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Mr-Bratt · 07-06-2001, 11:54 PM

Hi all,
OK here we go I have about 500 miles on the 400 rebiuld.and at around 5000 rpm it seems like it just starts breaking up .The motor idles and runs great except for this and it feels as though it is still pulling so I dont think it's at it's limit @ 5000 rpm's Here is what I have.75 firebird with---
400--.030 over
forged pistons
6x#4 heads milled to 87 cc (shop checked and said springs were ok)
068 cam
HS 1:65 roller rockers (w/poly locks)
edlebrock intake
edlebrock 750 carb
stock hei (untouched as far as I know)except for msd cap, wires,acell coil,and a MSD 6al box... I had to remove the 4 plug modual and run it as a mag pick up
headers
th350 w/shift kit
3:42 rear
2800 stall converter.
So what I'm wondering is could this be in the distributor? Bad springs? Miss adjusted rockers? I adjusted with engine running and went 1/4 turn past zero lash (had them at 1/2 turn so tried a little looser with NO CHANGE)
Should I check out the distributor better? Maybe a curve kit? Or get a new unit? Proform or MSD ? could this old one be bad and cause this? Any thought's, comments or ideas would be great. Thanks, Mr-B

Mr-Bratt · 07-06-2001, 11:54 PM

Hi all,
OK here we go I have about 500 miles on the 400 rebiuld.and at around 5000 rpm it seems like it just starts breaking up .The motor idles and runs great except for this and it feels as though it is still pulling so I dont think it's at it's limit @ 5000 rpm's Here is what I have.75 firebird with---
400--.030 over
forged pistons
6x#4 heads milled to 87 cc (shop checked and said springs were ok)
068 cam
HS 1:65 roller rockers (w/poly locks)
edlebrock intake
edlebrock 750 carb
stock hei (untouched as far as I know)except for msd cap, wires,acell coil,and a MSD 6al box... I had to remove the 4 plug modual and run it as a mag pick up
headers
th350 w/shift kit
3:42 rear
2800 stall converter.
So what I'm wondering is could this be in the distributor? Bad springs? Miss adjusted rockers? I adjusted with engine running and went 1/4 turn past zero lash (had them at 1/2 turn so tried a little looser with NO CHANGE)
Should I check out the distributor better? Maybe a curve kit? Or get a new unit? Proform or MSD ? could this old one be bad and cause this? Any thought's, comments or ideas would be great. Thanks, Mr-B

WDCreech · 07-07-2001, 12:32 AM

My first thought was that you're not getting enough fuel. What pump(s) are you useing? Is your fuel line big enough? etc.

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Bill

Mr-Bratt · 07-07-2001, 12:53 AM

Sorry I forgot to mention that I'm using a ac pump it has 9# of press. @ idle and is holding between 4-5 #'s at the time I'm getting the trouble

Torment · 07-07-2001, 02:30 AM

Since it's alway the obvious that gets me I'll throw this out. The 6al has a rev limiter, you don't by chance have it set for 5000rpm? Just a thought, not trying to sound insulting.

Mr-Bratt · 07-07-2001, 11:34 AM

No as a matter of fact I pulled out the 6000 chip and put in a 7000 rpm one.... And to see how it would act if it was the chip I tried it with the 3000 chip and it is a different type of prob, So I am thinking maybe the stock springs are shot even though the shop said they are OK?If they are bad can they be changed with the heads on the car??

[This message has been edited by Mr-Bratt (edited 07-07-2001).]

STripleduce · 07-07-2001, 03:12 PM

*

[This message has been edited by STripleduce (edited 07-07-2001).]

STripleduce · 07-07-2001, 03:15 PM

Yes. Use the rope trick.Pull the spark plug, feed in small diamiter rope till you have enough to hold valves up with piston. But first check your float setting 1/32 off can cause fuel starvation @ higher rpm.

[This message has been edited by STripleduce (edited 07-07-2001).]

Mr-Bratt · 07-07-2001, 06:54 PM

STILL NEED SOME HELP!! Ok, went at it today and the stock springs in the distributor were mangled real bad ......streatched and way out of shape...Put in the light spring from kit ran worse and still breaking up @5000 rpm... changed out and put in the MED springs ran a little better (out of the hole was alot more wheel spin) but STILL the same prob @5000 rpm. Maybe gonna try the heavy springs tomorrow? Cops showed up in front of the house so enough for today.But also am noting that if I keep the engine @ about 3000 rpm steady it seems like it's surging?? Any ideas to why its doing that??? I am thinking about changing the distributor first then the valve springs OR should I just get off my @ss and do the springs first?? Nedd some thought on all this, Thanks, Mr-B

Old Man Taylor · 07-07-2001, 07:42 PM

Try taking your chip out of the MSD completely. If it works I will tell you why.

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Jim

Blackcat · 07-08-2001, 04:10 AM

It's the springs! If they are not brand new that is your problem. I'll bet a cheese burger on this one. I have encountered it several times before. Last one was a friends 71 conv. It would run great till 4000rpm and then break up. Tried fuel pumps, Coils, Dist/HEI samd problem. Put on Fresh/new springs Voli'a No problem even to 6500.

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Gatomon
A car is cheaper than a girlfriend. Better than a wife. If it gives you trouble you can park it and forget about it!

Mr-Bratt · 07-08-2001, 01:05 PM

Blackcat or anyone else.... The heads are 6X #4 What springs can I put on without pulling the heads? AAre stock replacement springs fine? I have the 068 cam with HS 1:65 roller rockers.So the lift with 1:5 rockers is 407, 408 so I am not sure what it is with the 1:65's. The head shop said they were fine I guess maybe they were wrong,What kind or RPM should this run to? Thanks, Mr-B

herdsman · 07-08-2001, 06:26 PM

OMT, I just ordered the MSD6AL for my 65, the HEI kit comes with 3000,6000,7000,8000 limit chips this is the first dealings with the msd for me and I am curious about your response about the miss fire problem and leaving out the limit chip,the reason that I ordered the msd is that I to have miss-fire problems on my car with stock HEI @ 5000 rpm any help on the msd that I can get is appreciated. Thanks Tom

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Ecclesiastes 9:11

goathead68 · 07-08-2001, 10:15 PM

mr B,
Is it breaking up, or does it feel like a surge? If you bring the car up to 5 grand with no load, what does it do? What secondary rods are you running the carb? Just a few more things for you to look at, or think about. When you recurve the distributor, go with a heavy and medium spring, this'll bring your total in at about 3000. Try fattening up the secondaries a bit. Make sure all your electrical connections are good. Check all the obvious things, then check 'em again. Fuel filters OK? Check the plugs-how's the color? Wires in good shape? Don't panic, just take your time.

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Ken

Old Man Taylor · 07-08-2001, 11:53 PM

Herdsman - Do not be concerned about the MSD6AL. The problem is the MSD spark plug wires, or any other wire that does not have a good termination. Usually replacing the coil wire will fix it. With a poor termination (which you cannot determine), the signal gets noisy and it looks like more spark pulses to the MSD. Mine was shutting off at 5200 when the chip was 6400. It worked fine with no chip, and it worked fine when I replaced the spark plug wires. I have not used MSD wires since that time.

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Jim

Mr-Bratt · 07-09-2001, 06:24 AM

goathead68 & anyone else.
Thanks for all the ideas. The carb is the (1407 ?) edelbrock 750 cfm, Stock parts in it.I will try changeing the weights again in the dist. But If I keep the car steady at around 3000 rpm then it seems to be surging, And at around 5000 it is still breaking up (Pulled the chip in the MSD 6al as per OMT )It seems that it still does it with no load on the motor as well. So still at a loss? I am starting to think I better do as others have said and change the valve springs? Thanks to all, Mr-B

tonyk · 07-09-2001, 07:23 AM

If it is surging,it is probably your carb.Check your plugs.As for the springs,you dont need to pull the heads.Use an air compressor with a spark plug fitting.For around $7 buy the lever type spring compressor.

Mr-Bratt · 07-09-2001, 08:23 PM

Hello again and thanks for all the input.... So here is where I'm at The shop that did the heads says they did a mistake on the math and didn't add for the 1:65 rockers ( & it seems HS run a little higher) so they said I probably don't have enough seat pressure. They said come and see them tomorrow (with reciept.. which I do have) and they will get me some new springs that will fit with no head work (at their cost)They say I should have about 110 #'s seat pressure for this set up ? what do you guys think? does that sound about right? They say I might not need the melling 46612,46613 double springs, I have a few other sets of heads and will be checking installed height on them (6X , 4X , #46 1969 ) just to see what difference they are from my 6X #4 (off of a 350) Will check them all out in the morning, I want to leave the heads on the car as the headers were the worst I have ever dealt with and have some stuff planned for the car on Saturday, So If all goes well I will have the new springs by Wed, And can start the job by Thurs or Fri and finish on Sat... So thanks for all the help and I hope this takes of the Prob. Mr-B

Blackcat · 07-11-2001, 12:23 AM

Um Brad, You owe me a cheezeburger! Make sure that you don't have coil bind with the 1:65's The hight has to be tall enough to keep this from happening.

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Gatomon
A car is cheaper than a girlfriend. Better than a wife. If it gives you trouble you can park it and forget about it!

Mr-Bratt · 07-11-2001, 12:33 AM

Blackcat... If this solves the Prob I owe you and a few others more than a burger. The shop is getting me some comp cam springs ( I think he said #998) & they said that these will work out great. Plus not charging me for them as it was thier error.Also said that coil bind shold not Be a problem & If I have any more trouble or need other springs it's on them, WHAT SERVICE!! Thanks again to all. I think I'm going to send a carb out to cliff and Go back to my Q-Jet soon as well. Thanks again to all, Mr-B

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