Which type of Valve Cover ??

CQRT · 10-12-03, 12:03 PM

Greetings from Arizona:
I have a 74 Corvette coupe with w 4 bolt main crate engine- Edelbrock Performer intake, Holley 670 and Hedman under car headers. The new block came with painted valve covers- 2.5" tall that I'd like to replace with polished aluminum, but I'm confused about whether I need "tall or short" covers or if I need a type with "baffles". Also, does each cover need a fill cap and breather?
My local speed shop and E-Bay have a ton of great looking covers between Holley, Edelbrock and factory stuff-- but I sure don't want to make the wrong selection and do damage to my new engine!
Your collective wisdom is appreciated.
CQRT
Scottsdale, AZ

bossvette · 10-12-03, 12:23 PM

Tall valve covers are needed to clear some roller rocker setups and may cause a fit problem if your alternator or AC is mounted close to the valve cover. Baffles should be used on a street driven Car so you should have baffles and one fill and one breather/PVC hole per engine, tall or short is your choice you could go either way providing you have a stock valve train.
Craig sr.

10-12-03, 03:12 PM

I bought my 1972 in DEC last year off A dealership (A friend of mine his brothers dealership) I found out it had A crate motor. I decided that I wanted the Edelbrock non script valve covers and I went TALL for future upgrades. When I pulled the oridinal valve covers to replace I found out I had roller tip rockers. (short stories by GARY)

CQRT · 10-14-03, 10:25 PM

Thanks for the feedback and advice - - what's the purpose of the baffles ? Many don't seem to have anything on the underside of the valve cover.

Thanks
CQRT
AZ

corvetjerryd · 10-14-03, 11:01 PM

I believe the baffles are to catch the spashing oil and drip it on to the pushrod and pivot to help lubricate the rocker arms....
My 73 has the stock L82 aluminum valve covers on it and they don't have any baffels in them either.

Scooter76 · 10-15-03, 12:11 AM

The main function of the baffles are to help keep the PVC system from sucking oil into the intake manifold.

CQRT · 10-15-03, 12:44 AM

So, with my crate motor and Edelbrock intake with no pollution valve, baffles are less significant ?
CQRT

MaineShark · 10-15-03, 01:44 AM

Quote:

Originally posted by CQRT
So, with my crate motor and Edelbrock intake with no pollution valve, baffles are less significant ?
CQRT

Your new engine better still have a PCV. It has a small "anti-pollution" aspect, but mostly serves to remove excessive pressure and corrosive vapors from the crankcase.

The more powerful the engine, the more you need something like this. Race engines often use belt-driven "evacuation pumps" to keep the crankcase at a slight vacuum and remove the blow-by gasses.

PCV is an absolute must, and removing it will seriously harm both performance and the life of the engine.

Joe

bossvette · 10-15-03, 03:49 PM

Quote:

PCV is an absolute must, and removing it will seriously harm both performance and the life of the engine.

PCV=positive crankcase ventilation

early chev v-8 had a vent tube in the rear of the intake and the breather in the front where the oil fill was located which served to vent the crank case sometime in the sixties that was changed to PCV (positive crankcase ventilation) which used engine vacuum to vent the crankcase.

MaineShark · 10-15-03, 04:11 PM

Yup. As performance went up, a simple vent was no longer sufficient. Any reasonably-modern engine requires positive ventilation. Usually, engine vacuum is used, but a mechanical or electric pump can serve in its palce, as can a system that uses the vacuum between exhaust pulses in the headers.

On the other hand, if you feel the need for covers that don't have a PCV valve installed, you can mill a connection into the valley cover portion of the intake manifold, and evacuate the crankcase through the valley.

Joe

bossvette · 10-15-03, 04:27 PM

Baffles
notice the small nuts on the top of these valve covers, I have Brodix heads on my Vette and wanted to use their valve covers.
They had no baffles in them when I first put the engine together
many years ago, with my HVHP oil pump they would spray oil out the fill and PVC hole. I made my own baffles from aluminum channel to fix it.
So what I am saying is yes to baffles and PVC and your choice of tall or short, mine are tall

CQRT · 10-15-03, 11:21 PM

Sorry Gang-- I'm was apparently having major brain flatulence and was thinking of EGR valve and not PCV . . . yes, indeed we still have PCV but no EGR off the manifold..... but back to the question - - with a healthy little street motor, are valve cover baffles still an absolute MUST -- or just an added feature ?? And sorry again for the brain fade....
thanks
CQRT in AZ

corvetjerryd · 10-15-03, 11:33 PM

yep, P.C.V. valves are an absolute must,
I remember once triing to run an old set of mid year valve covers with out any p.c.v. and it blew the dipstick clear out of the engine and damaged the rear main crank seal....you have to have some kind of crankcase ventilation 'period'...now I run one in each valve cover with a T into the carb.