Shane4524

This discussion is more of your own opinion. I have been contemplating on whether or not I should build a 350 and throw it in my car. I have been talking to some auto shop owners and mechanics and numerous ones have said the 305 TPIs are good engines and the TPI has potential. My question for you all is if you have ever built up your 305 TPI and what have you done exactly? and if it wasn't a 305 TPI but the 350 TPI let me know and why did you stay with TPI and not go to something else?

**Edit May 2: I am thinking about putting a bigger cam in my 305, I know you can only go so big before the computer has to be reprogrammed. What's all this entail (swapping in the new cam, new lifter rods, where should I send the computer, recommendations)

quick90rs

iTrader: (3)

I'm following this, i want to to see where this goes, im wondering whether to build my 305 or go 350.

majobis

iTrader: (3)

I would do some searches. I know you hear that a lot, but otherwise, you're going to start getting the "go 350, the 305 is a waste etc". Just this month alone, there have been five posts. I'd start here: https://www.thirdgen.org/forums/sear...archid=4989646

Shane4524

Yea, I have heard that before, but things come into play like time, money, how much of a pain swapping can be. I am looking for pros and cons. Also, how people have built up their 305s and where they get their stuff.

Shane4524

Your link is a dead end.

Orr89RocZ

iTrader: (20)

What are the goals for the motor? Performance? IF so you will be limited by the small bore in the 305 unless you go nitrous or boost.

IMO the 305 is a good little motor for under 350hp on motor performance. you can get more but it wont be as easy or cheap. Most of the TPI setups will only do 340-350whp tops before running out of rpm on hot 350's and larger motors due to long runner design, so the manifolds will feed a 305 well enough. If you went short runner like miniram/stealth ram, etc, you will have MUCH more rpm potential to make power. You are limited on heads for 305's due to small bore. 1.94" intake valve is max possible that leaves enough clearance with the bore to keep it from shrouding the valve. Not many aftermarket heads have valves smaller than 2.02 these days.

With enough time and money, you can get a small valve head that has been worked over and flows enough to make some hp. With short runner intake, 450+ hp has been done in race motors/circle track type deals. You have to turn 7K rpm and more sometimes to get it tho. For most, this level of build is beyond their pocketbook and street practicality. 7K+ rpm in a 350, i'll show you near 600hp. Thats near 150hp more for same money or less.

If you are looking for milder performance under 350-ish hp on motor, which is say 300 and less wheel hp, then 305 aint bad. It should beable to get their with typical heads/cam/intake work. Wont make the torque a 350 or 383 will with the same hp but it will move a 3rd gen to the mid lower 13's if everything is set up right.

If you go 350-383, the swap is NOT difficult as long as you start off with a 350 roller block that the 87-92 L98's have and some of the late model sbc vehicles (trucks/vans/etc), if you have a 305 motor thats a hyd roller cam factory setup. The parts will be interchangeable. Cam's the same, timing chain the same, 1pc rear main so same oil pan, flexplate etc etc. Going from a 305 roller to a non roller 350 requires flat tappet cam and different stuff elsewhere like oil pan, and flexplate/flywheel changes. More of a pain and expense.

If you have a non roller cam 305, it may be easier to keep non roller 350 if you do the swap but its worth the upgrade to a factor roller style block. Roller lifters are superior.


Bottom line- limited bore and cubes means limited power. No real good head selection for 305 so limited power. If you want power, it will need RPM to make it. TPI is a long tube runner design that makes power in the 0-4500 rpm range. Smaller cubes can stretch that to 5000-5500. Some 350's i've seen still pull to 5500 with the biggest shelf TPI products, like FIRST TPI or AS&M big tube runners/ported aftermarket base. Some guys here are playing with custom fabbed HUGE runner diameter long tube setups and will pull to 6500+ rpm on 350+ inch motors. Not cheap but shows that runner diameter needs improved and base intakes need opened up to improve cross sectional area to pass the flow required to feed such motors.

Someday I will do a 305 build, kinda max effort to see what I can get out of it. Just have to find another project car or take out the twin turbo 401 motor for a summer...that I find hard to do

PhoenixFirebird

iTrader: (2)

I'm close to starting on a 305 TPI build-up, after I get a few runs in at the track with it completely factory. I have an 89 Formula. Right now my only plans are to get a different rear end gear (as 2.73 factory won't do much at the track), open up my air intake, insert a y-pipe before the cat for a cutout, and drop a new cam in it with 1.6:1 rockers. Eventually I plan on porting the heads, but for now, they're stock along with everything else. Aiming to break into 13s on the track. I'm racing Friday and Saturday night, so I'll post my stock times. I'll do some more runs once the new parts are in, and let you know the result.

Shane4524

Orr89RocZ- I really like all the information you are giving me. It's nice how you state facts not opinions.

As to the power band I am looking around the 300 ish range. I have heard of people messing up their 3rd gen by swapping a motor into it, maybe they just didn't know what they were doing. I'm good friends with an auto shop owner and they told me they do have a few 350s laying in the yard that do run. If I decide on the 350 what should I look for when sifting through the motors they have?

PhoenixFirebird- I am really interested in your results, so please post them on here. As you I plan on getting a new rear end, because as far as I can tell it's a one wheeler peeler or just a crappy posi. And I was looking into a cut-out also.

quick90rs

iTrader: (3)

For me there is no need to make a crazy amount of power id be happy making 280-
300 horses in my 305. How do i do it in my 305? without touching my heads. 4000-4500 range is fine with me, also i love the low end torque and would love to make some more torque. how? in my 305.

Shane4524

Yea, at this time I agree with what you are saying. Right now my car is pushing 190hp, which gets it going, but i'd like to get going better and bumping it up 100 horse would be great.

Orr89RocZ

iTrader: (20)

Block and head casting numbers and run them thru various resources on the net to see what the specs are. That will let you know key things like factory compression, cam specs, head specs/flow numbers, factory power levels, etc. Check to see if its driver side dipstick/passenger side dipstick, etc.

other than that, its hit or miss in the junkyard. Its best to find a block and start fresh with new parts or find a good set of stock crank/rods and recondition them at the machine shop.

280-300 hp will require a good cam and better intake upgrade. Preferably better heads...not all 305 heads are alike. Some are better than others. 300 on motor is doable fairly easily...thats in the 240-260whp range give or take. 280-300whp I think will require a nice cam and more rpm than 4500 rpm...think short runner intake like stealth ram or similar and cam likely around 224 deg duration. If you had better heads, you may beable to make it at 4500-5000 with TPI

quick90rs

iTrader: (3)

Stealth Ram on a 305 scares me, yeah the rpm range will go up but you lose some torque, dont want to have a dog in the streets. My car has a 305 LB9 TPI, Accel Coil, Flowmaster Exhaust, Headers, Moroso wires, 3.73 gears (posi). How much power do you think im making and how do you think i can make 300 horses and a little more torque?

quick90rs

iTrader: (3)

basically, whats another mod i could do thats easy enough , could give me some power, and wont require a tune

Orr89RocZ

iTrader: (20)

Nitrous? Thats your biggest power adder with no real tuning other than pulling timing which you can do via setting distributor 4-5 deg retarded over stock. If you have headers/catback, the only other thing is intake mods. May not require a tune then to replace the base/runners with larger stuff but it could gain with a tune.

You have a 90 RS? IS that a factory 305 TPI car? Auto trans? I'm not sure but some of the base 305's got the tiny cam. A good bit of power can be had with a cam swap but that would require a tune. Intake mods wont gain as much with a small cam 305.


HSR will lose alittle low end torque but flatten out the torque curve so there is a good bit available at all rpms. It tends to force rpm band up so more torque in the higher rpms. To combat torque loss you need more gear and converter if an automatic. Small motors need to rev up to make power so you need gear/stall. Thats why big inch motors and strokers are best for the street and strip sometimes. They can make loads of torque down low in the rpm range.

PhoenixFirebird

iTrader: (2)

http://www.gmtips.com/3rd-degree/dox/tips/cams/cams.htm

That might help a bit. Yeah, you have the same cam I do in my 89, unless you have a manual and it has the G92 option. If it's factory, does your tach have a redline at 5000 or 5500?

87TransAmws6

im doing the 305tpi my mods are hooker headers,ory straight piped to flowmaster 80 all 3 inch, 3.73's with posi, mcleod racing clutch, comp cams xr258hr12, double roller timing chain, lifters, all smog stuff gone, plenum egr walls ported, bbk fuel pressure regutaltor, beldon 8mm plug wires, and a ram air intake. car sounds amazing runs good too i also have a ported base and slp runners waiting to go on but im still thinking about bagging that and doing holley stealth ram but im affraid i will lose power.

quick90rs

iTrader: (3)

The engine in it is from an 87 IROC TPI 305 LB9, it is automatic. I know the HSR would help increase the RPM range but i just dont want to lose that power off the line i would actually like to increase my torque. Id like some numbers of a 305 HSR

PhoenixFirebird

iTrader: (2)

Yep, you have the same crappy cam I do lol. I'm getting rid of it fairly soon. A HSR was also suggested to me, but I think I'm going to stay away from that for now, until I build up a bit. I'd also like to see these numbers.

Anyway, I ordered a chip adapter from Moates today, and a buddy of mine has the equipment to program it. I'll be running complete stock Friday night, program a chip, and run with that Saturday night. Let's find out what just a reprogrammed chip can do!

quick90rs

iTrader: (3)

the 262HR-12 is a nice cam, you get some decent lift and requires no tuning, and no TPI mods at all

Orr89RocZ

iTrader: (20)

If you do a search for 305 and HSR, you'll find a few threads about HSR's on 305's. One of the well known swaps I've seen here was done by Zepher. He had a peanut cammed 305 with stealth ram that made 195whp/273wtq. Not to shabby considering how tiny that cam is.
https://www.thirdgen.org/forums/alte...o-numbers.html

iansane had a 305 with stealth ram and LT1 cam. Made 226whp on stock exhaust stock tune....240whp with longtubes. This thru a manual trans tho so the numbers are higher than autos.

quick90rs

iTrader: (3)

Little loss of torque I just find it more fun to have more torque off the line id be happy with 230 horse and 340 lbs torque

quick90rs

iTrader: (3)

Even 215 horse

Street Lethal

iTrader: (16)

Even the stock cam will benefit from some tuning, especially in the AE area...

Orr89RocZ

iTrader: (20)

Thats the problem tho...can you realllly tell the difference if theres more torque at higher rpms than at lower rpms if you have enough gear? what about torque converter? 2800-3000 stall on most street fun cars makes up for any lack of low end below 3000 rpm. It gets better on higher rpm setups...3600-4500 stall speeds If you never live below stall, power below that rpm becomes a wash. Also enough rear gear will generate wheel torque which will overcome the loss provided by the intake.

HSR loses peak tq over TPI, but torque is gained in the higher rpms and flattens the curve in the lower rpms. TPI is a peaky torque curve. Alot is made in the 2800-3200 rpm range but after that and before that its not much... you can really feel the torque onset as you approach 3000 rpm with TPI and stock converter trans, since below that there isnt as much torque and its such a peaky power curve. Once added 2800 stall, you just leave at peak torque and you dont ever feel the bottom end. You will feel a stronger top end pull with more higher rpm torque and thats where shorter runner intakes benefit.

I may have lost 30lb ft at peak torque rpm when i did HSR over stock TPI on my L98 but the gains made in the higher rpm band were worth it, and the flat torque curve improved my times. 2800 stall on both setups, I never really noticed the "low end" missing.

All in all, you cant expect to have a trans/gear setup for a low rpm motor run the same when you shift the powerband. It will feel abit sluggish and thus will require more stall speed and gear to make up for the power band shift. Once in the powerband things improve greatly.

Shane4524

I know from 85 to 86 Chevy put the smaller cam in and the Camaro lost 25 horses. So if I am mistaken can't I just throw an even bigger cam and get pretty decent power for my buck? I know I would then have to send in the computer to get re-programmed. Is that the ECM, PROM, DFI? And what would something like that run price wise?

Orr89RocZ

iTrader: (20)

If the peanut cammed 305's had the same heads as the other LB9's with L98 cam, then a good bit of power can be had with a larger cam.

Shane4524

Yea, i figured that. I am more interested in what needs to be re-programmed, I am having a major brain fart, but I am assuming the ECM?

quick90rs

iTrader: (3)

Buy a computer controlled cam with no need for tuning, new valve springs and you're good

Orr89RocZ

iTrader: (20)

Even computer controlled cams will need reprogramming to gain the most out of them. They really are just on a wider lsa to help minimize overlap at idle to keep o2's happy but you can get around that.....or ignore it and still be fine.

Yeah the ECM chip will need reburned. Likely want to mess with idle rpm settings, maybe some cruise rpm fueling but most MAF cars shouldnt need much there....MAP cars will. Then WOT definately needs changed. Simple to use the PE mode % enrichment tables...just increase where lean and decrease values where rich. Thats all there is to it for mild setups.

quick90rs

iTrader: (3)

The cam I was looking at is specifically designed for tpI with no computer mods needed whatsoever

Shane4524

If I am not mistaken, someone told me that if you buy a cam through Edelbrock (or maybe anywhere) you can just send the ECM in to a re-programmer and tell them what cam you put in and they can do all you need just from which cam you put it. I am not sure where I heard this from.

Shane4524

And no one?

Street Lethal

iTrader: (16)

People really make tuning out to be such a difficult matter. Bigger cams need more fuel, and whether your running sequential or batch fire injection, all the injectors do is release fuel to satisfy the ingested air. If you are looking to fine tune the ECM, and get all you can out of it, then yes, the tuner can focus on AE, SA, PW, etc. If you just want the engine to run the new cam based on the stock characteristics of the prom, then install an adjustable fuel regulator and simply up your fuel pressure to reach closer to 128-BLM. That's all it really is...

87TransAmws6

my 305tpi moves pretty damn good after the cam swap im very happy with it.

Street Lethal

iTrader: (16)

Good deal, which cam did you go with...?

87TransAmws6

all of my mods are in the post i did earlier number #16.

Street Lethal

iTrader: (16)

I rarely ever read every single post in a thread, mostly just the posts belonging to the original poster, so I wouldn't have seen post number #16. That is a pretty decent cam for the 305 that you selected, good torque down low, and very easy to tune. Do you have any times or power numbers with that cam, or did I miss that information too in post number.........

87TransAmws6

well i just got the work done not to long ago so havent had a chance to dyno or race it. if this helps for an idea i can fry off first, second and a nice bark into third.
Here's a short video of it
http://www.youtube.com/watch?v=7620-4RC9YU&feature=plcp

Street Lethal

iTrader: (16)

Nice! I'm glad to see more and more members sticking with the 305 small block...

WolfmanTA

Hi There! What is a good spark plug to run in a 86 305 TPI engine? Thanks..