Cascade Crew

[J-Dog-III]

So so i blew up my 2.8L v6 outta my 87 so now im either trying to sell it or put a new motor in it. I found a guy that will sell me a 305 with everthing still on it (starter, waterpump, etc) for $200 and a Turbo 350 tranny for $75. But i was wondering if i would even have to swap out the transmission? i've read a little on the v6-350 thread on tgo but i could use a little more help

[Quasi-Traction]

if you re use the 5 speed, you will most definately have to change the belllhousing, clutch and flywheel. Be aware that some sensors (oil pressure, temp sending unit..etc) are in different places and may require some wiring splicing to fit the new locations on a Small Block Chevy.

The K-member itself has brake lines in a different place between V6 and V8 cars...so you'll either have to do some creative bending or make new brake lines.

Do a TGO Search for the "V6 to V8 swap in a thirdgen" and you'll find a great guide to use.

Your V6 5 speed trans has a higher 1-2 gear ratio and probably a tighter rear end...if you're looking for performance, its a great way to go...there's kind of an open jury on how much power the V6 5 speed can handle.

[wanarunhard]

ya but what about front springs? dont they have to be changed too? i did one and didnt and the car bottomed out regarly

[Xophertony]

here is some stuff out of the FAQ on TGO this is the important parts. all of this and more can be found in the engine swap forum sticky.

5. The V6 rear end is as strong as a V8 rear end, because they are the same design. Only the ratio and/or posi/non-posi are different. Often, the V6 came with a more desireable ratio for performance than the V8's did. If you want posi, a PowerTrax can be installed with common hand tools. See the Tech Articles for beefing up the factory 10-bolt rear end for engines with higher horsepower than factory.

6. You may be able to use the radiator that came in your V6 car if the upper hose connection is on the driver's side and the lower connection is on the passenger side. Otherwise, get a V8 radiator.

7. Forget about using any of the factory-type V6 exhaust on the V8. This is a perfect opportunity to upgrade to headers and high flow cat on back. A good choice for aftermarket exhaust is '86-'90 TPI single cat application headers, cat, and cat-back, even if your swap doesn't match that description. Otherwise, use the donor car pieces.

8. If the transmission you are using didn't come from a 3rd or 4th gen f-body, you're going to need some means of mounting the torque arm. B&M makes a bracket that uses the tailshaft housing mount bolts for a TH350 or TH400. A good upgrade is a crossmember/torque arm kit from our site sponsor Spohn (see button above). The TH700 tailshaft housing can be swapped, so if you have a non-f-body TH700, you can put an f-body housing on it.
Side note: Transmissions from 4.3 liter Chevy V6's will mount to Chevy V8's.

9. The engine control module (ECM) from the V6 won't work. Use a V8 ECM. (You may be able to just change the PROM, depending upon the V6 & V8.) The V6 tachometer has a different resistance than the V8 tach. You can change the resistor, but it's typically easier to just get a V8 tach.

10. You may be able to modify the engine harness from the V6, but it's usually easier to get a donor harness. The ECM harness will come out in one piece. Remove the plastic fender liner from the passenger side, and you can get acess to the pass-through grommet/connector. Unplug it (take off clip from the inside). In the engine compartment, I disconnected and labeled everything that went to the engine, and unbolted sensors that went to the car (again labeling where they came from). Then, the entire harness w/sensors can be lifted out from the car and installed in the receptor car. (Note: The pass-through plug and therefore the pass-through hole on my '82 was smaller than my donor '86. Don't know when it changed, but I believe they're all the same size at least from '86-up. All I had to do was take a file to the '82 hole and enlarge it until the '86 connector fit.)

Part of the harness comes from the driver's side. The engine-specific part will separate from the chassis part so you can install your engine part from your donor.

If you are doing a non-emissions/non-legal swap, you'll typically need ignition power (if you started with external coil, the positive wire to the coil), tach (if so equiped), alternator, oil pressure, coolant temp, and possibly radiator fan wiring. All of these can be used from the existing harness, and since you labeled everything before you started taking it apart, you'll know which ones these are. There may be some length changes required. If your V6 was not carb'd, you may need to find or make a switched 12v source if your new engine's carb has an electric choke.

11. The engine mounts are two pieces; one half bolts to the chassis cross-member, the other "clam shell" to the engine. The chassis half is available as a replacement from the dealer or aftermarket. Reports vary on the engine half - may be able to get from the dealer, may work from some truck models, etc. - best bet is to get them from a factory equiped 3rd gen V8. The chassis half is mounted to the rear-most holes for the V6, and the forward-most for the V8. Getting to the mount nuts inside the cross-member is easiest when the front A-arms are dropped, but figure on using a spring compressor if you go this route (see #14, below). Otherwise, figure on sockets/extension/u-joint/very small hands/lots of time/many colorful words getting to those nuts. The right/front brake line mounts to the front of the crossmember for the V6, right where the V8 mounts need to go. Either use the V8 factory line, or carefully bend the line to the rear of the crossmember after the mounts are removed from the V6 position. The p-clamp mount holes are there for the V8 position for this line. Side note: '82-'84 used SAE-type brake fittings, '85-up used metric.

12. If the V6 is fuel injected and you are putting in a carbed V8, the fuel pressure will need to be lowered using a 3-port (with return) adjustable fuel pressure regulator. Or, drop the fuel tank and remove the in-tank electric fuel pump. If you keep the electric pump, be smart and use an oil pressure safety switch. Depending upon the V6, you may have to rewire the in-tank pump when the ECM is disabled. Also, if you eliminate ECM control and have an overdrive auto tranny, you will have to make provision for the torque converter clutch lock-up.

V6 and fuel injected V8 fuel lines go up the driver's side frame all the way to the engine compartment. Factory carb'd V8 fuel lines cross from driver's to passenger side in the transmission tunnel. If you're going carb'd with a mechanical pump, consider keeping the lines on the driver's side and crossing over on the front of the crossmember - it should be a cooler environment than the tranny tunnel and exhaust system. I used rubber hose with a slip-over braid for pressure, just rubber for return, and found some nifty nylon tie wrap anchors that you just push into a 1/4" drilled hole and then strap the tie wrap through it. Nifty. Remember, if you intend to drag race, rules limit the amount of rubber line you can use.

13. Most likely the V6 power steering gear will be fine. Just remove the pressure & return hoses from the gear and attach the V8 parts to it. There are some performance steering gears out there that the V6 probably doesn't have, but you donor car probably doesn't have it, either.

14. If this car is intended to be driven on the street, use V8 front springs and sway bar. Otherwise, you'll be bottoming out the suspension regularly.

[RSFreak]

[rjmcgee]

The V6 T5 has a smaller diameter input shaft, plus the gear ratio's suck for performance. Too wide of gap between gears. I think the V6 tranny has a 3.5:1 first gear and winds up with a 1:1 fourth where as the V8 tranny has a 2.95:1 first and winds up with a 1:1 fourth.

I'm not a big believer in the 300 ft/lb max on these transmissions.

[RSFreak]

V6 and V8 T5s are the same as far as their structural integrity, the case, strength wise. I was not referring to gear ratios.

I wouldn't put much more than 300ft/lbs through mine, but I know a few 5.0 Mustang guys who do.

[Quasi-Traction]

[RSFreak]

[rjmcgee]

[RSFreak]