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73-87 Chevy _ GMC Trucks => Performance => Topic started by: 79c10junkie on April 03, 2004, 12:14:00 pm

Title: Hei distributer:how to recurve?
Post by: 79c10junkie on April 03, 2004, 12:14:00 pm: How do you recurve a distributer on a .350?Any info is appreciated.
Title: re-curve
Post by: TORQUERULES on April 07, 2004, 07:25:00 am: Just buy a HEI re-curve kit. all parts go in your distributor under the rotor
Title: Re: re-curve
Post by: TORQUERULES on April 07, 2004, 11:09:00 am: Barry Grant

"Big cams and/or low-compression ratios usually require more initial timing--especially in a heavy car with freeway-type gears. Grant recommends 18-20 degrees as read on the harmonic dampner at idle, with correspondingly less distributor centrifugal advance."

I'm going to try this as soon as I get a timing light.
had a 305
have a 357
want a Big Block
Title: Re: re-curve
Post by: 79c10junkie on April 09, 2004, 10:58:00 am: Quote:
with correspondingly less distributer centrifugal advance
Quote:

what does this mean?To advance the timing, you have to advance the distributer.Could you be a little more specific?(ie:in laymens terms?)

79c10junkie

Edited by: 79c10junkie at: 4/9/04 10:02 am
Title: Re: re-curve
Post by: oscarone on April 09, 2004, 11:25:00 pm: Initial advance is read at the dampner. This is without vacuum advance or mechanical advance and is adjusted by rotating the distributor. Vacuum advance increases the timing based on engine vacuum. Mechanical advance increases timing based on the rotational speed of the disributor(engine rpm). It uses a set of weights, springs, and bushings. As engine rpm increases the weights are thrown out thru centrifugal force. They act on a cam and change the position of the magnetic pick-up that triggers your coil. As the engine slows down the springs pull the weights back. The bushings limit how far the weights can be thrown out and advance your timing. You can change two things with the mechanical advance: How much and how fast. By using lighter springs the weights will be thrown out at a lower rpm and at a faster rate. Stiffer springs, of course, will delay the effect and slow down the rate of advance. Using different diameter bushings will determine the maximum amount. So, let's say you set your initial timing at 10 deg. If you use a stop bushing that limits the mechanical advance to 25 deg. you would have a total advance of 35 deg. So, what TORQUERULES is saying is to set the initial advance(set by the position of the distributor) high with a lower mechanical advance(set by bushing size). Did that help any?
Title: Re: re-curve
Post by: 79c10junkie on April 10, 2004, 09:09:00 am: Thank ,Oscarone.That helped a little.It may have shed a little light on why my rebuilt .350 is bogging when I step on the gas.I Advanced the distributer to16 degrees bdc and the throttle response got better,but still bogging.Also the timing at 16 bdc was to high for starting the motor(the starter bareley turning)What could be the problem here,or better yet,how can I fix this?Thanks in advance to all replys.

79c10junkie

Possibly the carb? edelbrock 600cfm/manual choke
Title: Re: re-curve
Post by: oscarone on April 10, 2004, 10:26:00 am: What are the specs on your engine? I know it's a 350 and an eddelbrock 600cfm, but, what kind of cam...intake manifold...exhaust...? It sounded, from earlier post, that you installed a "bigger" cam? 16 deg. is pretty high. It will make a high load for the starter. Also, I wouldn't be surprised if you had detonation, especially under a heavy load. I run 10 deg initial on my 383. also, how long ago did you install the carb? There are a dozen things or more that can cause your problem...so, don't just focus on timing. If you set your initial advance at 8-10 deg. with a stock dist. you shouldn't be bogging down. Chevy set there stock engines anywhere from 2-8 deg. It may not be the "ideal" timing for your engine, but, it shouldn't be causing the problem.
Title: Re: re-curve
Post by: 79c10junkie on April 10, 2004, 11:50:00 am: The intake manifold is a holley strip dominater (single plane,4500-7600rpm)I m trying to get rid of the intake now in favor of a dual plane.The cam is a comp 268 high energy(choppy idle).454 lift. I still have stock manifolds. The catylytic converter has been replaced w/ a thrush glass pack,then straight pipe the rest of the way.(will have it dualed soon)ALSO,could it be the floats in the carb are mis adjusted?WHEN i hit the gas it bogs and wants to shut off.It also dies sometimes when downshifting or coming to a stop. If I take off very slow the truck will go ,but ifI push it for a little low end grunt, it doesn't comply.This is all happening w/ timing at 10 degrees bdc.

79c10junkie
Edited by: 79c10junkie at: 4/11/04 9:55 am
Title: Re: re-curve
Post by: 79c10junkie on April 11, 2004, 10:06:00 am: Hey, Oscarone.I was told when I bought the carb second hand that it was 600cfm. Upon closer inspection, it turns out it is the 1407 series.(750 cfm)Last night I played w/ the air adjustment screws.With the one on the left adjusted out 1 1/2 turns,I started closing the screw on the right.With the right screw completely in,the motor still ran like nothing happened.So evidently I've got some carb problems.I'm going to advance auto after work to pick up the rebuild kit.I'd rather just rebuild it and have that problem"COMPLETELY" fixed.I 'm still not sure thats the whole problem though.When idling in neutral the motor runs great.BUT once in gear w/ a little load,it runs like crap.What do you think.Or anyone out there who has had this problem.I could really use some help.

79c10junkie
Title: Re: re-curve
Post by: oscarone on April 11, 2004, 01:32:00 pm: It does sound more like a carb. or fuel delivery problem...the reason I asked when you installed the carb. When you installed it the float bowl was empty. This causes a sudden rush of fuel into the carb. on the first start-up. If there is some "funk" in the gas tank it can plug a fuel filter. It could be that easy. The other thing could be the float level. I had this problem with mine. If it is too high it can flood the carb. That would make the idle mixture or "air adjustment" screws useless. The float level on mine(and this was right out of the box from edelbrock) was so high when I pulled the top off the whole carb. was soaked in fuel. I could turn the screws all the way in and out and it wouldn't make a difference. Before you pull the casrb. back off I would check the filters. The other thing is it could be too high a cfm. I am no carb geneous, but, what I have heard is the performer carbs are more sensitive to cfm. A 750cfm Q-jet can be used on any small block and the big blocks. But, a 750cfm performer may be too big for a 350. Let me us know what you figure out.
Title: Re: re-curve
Post by: 79c10junkie on April 11, 2004, 01:43:00 pm: Thanks for the info,Oscarone.Ill let you know how it goes after I rebuild the carb.My first carb rebuild too.This should be interesting! lol

79c10junkie
Title: Re: re-curve
Post by: oscarone on April 11, 2004, 02:21:00 pm: It will be interesting! Just take your time and have fun. And, when you put it back on...flush the fuel system. That is,crank the engine a little and let the fuel flow into a can or something. That way if ther is anything in the lines you will get it out before it plugs a filter.
Title: dis.
Post by: 1quik86 on April 18, 2004, 01:36:00 am: Is this distributor the old style HEI, or the HEI with the electronic spark control (ESC)? If it has the spark control that could very well be your problem. It happened to me. You can bypass the ESC at the distributor wiring harness. You can tie the two outside wires together. I believe they are green and black. I think there are four wires making a flat wire. Kinda like a trailer light wire. Hope this helps.