Alfa Romeo Forums banner

carb isolator replacement

1350 Views 7 Replies 3 Participants Last post by  Gordon Raymond
I'm putting together my "to do" list for my newly acquired 72 Spider and sorting out what I'll do vs what I'll pay to have done. The car has Dellorto 45s and the blocks between the carbs and intake manifolds (isolators?) are cracked. First question is, since this is not the original set up on the car, how can I be sure I get the right parts, and second, can I do the replacement without messing up carb settings that I'll have to re-do? Any other secret gaskets/seals that need to be replaced at the same time, like a gasket on either side of the isolators? (I hate it when I tear into something, only to find that something else needs to be replaced, which delays completion) I'll probably replace fuel lines at the same time, since some look cracked too. I imagine that the cracks on the isolators may be messing up the mixture by admitting air, so some re-tuning may be required.
1 - 8 of 8 Posts
Contact Centerline. I believe they have the 45 mm isolators (not cheap:() you need, as well as the gaskets. To replace these you will have to R&R the intake manifold:rolleyes:. They will have the 8 isolator gaskets you need and the intake manifold to head gasket. Be sure they have these in 45 mm before disassembly, unless you are handy at making 40's into 45's. (not hard:cool:).
Yes you will have to re syncro the carbs:p. The 45 isolaters are singles, while the 40's have a double center. (You need 4, 45's, but only 2, single 40's + one double center 40.) :)confused:)
These things all deterioate over time from heat and age, and can actually cause engine damage if they lean the mixture too much at high speeds:eek:.
I hope this helps. :DGordon Raymond

That's just what I need to know. I have the Brookslands shop manual, which I suppose will lead me through this? It's been a while since I've done car surgery.
Insulator / Isolator replacement.

Just take your time;). If you have a question, STOP and post the BB:confused:. There are many here that will help:cool:. Centerline will advise as well;). Again any questions, post the BB:). Opinions vary, but there is a lot of available information here:cool:!
Best, :DGordon Raymond
Isolators for 45's are available. Anybody got a line on a place to get isolators for _48's_ ????

Thanks, Greg
Harder to find?

Isolators for 45's are available. Anybody got a line on a place to get isolators for _48's_ ????

Thanks, Greg
Hi Greg,
They do exist, but I never use them as they are too "iffy" to find at a reasonable price:rolleyes:. First I must ask, is the manifold really cut for 48's, full length, or just sort of a short funnel:confused:? I usually have at 45's with an air die grinder and open up the 48 end to 48, or if the manifold is correctly full length tapered for 48's, you can die grind 45's on both ends:cool:. If you want to spend the money:p, Pierce Manifolds in Calif. 408-842-6667 might have them, or you can try Anthony @ Fast Road Cars in G.B. >[email protected]<
You are only opening them up 3 mm, .117 inch total, about .06 per side. Not much, and not much to worry about, hardly necessary for anything but pure race useage:rolleyes:.
:DGordon Raymond
48 mm carby isolators--

Hey--thanks for the prompt reply and sales leads.

I didn't expect that they would be cheap. Nothing good or fun ever is---

And, yeah, the head, head and manifold, and head, manifold, and carby, assembled, are all three gonna spend some serious time on a flow bench.

In fact, the ports in the head may spend some time with a TIG torch inside them (after proper warming of the entire head).

No, not a race application, although it could be eef not for all their steeenkin' ROOLES an' politics !!!!

See less See more
The easiest way or go then Greg, would be to have at a set of 45's with your porting burr. Quite simple, (& you cam make gaskets fit right at the same time!).
Gordon Raymond
1 - 8 of 8 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.