Thread: carb question

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i got the edelbrock 750 with the intake. can i swap the tranny tailpieces and speedo between these 2 trannies? the caddy 400 tranny would fit then.

Barb the long tailshaft TH 400 that came with the 472 should fit with no problems, but you will need a shorter driveshaft (I’m running the long tail shaft version in my El Camino). At 67000 miles and likely never abused, I would sure consider resealing the tranny you have and use it and convertor you have, it will probably hold up great.

On the bright side if you have a short tailshaft Chevy TH400 with stall convertor you have good trading material.

You will need to relocate the crossmember back however, but you will need to do that for any TH 400 you use. Chances are the year of your Monte Carlo the holes are already there. The other thing will be the requirement for an electric kickdown switch either on the carb or the accelerator peddle.

If you do go with a different transmission the one that will work are from Buick, Oldsmobile, Pontiac (BOP) or of course Cadillac.

Barb, here are a couple of suggestions about your project. The beauty of using one of the big inch Caddy motors for a swap is that in stock form they produce a ton of torque at low RPM and are very reliable. In my mind the key is to play to those existing strengths which means throw out everything you know about small block Chevys.

The first thing you really need to do is figure out exactly what you want the Monte Carlo to do when you’re done (basically what is it going to be doing most of the time) and the RPM range you will be doing it at. From there it’s maximizing the efficiency of the engine at that RPM range. Basically on a street car these swaps like a gear in the 2.70-3.10 range depending on how you want to drive it.

Here are some dyno results from the Cad company you might find interesting.

http://www.cad500parts.com/catalog/page10.htm

Cadillac did an outstanding job in designing the 472/500s engine to make the maximum amount of torque in the 2100-2600 RPM range and that’s around 500 Ft Lbs. While aftermarket parts can make increases in both torque and HP those increases generally increase the RPM that the results are seen at. With the right parts those gains can be VERY impressive gains actually but the more impressive also get VERY expensive. In the case of adding an out of the box Edelbrock intake to an otherwisw stock 500, the results were an increase of peak HP but a loss of torque.

Personally it was reading the dyno results that was the determining factor for me to retain the stock manifold and carb combination.

BY the way I believe the stock Q Jet is in the 800-850 CFM range. While the Q Jets are more complicated that an Edelbrock, once properly rebuilt they are a good carb and work well with the Caddy motors.

Barb you could change the tail housing and use your original TH 400 case. Unfortunatly it also involves changing the output shaft which entails completly dissambling both transmissions as the tailshaft is the first part to go in when when the transmission is put together and the last part to come out when oyu take them apart. A shorter drive shaft is easier.

Mike thank you so much for all the help. i really want to use my original drive shaft as it is a competition one. so i guess i will sell the 2 caddy 400's and buy one that will fit. the reason that i am doing this conversion is because i have never owned a bbc before. only small blocks. as you well know the engine bay on the 71 monte is like that of the early caminos. huge. i just want a really nice moving car and when i pop the hood all i want to see is engine. plus i am hoping that with all that torque from the caddy that it will make my glasspacks sound even nicer than the 350 did.

jyardgirl I would say if Your Monte Carlo had the Factory Trans it was a TH-350 . First thing the Yoke for that TH-350 is much smaller . So if you really want to use your Drive Shaft as is you Could use a TH-350 Trans form a B.O.P G.M Car . Or use an adapter Plate to mount a Chevy TH-350 trans up . Not sure How well it would Hold up to that Caddy even with a Fresh Stock Rebuild ? And you can't be 100% Sure that were that Engine Mounts up that Your Trans will still sit in the same Place that it did with the Drive Shaft that you have now . I ran a Stock but Rebuilt TH-350 with a Mild 455 Pontiac in a 1969 Firebird . It made it through a Summer with some Drag Racing on Street Tires . Then I swapped the 350 Back in for the Winter that trans still was ok ?

i am going with the stock 400 tranny on the 472. i have a shorter driveshaft that will fit. now just wating on the ups man for the parts to come in. in the mean time i have to finish the z28 though i do not know how much i am going to get done this week. suppose to be 102 here today without the heat index.

It's been hot down here in Florida too, only in the 80' and 90's but the humidity has been up in 80% or higher.
Kurt

this heat is miserable.

Yeah, it's even hot up here in the "Frozen North."