They're basic over the counter service replacement open chamber heads.. Nothing special, should have been pretty cheap, they're ALL over..

 

I didn't pay anything for them, but whats Cheap?
Are they worthless heads, or are they worthy of use?

 

They are not nearly as bad or obsolete as a lot of folks will tell you. We had a set on a 2750 lb. bracket car with a glide and a 481 BBC roller engine. It ran 5.7-5.75 @ 116 mph in the 1/8 mile consistently. We put a set of the fully CNC AFR 315 heads and then ran 5.6-5.65 @117.5 with no other changes. The AFR heads had about 2 less cc's than the 990's so maybe a little of the et came from a slight increase in compression. Also remember we lost about 65 lbs. off the front of the car. We spent about $3500 for that 1/10 of a second. Not bad considering what the super stockers spend.

The 990's had a basic bowl port ( 88%) of the valve diameter. The intake valve was 2.25, the exhaust 1.88. stems were 11/32. Some work on the short turn to smooth out the mid lift turbulance. The CSA was still too big for the 481.

Camshaft was 274@.050 with .790 lift on the intake and 282@.050 with .740 lift on the exhaust, lobe separation was 110. Shifted at 7000.

 

Thats what I was looking for, Thank you sleeper
I know there not worthless, just never seen them, they came off a 10.0 2400# Henry J, with a very mild bottom end.

 

Depending on what the application is, there pretty good. But, for a street car, you may be better of with ovals. The 990's intake runner I believe is 325cc - very big. These rectangular heads like alot of rpms before they begin to shine. I think in a 3500lb+ street car w/steeet gearing though, oval will give you more torque.

 

The GM open chamber rectangles have a very lazy intake port. In a heavy street/strip car I wouldn't use them.

 

They work pretty nicely on a 496, particularly something with solid or solid roller cam where you can buzz it to 6500+. A bit of short turn work and some bowl blending and they're fine. They can't really compete with good aftermarket heads for all-out performance, but they'll hold their own as a good street or intro strip head, IMHO.

 

You guys are great, Thanks for your input:thumbsup:
Having played with BB buicks most, I have very little knowledge with these BBC. Sounds like they wouldn't work for my application. I will posts some pictures later of the heads, looks like they have been massaged a little.

 

Its not that they wouldn't work. In fact, they would work good. But oval will work BETTER!!!

A friend of mone has a 454HO Chevelle, which has similar heads. Doesn't really have the bottom-end that a big block should. But once it gets going in pulls real hard.

Again, those heads like a big motor in a light car with alot of gear for max perf.

 

The Oval/Rectangular port break even point is centered around 500 cubic inches. Above 500 cubic inches (496 cid stroked 454, or a 502 cid bored 454) the rectangular ports will perform on the street with better performance in the higher RPM range. IF your motor is going to end up being below 500 cubic inches then the oval port head will provide more port velocity and a stronger signal to the carb than the larger rectangular ports; which is very noticeable in the low to mid RPM range encountered in 95% of street driving.

Bear in mind those new rectangular port heads you have were first designed in 1963 for NASCAR competition on Dayton's high banked track. Chevy was tired of taking a back seat to Pontiac and those guys running the 413 and 426 wedge Chrysler's and that other antique cast iron wonder the 427 Ford side oiller. They were only intended for wide open throttle applications on 427 Mark II mystery motored stock car at a 160 mph.

If you are thinking of actually driving this thing, and are interested in street manners, then by all means swap the heads for some Oval Port PASS heads. But if you are like every one else I have ever met at a car show or at a meet, street manners are the furthest thing from your mind. You want a car that loads up at idle, has a rough idling cam that has no vacuum for power brakes, and sounds like you forgot to put mufflers on your build sheet. These '990 HiPerf heads help contribute to the loading up at idle by not letting the carb see and vacuum at idle.


Larger Dave

 

There is alot of good info here and most is true. I've ran 990's,188's,840's PLUS every Oval port GM ever made. Ovals will be better for a street car no doubt, but if you have 3.73 gears or better,and a loose converter or stick,those 990's will produce. Easily,and without any work. I've gone 10.60's with stock 990's @ 3600lbs with a .600 lift solid cam so they can make great power, but as everyone is saying.......Ovals will be better on a heavy street car.Torque will make it feel fast, My 71 chevelle with stock ovals and a .520 hydraulic cam flat out hauls !!!!! Never ran it but i bet mid to high 12's. I recently sold a set of 188's which is a later varient of the 990 for $650 so the have some value to them also.Although people say their the same,i think 990's are a better head. I almost forgot to mention........ i broke EVERY rule when i built the 454 for my 69 camaro conv. 9.0 compression, .566 lift 242@.050 cam, stock 990 heads, 3000 converter and 3.08 gears !!!!!!! It ran and felt awesome and ran 12.68 @109 street tires thru 2-1/4" exhaust.I could almost run the 1/4 in second gear !!!!!
To answer your question.......In my opinion....DEFINATELY WORTHY OF USE. Unless its a heavy/non performance street car, then trade em for a good set of ovals.


bob