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350 engine with 305 heads.

 
84ChevyTruck
I love my Chevy Chevette!
Posts: 1
Joined: 11/07
Posted: 11/27/07 11:41 PM

alright ive been told that puttin 305 heads on an 350 engine is pretty good.

because of the compression is better..
is that true. and will it mess my engine up in the long run???
Confused  

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55Guy
Administrator
Posts: 1153
Joined: 07/06
Posted: 11/29/07 10:03 AM

This has been debated a couple of times recently. I say no, this is not a pretty good swap. The 305's small chambers to the 350's large bore to me just aren't a good match, compression increase be damned.

I'd recommend finding a set of better performing 350 heads for your motor, and if you're looking for more compression ratio, then find a set with a smaller combustion chamber than the heads you have now.  

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FerstKlassRacing_1
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Posted: 11/04/08 07:14 AM

I have done this serveral times and if all the right things are done then this works out great. I have managed to make 330 dynoed rwhp with almost all used cheap parts.  
FKR

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86montess1
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Joined: 08/08
Posted: 11/06/08 02:01 PM

Can you be more specific, Im condidering doing the same thing.
Thanks  

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chevelle83
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Joined: 10/08
Posted: 11/07/08 11:12 PM

Well, I have run the 305HO heads 1.94 1.50 valves (Camaro, monte SS) with good results as far as this setup can be expected, they dont do well up stairs past 5500, and big cams don't help much, but in a everyday car or truck mild situation work fine. I currently have a set on my 1968 C50 dump truck 19,500 GVW!!! this engine started life in my first hot rod a 1981 Z28, when I built the engine(@16 yrs old) they were all I had, they work fine. I also have a 71 C10 LWB with them too, same results. Stay away! from big intakes and carbs, I use performer intakes and quadrajet carbs because of the small primarys, and vacuum secondaries. But dont spend a ton of time and money on this and just leave power on the table. You will be much more satisfied with a well matched setup.  

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FerstKlassRacing_1
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Posted: 11/08/08 05:49 AM

2 months ago I took a pair of 416 heads disassembled them and did some porting/polishing, bowl hugging and very light bore/chamber shrouding. Sent them in to be cut and reassembled with all the parts that I supplied, cut for 1.94 intake valves. .500 springs were put in as well. Used an Elgin E1015 .465/.488 cam with 1.6/1.5 full roller rockers. RPM intake with 1" spacer 650 holley carb and shorty headers. All on a stock internal 350. Put it all in an 88 Monte Carlo with stock 200R4 and 4.56 rear gears. Drove it around (NICELY) for a couple of days and then took it to the dyno, made 333HP @ 5800rpms. Started to have flame throwing problems at 6600rpms.  
FKR

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stempak
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Posted: 11/08/08 06:38 PM

It sounds like 330hp is all they will flow on a 350 so if that is enough go for it that's quite a bit of power. But if you put on say vortecs or worlds,darts etc you'd probably make 430hp brodix 530hp and up and up it's all in how much you want to spend. You can't bet the price of 700 ready to go for the new "bowtie" vortecs.

Here is a head flow chart with hp#'s it will show why a good set of heads is a major reason that can make or break hp and you can see how good the vortecs are for the money  www.users.erols.com/srweiss/tablehdc.htm  

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86montess1
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Posted: 11/10/08 03:06 PM

Thanks to everyone for your response.  

I have a set of 305 heads which has been fitted with 1.94 intake & 1.60 exhaust (YES 1.60 Exhaust) I've planned to use these on a 350 which has 8.5 to 1 compression using 76cc chambered heads. I have calculated that with 58cc chambered heads & .028 head gasket I should end up with about 10.3 to 1.  I also planned to use comp cams extreme energy 218 intake 224 exhaust @ .050 with 462 & 469 lift respectively.  
I will be using an edelbrock performer, a quadrajet & hooker competition headers.  The motor is in a 86 SS Monte with a beefed up 2004R with an 1800-2000 stall converter and 3.73 gears.  
What do you guys think?
Questions, comments, opnions very much appreciated.

Thanks  

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stempak
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Posted: 11/10/08 07:13 PM

cool, hope it runs good for you  

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86montess1
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Posted: 11/15/08 03:03 PM

Thanks for the reply  

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