus, no distributor of the top of the engine to worry about firewall clearance. But the TPI motors are good too. They are just more expensive to modify, and the stock intakes aren't all that great. Quote Link to comment Share on other sites More sharing options...
Dan Juday Posted August 17, 2003 Share Posted August 17, 2003 The tpi motor is about limitations. You will always be throwing good money after bad if you want to get more out of that motor than stock. There are not going to be anymore new aftermarket goodies made for that motor either. That market is going to the LT1 and LS1. You will not be able to tune your tpi computer like you can with the LT1 OBD I. There is a very good reason why you can pick up tpi motors cheap, you get what you pay for. Spend the extra bucks for the LT1 now, you'll thank yourself later. So what's in my Z? Quote Link to comment Share on other sites More sharing options...
fl327 Posted August 17, 2003 Share Posted August 17, 2003 Dan, its the infamous 305 TPI right? Quote Link to comment Share on other sites More sharing options...
Dan Juday Posted August 17, 2003 Share Posted August 17, 2003 Bingo. Quote Link to comment Share on other sites More sharing options...
fl327 Posted August 18, 2003 Share Posted August 18, 2003 You will have great traction with those 10" wheels though. Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted August 18, 2003 Share Posted August 18, 2003 everyone I know with a TPI likes the low rpm (100rpm-4000rpm) torque but HATES the way the intake just hits a wall on air flow and power in the 4000-4500rpm range where no more airflow can be pulled thru those restrictive runners. basically the 350 or 383 short block is a great starting point but the STOCK or EVEN PORTED TPI intake and HEADS ARE SEVERELY AIRFLOW RESTRICTED I found this info and I figured you guys might like to look it over, now the first thing I want to point out is where the DATA came from. and KEEP IN MIND ITS REAR WHEEL HP AND The TPI INTAKE IN THE TEST consists of 58mm TB, fully ported plenum, AS&M largetube runners, and highly ported Edelbrock base WHICH MEANS ITS ALREADY MAKING AT LEAST 25HP-30HP MORE THAN A STOCK TPI INTAKE) link to c-4 stealthram http://www.eecis.udel.edu/~davis/z28/winter01/dyno/ The engine was basically the same,in all the test except for the intake manifold, consisting of a ZZ4 crate motor, AFR190 heads, LT4 HOT cam, and SLP 1-3/4" SS headers. Trans is a 700r4 with a Vigilante 2800 stall converter. The Engine Control Module (ECM) was a '92 TPI stock ECM (MAP/speed-density) with a modified EPROM. I HAVE GONE TRU AND WILL PICKED OUT THE IMPORTANT POINTS TO SAVE YOU TIME IN THE CHARTs AND GRAPHS ON THE SITE TPI engine.....283 PEAK rwhp @4800rpm peak AVG. TQ 291.5 AVG HP 269.5 miniram 303 PEAK rwhp @6200rpm peak AVG. TQ 285.8 AVG HP 269.1 IT LOST 29 HP at 3800 rpm and MADE 48 MORE HP THAN THE stock TPI at 6300 RPM stealth ram 342 PEAK rwhp @6400rpm AVG. TQ 319 AVG HP 300 it lost 28 hp at 3600 rpm BUT GAINED 66 HP AT 6600 RPM over the stock TPI 342 rear wheel hp is aproximatly equal to 427 flywheel HP FROM A 350 SBC ENGINE, figuring a 20% driveline loss rate. the use of a longer duration cam and only measureing PEAK HP would tend to benefit the miniram and STEALTH RAM intakes to a MUCH GREATER extent than the TPI, THATS HOW claims of gains of 100hp are made for some intake combos, while its TRUE that you can make in excess of a HUNDRED EXTRA hp at 6600rpms is due more to the TPI not being able to flow air (LOSSES) keep in mind that a LARGER ENGINE DISPLACEMENT WOULD BENEFIT EVEN MORE from the steathram link to c-4 stealthram[/b] since I SPENT YEARS RESEARCHING THIS SUBJECT! LET ME POINT OUT A FEW THINGS (1) heres the flow numbers (2)no matter WHAT PLENUM DESIGN YOU USE,your MAX AIRFLOW WILL BE LIMITED TO THE MOST RESTRICTIVE OF THE TWO,(RUNNERS OR BASE INTAKE) that YOU PUT IT ON and THATS THESE FLOW NUMBERS FROM MATCHED INTAKE AND RUNNERS Stock intake manifold with runner Stock....................198.72 cfm ACCEL................213.52 cfm Extrude/ACCEL....217.11 cfm Super Ram............220.67 cfm the stock TPI has a hard time flowing 230cfm even with minor port work, look here most of this info is right off the accel,holley,edelbrock, and TPIS sites, add a little math and the results become much clearer!!! GETTING YOUR Intake....... length ....... port in -- out Stock GM Base--- 6.375"------ 1.47"- 1.96x1.2 TPiS base------ -6.125"------ 1.75"- 2.09x1.28 Accel base----- -6.125"------ 1.75"- 2.09x1.28 Holley base------- 6†runner 2.3â€- 1.9â€x 1.23 (2.337 sq inches) Runners Stock TPI----- -- 7.250"------1.470" round(1.70 sq inchs) SLP ----------- - 6.625"------1.600" round (2.01 sq inchs) Accel LTR------- 6.625"------1.615" round (2.05 sq inchs) TPiS----------- 7.625"------1.660" round (2.168 sq inchs) Mini ram -----3.5†LT1 ----------3†Runners (measured individually) Stock....................203.17 cfm ACCEL................242.02 cfm Extrude/ACCEL...275.83 cfm Super Ram............289.18 cfm Intake manifold with 3/8 inch radiused intlet .............................222.45 cfm Holley stealth ram ………..275cfm Stock intake manifold with runner Stock....................198.72 cfm ACCEL................213.52 cfm Extrude/ACCEL....217.11 cfm Super Ram............220.67 cfm Holley stealth ram …..275cfm ACCEL Hi-Flow intake manifold with 3/8 inch radiused inlet.........251.51 cfm ACCEL Hi-Flow intake manifold with runner Stock....................215.83 cfm ACCEL................232.53 cfm Extrude/ACCEL....243.21 cfm Super Ram............240.24 cfm Extrude-Honed ACCEL Hi-Flow intake manifold with 3/8 inch radiused inlet ............................275.83 cfm Extrude-Honed ACCEL Hi-Flow intake manifold with ACCEL runner ............................266.94 cfm Edelbrock Performer RPM manifold (Stock)..................286.51 cfm Edelbrock Victor Jr. .............................275.24 cfm HOLLEY STEALTH RAM the HOLLEY STEALTH RAM FLOWS at 275cfm out of the box, and has the potential when matched to the correct heads and cam to totally out flow most other intakes available,can easily reach 300cfm with minor port work and costs much less Stock…………………………… 275cfm Ported…………………………..300cfm Runner lengths Stock tpi manifold 8†runners 11.25â€, cylinder head 6†total 25.25†Accel super ram manifold 8†runners 7†cylinder head 6†total 21†Holley stealth ram manifold 6.26††cylinder head 6†total 12.26†Edelbrock performer RPM runners 6††cylinder head 6†total 12†Edelbrock vic jr , runner length 5.5†††cylinder head 6†total 11.5†take the time to read the links http://www.gmhightechperformance.com/tech/0307htp_holleystealth/ http://www.eecis.udel.edu/~davis/z28/winter01/dyno/dyno021105/webpage021105.html GAINS OF 60hp PLUS have been reported on mildly reworked engines and Im sure on a full race style, or engine designed to use the extra air flow engine the results would be far greater http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=2119&prmenbr=361 compare that to a super ram at $1370 plus flows about 240cfm to 275cfm with SERIOUS port work http://www.thunderracing.com/index.cfm?fuseaction=subcategory&subcategoryid=1125#P2944[/url] HOLLEY STEALTH RAM (intake ,plenum,fuelrails, regulator) about $460-$520 to convert your TPI plus cost of small base HEI ignition and small parts flows 275cfm-300cfm with port work custom height stealthram to fit under corvette hoods,LINK when you look at the choices the upgrade to the HOLLEY STEALTH RAM GIVES YOU THE MOST FOR YOUR MONEY, just like a 4 barrel carb potentially out powers a 2 barrel carb on the engine years ago its the increased airflow potential of the newer EFI intakes that limits to a great extent the power your engine can make now, your ECU matches the fuel to the ENGINES AIR FLOW AND IT THE EFFECTIVELY USED AND AVAILABLE AIRFLOW THRU THE ENGINE THAT MAKES POWER theres no contradiction at all ,look closely, this FLOW DATA WAS TAKEN and compiled from several differant flow benchs so the data differs very slightly but REMAINS VERY CONSISTANT ,what it says is that the runners by themselfs flow better than the runners when attached to the manifold base and that the ACCELL RUNNERS AND BASE OUT FLOW THE STOCK RUNNERS AND BASE INTAKES WHEN THEY ARE COMBINED when I had a stock untouched TPI flow tested several years ago the flow from the ports measured with the throttle body mounted on the TPI was under 180cfm per port. Runners (measured individually) WITHOUT INTAKE Stock....................203.17 cfm ACCEL................242.02 cfm Stock intake manifold with runner Stock....................198.72 cfm ACCEL................213.52 cfm the bottom line is that the TPI is HIGHLY RESTRICTED and EVEN THE HIGH FLOW BASE AND INTAKES AVAILABLE WHILE VERY HELPFUL, REMAIN VERY RESTRICTIVE. the STEALTH RAM IS FAR LESS RESTRICTIVE intake, a set of AIR FLOW RESEARCH 190cc heads on a 383 11:1 shortblock with a cam like a crane #119661 or CROWER #00471 and a STEALTH RAM will produce a VERY GOOD HIGH TORQUE and HIGH hp ENGINE FOR A (Z), 470hp/500tq should EASILY BE AVAILABLE OR EXCEEDED if your looking for max hood clearance the STOCK HOLLEY STEALTH RAM is 10.25" tall from block to the top the CUSTOM STEALTH RAM is 9" tall and can be easily machined to only 8 5/8" tall (LESS THAN A STOCK TPI) link to c-4 stealthram Quote Link to comment Share on other sites More sharing options...
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