350 engines to avoid for a rebuild

Lowend

Administrator. .a car, a man, a maraca.
Staff member
Lifetime Gold Member
Mar 25, 1999
16,809
San Jose, CA, USA
absolutely begin with a later block that either has OE roller lifters or can accept them.
JMO, 87-95 350 heads are lousy.
96-02 rpo L31 (350) engines have it all: roller lifters, one-piece rear main seal, thin metric piston rings, and best production heads yet (iron Vortec). Some of these blocks' mechanical fuel pump pads are Not completed. But with EFI, you won't be using a mech FP. L31 are ubiquitous but only in 96-02 Chev/GMC mid & light trucks when eighth character in VIN is "R". L31 also found in many marine and industrial applications. All OE 79 brackets & accessories should bolt up. FWIW, all 87-up crankshafts are for the newer one-piece rms and they all have a smaller bolt circle than earlier motors; requiring later flexplate. Flexplates are cheap to buy.
THIS
 

jeff swisher

Veteran Member
Apr 26, 2018
1,958
Yukon Oklahoma
Get this book.


I would get that now and decide if you want to bowl port or not.
I have been porting all kinds of heads and intake and exhaust manifolds for over 30 years.

Small valves do not hurt power as much as you would think in a 350HP or so V8 engine.
I ran some 1978 305 2 barrel heads with 1.72-1.50 valves on a 357" engine with flat tops.
I bowl ported them ..a quickie job.

Used the stock GM valves that came in them and topped with 110 seat pressure valve springs.
280H comp cam [email protected] .050 .480" lift.
Full weight 78 Nova. Converter in the TH 350 stalled to 2200-2400 and it ran 12.51 at 111 MPH
Shifting at 6700 RPM.
Later I built some 601 305 heads for it stuck 1.94-1.50 valves in those (ported) and a 292H cam it went 11.94 @ 115 MPH.

I have ran many 12's in the 1/4 with multiple vehicles and 305 heads with 1.84-1.50 valves and the 280H cam.

XE274 cam and the mid 90's swirl port heads every one tosses stones at went low 12's in a buddies Monty carlo. I bowl ported those heads and ran the stock GM valves.

I hear people tossing stones at many different heads but truth be told those stone throwers never ran a set of them with a little bowl porting.

I like to take what I have on hand and use it if it isn't broken.
Your HP goal is small and it does not take much to meet that goal.

That book above will be your friend and is good information for any head type.
 

JeremyM

Veteran Member
Aug 12, 2005
107
Rolla, MO
Found a 1997 Vortec 350 for 500. Sounds like this might be the way to go.

It looks like I missed out on a 87-95 350 block with 3973487 heads which I found were on the 1971 LT1. I contacted them today and someone was already scheduled to look at it. Intake was off so I could see that it was machined for the factory roller setup.

I have a set of brand new sealed power 2148 hydraulic roller lifters that were supposed to work in my Pontiac but I couldn't get it dialed in. I'm assuming these will work perfectly in an 87 and later SBC? This would save us some cost and I'd be able to use them.

Car has 245/45/17 tires on it now. WS6 trans am bars front and rear as I had them laying around from all the parts cars used to build my TA. 2.73 rear gear with no immediate plans to change. Trying to match the overall performance of a fourth gen which had 2.73 rear gears and the 4spd OD.

He wants to keep it as his daily driver now and through college so looking for a good balance of performance, mileage and reliability.

Thanks for all of the responses so far as they have been most helpful. I'm sure we can pull off the rebuild as I just finished my Pontiac 468 and it was never designed for a roller cam and fuel injection. I didn't want to necessarily build it myself but no one within 2 hours of my had any interest in building it. I could find shops that would do the machining but no one would assemble.
 

sandlapper

Veteran Member
Oct 9, 2020
1,465
SE CSA
? Did you get the entire 97 Vortec 350 for $500 ... OR just the block?

2148 lifters should fit the above block as OE & perform as OE.

Either x906 or x062 iron Vortecs will run circles around x487 heads ... all day, any day ... no comparison.
Many affordable hi-po, drop-in springs available for Vortecs; don't buy all the Bull they must always be cut/machined for hi-lift. Also google the "ghetto-grind" options; it works too. Shops need to eat as well, but let 'em machine or polish a crank instead cutting Vortec guide bosses.

RE: any (unknown history) iron Vortec head ... have a pro check and mag them (cracks).

BTW, x487 heads ARE good for the local circle tracks where they have "built motor" rules limiting valve lift & prohibiting 64cc chambers. Our "built motor" rules say 70cc production minimum; we mill the 76cc x487 to 70cc. Regardless; OE Vortecs (~64cc) will run off & leave 'em.
 

tom2win

New Member
Feb 9, 2022
3
My son wants to rebuild a 350 for his 79 Camaro to replace the 305. We will probably do a 4 speed OD transmission in the near future as well as its his daily driver.

I cut my teeth on Pontiac Motors and know what interchanges and what doesn't with them but Chevy's are new to me. It looks to me like pretty much anything 1986 or older should work fine with the possibility of a missing bolt hole for his over the plug exhasut manifolds.

Did things start changing in 87-89 with the centerbolt valve covers, different intake manifold angles on 4 bolts, and one piece rear mains which required a different flex plate?

The reason I ask is I found a 350 from an 89 cop car with a 700R4 tranny. It would seem like a good combo for a rebuild.

The goal is a street friendly roller cam, dual plain intake with most likely a FITECH throttle body and 200-4R or 700R4 transmission.

As I'm looking for potential rebuild candidates are there years of blocks that I should avoid? We want to use the factory alternator, PS, and AC to make the swap look as factory as we can.
Intake manifolds definitely different on engines with the center hole valve covers (Vortec v8 engines). The 89 cop car engine would probably be a good engine to use as it probably has a good set of heads. Set it up with self aligning rocker arms, cam and lifters of your choice and to save yourself a lot of hassle and headache use a after market dual plane intake with a 4 barrel carburetor instead of any fuel injection. Also standard hei ignition will be a dream to set up vs computer control bs
 

sandlapper

Veteran Member
Oct 9, 2020
1,465
SE CSA
I'll add another type of sbc which I avoid: Gen II '92-'97 ... heads can't interchange with other sbc, reverse flow cooling (not simply reverse rotation) and Optifart ignition. They run great; until they don't. Another of GM's better ideas. 🦃 YMMV
 

JeremyM

Veteran Member
Aug 12, 2005
107
Rolla, MO
I've got an LT1 in my Firehawk and it runs great as it's still low miles but I'm waiting on the Optispark to give me issues. Like it from the factory but never considered it for a transplant.

I went to by the Vortec today and it looks like I'm a day late. It was $500 for a complete motor with front accessories.

Glad the lifters I have will be of use. Bought them as a kit for my 468 and never could get them to work and had to go linked style. I was kinda of stuck with them and it wasn't worth the hassle to fight over the kit not working.

I'm looking forward to the computer part of fuel injection and the 4l60e swap. I've got Fitech on the 468 and it controls the timing too. Timing adjustments are a breeze with the computer and a little more flexibility. It did take some time to learn how to tune it but now that I am pretty comfortable with the system, it should be a breeze the second time around. I get 12-14 mpg around town if I baby it and 10.5 to 11 if I have fun with it. The old cam could get 22-24 on the highway with the AC on but I haven't had a chance to test it yet with the new cam. I'm expecting the same as the around town mileage is up with the roller cam.

I scored a 4l60e tranny tonight and am picking it up tomorrow. Part of the puzzle down. Planning on using the FITECH controller and the FITECH injection and it looks like the two play nice together.

Caden and I haven't decided which we will swap first, but we are doing one and then the other as I don't want two sets of variables. Get one system dialed in and then the other. I'm leaning towards the trans first so he can learn to tune it on the old motor.

Thanks again for all of the help.
 

Fixxer

New Member
Jul 9, 2018
10
Honestly, I would suggest leaving the SBC be and going for a budget junkyard LS swap. Go for a 99-06 4.8, 5.3, or 6.0. With all of the ready made brackets, parts, and adapters, they are very easy to install in about anything IMO. You can even use the factory wiring and fusebox from the truck (if you have the underhood room). There are ready made small fuse boxes that you can attach to the factory harness, or you can get a ready made drop in harness. The engines hold up great to high mileage- I used a 2003 6.0 in my 89 GTA with 256,000 miles on the clock that i found in a Yukon. I just dropped it in an drove it- 3 years later i am still very happy with that decision! Around here, good running genIII truck engines (with around 150-200K) can be had for $180 complete. I spent more on my K&N cold air kit than i did my engine. If you want, you can easily make 400+ horsepower on this platform with a cam and a tune. You should expect around 320hp to the wheels (5.3) in stock form. You could grab a 4l60E transmission with it and have overdrive in your rig as well as you would already have the computer to control it. Just my 2 cents
 




Latest posts

Top