what is procedure to install crate BB in 70 chevelle-help?

I recently bought a 1970 Chevelle 396, TH400, no a/c.

QUESTION 1: Would a GM crate engine (big block model) fit directly into my 1970 Chevelle or is there modifications involved? If it will, which one will "bolt in".?

QUESTION 2:If modifications are involved, where would I get these parts?

QUESTION 3: I would want to install a GM 4 speed automatic tranny, from a later year for the overdrive, would you know of any kits that I would need to do this install?


I appreciate any help here, I love the car, I just would like to have the performance and reliability of the newer parts.

My e-mail is LS1970 @ AOL.COM--THANKS.

1) any Chevy big block crate engine will bolt right up- except the new 650 and 750 horsepower 572 varaiants that will require different headers due to being taller and wider. but a 454 0r 502 will slide right in. you will need the proper late model flexplate for the crate engine, as well as the car oil pan that they sell seperately for whater reason. everything else SHOULD be a remove and replace effort.

2) you'd need the oil pan and flexplate, and these are available fro mthe dealer you get the engine from.

3)you could put a 700r4 in there pretty easily- they are about the same length as the TH400 and you MIGHT be able to use the stock crossmember and driveshaft with a yoke swap to a TH350 style yoke. but i think they are an inch or 2 longer or shorter, so you might need to move the crossmember forward or back a bit and either get the stock driveshaft shortened or get a longer shaft. all the cooler lines and shifter linkage will hook right up just like the TH400, and you can get kits to lockup the torque converter clutch without a computer when it shifts into 4th gear.

1. A crate motor will drop right in. I think the only difference not mentioned yet will be fuel pump. You'll need an electric pump if your going to run a Mark V BBC as there is no provision for a mechanical pump on the block.

2. You local speed shop, the place you buy the motor or any mail order service.

3. If you go to a 700R-4 or 2004-R you'll need a conversion yoke and a stand alone lock up system for lock up convertor function. The convertors are different. Driveshaft mods may be required depending on the tail shaft length your running right now. You may have to shorten yours. I'm partial to the 2004-R because I'm very familiar with it. I have gone thru a few back in my GN days, from lip seals to kolene steels. If you go to a 4L80-E which is the same thing a a TH-400 cept with an overdrive you need a complete stand alone computer to dictate shift firmness and points, o yeah its plenty heavy in both price and weight.

Not to steal the topic but what about dropping a 509 Merlin crate engine into a '71 model Chevelle?.....Will a 509 work the same ways as a 454/502?

Also since my car has a TH350 trans in it now and I'd want to go to a TH400 for the bbc swap would there be any mods and/or changes I'd have to make? (driveshaft, trans crossmember, etc)

Originally posted by Junkyard Dawg:
Not to steal the topic but what about dropping a 509 Merlin crate engine into a '71 model Chevelle?.....Will a 509 work the same ways as a 454/502?

Also since my car has a TH350 trans in it now and I'd want to go to a TH400 for the bbc swap would there be any mods and/or changes I'd have to make? (driveshaft, trans crossmember, etc)

Click to expand...

The 509 will fit the same (I'm going to be dropping in a 540 soon). With the TH-400 you'll need to move the crossmember back and get yourself a different transmission yoke and likely have the driveshaft shortened. Since that trans. option was available from the factory you won't have to get fancy. Good luck.

PERFORMANCE TRANSMISSIOM 2004R , INSTALLATION INSRUCTIONS; 68 TO 72 CHEVELLE
1) What bolts are used to connect a 2004R to the engine?
These are readily available at any auto wrecking yard or GM parts department. The threaded length is 1 1/8 inch.
2) What is the bolt type needed for the converter?
There are both metric and SAE bolts used on torque converters. You need to be certain you have the correct bolt. The easiest way is to take the converter with you to a transmission shop as most carry both types in stock. Test for proper fit.
3) Transmission fluid recommended?
Use a petroleum based fluid as that's what is in there. Valvoline, Kendall, Citgo. Citgo is what Precision Transmission mixes together, using Citgo power fluid too.
4) There are 2 galvanized sheet metal pieces with four mount holes in each piece with the torque converter. What are they for?
Mounting brackets for the transmission fluid cooler. They may not be needed in many installations.
5) What are the connector types on the 2004R for the cooler lines?
The lines used can be 1/4 or 3/8 inside diameter metal tubing. The connectors at the 2004R and to the radiators are double flared fittings. Some installations may need you to use a length of high pressure hose and clamps at the cooler and radiator to allow for vibration or routing. The hose is used to replace a length of the metal tubing. Fittings on the transmission are bottom is return, top is pressure out.
6) Where do I get an output shaft? (Will a stock GM piece work?)
You can find the output shafts at auto wrecking yards and at GM parts counters, The stock parts are strong enough for most applications. If your application requires a custom built drive shaft, consult with the driveshaft builder for output recommendations.
7) What is the 5 prong (Hella) electrical relay and how is it hooked up?
The "Hella" part is a Bosch relay. They are easily found at most auto parts stores.
It is the brake disconnect needed to unlock the torque converter when you hit your brakes. It is used in conjunction with a manual lock up switch that allows the converter to be locked in 2nd, 3rd or 4th gear even under Wide Open Throttle engine operation. Use of a LED in the dash is necessary to ensure the driver is aware that power is being sent to the converter. Converter lock up needs to be manually disengaged when the brakes are used or the converter will lock again when you remove pressure from the brake pedal.
Terminal #86 is connected to the brake switch power.
Terminal # 85 is the ground.
Terminal #30 is power from the relay switch used to send the intended 12V+ to Transmission Torque Converter.
Terminal #87A is power out to the transmission to lock up the Torque converter.
Terminal 87 is not used.
8) Is the lock up electrical connection through the two prong connector on the drivers side?
Yes, one is power in and one is positive power out for a "converter engaged" light or to a signal delay box . It does not matter which terminal is used for what purpose.
9) What mount do you use for the throttle cable and transmission TV cable?
Holly makes a mount (part # 20-95) for big block applications with Holly carburetors. It mounts to the mounting stud on the drivers side and holds both the TV and throttle cables. If using a Demon Carburetor the tab on the bottom needs to be removed and a 1 inch by 1/8 inch piece of welding stock can be welded onto the mount to secure to the mount location for the coil. There is a later model throttle cable (Motormite Mfg. Part # 04156) that has the square mount for both the firewall connection and the Holly mount.

INSTALLATION -
Fill the torque converter with transmission fluid and place it onto the transmission input shaft. Be certain it slides on far enough to fully engage the pump on the 2004R.
Connect the TV cable.
Install the transmission dip stick assembly.
Get the transmission in place under the car on a transmission jack. (Many hydraulic car jacks have a 1 inch pad that lifts out and a transmission adapter fits in that location.) Or have a strong friend over and about 20 2" by 6" pieces about 8 inches long and start stacking!
Align transmission and bolt in place. 3/8 inch drive extensions of about 3 feet in length will assist in reaching the mounting bolts.
Mount the rear transmission mount.
Install torque converter bolts. To install these bolts, remove the engine's spark plugs and turn the engine over manually.
Connect the transmission shifter assembly and verify proper shifting.
Connect the transmission cooler lines. If using both an auxiliary cooler and the radiator cooler, run the fluid into the auxiliary cooler first than into the radiator.
Bottom is fluid in on both the auxiliary cooler and the radiator cooler.
Fittings on the transmission are bottom is return, top is pressure out.
Connect the top vent tube to a fluid recovery container, the container should be higher than the top of the level of the fluid in the transmission cooler (s).
Holly makes a mount (part # 20-95) for big block applications with Holly carburetors. It mounts to the mounting stud on the drivers side and holds both the TV and throttle cables. If using a Demon Carburetor the tab on the bottom needs to be removed and a 1 inch by 1/8 inch piece of welding stock can be welded onto the mount to secure to the mount location for the coil. There is a later model throttle cable (Motormite Mfg. Part # 04156) that has the square mount for both the firewall connection and the Holly mount.
To adjust the TV cable, loosen the adjuster bolt on the end of the cable. For full light throttle to WOT operation and adjustment, a 1.75 inch radius is needed for the "throw" of the linkage. The provided pivot point on a Demon Carburetor is only one inch so a extension must be purchased or fabricated for full adjustability. Now, have someone floor the gas pedal while you check to see if the throttle plate is open all the way. Usually they are off a little and will wiggle. Do whatever you have to do to get it open solid. Now, with the pedal floored, pull the cable back as hard as you can and tighten the adjustment bolt. You now have the engine, transmission and gas pedal all in sync at WOT. Mark the cable so if for some reason it gets moved you can know where to put it again.
Connect the electrical systems used to lock up the converter and the "converter engaged light".
You can purchase a B & M handle with the momentary switch and modify it to use a true on/off switch to lock the converter. The momentary switch pulls out with a hard twist and yank with pliers. Purchase a similar size round Radio Shack switch and a metal washer that will fit into the B & M handle. Wire in the switch, attach the switch to the washer (you may need to drill out the washer's center hole for the switch to fit.) and epoxy the switch/washer assembly into the shifter handle. It cost less than $3.00 to do this modification.
Connect the drive shaft.
KNOWN INSTALLATION ISSUES IN 1968 TO 1972 BIG BLOCK CHEVELLES -
1) Remove the header from the passenger side and the starter to assist in installation.
2) 2 inch Hooker Supercomp Headers will need clearance work on the 2004R on the passenger side if Edlebrock or GM raised port heads are being used. Approximately 3/8 of an inch is necessary in dimple depth on the header or material removed from the dust shield area above the starter on the 2004R housing. This may be a problem with other headers.
3) The turbo 400 transmission pad will work. The rear cross-member must be placed into the frame and slid as far back as possible during the transmission installation.
4) On the deep Performance Transmission aluminum pan, the driver's side of the rear mounting plate will need to be trimmed back about 3/16 inch to allow for removal of one of the transmission pan's bolts.
5) The Performance Transmission needs about a 1.75 inch radius on the "throw" for the TV cable for full adjustment. Bowtie Overdrive has a kit with an extension for a Demon and for Holly Carburetors. I also have a template for one.