Chevy 366 hop up

[cadillackid]

Yeah I’m sure I typo. My fingers are too big for a little iPhone screen..

The Holley have been around for a long time and are proven to work good. I went with mega squirt as a total DIY on my last hotrod. It was a lot more work but I could dial it in exactly as I wanted .. me coming from the days of old GM I used to hack TPI and use that. I know a few running the last gen holleys are happy with pretty much installing out of the box. A TBI is easy to retrofit from a carb to EFI as you mentioned .

On my superior I’m doing more a restore to original than I am rest o mod so I have the 1405 carb. While it was never factory sold it was generally what any mechanic replaced the crappy international carb with. It’s natiral on a GM to find a Holley to replace what was once the old Quadra jet

[Mrmikeemmo]

EFI is indeed a wonderful thing. Personally I'll give up a little to know if I'm off somewhere though I've no sensor or wiring to shut me down. With modern communication equipment that's less of a concern than it once was.
Just 20 years ago I carried a point distributor with me as a backup, kept a coil mounted with a cap over it. I knew I could make sparks with it. Quick and simple swap. It actually paid off on one occasion.
A nice resonablly sized vacuum secondary carb is hard to beat. If EFI is out of the budget.
Use volumetric efficiency as your goal rather than hp or torque. A high percentage will net the other two as a byproduct.
This is a good thread, great to see so many helpful folks.

[BillyBob]

Originally Posted by hoser

I ONLY want info on the 366!!!!!! I know about diesels already I have owned a few.

I guess I need to emphasize STRONGER what I want to do, I will have to think about this for a while I thought I made it pretty clear with my first post, for now I guess all I can say is if you don't know anything about a 366 and how to sensibly add more torque then DON'T REPLY.

AGAIN I am working on a Chevy 366 GASOLINE ENGINE I have NO intrest in installing ANOTHER ENGINE I ONLY want to MODIFY the CURRENT engine.

I don't think you need to emphasize any stronger. Some people don't get it. Junkyard engines may have the better parts you are looking for cheaper. Just find a year engine that matches the specs you want. Even if the heads are off of a 454, they could be an upgrade but I really don't know. The bumpstick out of one may be an upgrade too but then again, I don't know. Good luck on the hunting. I was looking at a bus online that has a 366, I was hoping it was diesel but not so. DT366 may be a model number for a truck rather than the engine. Oh well, I'll keep looking.

[PNW_Steve]

I sometimes wonder at some of the responses I get to questions.

Sometimes I find myself asking "did you even read my post?"

[ACamper]

I have a 1984 366ci I am getting ready to change the carburetor and tune up. It is running a but rough I feel like the main problem is it has the original carburetor which i believe is and old Rochester, I plan on putting on a Edelbrock 1405 600 CFM.

It seems like these engines are mostly in farm trucks and school buses, so I assume they were not made for passing stuff by on the hwy. Probably designed to drive up and down farm rows and school bus routes. It has suited my purpose well I just need to drive around a small off road area.

[IanT720]

Do the 1406 it has the electric choke, and get the riser plate. It helps airflow plus you may need it to work with your intake manifold. Btw.. my 366 moves my 38' bus 75mph no problem

[ACamper]

Originally Posted by IanT720

Do the 1406 it has the electric choke, and get the riser plate. It helps airflow plus you may need it to work with your intake manifold. Btw.. my 366 moves my 38' bus 75mph no problem

I was planing on getting a 1/2" riser plate.

Where did you get the wire from for the electric choke ?

[MalteseFalcon]

Hi, I'm new here, and I don't own a school bus. I found this thread while looking for info on the 366 Chevy engine. I'm in the process of buying a '72 Trans Am that SHOULD have a Pontiac 455 HO in it, and will again shortly. It is inappropriately yellow and black, though, and in the picture below you can see the carb and air cleaner pushed up through the hole in the hood normally occupied by a shaker scoop by a Weiand supercharger sitting on a 366 Chevy. I'm told it was used for drag racing. I'm a Pontiac guy and I don't know much about Chevy engines and nothing about school buses, but from what I've read, a 366 would not be the hot choice for drag racing. Anyway, when I've bought it, I'll post here what I learn about how they built it and how it runs.

I will then be keen to get it out of that poor Trans Am as soon as possible. ;)

[cadillackid]

is it a true Tall deck 366 or is it an LS 6.0? a 366 wouldnt be my choice for a drag car.. the sheer weight of it for the cubes you get doesnt make sense.. I mean it is a BBC so you can put big cams in (be sure to use the tall deck pushrods).. the bores are small but you can bore them out .060 over without any issues. . and technically you could put in a 454 crank.. if its running aftermarket intake and carb then chances are it already has the spacers needed to make that work.. the stock intake flows horribly.. as do the heads..



its quite possible you already have a modified setup in there.. you might want to ID the heads and intake.. and of course its possible someone bored it or swapped the bottom end already.. no way to know unless you take it apart.



if it were mine I likely wouldnt put much into Hopping up a Tall deck.. I certainly wouldnt go to the trouble of machine shop work on the block.. if I were going to put that kind of effort into it then id likely go get another BBC, 455, or likely LS swap it since the car is already non-original. but then again im a RestOmod kinda guy..

[IanT720]

That’s a fun car! So far as drag racing. 366 isn’t the best but….. I’ve heard of people throwing tons of nitrous at them and they can be pretty damn good. FYI I just got the 366 on mine rebuilt. The builder said it makes 400hp and 550tq. Which is what I wanted for my bus. With a different cam you can get more power. And my bus is N/A. With a big blower that’s a very healthy engine.

[MalteseFalcon]

Originally Posted by cadillackid

is it a true Tall deck 366 or is it an LS 6.0? a 366 wouldnt be my choice for a drag car.. the sheer weight of it for the cubes you get doesnt make sense.. I mean it is a BBC so you can put big cams in (be sure to use the tall deck pushrods).. the bores are small but you can bore them out .060 over without any issues. . and technically you could put in a 454 crank.. if its running aftermarket intake and carb then chances are it already has the spacers needed to make that work.. the stock intake flows horribly.. as do the heads..



its quite possible you already have a modified setup in there.. you might want to ID the heads and intake.. and of course its possible someone bored it or swapped the bottom end already.. no way to know unless you take it apart.



if it were mine I likely wouldnt put much into Hopping up a Tall deck.. I certainly wouldnt go to the trouble of machine shop work on the block.. if I were going to put that kind of effort into it then id likely go get another BBC, 455, or likely LS swap it since the car is already non-original. but then again im a RestOmod kinda guy..

It's a 73 366, so definitely not an LS. I'm sure it's been modified, but I don't know how much, yet. It's mostly useful from my perspective in making the car mobile until get the proper engine in it. the current owner had sourced a Pontiac '71 455 HO, less the unique 1971 carb, and that will go with it, so it will be going back to more or less stock. It will probably get a T56 and I'm toying with fuel injection, since the correct 830 CFM 1971 455 HO carb would cost about the same.

[MalteseFalcon]

Originally Posted by IanT720

That’s a fun car! So far as drag racing. 366 isn’t the best but….. I’ve heard of people throwing tons of nitrous at them and they can be pretty damn good. FYI I just got the 366 on mine rebuilt. The builder said it makes 400hp and 550tq. Which is what I wanted for my bus. With a different cam you can get more power. And my bus is N/A. With a big blower that’s a very healthy engine.

Sounds like it could be making some serious torque and horsepower! I understand its "set up for nitrous" but has not been run on nitrous (I'm sure that must be true ;) ) But I won't be using it long - just to move the car around until I get the 455 HO in. Then maybe somebody will want to drop it in their rat rod or square body resto - or maybe somebody who wants a really fast school bus. ;)

[cadillackid]

Originally Posted by MalteseFalcon

Sounds like it could be making some serious torque and horsepower! I understand its "set up for nitrous" but has not been run on nitrous (I'm sure that must be true ;) ) But I won't be using it long - just to move the car around until I get the 455 HO in. Then maybe somebody will want to drop it in their rat rod or square body resto - or maybe somebody who wants a really fast school bus. ;)

I had a 454HD in a bus years ago.. did heads cam intake and carb on it.. oh that poor allison 545.. I dint drive the thing long enough to ruin the trans.. it really sounded sweet though and did go.. although my T444E as I build it up is getting faster all the time

[MalteseFalcon]

I'm afraid I have disappointing news. I did go to look at the car, and I will be buying it, but the "blown 366 Chevy" in this car is definitely a small block Chevy, not a tall deck big block 366 Chevy. So it will have been made into a race engine in the usual ways that a small block Chevy is made into a race engine, none of which will provide useful information for hopping up the 366 industrial engine.

I'm sorry for the confusion. I'd never heard of a 366 small block, can't find any reference to it in any engine or stroker kits, and I can't imagine the combination of standard bore or over-bore sizes that would result in that displacement. I think it might be a 383.

As I mentioned, that doesn't matter to me because I will be replacing it with the correct Pontiac 455 HO engine - they only made 1286 Trans Ams in 1972, and only 458 of them were 4-speeds like this one, so it needs to be restored.


Anyway, thanks again, and I'm sorry I don't have more useful information for you.

[cadillackid]

That’s great it will get its 455!! Love that motor. As for a 366 it was a thing. I call it sort of a pre Vortec 6.0 small block based on the LT1. Chevy may have even generically called it an LT2, you’d know it to see it as it was a much newer engine. Unless the owner stripped it to the bare block and built it up as old school. It was a factory roller cam block and designed for EFI. I suppose it could make an OK race engine but really I always just built strokers and could get 500 Street strip HP pretty easily.. but those 3666 are not common. I can’t think of any regular bore and stroke combo on a standard SBC that nets 366. The common bore but not stroke is a 355.

[MalteseFalcon]

Originally Posted by cadillackid

As for a 366 it was a thing. I call it sort of a pre Vortec 6.0 small block based on the LT1. Chevy may have even generically called it an LT2, you’d know it to see it as it was a much newer engine. Unless the owner stripped it to the bare block and built it up as old school. It was a factory roller cam block and designed for EFI. I suppose it could make an OK race engine but really I always just built strokers and could get 500 Street strip HP pretty easily.. but those 3666 are not common. I can’t think of any regular bore and stroke combo on a standard SBC that nets 366. The common bore but not stroke is a 355.

That sounds like it would be a decent engine, but I'm pretty sure that this one is not that new. The current owner said he thinks its a 1973 engine, and it looked pretty old school to me, too; it has a Holley Double Pumper on top of the Weiand supercharger, and M/T rocker covers. But the current owner is a Pontiac guy too. He probably checked the casting date for the block, but that's it.

I've tried using the calculators to see what would turn a 350 Chevy into a 366, and nothing standard comes close. As you say, a .030 over 350 is a 355. A .060 over 350 is a 360, and they don't usually bore them out more than that. The standard 350 Chevy stroke is 3.48", and a .030 over 350 would need a stroke of 3.587" to amount to 366.03 cid. Obviously, that's not a standard stroke for anything, and I can't imagine why anyone would do that. So the mystery remains, for now.

By the way, this is what it looks like now (in yellow) and this is what it it originally looked like and will again ( white with a blue stripe). I'll be spending the next couple of years reversing the "improvements". Cheers!