You could try putting in 1 heat range colder plugs, but it might just be that you are floating the valves, does it actually backfire..tail pipe or carb? 2 different dis have been tried, jets have been changed, spark plug gaps are correct? Plug wiere are not leaking spark...inducing a voltage into the primary side of the pickup,or tach wire? factory tach or aftermarket tach? Just shooting out things I have ran into
Holley Carb Tuning Problems --- Help
- Thread starter CdnCutlass
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I'm not saying your plugs are a problem but I had the same problem that I chased for two weeks that turned out to be the plugs - don't rule them out.
The heads are just too big for your set-up. You have a cam that's a good bottom - mid range and heads that are top enders. With 225 runners your not getting
runner velocity down low hence lose bottom end and the carb gets a weak signal. Have you ever had the car to the track?? An more ideal head for your set-up would have been180cc runners.
The heads are just too big for your set-up. You have a cam that's a good bottom - mid range and heads that are top enders. With 225 runners your not getting
runner velocity down low hence lose bottom end and the carb gets a weak signal. Have you ever had the car to the track?? An more ideal head for your set-up would have been180cc runners.
lilbowtie said:
No never taken it to the track because I have always had issues trying to tune it lol. The tuning has put me back over a year now. There are other things I would like to do such as rims and tires etc. but what's the point if it won't run right. If heads are a big problem I may have to look at swapping them over the winter. Any recommendations?
I agree with the above post, I've never used Patriot heads but like they said that is a big head for your combo, that is also why I kept steering towards some problem other than valve springs, if Patriot is worth a snot that head would run well past the rpm you are having problems with I would hope they would put a spring in it that could do the same, the lift number is more than likely the number when coil bind could happen, I would still try to figure out the problem before I tore the motor down. Look into a Dart cast head for your combo they are reasonable and you will have far less problems with a cast head, IMO
Well I look back at when I started this project. The original goal was to have a good running street car that produced a minimum of 450hp, and that I could take to the track 2-3 times a year. It's really never run like I had hoped it would.
You need to talk to Dart or PM me I will give you numbers to call, I feel your frustration 450hp out of a 400" motor is easily achieved with the correct components
450 hp is getting up there - What is the car going to be used for (week-end warior - main driver) @ what rpm do you want to this HP?? What kind of rotating asm do you have?? Do you want to be set-up for drag racing?? You would be amazed what a good set of vortex heads would do on your present set-up.
lilbowtie said:
Car is just a weekend warrior type, maybe the odd drag race. It would be nice to have 450hp in the 5500 rpm range.
Rotating assembly on the car is a high nickel 509 casting 400 sbc, bored 40 over, stock crank 20 over, with stock type 5.7 rods, keith black hyper pistons and all ARP fasteners.
Like Fox80 mentioned, I didn't think 450 was asking too much out of a 408 c.i. motor.
Have you tried the plugs yet?? No 450 hp isn't too much but you need the right parts and those parts all have to work together. Cam, intake, carb, torque converter, rear end, have to be matched for your combo. You are currently set up for bottom end and your package pretty much matches with the exception of the big heads. Your engine isn't much above stock; you have a point more compression and a little more cam so right now 450 hp is a stretch.
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