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Heads Question - 6/5/2008 6:57:07 AM

sbeasley

Posts: 4
Joined: 6/4/2008
Status: offline

I have a 1970 250/300 corvette coupe. It has a numbers matching block, transmission, and heads.

It has an eldebrock performer intake and a 750 cfm holley.

Recently the #2 lost compression and turned out to be a burnt exhaust valve. The heads need a valve job, and hardened valve seats put in. And it is going to cost $300 - the cost for valves, valve guides, and springs that might need replacing. Now getting them cleaned and magnafluxed is around $50 to make sure that there isn''t an actually crack in the head there, but I''m pretty confidant that it is just a burnt valve. So getting all new valve train parts is going to make it up near the $500 range if I''m not mistaken. These are the 1.94 type heads, not the 2.02 that were on the LT1.

So my question is should I rebuild or keep these heads and get another set that possible have the 2.02 and breath a bit better. I also am thinking about going with a 72 cc chamber instead of the 64 cc chamber to reduce the compression ratio which is currently at 10.25:1?

The best I can get is 93 octane in my area, and I''ve heard you need closer to 100 octane for 10.25:1

currently it has the wrong front end on it, and the wrong wheels for sure. The guy said that he wanted it to look like a 1973 vette, more likely he wrecked it and that front end was more plentiful.

Post #: 1

RE: Heads Question - 6/5/2008 9:31:43 PM

Rich G.

Posts: 107
Joined: 1/12/2007
Status: offline

93 octane is plenty if thats what you are worried about. If you were happy with the way it ran before the valve went bad the just fix what you had. Changing parts tend to cause the domino effect and before you know it your changing the cam. pistons carb, .... just my 2cts. Good luck.
PS you can always put thicker head gaskets on to lower comp. a bit depending what you had on.

(in reply to sbeasley)

Post #: 2

RE: Heads Question - 6/6/2008 7:25:12 PM

73shark

Posts: 1097
Joined: 4/18/2006
Status: offline

I agree with Rich G. 93 will support 10.25 CR. A lot depends on cam and timing.

_____________________________

So many toys, so little time

(in reply to Rich G.)

Post #: 3

RE: Heads Question - 6/8/2008 2:31:35 PM

78buckshot

Posts: 654
Joined: 1/28/2007
From: Michigan
Status: offline

Lots of words have been written about factory cast iron - good and bad. I would have your heads rebuilt and use composition gaskets, this will lower the C.R. only a small percentage but offer a long term seal. Along with the Edelbrock and some refreshing of the carb and ignition system, you should have a good dependable mill for years to come.

(in reply to 73shark)

Post #: 4

RE: Heads Question - 6/9/2008 9:33:03 AM

Texas Jim

Posts: 445
Joined: 12/15/2005
Status: offline

Unless you know a machine shop that is for sure reliable and does really great work, I''d compare what you''ll spend on the rebuild and what a new set, for example; the "house-brand JEGS" heads cost. I know for fact that the JEGS brand f/ the SB Chevy are runnin'' heads.
It is true about doing the top end and not the bottom and vise-versa etc., one of the prior replies...
And the 2.02"/1.60" heads are always better if your motor has any guts at all. I hear the arguement all the time that the smaller valves are better w/ a stock motor, etc. ... but a healthy stock motor will accept the bigger valve heads w/ no problems.

(in reply to 78buckshot)

Post #: 5

RE: Heads Question - 6/15/2008 6:17:15 AM

blknblu68

Posts: 207
Joined: 4/4/2007
Status: offline

93 octane is fine for anything 10.5:1 or less. i would deffinetly go with a 2.02 valve as most of any motors hp is made by the cam and heads! the better a motor can breath the better it will run!!

(in reply to Texas Jim)

Post #: 6