So my son bought an 85 Firebird with half dead 2.8 V6 in it. Car is nice an solid with a few normal issues. We sourced out a 79 Impala with a 305 and a TH350 tranny to swap into the car. Want to give the 305 a little help lol! Going with a 600 cfm 4bbl, a mild .420/.443 lift cam, flat top pistons, and Hooker headers. My big question is about the 1.72 intake valve in the 305 heads. Don't want to drop a ton of money into the engine, and all the previous parts were sourced for around $500 bucks total. Will it be worth it for me to have the machine shop cut the intake valve for 1.84? Momma doesn't want a 400hp engine since boy is still on our insurance lol. Just wondering what we can expect for performance with the heads rebuilt with the small valve and some mild porting in the bowl and runners. Is 225 to 250 a reasonable expectation? That would be more than enough for him to get in trouble after school

 

Is that to the wheel or to the crank?

 

To the crank.

 

That is more than reasonable considering that factory cars were within 30ish hp of that number.

 

Go to an 80s 305 truck or van in the bone yard and grab the 14022601 heads off it. They have 52cc chambers and 1.84/1.50 valves. Another alternative would be 502/059 casting 305 Vortec heads. I would go with a 218/218 cam rather than the 204/214.

From what I remember the older 305s had a 434 casting. 60cc chambers and 1.72/1.40 valves.

 

You'll want a complete and functioning V8 thirdgen for a donor car. Or just buy a V8 thirdgen for the project. Because, you'll need everything from a V8 car to convert a V6. Any transmission that didn't come from a third or fourthgen Camaro/Firebird, isn't going to have the torque arm mount a thirdgen needs. While there are solutions to relocate the mount, it's usually not worth the trouble.

Now would be a good time to point out the usual anti-305 manifesto. Whatever you spend on a 305 could be better spent on a 350. General rule of thumb, you'll spend more money rebuilding a 305 than a more common 350. Better still, you can usually find a crate 350 that costs less than rebuilding an older tech 305/350. If you're doing a swap, you might as well take advantage of one piece rear main seals, centerbolt valve covers, roller cams, and so on. Unless you like oil leaks...

 

He said a max of 250 CRANK. This would actually be a perfect application for a 305. I understand the hatred towards small bore blocks runs deep but, when it makes sense...

 

Yeah, I might be reading a bit into it... But really, a 79 305 isn't much of an upgrade over a MPFI 2.8 or 3.1, and it's a very labor/part intensive swap to do the job right. For what it'll take in $$$, and effort, a low output 305 will be an extreme disappointment. I understand not wanting to stick a kid in a 400hp monster, but there's a ton of margin between a basic truck 350 and a 400hp 350.

I read swapping a 79 Impala drivetrain into a six cylinder Firebird, and it translates to a recipe to be disappointed. A little more care and info going in could make for a much more usable and enjoyable finished product, with potential for growth that a smogger 305 wouldn't have without tossing out the engine. I mean who hasn't done the mental math to shove a couple junkyard salvage donor parts together and have something that would be kinda neat, then after getting into it, you realize you should have done things differently, and the car ends up sitting or taking far far more effort to go back and correct.

 

Yeah the 305 - even a top of the line TPI 305 from the late 80's, with basic bolt on's - is barely capable of 200 at the wheels. It's not the best starting point nor the cheapest. Especially some old 70's block with some of the potential block problems of that era.

GD

 

Did anyone read past the "79 Impala" part? He's talking about changing the pistons and cam. I do agree he should probably find some better heads. Even a set of stock 305TPI heads which can be had for peanuts will probably get him to his goal. Even 85, the first year of the LB9, was rated 215 bone stock.

 

Front springs (V6 ones will sag under V8 weight)

Radiator is different

Complete exhaust system

Means to attach the rear axle's torque arm since he'll be running a turbo 350 which has no torque arm mount (79 Impala has no torque arm)

Tachometer , the V6 one will not read correctly the RPMs of a V8 engine

If the car has A/C , and you want it to work , the V6 A/C hoses won't work for the V8


There will likely be other things that will be needed , but the above list will give the OP an idea of what all will be involved ....


Something else here that just popped into my head , maybe some of you more familiar with these swaps can clarify ;

The factory six cylinder differential gear ratio is 3:45 to 1 , designed that way to provide some acceleration from a stop in first gear and to provide a low ish RPM cruise on the highway with the 700R4 in fourth with it's converter locked . If the OP puts the 8 cylinder in with the turbo 350 (which doesn't have overdrive I presume ?) won't his gearing have the poor engine turning crazy high RPMs when trying to drive at normal highway speeds ? The 8 cylinder has a 500 RPM lower redline than the 6 cylinder does , further exaggerating the high RPM on the highway noise , yes ?

Since this thread appears to have become a bit of an opinion fest , here's just one more ;

With all that's involved in an 8 cylinder swap , and the fact that "Momma doesn't want a 400 hp engine since boy is still on our insurance lol" , maybe the OP's best move for getting the car actually driveable somewhat soon would be to find a good RWD 3.1 or 3.4 and slap that in and go ? Consider the six banger as a good set of training wheels for the kid and then if he wants the fire breathing 8 in the future after he's fully learned to drive it with the 6 the foundation will still be there to build up anyway he wants to . Father & Son can still have plenty of good bonding time replacing the 2.8 with a 3.1 or 3.4 and will likely be able to finish it FAR sooner than the complete car rebuild that the 8 cyl swap would entail .

Like I said , everyone's got their opinions , it's just the matter of how soon they want it on the road VS how much of a project are they actually looking for .....

 

Tank and magnaflux the block, bore the cylinders, deck the head surfaces, new cam bearings, polish the crank, refurb the connecting rods, balance the new pistons, new gaskets, new bearings, basic bitch cast or hyper pistons, cheap flat tappet cam... You're going to be into rebuilding that 305 for about a grand without touching anything performance related. Factor in refreshing a junkyard set of 416 heads with milling, valves, a valve job, new springs, keepers, etc and you're looking at closer to $1500, if not more.

Meanwhile... You spend just a touch more, you get all new stuff, with a GM warranty, no waiting for the machine shop to get to it, no hauling away the donor car, no greasy mess where you tore it down, 50 more cubes, roller cam, 1pc rear main, etc etc etc...




Just saying. There are a ton of rotten thirdgen corpses on Craigslist and the like that started out as tired but running and driving cars and a 79 impala donor car. It doesnt work out far more often then it does.

 

Unless he wants to deliberately leave the option for his son to easily upgrade later down the road, he stated he wants a 305 and has good reasons for it. Who said he needs to have machine work? Plenty of good 305s can be had for no more than $100-$200 including the heads. Although I wouldn't personally recommend it, machine work is not required to change pistons if you're doing it on a budget.

Spending a ton of money is also not required if you know what you're doing. My last engine that came out of the car was a .040 305 with 601 heads. That engine went 15.008 in the 1/4 and 60d @ 1.95 with valvefloat at 4500rpm and would have easily made the high side of his goal even with its **** poor 14cc dished pistons by just changing the valvesprings. It only had 30k and plenty of crosshatch left. I literally tried giving it away after having it for sale for $100 and nobody bought it. I left it in the back of my last truck after it got wrecked. No idea what happened to it. Quite pathetic actually. It would have been an absolute perfect candidate for a project like this.

I also 110% agree with everything OrangeBird said. Which is just another reason the OP does not need to spend 2-3k on the engine alone. OP has not provided us with enough information to automatically recommend a bigger engine. What is his budget? Does he want to leave his son with the option of making big power easier later down the road? Does he have a specific reason for wanting a 305 other than keeping power levels down?

 

It would be less expensive to buy a 350 crate engine than to properly rebuild a 305. You're not gonna get 250 hp from a 305 without after-market heads. If your on a tighter budget, try to find a good used 350 that still has some life left in it. Read the Sticky on the V-6 to V-8 engine swap. Off hand, I can tell you that you need V-8 motor mounts, fuel lines must be moved to the passenger side, a full exhaust system and front springs (as already mentioned).
What you really need is a complete V-8 equipped thirdgen donor car...

 

 

What I read what that a father wants to take on a project with his son. Perhaps to show him the means to actually assembling an engine themselves, doing the swap themselves, bonding together and enjoying themselves. Shame on them for that.

 

I'm sure your post will be very helpful...

 

The 200K mile flat top piston, 601 head 305 with a 218/218 cam, performer rpm q-jet intake and thorley tri-Y headers into factory dual 2.5" 1-ton van exhaust tubing with glass packs made a stock stalled 700r4/3.08 geared 5,300 lbs G20 van run a 15.6 @ 88 mph on a 2.2s 60'

 

Case and point.

 

Please shut up and learn a thing or two. That statement right there shows you know nothing about what you speak.

The 305 Marine engines were 230-260 hp depending on the year and used cams under 200° @ 0.050 duration.

Car Craft did a LG4 bolt on build. They got to 230 hp with headers and a performer RPM intake on a stock early 8.6:1 LG4. They put the tiny Comp XE262 cam into it never even changing the springs and got 270 hp out of it. Something like a XE268 cam in a 9.5:1 305 would push it closer to 300 hp. Factory 305 Vortec heads would get it into the 330-340 hp range.

 

NapaDan,

A great project! From what I know, that 79 305 with the cam and exhaust will probably be just over 200HP but it isn't going to make much lower rpm torque due to the carb and not much hp due to the heads. Even if you get the valves enlarged, my guess is the heads just won't flow well. That being said, if the cost is the same, then yes, go for the bigger valves! The headers will look cool but probably aren't worth the trouble in that third gen. I wouldn't do anything more than you are already doing to keep the costs low and the hp will be what it is. Just MHO. Good luck with the build. If he is into it, your boy will remember that project forever. I know I do.

If it's a carb and a TH350, you won't need any electronics. A few "trickeries" that will need to be addressed:

1. I'm not sure how one would drive the factory tachometer using a manual distributor. Maybe there is a kit out there or someone has already done it,
2. gas pedal cable to carb throttle
3. radiator cooling fans will need to be driven by an independent thermostat.
4. Fuel. The carb cannot use the current pressure of the fuel injection rail. Maybe someone makes a fuel pressure regulator that lowers the pressure to carb levels. Seems like an easy way to solve the fuel supply issue. You will need to make a wiring change to turn on the fuel pump manually when the car is in run.

 

Talk is cheap, pal. By the time you spend money on valvetrain upgrades that can rev that high, bottom-end upgrades that can withstand that kind of RPM, machine work to make those stock heads flow enough cfm, and an intake and exhaust system to match, you could have bought something better and more streetable. There's a reason no thirdgen with a 305 ever produced 250 horsepower from the factory.
The O.P. has already implied that he doesn't want to spend a fortune. Those car magazines publish a lot of B.S. to sell their sponsor's parts. They claim a stock Ford 302 made 400+ hp with their bolt-ons. So sit your @$$ DOWN...

 

Well napadan, it been nice having you around



Yes there are probably some better options to the questions you ask, but truth be told you likely have a solid plan. If keeping costs low and raising the fun factor is your goal, don’t sweat the small valves. You’re not building a high rpm screamer, but something as you said to get the kid in trouble after school. If the heads are a concern, there probably are some better 305 options as others have mentioned. Slightly more cam might be good as well, but what you have will work just fine. If I could offer any deviation from your plan, I would suggest sourcing an Fbody 700r4 to install behind it rather than the TH350 for two reasons. One, it will allow you to attach the factory torque arm with no issues, and two you’ll have the benefit of the lower first gear for better take off. If you are adding headers, you’re already planning on doing exhaust so no worries about that. Radiator, lots of options there and willing to bet the low output 305 would probably run with the original V6 one just fine. Sure there will obstacles to overcome as with any swap, but nothing that’s a deal breaker by any means. In the end, your son will have a car that sounds cool, runs decent, and have pride in learning and doing the work himself with the help of his father. Really don’t see any wrongdoing there!

 

Intake and exhaust are the same regardless if you are running a 305 or 350.

Its a small block. The valvetrain does not need much work until you start running it over 6,500 rpm.

Same with the bottem end. The plain jane Vortec 5.0L truck engines you would find in a work truck or van had the rev limit set at 5,600 rpm. 2 bolt main, stock rods, stock hyper pistons, cast crank, weak valve springs and all. I had the limiter set at 6,200 rpm on the cammed 305 Vortec engine in my 99 Tahoe. It had a 300K mile Express van engine that had new rings, bearings, a cam and the springs upgraded. It laid down just under 280 hp at the wheels.

A stock 416/601 casting head has no problem breathing enough to make 300+ hp. They outflow the old power pack 283 heads that did quite well on the old generation small blocks.

 

Front springs (V6 ones will sag under V8 weight)

Radiator is different

Complete exhaust system

Means to attach the rear axle's torque arm since he'll be running a turbo 350 which has no torque arm mount (79 Impala has no torque arm)

Tachometer , the V6 one will not read correctly the RPMs of a V8 engine

If the car has A/C , and you want it to work , the V6 A/C hoses won't work for the V8


There will likely be other things that will be needed , but the above list will give the OP an idea of what all will be involved ....


Something else here that just popped into my head , maybe some of you more familiar with these swaps can clarify ;

The factory six cylinder differential gear ratio is 3:45 to 1 , designed that way to provide some acceleration from a stop in first gear and to provide a low ish RPM cruise on the highway with the 700R4 in fourth with it's converter locked . If the OP puts the 8 cylinder in with the turbo 350 (which doesn't have overdrive I presume ?) won't his gearing have the poor engine turning crazy high RPMs when trying to drive at normal highway speeds ? The 8 cylinder has a 500 RPM lower redline than the 6 cylinder does , further exaggerating the high RPM on the highway noise , yes ?

Since this thread appears to have become a bit of an opinion fest , here's just one more ;

With all that's involved in an 8 cylinder swap , and the fact that "Momma doesn't want a 400 hp engine since boy is still on our insurance lol" , maybe the OP's best move for getting the car actually driveable somewhat soon would be to find a good RWD 3.1 or 3.4 and slap that in and go ? Consider the six banger as a good set of training wheels for the kid and then if he wants the fire breathing 8 in the future after he's fully learned to drive it with the 6 the foundation will still be there to build up anyway he wants to . Father & Son can still have plenty of good bonding time replacing the 2.8 with a 3.1 or 3.4 and will likely be able to finish it FAR sooner than the complete car rebuild that the 8 cyl swap would entail .

Like I said , everyone's got their opinions , it's just the matter of how soon they want it on the road VS how much of a project are they actually looking for .....

 

You wont feel any difference putting larger valves in just leave it stock put that cam in and run it.DOnt worry you wont come anywhere near 400

For the $ Id orderup a base GM crate for 2k he can still learn about engines
Sorry not a 305 fan.

 

No Sir , the water inlet and outlet are on opposite sides of the V6 radiator VS the V8 , you'd have to be running some pretty strange plumbing to make that work .

 

LS Swap.

 

Like using 3.4 4th gen radiator hoses?

 

Perhaps I should have said "different heads" rather than 'after-market'. My point was that those '79 305 heads aren't gonna cut it. And the 350 has bigger intake valves (1.94), but that's neither here or there.
My Goodwrench 350 crate has around 245-250 hp (probably 260 if it had headers) with bigger bore, intake valves & ports than a 305, a mild Comp performance cam, and 740cfm Quadrajet. The heads are the weak link...

 

https://www.thirdgen.org/forums/engi...swap-read.html

I was basing my answer on item #6 in this thread . The 2.8 does have it's radiator connections opposite of the V8 (the 2.8 is upper on passenger's side , lower on driver's side , VS the V8) and if 4th gen hoses are a workaround for that maybe it should be added to that thread

Anyway , whatever the OP ends up doing , I hope it goes well . As long as he and his Son are into it for a fun project VS having a car to drive next week I'm sure they'll do just fine

 

4th gen 3.4 uses a V8 radiator. Driver side inlet on the water pump.

 

How do we get from a 1979 305 to equating a Vortec 305 from 20 years later? 305 apologists are weird.

It's too bad if the OP feels like we're discouraging him, or trying to run him off. Everyone replying is trying to help, whether it's encouraging him to go forward with his plan, or pointing out some of the pitfalls he'll likely run into. It's a lot better to have more knowledge and understanding going in, then to get deep into the project only to be disappointed.

 

You've got to remember who we’re talking about here lol

 

I only mentioned the Vortec 305 because he mentioned spending money putting larger valves in the stock heads. I mentioned 4 different castings better than the 79 heads for flow and compression that would bolt on.

I also mentioned the Vortec 305 because the basic block really did not change much compared to a 79 block. Its still a cast bottom end 2 bolt main block.

 

One more thing I may mention. 20 something years ago I built a 355 with dart aluminum heads TPIS cam headers prom etc to replace the weak 305 TPI in my ‘88 T/A. The car went a full two seconds faster than it did with the original engine, but within a couple months I was picking up a 400SBC to build an install. Bottom line, you’ll always want more. Nowadays I view engine cubes very differently lol

 

Father son project is cool and all if power isnt a concern just dont expect as much as you read. It will take some work to get over 350 hp from one.
powerpack heads...eesh. What were those like 150cc runner? horrible lol
there are newer tech iron heads that work pretty good and dont cost much...many overlook them as aluminum is so popular. The head doesnt know what material it is!

 

Yea those power pack heads are terrible but still got some 283s over 300 hp from the factory. Point was take your 80s 305 head of choice and it can still lay down 300 hp.

You can run a higher compressiom ratio with aluminum and that makes more tq across the board.

Speaking of aluminum. The 128 and 113 Aluminum L98 Vette heads work well on a 305 as well. I had a 305 that made 423 hp with some lightly worked over ZZ4 heads.

 

That 283 did not make a real world modern day 300HP. Neither will a mild cammed LG4 with headers, flat tops and $#it heads. I took an LG4 in my 87 Formy and used a K1103 cam, headers, Holley 650 DP, MSD ignition, etc and it barely broke high 14s in the 1/4. That stopped me from ever building a 305 again.

 

Sorry to hear that. My old 8.5:1 305 that wouldn't rev past 4500rpm in gear due to soft valve springs, with a TPI ontop, peanut cam, shorty headers, 601 heads and stock ignition ALMOST broke into the 14s. 15.008ET was the best I ever got out of it.

YMMV

 

My stock 91 LB9 auto car was a tick faster @ 14.76 It was hard to believe.

 

I agree the poo-poo heads will hold it way back. But 305s can still put down some decent numbers especially for his goals.

 

If op wants to grind on those 305 heads pm me I got a bunch of extra stuff Ill probably be tossing your kid can play with. Old carbides, sanding rolls etc.
Keep it cheap and fun.

 

I see a terrible combination, not surprised it barely broke out of the 15s. That 1103 cam is garbage and a terrible choice for an engine much less a 305. With a restricted bore the LSA needs to be tightened. Since the 305 has a small intake valve vs cylinder volume the LSA needs to be tighter than a typical 350. On a 1.84 valve 305 if you go by David Vizard logic the chart calls for a 107 LSA. I have run 106 and 108 LSA cams in a 305. They perform noticeably better than a 110 or 112 LSA cam. Second a 305 does not need a 10* split. In fact with the 350 size exhaust valve and port with fewer cubic inches per cylinder they tend to run better with a single pattern cam. With the smaller intake port and shrouded valves you need the longer intake duration and increased overlap to help scavenge the chamber and get a decent intake charge into the cylinder.

The 1103 cam is junk because it has very slow ramps and too much seat to seat duration compared to its mediocre 0.050" duration. Not to metion the 10* split @ 0.050.
288/298 @ .006
214/224 @ .050
.443/.465
112 LSA
107 ICL I believe
Lobe intensity
Intake 288 - 214 = 74
Exhaust 298 - 224 = 74

The Isky cam I would have run in your build.

268/268 @ .006
224/224 @ .050
.450/.450
107 ICL
107 LSA
I would have advanced it to a 102 ICL.
LOBE INTENSITY
INTAKE/EXHAUST 268 - 224 = 44


I built a 305 with this cam and a set of 601s a few years ago. It ran remarkably well.
https://www.summitracing.com/parts/i...make/chevrolet

I know a ProStock class 220 hp 283/cast iron Powerglide/4.88 gear 57 chevy that has run 13.40s at ~3,500 lbs. The rules are pretty strict. No visible porting, stock lift rule, no headers, still runs the rochester 4GC carb as well. That car is every bit of 300 hp to push the car to that ET.

The old 283 guys used to run 102 LSA cams to get air/fuel through the chamber with those small 1.72/1.4" valves.

 

Interesting info. What would that same cam do is a 350? And not to **** anyone off here, but what would it do in a 302 SBF?...

 

You could take a stone stock Vortec 350, go to that to that flat tappet cam, and depending on the intake/carb/headers make ~380-400 hp out of it. It is actually a vacuum rule cam as well. Should make about 16 in/hg @ 1,000 rpm and about 14 @ 750. In a 350, I would probably advance that cam to a 104 ICL. In a 305 advance it to a 102 ICL. Advancing the cam would bring the whole powerband down about 400 rpm. The additional advance on the 305 would be to keep the 305s powerband similar to what it is rated in a 350. 1,600-6,000 rpm. Would work really well with a 2,500-3,000 rpm converter and 3.42 or 3.73 gears.

As for the small block ford. No clue. Never have really studied any ford cam stuff.

Helped dial in another 305 a few years ago in a friends T-bucket. Had a T5 behind it and 4.10 gears. Was just an 80s truck 305, punched 0.030" over, flat tops with 1.56" compression height, zero decked, 0.038" thick head gasket, stock 601 heads, used a Crane 274H06 cam and an Offenhauser cross ram intake with dual 390 cfm holleys on it. Vertex street magneto. Was meant to look 60s style. That lightweight T was SCARY!

 

OK, so we just went from the 79 Impy 305 that HE HAS, to some arbitrary 350 Vortec that he DOESN'T.

NOT saying that the 350 Vortec won't kick that other POS's A$$ 40 way to Sunday; NOT saying you're wrong; NOT NOT NOT NOT NOT. NOT saying that the 350 wojn't make more power. NOT saying he couldn't go the junkyard and get a Vortec 350 that would completely eclipse what that POS 305 could EVER do with ANY cam heads intake carb exhaust compression heads whatever whatever whatever. NOT NOT NOT NOT. NOT saying that the 79 Impy 305 is "the schinznit". NOT NOT NOT NOT NOT. Not saying that the cam he's talking about is or is not a POS (it IS). NOT NOT NOT NOT. It's not about any of that.

Only, beating him over the head about "Vortec" isn't real productive, other than demonstrating how you wish to demonstrate that your goldmember is bigger than [whoever]'s.

That said, I COMPLETELY agree, a 79 Impy 305 is arguably one of THE ABSOLUTE WORST POSSIBLE candidates for a swap. What a totally lame-a$$$ worthless POS. You are ABSOULTELY CORRECT in that regard. OTOH, once there's a V8 in the car, A WHOLE WORLD of possibilities opens up. Which once it's done, and a compatible functionable transmission is installed, and the exhaust becomes proper to a V8, and the gears are right, and and and and ... it's a start.

I would NOT, in any universe I can conceive of, swap a 305 into ANYTHING that came without a V8. ANYTHING. The money time effort risk work uncertainty expense whatever is EXACTLY the same to put a 79 IMPY 305 :barf: into anything not previously equipped with a Chevy V8, as putting a 70½ "Z/28" "LT-1" into it. We can go all day long about that. I think it's a dumb thing to do, apart from, I have adult children who needed to learn that you start from [some arbitrary level of poop and pond slime] and grow become expand learn evolve develop into something ... ,, ..... greater. NO MATTER where we start, if we're not mired too bad in "human" (or "van"), we can reach ever higher, toward the next thing. Part of that is, realizing that whatever we did in the past, is inadequate; either it didn't give us the results we wanted, or the same results could have been achieved with less expenditure of resources, or the same resources we expended could have garnered us more results, or the results are hollow and unsatisfying in and of themselves no matter how much we wanted them at the time, or whatever. It's called LEARNING.

Let d00d learn that part of it on his own. While not all of us want to put vans on chassis dynos 24 hrs a day and post graphs of [whatever] to however many message boards about how great our "van" is, at some point, if somebody is interested in participating in this hobby, they gotta start turning bolts at SOME point. Let him LEARN from what he does, one step at a time.

 

Looks like OP has been thoroughly scared off.

 

How to start an argument on social media groups: Mention swapping in a SBC instead of swapping an LS.

How to start an argument on TGO: Mention swapping in a 305 instead of swapping a 350

 

I'm hoping they took my advice and ditched the V8 swap altogether , picked up a nice running 3.1 and slapped it in over the weekend , and right now the kid is out driving the Hell outta it

...... He can always pick up a nice native V8 car for his NEXT thirdgen , , , they're kinda like potato chips ya know , , , , you CAN have more than one !!!!!!