1979 corvette doesnt pass 90mph???????
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1979 corvette doesnt pass 90mph???????
hello i have a 1979 corvette that refuses to go past 90 mph, the car has a 350 with slight modifications such as a edelbrock high rise intake manifold, holley 600cfm carb, side pipes with the catalytic converter delete and a th350 trans. the car hits 3400rpm when cruising 65 mph. and i am just lost as to why it only goes 90 mph, when i hit 90 mph the rpm is at 4500rpm which is right at the yellow line. I feel the engine has alot more power but refuses!
I have an option to put in a 406 if all else fails with the following modscamel hump heads, aggressive comp cam, edelbrock intake, holley 650 db pump, crane cam rockers, hedman headers, high performance fuel pump.
Please help just got smoked by a 2003 mustang is how i know the cars speed limit!
I have an option to put in a 406 if all else fails with the following modscamel hump heads, aggressive comp cam, edelbrock intake, holley 650 db pump, crane cam rockers, hedman headers, high performance fuel pump.
Please help just got smoked by a 2003 mustang is how i know the cars speed limit!
Racer
Joined: Mar 2010
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From: NW sub of chicago IL
what is your differential geared at? it sounds like your differential has a high gear. I have a 3.08 so I am going 90 at a little over 3500 rpm. you may need to get a lower gear or improve your engines breathing if you have a need for speed.
One last thing our cars are designed to be less accurate about our mph above ninety so grab a gps to check the accuracy of your speedometer
One last thing our cars are designed to be less accurate about our mph above ninety so grab a gps to check the accuracy of your speedometer
Burning Brakes
Joined: Nov 2011
Posts: 1,170
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From: Willoughby Ohio
Your factory camshaft is pretty much done making power at 4500 rpm.
Ther engine will continue to rev but will not make any power.Your options
are a gear swap or a cam swap with the 350.Or just replace the engine with
the other parts that are available.It sounds like you have a 3.70 rear gear.
Have you checked it?I would skip the double hump heads and go with an
aluminum aftermarket head,you'll be much further ahead performance wise.
Ther engine will continue to rev but will not make any power.Your options
are a gear swap or a cam swap with the 350.Or just replace the engine with
the other parts that are available.It sounds like you have a 3.70 rear gear.
Have you checked it?I would skip the double hump heads and go with an
aluminum aftermarket head,you'll be much further ahead performance wise.
Burning Brakes
Joined: Sep 2012
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From: coon rapids mn
mite be bad or worn out valve springs.consider a new valve train with good springs ,and a new timing chain .install a modern cam and make some HP.what is your fuel pressure at WOT ?consider new plugs and wires ,and check out your distributor for a possible rebuild.
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Le Mans Master
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From: Tuttle OK
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Thanks for the replies guys, i took it to my mechanic and he said I have 373 gears and I have no clue what the guy put into the engine before I got the car as a surprise, you think I should stay with my engine or swap it out for the 406 I could get for dirt cheap like 500 bucks 
Drifting
Joined: Mar 2011
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Something is wrong. My '74 L48 w/4 speed, 3.36 gearset, would nearly hit hit the (only 5300 RPM) redline in top gear, completely stock. That should be something like about 125 MPH.
Going down a hill, MANY years ago, I once saw 135 MPH on the speedo. When I realized I was past the redline, I backed off.
As if any of the dash gauges were accurate. Probably not.
All done on empty interstate highways, by the by.
Haven't done anything like that in a long time.
I had no fear those days. That was in my irresponsible youth. Now I'm old and boring. 110 MPH max.
Going down a hill, MANY years ago, I once saw 135 MPH on the speedo. When I realized I was past the redline, I backed off.
As if any of the dash gauges were accurate. Probably not.
All done on empty interstate highways, by the by.
Haven't done anything like that in a long time.
I had no fear those days. That was in my irresponsible youth. Now I'm old and boring. 110 MPH max.
Safety Car
Joined: Sep 2012
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From: Palm Harbor, Florida
Thanks for the replies guys, i took it to my mechanic and he said I have 373 gears and I have no clue what the guy put into the engine before I got the car as a surprise, you think I should stay with my engine or swap it out for the 406 I could get for dirt cheap like 500 bucks
Race Director
Joined: May 2005
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From: Millington Illinois
St. Jude Donor '08-'09
406 is a small block. I bet your not getting wide open throttle or your secondaries are not opening.
Last edited by 63mako; Dec 16, 2012 at 07:37 PM.
Safety Car
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From: Palm Harbor, Florida
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Wait what!? The guy told me everything would fit just the way it's is... Is this not true? He said to put a shifter improver kit and a 3500 stall and I am ready to bolt on an go! And to be honest I don't know very much about carbs and if it is opening a wot or if the secondaries are opening I am sorry for my beginner language, but I am trying!
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And I don't think I want to change the heads to aftermarket because the guy says it makes 450 hp and I heard that's a perfect range for the th350 with an improved shifter kit by tci if I am wrong or I should please let me know you guys know better than I do!
Le Mans Master
Joined: Sep 2004
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From: Livonia MI
You've obviously got some problems, as had 4 cyl daily cars with less that 100 hp, that would do better than 90 mph. Sounds like you have a fuel delivery problem. First thing I'd check, is the carb linkage. My brother had a 289 Mustang years ago he put a new carb on. I drove it to school once, and wouldn't top 60. I checked the linkage, and he really messed it up. Thing wouldn't even go half open. I fixed it, and was like a new car.
Safety Car
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From: Algonac Michigan
I'm thinking you need to get your car to someone who knows how to work on a car of your vintage and get a good tune up.
A properly adjusted carb and the distributor working as it should will probably bring sufficient results.
A properly adjusted carb and the distributor working as it should will probably bring sufficient results.
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I have taken it to so called corvette experts who only messed things up further two times they adjusted the carb so bad that it would stall everyte at temperature and 400 dollars later here i am. I am attempting solutions myself but there is a guy willing to help me put in the 406 but is there any modifications needed to do this because I don't even know what is in the engine other than why I could see, it looks like nothing major since it still has the original headers