Hi there, I have a chance to get a 305 chev short block with block casting #355909 for my 34 coupe . Can 350 or similar heads be ok for this block or do the heads have to be modified? 305 heads seem to be hard to get down here.
They will fit, but most 305's came with a 58cc combustion chamber to increase the compression, where as most 350's have a 68cc combustion chamber, When you put 350 heads on a 305 you get a crappy performing very low compression motor. Unless your willing to put new pistons in to bump up the compression i would not bother. 305's are sorta a waste of money, might as well get a 283,327, or 350.
I agree, you would be better off finding something else if you can. The 305 isn't a great performance motor, and it should be just as easy to find a 350.
True on the heads...but harsh on the 305. 327's and 283's in good shape don't grow on trees and even 350's are not as easy to get as they once were...might be a lot harder to find in New Zealand!!! BTW...go to the TECH ARCHIVE here...Fat Hack did a good little review of 305 mods a couple of years ago and they CAN be made to perform...although they do have kinda small pistons to go with that 350 crank!
Chevy 305s have a smaller bore than Chevy 350s. So 305 heads not only have 58 cc combustion chambers they also have smaller valves that are closer together. If you use 350 heads on a 305 you may have valve clearance issues. A 305 costs as much as a 350 to rebuild. So it makes $ence to use the bigger bore motor if you can find one. At one time some very good Chevy performance heads (and street replacement heads as well) were being made in New Zealand. If you are stuck with a 305 it might be possible to score a set of new, compatable heads locally.
Man I gotta tell ya, I thought the same thing about the 305 but after more less being forced into using one for now due to money issues, that little shit of a motor does ok.I run Hooker super comps through 2 1/4 in. exhaust, a Crane 278 cam ,Edelbrock performer carb and intake against an M-22 Muncie with just 3:55 gears. It sure as hell won't scare ya but it's decent performance and about 19 mpg.Point being if you can find the heads, put it together. Mine has surprised some guys that turned there noses to the sky before they saw it run
I've seen 305's with around 400 horse, so I'm not gonna knock them. As stated before though, compresssion will drop with 350 heads but you can always have them milled some and run a thinner head gasket, it's not going to be the same as original but it will be close, a set of Vortec heads have 64cc chambers and flow really nice with an aftermarket 4 barrel intake to match, these may be alittle easier to find over there as they are newer. Ocassionally you can run across a 62cc 350 head as well, or get yourself a set of 283 power pack heads with small chambers if you can find them, they are close to the 305's CC
Don't forget EPA CAFE (Corporate Average Fuel Economy) mandates pressured automakers to dramatically improve fuel economy. The 305 was configured for better fuel mileage with it's long stroke and small bores to provide enough torque for low rpm highway cruising. When Chevy switched to TPI in the 80s those 305 Camaros were knocking down 25 mpg. It's a matter of defining your goals. If you want more performance a 305 is not a good choice. If you want V8 economy, it is.
This is good stuff, I was planning to use tri power set up on the 305 with a performer-plus or torker- plus cam and in a light fiber coupe I hope it may be alright in performance for the street.
Try to keep in mind that the 305 typically needs a 500cfm carb. Mine is a 600 manual choke with 98 jet size in the primary.It runs kinda rich but the response is great. If you use the tripower make sure you don't way overcarb. it. The crane 278 cam is good and lumpy and I degreed mine to the max. torque setting on the keyway. The performer intake is a dual plane where as the torker isn't but I think the dual plane works better all around. If you put that combo in a fiber coupe it should be strong and get good mpg's. Good luck
Everyone bashes the 305 but it is still an over-square design, don't run 2.02" valves though, I don't think they'd hit the bore, but they would be shrouded. Actually, 1.94's are large for that motor, lots of 327's ran the 1.72's like the 305's had. Now for a disclaimer; this is all off the cuff/to the best of my memory, please correct me if need be.
Bib is correct. The 305s do have valves closer together. You can get 1.95-1.50 valves for these engines w/o bore clearance problems. There are even different Vortec truck heads for the 305 vs 350. The 305 vortec heads are the way to go in my opinion (I will be using them on my 307 build) but the do need a vortec manifold. Some people have tried to "adapt" the bolt pattern on the heads to fit conventional manifolds but they usually have intake leaks. World Products also makes a great replacement head. http://www.worldcastings.com/prods_pages/043600.htm
You can use all but the 202/160" valves in a 305 without notching the bores I believe. To use a 350 head you have to use 350 head gaskets. Depending on the casting you will probably loose compression. You could change to different pistons and or angle mill the heads if you want a higher CR. 305's are underrated by lots of people, but if given a chance and not put into 4000 pound tanks they run very well. Just don't get carried away with the induction system and cam if you want a street driver. Ive run them with a 500 CFM 2 barrel and the are strong as long as your gearing ins't too high. A vacuum operated quad would probably give better throttle responce under load though. Good Luck.
If it's for performance use move on to something else. They make great motors if targeted to their strong point, mid & low torque, a 5500 redline, and decent economy. They'll never make enough power (naturally aspirated) to push the limits of the block, crank, or rods, thus rewarding the builder with extreme durability. Because the small bore & large valve interference mentioned above, the valves are shrouded and they just don't breathe. If you ever wondered why the chevy & ford 302 is a popular performance engine, but the 305 ain't, that's it. The 302s (and 327/250) have a 4" bore which unshrouds the valves and lets em breathe. good luck with the project
I think the 305 is a good choice for your project: good fuel economy and power right where you want it- low to mid RPM range. And in a light '34 coupe it should be pretty fun scooting off the line, spinnin' the tires, and still getting 25mpg. I had a 305 out of a Trans Am in my '55 Chevy truck and that sucker would git, but good. I also had one in my '52 Ford; lots of torque and 26 MPG on the highway! Use the 305 and have fun!
My son and I put this together from junk, scrap etc runs great. Total investment about 350$ includes new clutch kit pressure plate etc. Hint if you have to hog out intake holes to use carb easier to do with aluminum manifold. Note evenrude ski twin for possible hydroplane project in background.
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