Fitting a 3 inch air cleaner housing

Looking at the new ad for a lumped XJ6 I was reminded of a question I wanted to ask a while ago but forgot.

When fitting a lump with standard Holley configuration, eg a 14 by 3 inch drop base air cleaner housing I assume a portion of the under-bonnet cross member has to be cut out to accommodate.

My lumper was first equipped with a 2 inch air cleaner with a drop base which caused the engine to fail after only 4000 klm because it suffocated.

I have a freshly built 383 with injection nearly ready to go in but want to make sure this time there is plenty of room for it to breath. I have bought another bonnet/hood and I’m curious how others have modified the cross member.

i’d question the cause of the 2" air filter that suffocated and killed your engine.
while i agree the engine is nothing more than an air pump and “may” perform silghtly better with a 3" vs 2", there’s millions of cars that were built using a 2" or less air filter and a very small oval opening at the end of the air cleaner assembly

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Me too! not sure how a lack of air would result in an engie failure. what failed? Hled pistons, over fueled gas washed cylinder wals

Yes but the very small opening fed a much larger chamber above the carb. No such chamber above a 2 inch air cleaner with a drop base.

I could be wrong but I should explain what I found. Carl nailed it about leak-down. What I found was with the engine hot and the air cleaner off, the choke butterfly was vertical but with the air cleaner fitted the lid pushed the butterfly down a tad.

The engine was thus sucking fuel, washing down the bores, causing excessive fuel use, massive leak-down and low compression.

I made my discovery by noticing a faint mark on the underside of the air cleaner lid. I made up a dummy housing the correct height and watched the butterfly behavior as the cleaner top was put on. Sure enough. the lid tapped the choke down a bit.

I was actually pretty pissed because I only made the discovery on the second engine as it was going the same way as the first which was totalled.

could be why these seem popular on carb’d lumps??

i don’t recall what filter i had on my last carb’d lump

I’ll see how the single point Sniper goes. Gotta be better than farting around every weekend with old tech Holleys. Plus the injection body sits a bit lower. I have a spare series 3 bonnet I can cut and modify so no loss to the original.

what size carb was on the engine that died?
most of the guys i know that went sniper or FI tech want to go back to carbs,
for the injection systems to “learn” you’ll need several hundred miles on them, probably close to 1000. most aren’t patient enough or don’t drive them enough and are unhappy with the FI conversions. if the carb is set right from the get go, no need to mess with it every weekend

First it was a 625 cfm Demon then swapped to a 670 Avenger whilst searching for the problem I needed a solution to. The disconnect was that the engine was tuned on a out-of-chassis dyno and ran perfectly but this was before I got the car.

I don’t know any users of the Sniper to get an overview so have to rely on interwebz homework.

Good luck, i’m working on a friend’s FI Tech. 72 Firebird, 400cu 11.5:1 compression, big cam, forged internals. my 1st question was why put a $1000 FI unit on a $35k engine that dyno’d 575Hp out of the car?
Needless to say he’s not happy with it. Doesn’t start when hot, down on power, etc.

I’m committed now. Once back on the road I’ll give it some time and if not happy I’ll whack the Avenger back on.