The Classic Cadillac Forum Discussion, Holley on a 1970 500? in Past Cadillac Vehicle Discussion; Hey all,
I'm looking for any experience, wisdom, etc. regarding my Eldorado's 500c.i. Engine and Holley carbs.
Basically, I want ...
Im assuming that Qjet is a spreadbore? I dont think Holley makes a spreadbore larger than 650 cfm which will starve that engine. You will have to swap intakes or run an adaptor which is less than optimal. I like the Avenger series because they come with electric choke, quick change secondary springs, clear sight plugs, and reusable gaskets on the bowls and metering blocks for jet changes.
Yes, they sell adapters to go from square bore to spread bore. I don't know what the implications of that are on efficiency/performance. That said, the intake manifold is nearly flat in order for everything to fit under the hood. So fuel and air literally make a 90 degree turn already.
So, yeah, I'm looking at an adapter above 650cfm. I just have to make it all fit under the hood.
I still think your best option is to find a good Qjet builder. If done properly they are great carbs. I have been running them on my Buick Gran Sports for years. Get with these guys http://www.thequadshop.net/
I would stick with the qjet it is a really good carb. Rebuilding them aren't that bad when you get used to them, just more parts than edelbrocks and holley. Just becareful not to bend the rods when putting back together. If you don't like the chokes you can run it without them no problem.
Back in the 80s when I was younger I wanted to hot rod my old caddy. It was a 68 Calais. I dueled out the exhaust, put the adapter on the stock intake and slapped a Holley 750 on it. Aside from the normal stuff I remember having to change the front bowl to a side loader to clear the AC compressor and dremeling the exhaust manifold to fit the throttle. In hind sight I'd say it probably suffered from too much carboration. It didn't bogg out or run poorily, a matter of fact it was a little quicker off the line. But that was negligable compared to the smell of all that exhaust/unburnt fuel flooding the car when you took it for a cruise. For what it's worth I'd stick with the Quadrajet. I've had a 70 Coupe since 2000 and ran the same Quad on it all this time. It does fine. It's not a race car.
I know I posted them in other threads as well, but these guys helped me out with a lot of questions on the 500cid and I just received new (custom) headers from them for my 70 eldo, so i really like to recommend them:
They have a lot of parts especially for the 500cid and have a lot of experience and knowledge on tuning and racing with them. They can help you out with the Q-jet or other carbs as well.
I have yet to find an intake manifold, other than original, that will fit under my 1970 Eldo's hood. In fact, until I put new rubber bumpers on, the air cleaner hit the hood insulation with stock parts. And I haven't quite talked myself into cutting a hole in the hood. Lol