350 engines to avoid for a rebuild

JeremyM

Veteran Member
Aug 12, 2005
107
Rolla, MO
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.
 

sandlapper

Veteran Member
Oct 9, 2020
1,454
SE CSA
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.
 

JeremyM

Veteran Member
Aug 12, 2005
107
Rolla, MO
If I go with the 89 as the price for the motor and trans seems more than fair and its relatively close, is there something that can be done to the 89 heads while they are off? We are looking for 325-350 HP and maximum torque with a useable range of idle to 5500.
 

jeff swisher

Veteran Member
Apr 26, 2018
1,957
Yukon Oklahoma
All early GM heads can benefit from some bowl porting.
I never like changing cams until the heads are worked over.

I would be very tempted to run the sons 305 heads on that 350 block.
Some unshrouding in the chamber and some bowl work and those 305 heads are killer.

I would check both sets of heads and whichever one had the best valve guides i would run those.
Ported of course.
 

manicmechanic

Veteran Member
Lifetime Gold Member
Oct 24, 2000
2,157
Tulsa, Oklahoma
I currently run a 388 in my 80Z, the heads from those years are prone to cracking around the bowls and other areas, not to mention that the HP ratings of those years were weak. I updated to a set of vortec heads and a edelebrock rpm (vortec) manifold, comp roller cam and retrofit lifters with a 200-4R transmission and 3.42 rear. I could possibly go to a 3.73 with little issue. Keep in mind what your going to run for wheels, stock 15" or 16-17". I like to run a 50 (275) series 15" and finding those sizes are getting harder.
 

Sparkee

New Member
Oct 9, 2008
1
Central IL
That '89 350 is a good starting point and I agree with sandlapper that the 87-95 TBI heads completely suck for performance, I have had multiple engines with them. Those heads have a little bump in the intake ports meant to slightly change the direction of airflow for better throttle response, I will warn you that grinding that feature off while porting does hurt throttle response a bit. Those heads were never meant for high horsepower.

The 305 heads had low compression on the 305, but on the 350 would bump the CR up a bit compared to the stock 350 heads. However, they also have slightly smaller valves which does limit airflow and HP. The TBI heads have the 350 sized valves, but low CR. You could port either set of heads and be better than stock, but neither option is great for power.

I do not know your budget or horsepower goals, are you totally against getting a different set of heads? There are 2 other stock head options to consider:
1. '96-00 Vortec heads, they have 64 cc heads for decent CR and flow great. There are 2 versions out there, one is more desirable than the other, but I forget the casting numbers. You will need a Vortec head intake manifold, which does cost a bit more and the EGR system needs some modification/fabrication, if emissions testing is involved.
2. L98 TPI heads, they have the same intake bolt pattern as the TBI heads and would bolt right on. Please note there are 2 versions of the L98 heads, the version used on TPI Vettes are made of aluminum with 58 CC chambers, which will bump up the CR quite a bit. The F body version of L98's are made of iron with 64 CC chambers, which is also decent for CR. I previously had an entire L98 350 from a Camaro that I put in an old 4WD Silverado I used to have. I used the stock short block, ported the iron L98 heads, roller cam, 1.6 roller rockers, heavily ported TBI manifold, larger Holley TBI unit and custom tuned stock TBI ECM. That combo made over 300 Hp, had awesome torque and throttle response and had no problem with burnouts, even with the larger 285 tires I had on the truck.
 

T/A Tom

Member
Apr 29, 2019
89
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.
You should be able to find a complete rebuildable ‘96 & up Vortec 350 for a few hundred bucks. It’s compatible with a 700R4 or 4L60E. You’ll have the good heads and a roller valve train. Should be a great father son project! Keep us posted on it!
 

nwhite53

New Member
Jul 7, 2011
4
Cheyenne Wy
Since the topic of transmission has mostly been left out of the replies, I will throw in my 2 cents. The 200-4R is the same length as the TH350 and will not require a driveshaft change. The 700R4 will. This was why I went with the 200-4R for my Third gen Firebird. It is a lighter transmission and takes less power to turn than the 700R4. Either transmission will need to have a lockup pressure switch installed for 4th gear lockup, otherwise the TC can get burned out. Non lockup TC are made, and you may want to go with one, but the switch is very cheap. Either transmission will also require an aftermarket Transmission crossmember because the mount lands differently than the TH350. Some say the TH400 crossmember from a Camaro would work, but good luck finding one. Main downside is harsh engagement into drive unless you find one in the junk yard that is the latter year of the run as these had many issues fixed (88,89). I live with it and the transmission works wonderful, came out of an 85 Caprice. Second downside is the tail shaft housing is not removable like on most GM Auto's, and replacing the bushing requires either a complete teardown or a special tool, which I have yet to find. My shifter is just the regular 3 speed, and it works perfectly fine for 4 speed. Either transmission do not use a "kick down" cable but a "Throttle Valve" cable and requires a special bracket on the carburetor for proper throw, otherwise you will burn the clutches out real fast. That cable is a MUST to be connected to the carburetor, unlike the old kick down's of the TH350 and 400's. So there are things to consider and be aware of when jumping into a 4 speed conversion. Rear end gear ratio is another to consider.
 

MLMski

New Member
Mar 8, 2013
9
New Iberia, LA
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.
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.
ZZ350 short block, Trick Flow 175 DHC heads, Comp Cams xr270 or 276hr hydraulic roller cam with an Art Carr 200r4 trans (better gearing than the 700r4) & 3.73 gears world be a good combination. About 9.9:1 compression. This would work well with a FiTech 600hp setup.
 




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