Need Engine Help

[72C10OK]

OK well here is the deal, I had my 350 rebuilt last year and it is "Supposed" to be a 383 stroker now. I just cannot get this sucker to run very good at all. I noticed it had a 350 damper and 350 flex plate on it and when trying to time it the vacuum advance would almost be hitting the tranny dipstick. I put the correct 400 items on it and now the vacuum advance hits the intake to get it to run. It has a MSD HEI distributor and was dropped in with piston 1 at tdc.

You can sit with it in park and will rev great and everything, but once you put it in gear it has hardly any power and tries to die. I have tried the timing from 10 btdc to 40 btdc and nothing seems to improve the way it performs.

It has a 600 manual choke holley and have also tried a 750 electric choke holley. Both carbs were tuned after being put on.

I am at a complete loss as to why this thing will just not perform. I have over 2k invested in the rebuild and don't want to give up on it till I have tried everything to get it right.

Any help would be greatly appreciated.

Thanks

[chevybuldr]

Are you sure that you have the distributor in right? How does it start? Hard or does it diesel when shut off? Maybe the cam timing is off.

[1968SWBBigBlock]

1-Check for vaccuum leaks (intake and carb are most common)
2- get a vaccum gague and follow the instructions on testing the engine - this will go along way towards identifing the condition of the internal part of the eng
3 - run a compression check on each cylinder - when you do this compare each plug to see if the engine is burning fuel even or if you have 1 or more bad cylinders
4 - if you switched to external balanced flex plate and damper something does not sound right - 400/383 is an external balanced motor the 350 is internal - you assembly (crank, rods, pistons, flexplate & damper should be a balanced assembly - you should speak with the engine builder to see how all of this was assembled before making this change.

[72C10OK]

It fires right up and no dieseling when I shut it off.

[72C10OK]

Ok no vacuum leaks. The rebuilder told me it was externally balanced, but he left the original stuff on because it was still good. LOL been doing alot of reading and don't think he really knew what he was doing. I'm starting to get the feeling I'm going to have to go back to square one and take it to someone who knows how to rebuild a engine right.

[72C10OK]

Ok did the compression test and every cylinder is at 151 to 153. Everything I have seen says between 125 and 160 and need to be within 5psi. So think my compression is pretty good.

Not sure what else it could be.

[cdowns]

before checking the timing did you actually put the number one cyl at TDC and check to see if the timing pointer and the timing marks lined up?

[72C10OK]

Yep it went in at TDC. Dropped in with no problems facing #1.

[fixit-p]

Are you getting full batt voltage at the dizzy no resistor or resistance wire.

[americanmusc1e]

Originally Posted by 72C10OK

Ok no vacuum leaks. The rebuilder told me it was externally balanced, but he left the original stuff on because it was still good. LOL been doing alot of reading and don't think he really knew what he was doing. I'm starting to get the feeling I'm going to have to go back to square one and take it to someone who knows how to rebuild a engine right.

you CANNOT use a 350 balancer and flywheel (internal balance) on an EXTERNALY BALANCED 383, scat and eagle do make internally balanced 4.75 stroke (383) cranks but i don't think you have an internally balanced engine

[americanmusc1e]

forgot to add,

you can balance an internally balanced engine but you don't have to, you HAVE TO balance an externally balanced engine

[My72BB]

Can't help on the balancing thing...but

I am confused on the timing issue...I don't know your whole situation as far as cam/carb/distrubutor mods...etc.

It sure sounds like you problems are ignition related...If you rotate distributor one way or the other and at max adjustment in one direction it "almost" runs good but cannot keep adjusting in the correct direction to get it running even better...Have you tried pulling distributor out and moving 1 tooth. You have a lot of adjustment in where you want your distributor to sit as long as you maintain firing order. I would really take a look at the firing order...Also, has there been any backfires through carb since you started new engine??? Meaning 180 degrees off...This might not be so good for your carb!

Do you have a confidence in how the timing chain was installed...If its off there is NO adjustment with the distributor that will help you out.

As far as balancer...This will not have anything to do with how it runs! It is really going to have a impact on how long it runs as this thing will come apart pretty quickly if you don't get that resolved 1st.

Just my $0.02

[cdowns]

Originally Posted by 72C10OK

Yep it went in at TDC. Dropped in with no problems facing #1.

didnt answer the question i asked

did you put the number one cyl at TDC then check to see if the timing tab and timing marks on the balancer lined up??// setting TDC with a piston stop is a pretty accurate way to do that

[72C10OK]

Yeah everything was lined up. #1 up and 0 on the tab lined up, dizzy went in facing #1.

Asked in another post about spark plugs.

Well my power wire going to the hei dizzy wasn't very good so replaced it and put in AC Delco R44TS Plugs gapped at .045 and truck it running like a champ now.

Thanks for all the help and suggestions guys. I really appreciate it