93z71

Well im new hear I've always seen the site and found great info here im a truck guy (always wanted a iroc almost bought a transam).. I came here in search of people more familiar with tpi since im a noob.

Im building a 383 ported heads, big valves, h beams, 10.1 compression, roller cam I think its 234 236 at .50 in the ball park of .550 lift dont quote me I forget what my builder decided on. Anyways to make a long story short I was dead set on tpi forever then got talked out of it saying it would never flow enough without a boat load of money blah blah blah get a hsr wayyyyy out of my budget.

Right when I was ready to give up I saw this dyno comparrison http://xtremecarzone.com.au/index.php?showtopic=386

It has now brought me new hope of making tpi work without giving up an arm and a leg the steady tourque curve of the extrude hone setup and tpis bigmouth setup looks super pleasing since its going in a truck.. Any advice or help would be great as far as runners brands, porting and working over my stock intake or after market, ported plenum or siamesed plenum? Thanks guys!

86T/A_Ram_Air

You can make power with a TPI set up. You do have to remember that it was designed to make more TQ than HP. You can open up and port match the Base, the runners, and the plenum. Also you can simese the plenum and base ports as well as the SLP runners. The deeper you can siamese the runners the more HP you will gain, but you will be trading TQ for it. It will also bump your powerband up to a higher RPM thershold. It all depends on what the primary use of the engine will be. If its going to be a mostly street car you might want to not go so deep to retain some TQ numbers since thats what get you moving. I hope that was of some help.

93z71

Very very helpful I really appreciate it. The tourque curves are what drew me back into the tpi instead of the carb the extra mpg is just a nice addition .

The motors going to be a daily driver in my truck about 6000lbs so I take it siamese would probably be of no benefit to me since the truck wont see wfo passes unless my buddies want to try and roll on me or a pesky rice burner tail gates me. Acceleration is where all the fun is.

Orr89RocZ

iTrader: (20)

If you can swing it, buy the FIRST tpi setup

93z71

At 900 bucks its very tempting What size injectors would go with the setup good 24lbs? I figure i'd have atleast 500 in just that quick fuel carb without an intake

93z71

the only downfall is ill still need wiring and such I want to try and make this thing run good and respectfully without spending a hell of alot more then I would for the carb'd setup.

Orr89RocZ

iTrader: (20)

30's would work well. 24's would be pushed hard on that setup if heads are any good but doable if you ran higher fuel pressure

93z71

Heads are worked over stockers should flow pretty good they are not tbi heads I forget what the castings are. Maybe I can find 28s I dont want to get to big of an injector im afraid ill have to cut down on fuel pressure so much theyll just drool

93z71

Heads are worked over stockers should flow pretty good they are not tbi heads I forget what the castings are. Maybe I can find 28s I dont want to get to big of an injector im afraid ill have to cut down on fuel pressure so much theyll just drool

Orr89RocZ

iTrader: (20)

Do you have info on what the heads flow and what the port size is now? Best ive seen out of l98 irons is 270's cfm on a heavily ported big valve mod. Lots of time and money to do that. Need to know how much work was really done because it will determine power output and thus injector size. 24's at normal pressure will do 350's whp which is about all you will see with standard out the box long runner tpi. Siamesed for more rpm for that nice cam will make more if head is good. 30's will definately cover all you should get out of that motor. If it ever became a problem adjust fuel pressure up 10-15 psi as long as you have a good fuel pump like a walbro 255. First tpi with its large diameter passages should make more power and rpm than all the other tpi's that arent siamesed so potential higher power may dictate need for larger injectors.

Its gonna come down to tuning. There isnt a cost difference between most injectors between 24 and 60 lbs depending on brand and models so its safe to over estimate. Now some guys claim to be faster when running smaller injectors at higher pressure because of improved spray patterns. Higher pressure should "atomize" fuel more and thus make for better burn and power. But the tune will determine how engine will run. You could throw 80's in there and run fine just have to run a low pulse width which the injector may or may not handle but i know siemens 80's work with .80 ms pulsewidths which are really low so it could be done but obviously not optimal.

93z71

Well I do not have flow numbers there not l98 heads theyre 082 or 882 casting if I remember. The biggest drawback of this build will be the heads me the builder and everyone else knows that but I didnt have the extra 600 for aluminum heads.

93z71

If they are 882 heads they must be milled down because I could've swore he told me they were 64cc heads and I know they have a good bit of work into porting bowl blending and the valve work.

86T/A_Ram_Air

Since it is going into a truck I say just port everything out and gasket match it all. Don't bother siamesing because your will need all that TQ to get you moving