305 heads on a 350

so great pull my valve cover off today and for the first time remembered to run the casting number came back as 305 heads on a 350 aint to happy about it but want to know more does anybody have any information

i tried to buy 2 "so called 350" motors and none of them were 350s both 305s. now that you checked your heads i think i need to check mine and make sure everything is 350. lol. i doubt id have a 4 bbl on a 305 tho

I don't recall hearing of a 305 4 barrel until the 4th generation Monte Carlo SS.

Sigh...... let's take this in order here.

Billy Ray, double check your block casting to make sure what motor you have. List the #s here & I can help out. Same goes for the heads. I can't say much good or bad about the 305 heads until I see a casting #. 416 or 601 heads aren't that bad for a street car, especially if they have bigger valves installed.

Brandon & Kyle, I believe 1980 or 1981 was the first year for a 305 4bbl. My grandfather's 83 truck has one. Z/28's had them, Monte Carlos (even lower models) had them too. In the 80's, the two barrel carb was pretty much dead. Brandon, I would check your castings too, because being a 30 year old motor, it could have been swapped 15-20 years ago & appear factory from all of the built up crud.

Rago wrote:Sigh...... let's take this in order here.

Billy Ray, double check your block casting to make sure what motor you have. List the #s here & I can help out. Same goes for the heads. I can't say much good or bad about the 305 heads until I see a casting #. 416 or 601 heads aren't that bad for a street car, especially if they have bigger valves installed.

Brandon & Kyle, I believe 1980 or 1981 was the first year for a 305 4bbl. My grandfather's 83 truck has one. Z/28's had them, Monte Carlos (even lower models) had them too. In the 80's, the two barrel carb was pretty much dead. Brandon, I would check your castings too, because being a 30 year old motor, it could have been swapped 15-20 years ago & appear factory from all of the built up crud.

yeah well im pretty much positive its a 350. the vin number says came factory with 350 4bbl, and the engine has been rebuilt 12,000 miles before i got the car.

i positive the block is a 350 came out of a 72 pickup truck according to casting 14022801 is the head cast number came back as a 80-86 305 head
might be 601 because i couldnt see it too well but i highly dought it

whats a good cam for this setup

No experience with 801 heads, but seriously even if you pulled the motor out of the truck yourself you still didn't know about the heads. Who's to say someone didn't drop in a 305 years ago? The heads have 1.84/1.5 valves, which are decent for a 305, but tiny for a 350. I'm assuming since they are truck heads & not H/O heads that they are run of the mill stuff not capable of supporting a whole lot. They did bump your compression up though which should be noticeable. If you get a cam, stick with about 260-265 adv. duration or around 210-220 @ .050 if you want to be realistic. Any more & you are just wasting gas & not making more power with those heads IMHO. Carb should be somewhere between 600-650 cfm, keep the intake on the small side as well. A single plane is gonna run like crap on that motor. I'm assuming if it is a 350, then it probably has stock dished pistons or you would have noticed detonation by now correct? Probably in the 9:1 range depending on piston dish, gaskets, & actual head cc's (which should be in the 56-58cc range).

Try you might like it they have small chambers and that means a lot of compression. My friend needed a set on his Camaro so all they had at the machine shop ready to go were a set of 305 heads and the car runs strong down low so who knows.

yes but they have small valves, 1 point of compression higher is generally only 3.0% increase in power, but youll lose more than that in the loss of air flow. Keep 305 heads where they belong, on 305s

ya thats what ive been noticing thinking of swapping in a 400 figure the price of building the 350 be more expensive espcially if it has dished pistons

72 should have had a flat top piston and like black said the compresion you gain is killed by the fact you are in essence choking the motor

77malibu77 wrote:i tried to buy 2 "so called 350" motors and none of them were 350s both 305s. now that you checked your heads i think i need to check mine and make sure everything is 350. lol. i doubt id have a 4 bbl on a 305 tho

if its not the original motor then its up in the air...the 305 in my elco when i got it had a 4 barrel 600cfm edelbrock

I had 305 heads...."swirl polish"...




You can do a Vortec upgrade for around $1,000 including performer intake...(EDEL 2116) This eliminates the cross breather that alot of older cars have in their intake from GM. Might have to change brackets (or bend to fit) but this is the solution I came up with so that the car breaths better...& you can say good-bye & good riddance to EGR if you have that set-up now. I'm in the midst of doing this & am putting things back together to fire up the car in the next day or so. I'm happy w/ it and should turn my stock 250 HP motor up around 320-340 or a bit more w/ my Magnum Rocker set up from Comp Cams. New heads are RHS 12410 Vortec, there a a couple of configurations available. My block is 87-88, 5.7 L...not positive this will work for original 73-77 motors best to verify that it will.

Hey im dead in the middle of putting some vortec on my 77 Monte right now! What did you do for the throttle bracket? I got the whole set up from scoggin dickey with the upgraded heads.