74 Z28 engine modified vs original what to do?

[eagledriver]

Some background on my car.

When I bought my 74 type LT Z28 in 2009 the PO gave me a couple crate loads of original parts from my engine. The car runs great like it is but the PO clearly made performance related changes to the engine over the years but gave me all the old parts. The 350 has a custom cam, link bar hydraulic lifters, world brand custom heads, edelbrock air gap intake and a Holley 4150 mechanical secondary carb, hooker headers with X pipe dual exhaust. As I said this combo runs great and I’m pretty happy with the performance over my prior original 74 4 speed car I owned back in the day

I have checked and the chassis number part of the VIN from the car is stamped on the block so I’m pretty sure the block is original to the car. Some of the parts he gave me included the heads, dual snorkel air cleaner with nice chromed lid, smog airpump, diverter valve, the associated hoses, smog tubes and shields, 340261 EGR intake, 7044209 quadrajet carb, exhaust manifolds and other internal engine parts like rocker arms pushrods etc. He even included the original EGR valve and hold down clamp and hardware.

I want to run my original air cleaner but can’t find a way to get it to fit over the Holley carb and I don’t want to cut it or modify it since it’s really in pristine condition. That said, I’m thinking of changing back to my original carb and intake so I can use my original dual snorkel air cleaner and ditch the aftermarket set up I’m using.

My question, is this a silly thing to do since I’m assuming I’ll be giving up some significant hp just to get a more original looking set up? just looking through the original parts, it really makes me want to use some of this stuff to make my set up more original looking. Before anyone says “it’s your car, do what you want”. Im aware of this but I really like the original stuff, but on the other hand I really like the power and torque that the car has now. I guess I’m just struggling with how much performance I’ll be trading off using the original intake and carb. Any thoughts from you guys that have been through this?

 

[mallard]

Interesting you bring this up. In 1984 I bought my '74 z28. Even more interesting I bought the car with the "full knowledge" the original engine was gone and the engine in it had been built to resemble an LT1. It did not look at all original under the hood but hadn't been at all butchered and it had gobs of power.

I had no original parts but after doing some closer inspecting, it turned out whatever mods the engine had gone through it had aftermarket LT1 heads (492 casting), solid lifter cam, but the ORIGINAL "born with" numbers matching block. So after some searching, I found a badly rusted '74 that still ran and drove and used a bunch of the original parts from that and put on mine, plus bought quite a bit of NOS stuff while it was still available from GM. I've kept the LT1 heads on it but with the LT1 intake and carb taken off it (and I do regret selling that) NOS Qjet, stock exhaust manifolds vs headers, stock dual snorkel air cleaner, it is somewhat slower.

Do I regret making the changes? Maybe a bit but I left the most important parts, heads and solid lifter cam, so it still has plenty of get up and go but a more stock appearance. The car had 46000 miles on it when I got it 39 years ago, and 56000 miles today. I'm 70 now and only drive it on occasions and particularly when the grandchildren want to ride in it.

If you have the stock Qjet if possible, you might be able to put that on and then use your stock air cleaner. Even that small change really looks good. Just some thoughts.

 

[eagledriver]

Thanks for the input mallard. Sounds like you have a nice car. I looked at your suggestion about using the original qjet but my air gap intake is a spread bore design for the Holley carb so it won’t work with the Qjet larger rear throttle bores so I’ll need to change the intake. You do bring up an interesting point though. Perhaps I can find an aftermarket higher flowing intake to wrk with the Qjet. Hmmm..

 

[FS87LT]

(Holley 4150/4150 = square bore, QJ = spreadbore)

 

[sandlapper]

FYI
edelbrock does offer an Air-Gap intake with spreadbore pattern for Qjet --- pn 2601
there may be similar eb offerings as well ?

there's also the possibility to source an adapter to fit the Qjet to a squarebore intake --- I detest adapters!

 

[mallard]

Actually, I'm using an edelbrock spreadbore intake for my Qjet.

 

[COPO]

Buy a repop 70-72 Z28 air breather which will fit that Holley. If you have a HEI distributor then the 70-72 breather will hit the rear. If you have an early ‘74 then it will fit the points distributor.

 

[mallard]

COPO raises a good point. The ‘70-‘72 air cleaners look much like the ‘74s, black base, chrome lid, twin snorkel & are made for holly carbs. I think they may be a little larger in diameter but look very good.

 

[Z28_1974]

Interesting topic. I'm the original owner of a 74 Z28 Sport Coupe. Over the years I've made some mods to the engine and replaced the horrible GM 4 speed shifter with a Hurst Comp Plus. I installed aluminum Edelbrock heads and Performer intake , but kept the original Quadrajet and air cleaner. I replaced the point distributer with a GM HEI. Plus I installed headers and a true dual exhaust. I've kept all of the original parts with the idea that if the next owner wants all OEM, he can re-install the original parts. In the meantime the engine bay looks reasonably original and I have the enjoyment of driving with a stronger engine.

 

[eagledriver]

Yea man it’s certainly a trade off.