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Just looking for guys who have already been down this road and need advice, If you guys could post some of your builds and results I would really appreciate it. Just looking to have them all in one place so I don't have to keep searching all the different ones. Thanks guys
The first thing of importance is to recommend scrapping the 305 in favor of a 350+cid.
Trying to upgrade a 305 is a waste of time, money, effort, and enthusiasm. The only possible reason is to meet the rules of some racing organization, or to stay "legal" with some Government's over-bearing regulations. I've heard some dirtbag Socialist European countries get really touchy about engine transplants.
The first thing of importance is to recommend scrapping the 305 in favor of a 350+cid.
Trying to upgrade a 305 is a waste of time, money, effort, and enthusiasm. The only possible reason is to meet the rules of some racing organization, or to stay "legal" with some Government's over-bearing regulations. I've heard some dirtbag Socialist European countries get really touchy about engine transplants.
Granted a 4+" bore can make more power it quickly becomes a snowball effect of upgrading. He trans and rear end might as well be glass with any real power.
That being said a 305 can run very well. Like any engine it will make decent power opening up the induction, exhaust and cam timing. A better set of heads would also provide more hp on the redline end of the engines powerband. If the engine has higher mileage leave the long block alone and put bolt-ons on the exterior. Tune it up, upgrade to a decent set of headers, a better y-pipe, high flow cats, better catback exhaust, upgrade to a better air cleaner, add underdrive pulleys and delete the air pump if your area does not require a smog check, advance the timing a little, make sure it has decent fuel pressure (13-14 psi) and put a decent set of gears in the rear end. Then concentrate on chassis prep to make the car hook and hold up to the abuse of more power. When it comes to exhaust avoid anything designed to be a bolt-on improvement for a LG4 or L03 and get stuff for a L98.
Save your money, find a running vortec 350 and do the budget vortec build when you have the rest of the car upgraded to handle the power of it.
While saving for a 350 you can do some things you can carry over. 3.42-3.73 gears and posi, 2200-2400 stall or an S10 converter as I use same thing, headers+ 3in exhaust. A 14lb spring in my TBI helped my L03 as well.This will make the car much more fun and are all things you can use when you do go to a 350. Find a good L31 or good used L98 to drop in later don't spend $ on a 305 you will be dissapointed. I've done it before it ran just ok, 350 much better.
Car only has 31K miles on it. Just trying to make it run low 14's maybe high 13's. Already did 3.42 swap and T56. If I ever swap engines it will be LS. Just trying to get the most out of the little L03. Thank you
Car only has 31K miles on it. Just trying to make it run low 14's maybe high 13's. Already did 3.42 swap and T56. If I ever swap engines it will be LS. Just trying to get the most out of the little L03. Thank you
Headers, 3” Exhaust, increase base timing to 6BTDC, high flow air filter assembly, 1.6 rockers and the 3.42’s you already have will be in the mid-high 14’s.
You could do heads and a cam, but it’s a lot of money and labor to spend on a 305, even with the low mileage on the current motor. There are a number of crate 350’s that aren’t that expensive and would be a better in the long run than building the 305.
I bought a set of used headers and LT1 cam just need to put them on. Been thinking about heads but still not sure about which ones, Thanks
The LT1 cam is a decent choice for a mild upgrade on a 305. If you already have the cam and it's in good shape, sure, swap it out. It's mostly just your labor at that point and the cost of new gaskets. Also change the valvesprings. I would leave the L03 heads and just run it with the LT1 cam. It will run well.
There aren't a lot of good cylinder head choices for a 305 because of the small 3.74" bore. The stock heads are 58cc chambers and most performance SBC heads will be around 64cc, so you would see a drop in compression. Also, many of the performance heads for a 4" bore have bigger valves that will have clearance issues with the smaller 305 bore. World Products S/R heads are a popular choice for 305's since they are available in 58cc. You will probably need to elongate your center intake manifold bolt holes since those heads have the the 86' and earlier intake bolt pattern. There may be other heads that are set up for 87' and later, but I didn't look that hard. The World Products heads are about $1,200 for the set, plus head bolts, gaskets, etc. and you are about $1,500 or so. That's getting pretty close to the cost of an L31 350 crate motor.
There aren't a lot of good cylinder head choices for a 305 because of the small 3.74" bore... ... Also, many of the performance heads for a 4" bore have bigger valves that will have clearance issues with the smaller 305 bore.
The Ford "90 Degree" or "Fairlane" 302, and the Pontiac 301 both have reasonable bore/stroke ratios. The Chevy 307 has an adequate bore/stroke. The Olds 307 has a decent bore/stroke ratio.
The Chevy 305 is a total turd. The bore/stroke geometry dooms the thing. The ONLY reason that the 305 exists is to make use of the same crank-grinding setup as the 350, since they share the same stroke (but not the same balance). There is NOTHING you can do to a 305 that wouldn't be better done on a 283, 307, 327, or larger engine having a bigger bore to allow bigger valves and bigger ports.
The only engines worse than a 305 are the 262 and 267, and maybe the 265.
The Ford "90 Degree" or "Fairlane" 302, and the Pontiac 301 both have reasonable bore/stroke ratios. The Chevy 307 has an adequate bore/stroke. The Olds 307 has a decent bore/stroke ratio.
The Chevy 305 is a total turd. The bore/stroke geometry dooms the thing. The ONLY reason that the 305 exists is to make use of the same crank-grinding setup as the 350, since they share the same stroke (but not the same balance). There is NOTHING you can do to a 305 that wouldn't be better done on a 283, 307, 327, or larger engine having a bigger bore to allow bigger valves and bigger ports.
The only engines worse than a 305 are the 262 and 267, and maybe the 265.
While there is truth to this and there are better options than a 305 for a performance build, it’s not a terrible motor. The smaller bore doesn’t really hurt horsepower until above 300hp or so. The bore/stroke ratio isn’t the issue, it’s the small bore diameter that shrouds the valves and limits the size of the valves and port flow. But, for a mild upgrade over stock, it’s fine.
Hotrod did an interesting test between a Chevy 305 TPI and Ford 302 HO a couple of years ago. In stock form, they put out almost identical horsepower and torque. As they built them with heads, cam, induction, the 302 pulled away from the 305.
The issue comes when a 305 needs a rebuild, and then it’s completely not worth it. The money spent on rebuilding a 305 is the same as rebuilding or buying a crate 350 and the 350 is going to result in more power for the same cost. No brainer there.
In the OP’s case, he has a good running, low mileage 305. That does change the equation a bit. Mild upgrades, within reason can wake up the 305 and make for a fun street driver. Headers and the LT1 cam would be a reasonable upgrade, even with the stock swirl port heads. Aftermarket heads would certainly help, but for the cost, I think I would pass on doing them and that’s where I would swap the motor if I was looking for more power.
While there is truth to this and there are better options than a 305 for a performance build, it’s not a terrible motor. The smaller bore doesn’t really hurt horsepower until above 300hp or so. The bore/stroke ratio isn’t the issue, it’s the small bore diameter that shrouds the valves and limits the size of the valves and port flow. But, for a mild upgrade over stock, it’s fine.
Hotrod did an interesting test between a Chevy 305 TPI and Ford 302 HO a couple of years ago. In stock form, they put out almost identical horsepower and torque. As they built them with heads, cam, induction, the 302 pulled away from the 305.
The issue comes when a 305 needs a rebuild, and then it’s completely not worth it. The money spent on rebuilding a 305 is the same as rebuilding or buying a crate 350 and the 350 is going to result in more power for the same cost. No brainer there.
In the OP’s case, he has a good running, low mileage 305. That does change the equation a bit. Mild upgrades, within reason can wake up the 305 and make for a fun street driver. Headers and the LT1 cam would be a reasonable upgrade, even with the stock swirl port heads. Aftermarket heads would certainly help, but for the cost, I think I would pass on doing them and that’s where I would swap the motor if I was looking for more power.
Great post. Many of us with 305s arent looking for 450 rwhp. We would just like our cars with a little more go go than factory while still maintaining the originality of our cars and decreasing the total amount of modifications that will ultimately need to be made for engine swaps etc.
Will you please list the modifications needed to slap a one-piece rear main seal 350 in place of a one-piece rear main seal 305?
No idea, Can I use all the intake from my 305 etc? Manifolds and or headers/exhaust? Fuel delivery, tuning? I am as GREEN as they come here on this site. Most of what I see are LS swaps or LT swaps from which I gather can be quite extensive? My point was for those that want to upgrade the original 305 if someone has useful information for them, great. If all they have is put a rope on it and use it as a boat anchor just skip to the next thread.
If I knew I could build a 350 or get a crate motor and not have to replace a million things, I would be more open to doing it. My 305 has 56,+++ miles on it. My thoughts were to just upgrade it a bit. My wife enjoys driving the car some so I want to keep it fairly mild for her.
So, I will flip this question to you, What modifications would I need to swap my 305 for a 350? I am legit looking for information. I have been hesitant to create a thread but have spent HOURS reading through this site looking for information. I agree with the OP of this thread that alot of the information here goes back 20 years and does not seem applicable anymore. Its really hard for someone new to filter through it all. Please feel free to P.M. me if you would prefer to not hijack the OP's thread.
No idea, Can I use all the intake from my 305 etc? Manifolds and or headers/exhaust? Fuel delivery, tuning? I am as GREEN as they come here on this site. Most of what I see are LS swaps or LT swaps from which I gather can be quite extensive? My point was for those that want to upgrade the original 305 if someone has useful information for them, great. If all they have is put a rope on it and use it as a boat anchor just skip to the next thread.
If I knew I could build a 350 or get a crate motor and not have to replace a million things, I would be more open to doing it. My 305 has 56,+++ miles on it. My thoughts were to just upgrade it a bit. My wife enjoys driving the car some so I want to keep it fairly mild for her.
So, I will flip this question to you, What modifications would I need to swap my 305 for a 350? I am legit looking for information. I have been hesitant to create a thread but have spent HOURS reading through this site looking for information. I agree with the OP of this thread that alot of the information here goes back 20 years and does not seem applicable anymore. Its really hard for someone new to filter through it all. Please feel free to P.M. me if you would prefer to not hijack the OP's thread.
I agree. I have done an T56 trans and 5.3 LS swap on my 72 El Camino. Not trying to build a crazy TBI 305 just a fun daily driver around 300HP and keep it pretty stock looking. If it was high mileage I would without a doubt do a 350. Just looking for some tried and true advice on stuff that works well.
If I knew I could build a 350 or get a crate motor and not have to replace a million things, I would be more open to doing it. My 305 has 56,+++ miles on it. My thoughts were to just upgrade it a bit. My wife enjoys driving the car some so I want to keep it fairly mild for her.
A 305 to a 350 swap is about as plug and play as it gets, as long as it is the same configuration (rear main seal type, cylinder head type). The L03 is a 1 piece rear main seal with center bolt valve cover non-vortec head motor. All of the parts from the L03 will swap to a 350 from 87'-95' out of a pickup truck (L05), Caprice (L05) or F-Body (L98). 350 injectors from the L05 and a tune would be needed and that's it. A 96' and later L31 Vortec 350 will also work, but would need the GM Performance Vortec TBI intake manifold and external EGR kit, or delete the EGR from the tune. Simple as that.
A 305 to a 350 swap is about as plug and play as it gets, as long as it is the same configuration (rear main seal type, cylinder head type). The L03 is a 1 piece rear main seal with center bolt valve cover non-vortec head motor. All of the parts from the L03 will swap to a 350 from 87'-95' out of a pickup truck (L05), Caprice (L05) or F-Body (L98). 350 injectors from the L05 and a tune would be needed and that's it. A 96' and later L31 Vortec 350 will also work, but would need the GM Performance Vortec TBI intake manifold and external EGR kit, or delete the EGR from the tune. Simple as that.
That's awesome information thank you! I have the LB9 TPI. What applications would be plug and play for it?
That's awesome information thank you! I have the LB9 TPI. What applications would be plug and play for it?
Same options for an 87' and later LB9. However, an L05 (unless you are just using the short block and swapping the heads and cam) puts out about the same horsepower as a peanut cammed LB9, and less power than the LB9/5-speed with the hotter cam. L98 or L31 would be a better choice as a drop in replacement. A new L98 long block is not available, but you can still buy a new GM L31 350 long block. A brand new GM crate motor would be my choice, rather than some used unknown motor or something I had to rebuild. With the L31 and TPI, you would need to use the Scoggin Dickey Vortec TPI lower base, but everything else should bolt right up.
Same options for an 87' and later LB9. However, an L05 (unless you are just using the short block and swapping the heads and cam) puts out about the same horsepower as a peanut cammed LB9, and less power than the LB9/5-speed with the hotter cam. L98 or L31 would be a better choice as a drop in replacement. A new L98 long block is not available, but you can still buy a new GM L31 350 long block. A brand new GM crate motor would be my choice, rather than some used unknown motor or something I had to rebuild. With the L31 and TPI, you would need to use the Scoggin Dickey Vortec TPI lower base, but everything else should bolt right up.
Thank you again for the information. I will check into this.
FWIW, that's what I did. You'll need a custom tune and L98 knock sensor. Pretty much everything else from the LB9 will bolt right up (except, of course, the lower intake, as he said). You should also replace the injectors (LB9 came with 19 lb,; L98 came with 22's). If you go L31, make sure to install the correct spark plugs, too. They aren't the same as the L98 plugs.
FWIW, that's what I did. You'll need a custom tune and L98 knock sensor. Pretty much everything else from the LB9 will bolt right up (except, of course, the lower intake, as he said). You should also replace the injectors (LB9 came with 19 lb,; L98 came with 22's). If you go L31, make sure to install the correct spark plugs, too. They aren't the same as the L98 plugs.
Did you go the crate engine route? Im seeing about $3,000 to $3,500 for a crate L31?
Did you go the crate engine route? Im seeing about $3,000 to $3,500 for a crate L31?
Yes, but I bought in Nov. 2019 before the price went up. Paid $1,979 to my door for GM Performance L31, but I know they are almost twice that now. OTOH, the "new" more expensive GM Performance L31 crate engines are supposedly improved over the version I purchased.
Yes, but I bought in Nov. 2019 before the price went up. Paid $1,979 to my door for GM Performance L31, but I know they are almost twice that now. OTOH, the "new" more expensive GM Performance L31 crate engines are supposedly improved over the version I purchased.
Looks like my most cost effective solution to go that route would be to go to the local junk yard and get one or a pull apart. Then rebuild it. I would save the labor on the rebuild as i have a couple good friends that own mechanic shops. One of them builds derby motors all the time so he would be my best bet i think. Couple dime bags and a pack of smokes will probably get it done. Lol.
Looks like my most cost effective solution to go that route would be to go to the local junk yard and get one or a pull apart. Then rebuild it. I would save the labor on the rebuild as i have a couple good friends that own mechanic shops. One of them builds derby motors all the time so he would be my best bet i think. Couple dime bags and a pack of smokes will probably get it done. Lol.
Maybe less expensive, maybe not, depends on what you run into when you tear into it. Then, there is the possibility of overlooking something and it all comes back apart again. When it was $2K last year, it was a no brainer, but even at $3K, I would still go that route before rebuilding an unknown junkyard motor. Hard to beat a brand new GM motor.
Never mind. Had a bad experience with an atk engine on my old pickup. Guess i'll stick with my LO3. It's a complete turd, but at least it still runs after 300k miles.
Last edited by Pyramid_Head; 02-23-2021 at 04:21 PM.
My vote is to freshen a L31 rather than buying a new one. My run to death one in my Express van needs some lower end work but it is still a solid engine. Going to re-ring it with new bearings and slap a set of aftermarket vortecs on it with a larger cam and put it in the 1980 Z28 I have.
For the $ a Vortec is the way to go. They are a simple cam swap and spring upgrade from being 300hp engines.
With a dual plane intake and headers they already make 300-310 hp on an engine dyno. Springs and 1.6 roller rockers alone will add 10-15 hp. More cam and they will crank out 380-420 hp without touching the rotating assembly or heads. Put a 0.016" compressed head gasket on it to squeeze a touch more compression out of it.
I ran a flat tappet Herbert cam 218-218 465 lift, flat top 350 with Vortecs and 650 Double Pumper carb on an 87 T/A and it turned 13.6-13.7s IIRC - on crappy gears and a sloppy transmission. If I had the transmission, converter , and gears I have now it would be LOW 13s easily.
OP if you're still looking to build your 305, look up robertfrank on this forum. He built a combo like what you're looking for that ran pretty good for what it was. If the motor is in good shape and you don't mind the time then go for it. The "get a 350" crowd will always try to steer anyone away from building a 305, and they have a lot of valid points in doing so. But with the goal you have in mind a 305 will work, and the parts can carry over to a bigger engine in some cases. It's your money and time so do what you want and good luck.
OP if you're still looking to build your 305, look up robertfrank on this forum. He built a combo like what you're looking for that ran pretty good for what it was. If the motor is in good shape and you don't mind the time then go for it. The "get a 350" crowd will always try to steer anyone away from building a 305, and they have a lot of valid points in doing so. But with the goal you have in mind a 305 will work, and the parts can carry over to a bigger engine in some cases. It's your money and time so do what you want and good luck.
OP if you're still looking to build your 305, look up robertfrank on this forum. He built a combo like what you're looking for that ran pretty good for what it was. If the motor is in good shape and you don't mind the time then go for it. The "get a 350" crowd will always try to steer anyone away from building a 305, and they have a lot of valid points in doing so. But with the goal you have in mind a 305 will work, and the parts can carry over to a bigger engine in some cases. It's your money and time so do what you want and good luck.
My point was not to steer anyone out of a 305 build. Personally I have had several that were very quick and a friend of mine that I regularly chat with, David Kauffung ran one in engine masters that made quite a bit of power.
I guess it's a good thing I was browsing in here as I noticed my name was mentioned. I did have a stupid fun 305 TBI back in the day that too be honest, I was just scratching the surface with that build. Here's what I did....
Mildly worked ZZ4 heads with a ZZ4 cam with 1.5 rockers on the intake and 1.6 rockers on the exhaust
port matched RPM intake with a trans-dapt plate and a ported stock TBI unit with an xtremefi adjustable regulator along with 55lb flow matched injectors. I was running the Hooker 2055 headers with an full 3 inch Aerochamber catback. All of this was tuned by the EBL FLASH using a Zeitronix ZT2 wideband run in open loop. It was a damn fun build that put the hurt on many cars. I plan on copying this again sometime later
If I had to do it over again, I would've put in flat top pistons, an xfi268 cam and did some better port work on the heads. Also, I would've went with longtubes over the shorty headers. I think I left a good bit of power on the table with my build.
If I'm to make a different recommendation as it's what I'm building right now for my 91 Camaro is...... go with an LT1 and use the carb LT1 intake. I'm doing an LT355 with ported heads, ZZ4 cam and the GM lt1 carb intake with an adapter plate and a 454 tbi unit.
I guess it's a good thing I was browsing in here as I noticed my name was mentioned. I did have a stupid fun 305 TBI back in the day that too be honest, I was just scratching the surface with that build. Here's what I did....
Mildly worked ZZ4 heads with a ZZ4 cam with 1.5 rockers on the intake and 1.6 rockers on the exhaust
port matched RPM intake with a trans-dapt plate and a ported stock TBI unit with an xtremefi adjustable regulator along with 55lb flow matched injectors. I was running the Hooker 2055 headers with an full 3 inch Aerochamber catback. All of this was tuned by the EBL FLASH using a Zeitronix ZT2 wideband run in open loop. It was a damn fun build that put the hurt on many cars. I plan on copying this again sometime later
If I had to do it over again, I would've put in flat top pistons, an xfi268 cam and did some better port work on the heads. Also, I would've went with longtubes over the shorty headers. I think I left a good bit of power on the table with my build.
I put milled Etec 170s on the 305 Vortec in my 99 Tahoe. It was a very good runner even with a flat tappet cam and the stock vortec pistons. It had long tubes and dual 2.75" exhaust to the muffler. Made 280 hp at the tire and right at 290 tq.
I put milled Etec 170s on the 305 Vortec in my 99 Tahoe. It was a very good runner even with a flat tappet cam and the stock vortec pistons. It had long tubes and dual 2.75" exhaust to the muffler. Made 280 hp at the tire and right at 290 tq.
i just added a little life to my LG4 305 all while it was in the car :
1) L31 vortec head swap ,350 thin head gaskets.
2) edlebrock performer rpm intake
3) L-82 flat tappet cam (from a crate 290/350) as well as lifters,comp cams timing chain
4) Holley 650 ultra double pumper and moroso 1"spacer
5) hooker 2460 ceramic headers(they were on an $850 gta i parted out ,also got a L98 and tons of other parts)
6) dougs d9101 stainless y-pipe...fit PERFECT
7) magnaflow cat and catback with tips
i tell you its night and day,easily as quick as the two L98 cars ive had,probably quicker TBH.
having a 5 speed makes it a lot more fun,also threw in a 9 bolt with 3.27 gears(bye bye 2.73's)
quote: Usually when people do another person's work, they get paid.
the reason this was a reply was because someone was being impatient,asking for something "NOW"
honestly,in my experience ask a question on third gen.org,you will get an answer BUT if you demand
an answer you will get this >>>>>quote: Usually when people do another person's work, they get paid.
its all relative,you want free advice,wait till it arrives
02-10-2021, 05:21 PM
