a reasonably effective TPI COMBO



a reasonably effective TPI COMBO

Postby grumpyvette » January 21st, 2009, 11:11 am

One of the most frequent questions I get is what’s the best route to go on upgrading my TPI corvettes engine combo, so lets look into that a bit, with the idea of building a kick butt TPI combo but still retaining a good bit of the low and mid rpm torque curve that the TPI is famous for but without restricting the potential power, so Ill suggest the build be done in two stages.

Stage one
here ILL ASSUME your looking for a noticeable boost but you don,t want to sink thousands of dollars into the project, or race the car and you want to retain the stock drive train, and basic rotating assembly, untouched.The basic STOCK tpi engines main restrictions too making better hp are in the restrictive STOCK intake and STOCK head flow rates and to some extent the cam timing.
If there’s one factor that needs to be addressed its that the heads and intake flat out SUCK from a potential hp potential stand point as the combo limits you to UNDER about 195 cfm. THATS THE MAIN RESTRICTION TO POWER.

So your choices are, do some minor port work on the stock plenum, runners and heads, or replace them with aftermarket components, obviously the stock stuff will be far less expensive but very limited in its potential, simply because there’s just not that much that can be gained by the typical home port job on the stock components.

Here is some links

viewtopic.php?f=52&t=462

viewtopic.php?f=52&t=796

viewtopic.php?f=52&t=401

viewtopic.php?f=55&t=431

viewtopic.php?f=71&t=741

viewtopic.php?f=52&t=181

viewtopic.php?f=52&t=975&p=1700&hilit=porting#p1700

http://www.gmtips.com/3rd-degree/dox/ti ... t/port.htm

So youll need to make a choice between adding a cam. and doing some basic port work on the TPI intake, base,plenum,and runners, and the stock cylinder heads or possiably upgrading the components
if your going to be happy with gaining about 50 hp or more depending on the components selected, at a reasonably low cost, and if your going to do the port work Id suggest the addition of a mild cam like a CROWER (BELOW) to take advantage of the slight flow rate improvements

http://www.crower.com/misc/cam_spec/cam ... &x=26&y=10

(IF ITS A FLAT TAPPET TPI ENGINE)
or a CROWER ROLLER

http://www.crower.com/misc/cam_spec/cam ... 2&x=29&y=6


if its a later roller cam engine will boost hp at least into that range if headers are added also.
and on these low duration cams adding 1.6:1 roller rockers tends to help as it usually adds about 2-3 degrees of effective duration and .25 extra lift
this is the basic route and its well worth the effort if you just want a noticable boost in performance.
ANY TIME YOU SWAP PARTS CLEARANCES NEED TO BE CHECKED

now swapping to a much better flowing heads and intake will provide a far bigger boost in power, than just porting the stock components will, but were talking big bucks to do so, intakes like a superram, mini-ram, or the FIRST TPI, provide a great deal more hp potential,IF MATCHED TO DECENT HIGH FLOW RATE HEADS, and heads like TRICKFLOW,BRODIX, or AIRFLOW RESEARCH can provide, those flow rate improvements that will be almost mandatory if you want to maximize your hp potential.
NATURALLY all those engine changes that take advantage of the higher flow rates and greater cylinder pressure and rpms that build the extra hp,will require matching drive train mods in the converter stall speed and rear gear ratio to allow the engine to operate efficintly in its new higher average rpm band.

STAGE TWO,

GOING FOR THE MAX SEMI-REASONABLE STREET COMBO

IF youve got a significantly larger budget you can do a good deal more and boost power to almost or even over double the orriginal 230-245 flywheel hp range, but it generally requires better heads, a decent cam and intake upgrade, and it sure helps if you go to a higher compression ratio, on a larger displacement engine like a 383-406 SBC short block and youll need too upgrade the drive train to match the new higher rpm potential the cam youll need to use in that larger displacement and higher compression engine combo, so that it can effectivelt use the engines better breathing potential in the higher average rpm band necessary to produce significantly more hp/tq.
youll want to build if the cars intended goal is significantly higher hp/tq than the stock combo can provide.
Here is a good place to add a few links on info you might need

viewtopic.php?f=44&t=742


viewtopic.php?f=52&t=90


viewtopic.php?f=52&t=796


viewtopic.php?f=52&t=965


viewtopic.php?f=52&t=181


viewtopic.php?f=44&t=38


viewtopic.php?f=53&t=510


viewtopic.php?f=53&t=247


viewtopic.php?f=56&t=495


http://www.firstfuelinjection.com/PDRM1966.JPG

http://www.firstfuelinjection.com/products.htm

Read this

viewtopic.php?f=55&t=823

viewtopic.php?f=69&t=433&p=532#p532



A correctly ported stealth ram still has that beat, I’ve seen tests where the HSR pulled an extra 67hp from an engine over the stock TPI, but you might want to keep in mind a few factors, its NOT so much that the HSR is such a fantastic addition as its the TPI is such a HUGE restriction to power potential

look the formula for hp is
tq times rpm divided by 5252= hp
If you make 350 ft lbs at 3500 rpm that’s 230 hp (the stock hp)
If you allow the engine to breath better and can make the same 350 ft lbs at 5500rpm that’s 366 hp, you’ve effectively gained 136 hp simply moving the rpm band higher, the stock TPI intake flow and cam design basically falls on its face at about 4500rpm, and the stock heads only flow about 190- 200cfm.


(Remember the airflow potential and the basic rpm range of the parts combo must match)

Add the correctly ported HSR and a cam in the 230 duration range and heads that flow a minimum of 250 cfm at .500 lift, and you’ll quickly find you need a rear gear in the 3.73:1 range a higher cpr near 10.5:1 and a 3000rpm stall converter to make it run correctly, but the intake flow will now allow you to make ALOT more hp.


HERES one of the best street combos IVE yet found that can be built from the stock block

AFR 180CC heads
http://airflowresearch.com/180sbc_sh.php

CROWER 00471 HYDROLIC ROLLER CAM (slightly more hp)
http://www.crower.com/misc/cam_spec/cam_finder.php?part_num=00471&x=23&y=6
OR CRANE 119661 HYDROLIC ROLLER CAM, (what IM using as its more street friendly)
http://www.jegs.com/webapp/wcs/stores/servlet/itemproduct_10001_10002_67066_-1_744662_10707

You’ll need 36 lb injectors and probably a new CHIP burnt, a good MSD ignition won’t hurt either

COMP 1.6:1 roller rockers
http://store.summitracing.com/partdetail.asp?part=CCA%2D1302%2D16&autoview=sku

a 383-404 short block with 10.5:1 cpr
http://www.ohiocrank.com/sbc_short.html

1.5/8" long tube headers
Low restriction exhaust
3000 rpm stall converter
3.73:1 rear gear

And add WET NITROUS

http://store.summitracing.com/partdetail.asp?autofilter=1&part=NOS%2D05151NOS&N=700+115&autoview=sku

HERES MY CURRENT COMBO, its CERTAINLY NOT THE ONLY ROUTE OR THE BEST BUT IT GIVES YOU SOME IDEAS
viewtopic.php?f=69&t=263
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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