What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

305 heads on a 350???

I heard someone on here mention that 305 heads have a 57cc combustion chamber which could raise the compression up to high to run pump gas...

I don't know for sure, but that might be something I'd look into first.
 
305 heads jump your compression up quite a bit and flow like crap. All in all they are no good for a 350.
 
Pass on those heads
No good on a 350. 350s and 305s have diferent size bores. Stock 305 heads are designed for the smaller bore of a 305. Putting them on a 350 shrouds the valves screwing up the flow on a head that already does not flow very well. Also only have small 1.84/150 valves. They can be made to work good on a 350 with machining the combustion chamber, larger valves(194/160 will fit no problem), and a good port job. But you can buy a good set of aftermarket 350 heads or vortecs for what that costs.
 
BUT they do work fine as a daily driver,,, i had to put some on a rebuilt 350 block,,,cause it's all i had at the time, and needed it to run, runs and drives great,,has good power, would most definately have better with 350 heads,,,but hey, they work.
 
when I bought my truck I drove it for about a month and then all of the sudden it was like the timing or something was outa wack...well we messed around with it for a few days and we still couldn't get it to start..then we got it to start and it had so much compression that it broke the starter bracket in half...so I had it towed to the shop and sure nuff it wasn't the timing but it had 323 heads on a 350.....I ended up haveing the whole top end rebuild b/c of the idiot that put them on.
 
305 heads have 58cc combustion chambers but there is a piston specially made so that you can run 305 heads on a 350 without raising the compression ratio. Without tearing the engine apart you would never know this though.
 
Thunder said:
350s and 305s have diferent size bores. Stock 305 heads are designed for the smaller bore of a 305. Putting them on a 350 shrouds the valves screwing up the flow on a head that already does not flow very well.
Click to expand...

actually, you've got it reversed. a set of 350 heads on a 305 would shroud the valves. as far as valve shrouding, 305 heads are ok on a 350. better than they are on a 305 anyways. but, they still dont flow for crap.

4X4HIGH said:
305 heads have 58cc combustion chambers but there is a piston specially made so that you can run 305 heads on a 350 without raising the compression ratio. Without tearing the engine apart you would never know this though.
Click to expand...

there is no piston made "specifically" for this application, just different style and displacement pistons. even still, the 305 heads are inferior to ANY 350 head.
 
im running 305 heads on my 350. works good i have great power. flow is not a problem cause i only have a 425 propane carb anyways :laugh: next time id get some close chamber ones tho....
 
beater_k20 said:
there is no piston made "specifically" for this application, just different style and displacement pistons. even still, the 305 heads are inferior to ANY 350 head.
Click to expand...

Maybe you better do a little research before making a statement like that. Silvolite pistons makes a 350 piston for use with 305 heads and it is part number 1472 and is intended for use in 1969-1990 350ci engines.

I copied and pasted the info directly from their website.

General Motors
V 8 350 / 5.7L
1969-90
Chevrolet


STD. BORE SIZE
4 / 101.6mm


COMP. HEIGHT
1.54


PIN DIAMETER
0.9273
offset


COMPRESSION RATIO(s)
8.4

Part
Number 1472


SIZE AVAILABILITY


VIN CODE



RING PACK
2-5/64
1-3/16


NOTES
For Use With 305 Heads. 3.300' Dia. Head Recess .270' Deep.


WRIST PIN P/N
LOCK PIN P/N
APPROX. OVERALL LENGTH


RECOMMENDED FINISHED BORE DIAMETERS
PISTON MAJOR AXIS MUST BE MEASURED PERPENDICULAR TO THE PIN CENTERLINE AT 70 DEGREES FARENHEIT 3.710" DOWN FROM THE PISTON HEAD

Piston
Oversize Piston Major Axis
Diameter +.0000/-.0005 Recommended Finished
Bore Diameter







Silvolite Pistons

Here is a link to the exact page. http://kb-silvolite.com/spistons.php?action=details&S_id=253
 
yeah? its a dished piston, it will work just as well with any head as it will with a 305 head. there's nothing "305 head specific" about it. i see them used all the time with 76cc heads on blown street engines. nothing special there.
 
If you look at the specs on the piston you would soon find out that the dish is 3.300" in diameter and .270" deep which results in a compression ratio of 8.4/1 with 305 heads, if you used that piston with 350 heads you would have a compression ratio of only about 7.4/1 which is too low.

Also turbo or blower pistons are made much differently from naturally aspirated pistons. The top of the piston is much thicker, the first ring land is farther down the piston, and the piston is made of a different material and also forged.
 
You must log in or register to reply here.

Latest Posts

Top Bottom