305 heads on a 350

by McCauley5983 Tue Sep 14, 2010 11:51 pm

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

by 77malibu77 Wed Sep 15, 2010 9:50 am

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

by 74MonteCarlo Wed Sep 15, 2010 9:54 am

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

by The Dude Wed Sep 15, 2010 10:29 am

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.

by 77malibu77 Wed Sep 15, 2010 12:47 pm

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.

by McCauley5983 Wed Sep 15, 2010 11:13 pm

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

by McCauley5983 Wed Sep 15, 2010 11:16 pm

whats a good cam for this setup

by The Dude Thu Sep 16, 2010 10:09 am

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).

by ant7377 Thu Sep 16, 2010 5:14 pm

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.

by BlackChevelleSS Fri Sep 17, 2010 1:41 pm

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

by McCauley5983 Fri Sep 17, 2010 7:16 pm

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

by dragons_lair59 Fri Oct 22, 2010 12:13 am

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

by TWBouska AKA Wooderson Fri Oct 22, 2010 1:25 am

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

by 77mali Tue Oct 18, 2011 8:25 am

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

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.

305 heads on a 350 P1010613

by ant7377 Tue Oct 18, 2011 7:30 pm

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.

by 77mali Tue Oct 18, 2011 9:32 pm

Edelbrock sells a bracket w/ provisions for the kickdown, throttle & cruise in a 2 piece bracket. I am mickey mousing mine for now because I do not have cruise and think the provision for that would look like crap on mine. In my case I believe I can bend the bracket to fit the bolt holes as they are close. Might also be able to cut some away to adapt it. Also, you can not re-use the factory engine lifter brackets any more...at least I can't because the one up front where the throttle return spring hooks into (on the cast iron intake) are recessed and the Edel 2116 are not, plus the holes are not lined up the same, so I may shave a bit off & reuse the little one from the back of the old intake to get by until I can have one made. I'm still putting all the stuff back on to fire it up but rain is coming so i will be delayed...as i have no garage. Sad

I posted some pics of what they look like a while back "dry-fit" on the car.
https://www.g3gm.com/t4500p15-1977-chevelle-malibu-classic-progress-photo-s-aka-mali See page 2.

by ant7377 Wed Oct 19, 2011 7:06 am

I figure I am going to just take the one I have and cut the bottom off and just weld a new bottom on it that fits the bolt holes on vortec manifold it wasnt the stock bracket anyway. Its the steel one Edlebrock sells. What about your plug wires ? I am using the center bolt valve covers. How are you retaining them? The regular retainers have no place to bolt to.

by 77mali Wed Oct 19, 2011 7:39 am

I have pretty thick insulated plug wires & they have "socks" on the ends where they snap into the plugs. I'm not 100% sure but I think there are retainers avail that go under the center bolts.

by ant7377 Wed Oct 19, 2011 5:23 pm

Yeah I looked today they do make a retainer for that. There is also those little holes on the sides of the heads.Im going to see if I can use them, they are threaded.

by ant7377 Wed Oct 26, 2011 8:26 am

Try Moroso part # 72143 for the wire looms I bought them and they work great .
http://www.moroso.com/catalog/categorydisplay.asp?catcode=40009

by 77mali Wed Oct 26, 2011 9:56 am

What re-seller did you use? These look great.

by ant7377 Wed Oct 26, 2011 9:32 pm

Summit racing. I just started the car up tonight. it started freakin raining just as I backed it out of the garage.The weekend looks nice though so we will see how it goes.

by 77mali Fri Oct 28, 2011 9:12 am

What heads & manifold set up did you use? Do you still have the cross breather type or did you eliminate it? I found some brackets online, gonna check out @ auto zone from Spectre they are normally a stock item. $20 for the TB bracket (bolts to carb stud & tightens via allen wrench to the side of the plate) & cheap money for the return spring bracket here's a link for that & pic of the TB set up http://www.spectreperformance.com/#CATALOG.4708
305 heads on a 350 Spectr10

by ant7377 Fri Oct 28, 2011 10:14 pm

I used the GM heads and the Edlebrock manifold (Performer).I got the whole set up from Scoggin Dickey bolts gaskets and all.My buddy uses that bracket on his truck Its a little flimsy but he got it to work you are going to have to mess with it. On another note I took the car out tonight for the first time it pulls really good.Better that the old Camel hump heads I had on there and Its not all dialed in yet, BUUUT snow tomorrow, so I may not be able to use it for a while

by 77mali Sat Oct 29, 2011 11:37 am

I ended up buying the return spring bracket. Had to bend it a little but worked out good. Don't know what I'm doing yet w/ the throttle body & kick down yet. I agree the other was a bit flimsy so may end up using mine and making some bends to fit. problem is w/ my Edel 2116, the middle drivers side bolts are not used to bolt to the cylinder heads. I suppose they are there for the bracket but it does not line up well so I have to adapt it to be used towards the rear of the intake. I just don't like the look of the Edelbrock bracket. Maybe I can find another but for now what I have will do. Glad to hear you took it for a spin! Noticeable difference, huh? Snow is coming here too 3-6" *&@^%! But I am headed out to work on the car anyway!

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