SLP IROC-Z

iTrader: (1)

ive been pondering dumping my 305 for a 350, seeing that its been fun pulling the times it does i do have a need to go faster and everyoens sayin go with a 350. i really dont want to, i like having less displacement and i also want to retain my original engine. in my opinion the 305 tpi 5spd combo will adapt to mods and go quicker cheaper and more easily then a 350/auto car at first. but the 350 always has more potential to go faster. in all honesty it is 45cubes but the 4" bore opens up a world more potential. i love my 305, hittin a 13.9 with it was impressive, then doin the LT1 cam swap wich everyone said was a waste of time yeilded me 2-3mph gains at the end of the track with 100mph trap speeds, id say the 5 hours was worth it, plus it was a ****ty day so i didnt want to drive the car anyway. the delema i have right now is, since most people say dump the 305 for the 350 im having a hard time getting advice on thigns to do. i believe the engine is at the point now where to go faster i need to pull the heads, put in a larger cam, or change the induction. but i dont know waht to do first. id love to keep my stock heads and the current lt1 grind cam and just modify my TPI or swap to a super ram. what do u guys think? i need to rebuild the engine and id like to put a stock LT4 grind cam, port my stock heads, spin balance the lower end, port or buy a new base, SLP runners and the already modded plenum. or swap out to another induction? id like this car to power right to 5500. it goes right past 5k as it is but its obvious the TPIs restriction a little before 5k. im aware of the LTRs disadvantages but on a STOCK 305 with a STOCK TPI, what is it good to RPM wise? sometimes i get the feeling the LTR TPI setup is perfect for the 305 and other times i feel an LT1 intake or somethin would be much nicer. when ive modded this car ive taken a lot of time to think things threw and match my parts, do the little **** that makes a difference and not go over board. a power adder such as a ATI procharger has been on my mind lately as a mod id like to do a ways down the road. but for now can i get any insight on an induction thatll power to 5500? keeping the LTR TPI would be nice. my quest is to retain as many OE peices and get it to go as quick as possible. so far ive used an OE 3.27 rear, stock LT1 grind cam, ported plenum, modified maf. then the things that have to be afteramrket such as Headers, exhaust, filters, plugs and wires. what would i be lookin at if i were to port the stock heads, use a stock LT4 grind cam, port the base to the same dia. of SLP runners, siamese the SLPs 2.5-3" and have a spin balanced bottom end?

last yera in 35* weather i got my best mph and 1/4m time the 13.952 @ 97.08

this spring with the new 3.27 rear and the LT1 shaft it was pullin 100mph passes. the weather has gotten warmer and i lost some mph, mostly due to the fact im running lean from my maf, i believe the injectors are maxed out for the stock fuel pressure setting. but even still my mphs are quicker then the fastest of last year, so i know im gettin somewhere. just need traction and itll be a solid 13 second car. it sounds far fetched but if i can get up to that 100mph mark again and have the same 35* weather this fall i hope to be in the very low 13s with some 1.8 60 foots. thats considering everything on the car stays the way it is except for an AFPR and ET streets.

JesasaurusRex

iTrader: (3)

Well in all honesty its fun to build a 305, mines easily good for 13s on street tires, (didnt do it myself cuz imma bad driver , 2.28/14.1) added my nitrous and was looking for 12s. Nitrous solenoid i found out was broken so never went to the track and im leaving on sunday for the marines so I wont be going anytime soon. So yes they can go fast, fast being relative. But like most other 305 owners out there (who have actually built their 305s, and not just said it was a waste of time) i have to admit id rather have a 350 or better yet a 383. My 305 is for sure not slow, i rape most cars out on the street, however I also know with what I have done on a bigger engine id see 12s n/a and not with the bottle. Only reason I really did it cuz i wanted a manual transmission car, and being only 17 when I bought it (now 18) I did not have the money for a 350 swap. So learning what I did, most of it from thirdgen.org :hail: i found out that everything could be swapped over later i said what the hell and started buying parts. Took a lot of blood, sweat, and tears but I am extremely happy with what I have accomplished. Its entirely up to you, hands down a 350 is a better engine. Coming from a 305 maniac so just be happy with what you do. Work with what you got or if you have the money dump it. Hope that helps.

jrg77

Anybody wanna revisit the 7000 rpm thing in a 305? I understand plainly that a 305 will make less power than a 350, and that it will cost the same to build in terms of acquiring parts. I just like the sound of a high revving v8. If I can do that and not go to the junkyard and guess at an engine, or spend $1000+ on a brand new block to throw stuff in cool.

What parts have to be replaced? What parts will hold it together? Can an engine with a 7000 rpm redline idle and drive at part throttle smoothly?

PETE

iTrader: (1)

Here is a hypothetical for you guys. IF I'd wanna try this what would be the limitations here the block or running out of cylinder volume no matter how much boost(airflow) is supplied by FI. Not for anything other than i'd like to do it.

First thinking about limitations of the 305 block in general will be lengthy. The block would get billet 4 bolt caps a girdle and partially filled with hard blok. Hopefully this will keep it safe and sound. The one extra head bolt percylinder should help hold the hg's.

My thoughts are to grab a forged 350 crank, forged 6.00in rods, and forged 3.75in. pistons. Using fastburn heads(either the aluminums or irons). If I go irons it would get 1.55 exhaust valves and stock 1.94 intake and the holy mother of port jobs(concentrating on flow with trying to minimalize the dramatic increase in cross section ruuner size, effectively trying not to kill velocity and as such street manners).

If I go the aluminums by chamfering the cylinders and limiting valve lift I shouldn't mate the valves to the cylinder wall. A 214/222 roller cam I haven't thought of the turbo yet. Maybe a 76 or bigger. Not a lot of cam, but the consensus is that turbo cars do not need a lot.

My reasons are controlling the flame front and reduce the risk of detonation by using the small bore(easier to tune with high boost), not wanting to rev to the moon just make a very good street based motor, get good gas mileage, try to keep it together and blowing serious air into it(30psi) try fo a low 10 or 9's. By not revving it skyhigh I don't have to invest in costly valvetrain components to stay together. Instead that money will go to a rear and tranny cause you know they'll need it

The rear would be a race prepped non b.o.p. pattern 2004r with a 3000 stall 10" and 3.23 gears. Might have to go 400 if the power gets out of hand.

What are your thoughts. Remeber this is a hypothetical, but I've wanted a third gen camaro back ever since I got rid of my first one! I'm sure I've missed some other pertinent info, but for the guys with experience you get the picture.

PETE

83 Crossfire TA

iTrader: (2)

stock 305 and 350 cranks have the same casting # but the 305's are much lighter. Using a 350 crank will require a lot of balancing work.

Why the hell would you do that? You can get the flow on a set of vortec exhausts within 95% of the intake with the stock 1.5" exhaust valve.

Chamfering? Do you mean clearancing for the larger valves?

I'd be surprised if you could build a turbo motor that that would be the optimum cam for.

Do you actually need a turbo that big?

Most 200's have both patterns.

PETE

iTrader: (1)

To answer them.

I feel it's all about airflow, if you could open up the heads as much as possible you'll run less boost to achieve the same power. Try to minimialize the stress put on the deck to keep the heads down. Really just throwing out an idea to see what the limits of the 305 block could be as well as this or a similar combo.

As far as chamfering/ clearncing dont know if a mild lift cam would interfere with the small bore when using 2.00/1.55 valves. I've heard .462 with 1.5 rocker would be max on a stock bore 305. Heads may be too big in the first place.

Using a larger exhaust valve in the head in theory would help(due to the larger area) expell the gas to the turbine housing quicker providing there hasn't been a great change in velocity. By doing that less cam can be used to achieve the goal. Less cam means less fuel consumed when not in PE and better part throttle gas mileage.

214/222 Goes along with trying to evacuate the cylinder completely. You could also try with scavenging by way of primary size and length of header, but i feel this will tend to cool the exhaust in which case hotter is better to get the turbine to spin.. It can get more exhaust energy to the turbine to do it's job. Doing this may also help to keep down the radiant temp of the cylinder and not heating the next charge coming in helping out detonation control.

As for the turbo a 76 is quite huge, however for a given psi( i believe i mentioned 30 or so) it will move air more efficiently. Less heating of the intake charge means a smaller IC to work with giving you the ability to not have compromises with your cooling system.

Just thinking of a efficient high power package that could also be docile when not in boost while using the restrictions of the small bore engine.

bnoon

Wow, good reading guys (for the most part). Keep it going.

Side note: I'm just starting an LT1 intake 305 with 1.94/1.50 under cut SS valves in the P&P LB9 TPI heads. Retrofit roller cam (using stock "type" parts instead of aftermarket) with .510/.524 lift cam (with 1.6 rockers)... Headman 3/4 length headers... All pretty much have been mentioned in here. Feeling good.

83 Crossfire TA

iTrader: (2)

Boost has almost no effect on the force on the deck surface. Cylinder pressure does. The more boost you run the greater your average cylinder pressure will be but the lower your peak pressure and the lower your variation will be. Pressure spikes are what cause detonation and parts breakage. At the same output the application using more boost will be easier on the bottom end.

I'm assuming that you're talking about cutting valve clearance notches in the deck surface?

I'd have to see that to believe it. You'd need a killer exhaust design and very short cam timing to keep this from loosing you power on a turbocharged application. I haven't seen anyone build something like this on a street going V8 and I don't expect anyone to do it soon.

I don't see the point in making that end of your job any harder if you can get more then enough flow out of a set of 1.94/1.5" valves on a decent head. I recently ported a set of vortec heads that flowed over 200cfm through the exhaust ports at everything over .400" lift. Why would you need any more then that for this?

None of this makes any sense if you've got enough exhaust flow and an appropriately designed header/manifold.

Too big a compressor will be just as inefficient as too small a compressor. If you don't need a 76, going with a smaller, more appropriately sized compressor will give you more power, less heat and better response/street manners.

83 Crossfire TA

iTrader: (2)

EWWWW, YUCK!

bnoon

Don't worry, these heads will flow more than they are "supposed" to thanks to some epoxy/reshaping on the intake side. The exhaust side will flow well enough with some clean up work and the dual profile cam.

Part of deshrouding the larger intake valve will come from an angle mill... All for a case of beer. I love having friends in the right places.

83 Crossfire TA

iTrader: (2)

Do you have any pics? I'd love to see what you're doing with reshaping…

Be careful there…. The area that you really need to cut to deshroud the valves properly has a coolant passage right behind it. Get that spot too thin and you'll ruin the heads in a "there's no fixing it" way.

You can say that again… a buddy of mine just got back to me and told me that his brother owns a tow truck and has some connections that could help me do something that I've been trying to get done unsuccessfully for over a year

PETE

iTrader: (1)

Crossfire, This isn't a pissing match. You know as well as I do that there is almost no room for a decent turbo header on a 3rd gen.

Being stuck with log manifolds, (most common) although do work an inefficient manifold wont maximize the combo.

Why not try to maximize the exhaust flow by emptying the cylinder as much as possible(aka scavenging)? With the right turbine housing and enough exhaust volume,pressure, heat, etc. It would get the turbo spooling just fine.

PSI is just the restriction of the compressed air getting to its destination. Running too much boost overheats the air charge temperature and could cause problems with detonation. Combine that with higher temps of the unburnt/expelled gasses in the cylinder and it's a recipe for preignition.

It wasn't too long ago that a dual pattern cam was considered herecy in the turbo world. You can only go so far with a cam before you end up bleeding off valuable exhaust or better yet causing reversion into the intake tract. My point simply is to use a mild cam while maximizing the valve size, port flow and velocity for a given combo.

Again I mentioned 30 psi ever try to run 30psi out of a 49(60trim)? Better off hooking a flame thrower up to your TB! I've ran 28psi(wastegate prob.) from a(60-1) 60mm wheel and even then it's tricky with the tune. If it weren't for the unknown Hyperucrappy pistons that were in my motor it would've probably survived.

stevedave454

i have a question... go to this thread i made awhile back, scroll just past half way down https://www.thirdgen.org/techbb2/sho...hlight=377+383 , "sweetS10v8" made a post about car craft or something doing a test between a 377 (400 block, 350 crank) and a 383 (350 block 400 crank) where they kept everything internally as close as possible... same comp ratios, rod length, cam, etc, and everything bolted to the motor - heads, intake, headers, carb, etc was identical... and the 383 made more torque down low, and the 377 made more power over 6000 RPMs... im not disagreeing with you, im just asking if you can explain this because i really dont know... i've always been told that a shorter stroke motor can rev higher (safely) and you go with the bigger bore to get some more displacement, and when matched with the right cam, intake and heads, you can (potentailly) get better VE's at higher RPMs

83 Crossfire TA

iTrader: (2)

Pissing contest? I'm not sure what you're referring to, but I assure you that if that was what I was looking for I would have packed up and found some real competition…

Huh… funny, the last thread I replied to you mentioned how well they work, that even the cheesy factory 3.8 ones are good for 10's on a GN. So here we're talking about 30-50% more engine in a chassis that's typically as much as 400lbs lighter. Maybe I'm missing something, why wouldn't that go MUCH faster??? How about if you built a properly designed log manifold (start reading some old school theory for turbocharged exhaust design and you'll find that a modified log is actually the only "correct" way to go for maximized power)? The limitation becomes more about how fast do you want to go (what do you want to break), not how fast can you go.

Explain to me how you're going to get scavenging under boost on a turbo setup

In which "turbo world?" Single pattern or even reverse split duration cams were the way to go in the GN world because no one was bulding engines that needed to rev to make power. As you move more towards NA conditions and powerbands your cam requirements become more normal. Now again, you're talking about 30-50% more cubes then the GN world that you're comparing things too… that pretty much means that you need that much less rpm or boost to do the same thing. In addition, you actually have fewer cubes/cylinder and heads that flow much more with bigger valves to start with. All of these conditions add up to not needing that bigger split duration cam and choosing something more old school again…

Of course, if we were talking about building an optimized exhaust with twin split scroll turbines then this would all change.

PETE

iTrader: (1)

As far as logs yes they do work however an individual primary dedicated to each cylinder would optimize a turbo system better. On a 3.8 turbo motor the logs do become inefficient. Most tend to swap to the above mentioned setup when running stage or hp stock block combos to maximize their setups.

For one, pulse vibrations from each cylinder going into the same primary tube isn't the best way to go. It may be possible to do some tweaking and use the pulses to sort of push the other cylinder's gasses along in the tube(kinda like how TPI uses these pulses to slingshot the incoming air into the runners). It may also be possible to build a header to help scavenge the exhaust a little better(this is talking an all at combo). Possibly running different length primaries maybe emptying one cylinder into the other and varying the length of each primary as well as diameter finally ending up with a 2 to 1 collector/ turbo flange at the end.

I didn't really get your whole point on the larger valves and head flow(I assume you're talking about the chevy motor). In that case yes you are correct about running less boost to attain the same power(as compared to a GN/TTA), but with the extra cubes and flow it should.

I was saying that by maximizing the head/intake(eliminating the restriction) the Turbo will have less backpressure, you wont have to run lots of boost to attain a certain power level(as compared to stock type heads/intake of that same engine) which would give you a reliable induction system and not stress the turbo . Depending where the combo makes it power you could also factor in less stress on the valvetrain if you do not have to rev it to the moon to make power.

The original idea was for it to be decent on gas, make lots of power in boost, yet be docile enough while at part throttle and be reliable.

Thats all sorry if i made something outta nothing.

bnoon

No pics yet as the heads are still totally stock, sitting in the corner of the garage at my friend's house, de-oiling themselves into a pile of oil dry before I will bring them home. It's been so cold here this weekend that I didn't even see my own garage from the time I got home Friday until this morning... and I have a furnace!!! I will post pics in the TPI forum most likely since they are 416 TPI castings.

As for the reshaping, it's rather minimal. There's a small pocket that must be filled, just in front of the guide, and that's about it. The rest of the port will be taken out to it's maximum, which really isn't a whole lot on 305 stock castings. about 170CC IIRC from what he said. Hopefully we won't hear the dreaded "whisper" of a thin coolant wall.


The angle mill will take at most 1-2 degrees off IIRC. Steve (friend that's doing the work) mentioned something similar about the maximum we can take off. The cool thing is that the angle mill costs us nothing more in machine time than a flat mill. Even if we do bust through, he has 416 castings just laying around that people have discarded... He keeps some around for the "roundy round" dirt trackers that build cheap claimer engines and like the added compression of the closed chamber heads.


Hey, it's practically free. Offer up some beer and I'll bet you get that tow truck over there quicker! Seems like most of the machinists/garage type of mechanics are up for almost anything then! Heck, I just put 144 new studs in my friend's snowmobile track a few weeks ago for a six pack!

83 Crossfire TA

iTrader: (2)

416s… that changes things a little… I wasn't sure that they ever came on TPI engines but if they did they had to be '85 or '86's. Port and chamber configuration wise they are MUCH better then the later heads and L98 heads (I would choose these over the aluminum 'vette L98 heads). With some work those are actually very similar to the vortec castings but with smaller, 58cc chambers. Install larger valves (1.94/1.5) and some minor cleanup and you end up with something that has very similar flow and swirl characteristics to the vortecs.

FWIW, I'd go over them very carefully before spending any time on them. They have a tendency of cracking around the inside head bolt holes… usually you can spot the cracks by just going over them with one of those scotch brite cleaning pads

Huh… are these going on a 350 or 305? Angle milling those is a somewhat scary proposition, since on any good size engine your compression will go through the roof. You're starting with 58cc chambers, how small do you want to go? I guess that at least you're not milling the side that usually cracks on these.

A lot gets done by the power of a six pack. In this case the guy happens to be the brother of a guy that used to be one of my students, who calls me regularly for "tech support" and help passing certification exams. As it stands now I feel that I own him for letting me borrow his trailer a couple of times and I’m pretty sure that he's feels the same way for some help that I've given with his assorted work projects…. Actually, I think that he holds the record for working out wicked deals along these lines; he showed up one day at a construction site down the road from his house with a couple of buckets of KFC for the guys… end of the day they stopped by with 2 dump trucks of fill dirt and graded his whole yard…

bnoon

Two heads come on the 305 from '82-'86, the 601 TBI (IIRC) and the 416 for the TPI. The two engines I have are both '86 TPI 305's (one in the car, the other at a friend's garage). I too have seen the flow numbers for the 416 heads with the 1.94/1.5 valves. That's what I'm after, and for far less money than a new set of Vortec heads... not to mention, the Vortec heads wouldn't fit the LT1 intake swap that I'm going to do as well.

The larger valves are slightly shrouded by the smaller bore of the 305, that's where reshaping the chambers and the angle mill come into play. It still won't flow as much as a larger chamber and larger bore of a 350+ engine would, but it greatly increses the flow on the smaller bore by changing the approach angle of the incoming air against the edge of the chamber.

Cool, I'll be sure to check them in those areas. We'll be mag testing them anyway, so I'm sure any cracks will show up.



305. With the proper head gasget and chamber work (staying near the stock chamber size by opening it up a bit on the edges and taking out a bit of the spark plug boss), we should come out right around 9.7 to 9.8 to 1. We could go as high as 10-1 or over if we used a 6" rod set up, but I found a great deal on some 5.7" GM PM rods that I couldn't pass up. Totally depends on if we have to do any clean up to get the heads straight or not as to how much of an angle they will support, if any at all...

83 Crossfire TA

iTrader: (2)

FWIW, 416s come from the factory on 305s that had 9.8:1 compression (ex, my crossfire TA), and ran beautifully on 87 octane (even here at sea level), much better then the later setups did crappier heads and 9.3:1 compression. Cleaned up/built right on a 305 they should work very well on pump gas into the high 10:1 range (I've gone just slightly over 10.8:1 and it ran great on pump gas but on hot days it either needed the timing retarded about 2* from where it makes best power or 92 octane…). I'd bet that with a carefully built setup they could be made to work well with as much as the low 11:1 compression range on pump gas.

Heh, I think I just snagged another set of 416's last night… but I'm really looking for something with larger chambers for my current project.

bnoon

Huh... Everything I have shows 9.5:1 for the L69 and LB9 305's. What's the engine code for the crossfire? LU5? I see that as 9.5:1 also...

Oh well, everything will be computed, checked for cc's, and checked for clearance (piston to valve) anyway. I'll stay under 10:1 though as winter gas sucks and summer heat can be just as bad on summer gas. The daily driver doesn't need to have those extra 2* of advance. Maybe when/if the 400+ cu in engine project gets built...

83 Crossfire TA

iTrader: (2)

The crossfire is an LU5. The FSM shows it as being 9.8:1, and the one that I checked years ago was right around there (I think I remember it working out to be 9.77:1 or something). Maybe if I have time I'll check the deck height and where the pistons on the 305 in my TA… while pulling the rest of it apart (I did say that I was just going to take a few things and then get it towed away, but the more I mess with it the more I realize that most of what I can get to on it is in better shape then what's on my formula now and on 90% of the 3rd gens out there and the pile of parts that I'm keeping keeps growing…)

bnoon

What's FSM? Field Service Manual?

The Chilton's Manual I have shows 9.5:1, same 58cc chambers, same head gasket, same piston for the LU5, LB9, and L69. The tech portion of the thirdgen.org main site has it as that also... Guess I won't know until I work the numbers.

83 Crossfire TA

iTrader: (2)

Factory Service Manual

Donno… after looking around I'm coming to the conclusion that we should just stick to "mid 9's" since it seems like everyplace lists them differently, although the 3rd gen sites seem to agree with 9.5 for the earlier ones and 9.3 for the later ones.

JASONN20