help with new 383 stroker issue

[88Stanger]

sorry it is a bit long.....

background: 383 eagle specialties stroker kit -
5.7 i-beam rods
new crank
floating pin pistons with 12cc dish/valve reliefs
block .040 overbore
block clearance for stroker motor
Edelbrock head gasket - 4.125 bore with .041 compressed thickness
Edelbrock aluminum RPM heads with 70cc
Edelbrock aluminum RPM air-gap intake
large try y headers
Howards full roller cam and lifters
219 degrees @ .050 = intake
225 degrees @ .050 = exhaust
525 lift
106 intake lob centerline
110 separation
Fitech 600hp power adder system with FCC
full MSD new ignition, billet dist., coil, wires, and MSD6AL box
should be about static compression ratio = 10.0 to 1
initial timing set to 14 degrees
compression check = all 8 cylinders avg 190lbs

issue: starts and idles, but if you stab the gas pedal it pukes up and out the carb. i have removed the MSD and replaced with 1 wire HEI, still did it, removed the FI-Tech system and installed a 600cfm carb and it still did it. i Called Howards and talked with them on it and they suggested that the cam is too small and could be the cause of very high compression numbers (190lbs) and this with the smaller duration causing the higher compression and then forcing a backfiring up and out the carb.
Does this make any sense to anyone?!?!
any help is greatly appreciated!!
sorry this is so long.

[88Stanger]

suggested new cam from Howard's = Howard's 110325-10
225 intake @ .050 duration
233 exhaust @ .050 duration
.530 lift

[AussieinNC]

mmm...drop the exhaust pipes off at the manifolds and try the "stab the gas" again...if it runs fine then, go check the muffler for blockage...

I have seen this in person when the cat or muffler is partially blocked...

[67 chevelle]

try pulling some timing out , 10 initial , maxing at 34 degrees at 3000 rpm

[KQQL IT]

Less timing won't help. Double check 5 - 7 wires aren't crossed easy to do and give weird run problems.

Afr meter and see if it is going lean

My 400 wanted a bigger accelerator pump cam

[88Stanger]

Originally Posted by AussieinNC

mmm...drop the exhaust pipes off at the manifolds and try the "stab the gas" again...if it runs fine then, go check the muffler for blockage...

I have seen this in person when the cat or muffler is partially blocked...

Appreciate the thought, to be honest the exhaust out tontips is all new also and it is breathing.
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[88Stanger]

Originally Posted by 67 chevelle

try pulling some timing out , 10 initial , maxing at 34 degrees at 3000 rpm

Good idea. I'll try anything at this point.
Posted via Mobile Device

[88Stanger]

Originally Posted by KQQL IT

Less timing won't help. Double check 5 - 7 wires aren't crossed easy to do and give weird run problems.

Afr meter and see if it is going lean

My 400 wanted a bigger accelerator pump cam

I had a buddy check my wires just to make sure I was not mistaken, all is good there.

AFR is a good idea though. Fitech has one built in but that could be off.
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[randy500]

Quit stabbing the throttle with no load it proves nothing. Have you driven it to see how it performs?
What is your base and total timing
Are you using vacuum advance? Is it hooked to full or ported vac?
It sounds like a lean misfire or incorrect firing order
What exactly does puke out mean? Does gas fly out or does it pop through the

[randy500]

Check the firing order with this method...

1. Ignore the distributor and leave the cap on.
2. Number one cylinder is the front drivers side, remove the spark plug
3. With a helper you hold your finger tightly in the plug hole while the helper turns over the engine with a ratchet at the crank bolt.
4. When pressure builds on number one have the helper continue turning engine over until 8 degrees before TDC
5. Remove the distributor cap and determine which plug wire the rotor is pointing
6. Check firing order, distributor rotates clockwiise

A one person method to find TDC on number one is to attach a hose to a spark plug air pressure valve holder then you can turnover the engine with one hand while having your finger over the hose to feel pressure building in number 1 cylinder

[88Stanger]

Originally Posted by randy500

Quit stabbing the throttle with no load it proves nothing. Have you driven it to see how it performs?
What is your base and total timing
Are you using vacuum advance? Is it hooked to full or ported vac?
It sounds like a lean misfire or incorrect firing order
What exactly does puke out mean? Does gas fly out or does it pop through the

Stabbing the throttle as in hitting the throttle quickly.
Cannot drive it because of this problem.
Timing - 14 degree initial, 34 total
Vacuum advance connected to proper ported vacuum source
Firing order checked multiple times by multiple people
Puke - backfire up and out carb with fuel sometimes spitting out also.
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[randy500]

And BTW, that cam is not too small for the static compression ratio unless its very advanced which is highly unlikely, forget about the fatal flaws and do the basics like timing and firing order

[randy500]

Could an intake valve be slightly open which would introduce flame to the intake and cause a backfire?
Check this with a vacuum gauge at idle the gauge should be steady, if it fluctuates quickly then an intake valve is open. Make sure the gauge you use is not highly dampened, some gauges have a tiny hole which restricts vacuum and smooths the gauge reading, I have a sun vac gauge that is useless as it has a hole which is about .010 in diameter or smaller, its tiny

[randy500]

Originally Posted by 88Stanger

Stabbing the throttle as in hitting the throttle quickly.
Cannot drive it because of this problem.
Timing - 14 degree initial, 34 total
Vacuum advance connected to proper ported vacuum source
Firing order checked multiple times by multiple people
Puke - backfire up and out carb with fuel sometimes spitting out also.
Posted via Mobile Device

Ported vacuum is actually and emissions thing, disconnect it and see how it acts, usually it doesn't matter but it can.
Check the firing order with the exact method I wrote otherwise you don't know if it's right or not. Just because multiple people checked it doesn't mean it right, do it yourself with the method I wrote and YOU will know for sure it's right.
The vac gauge test will be informative too and is a must,

I just had this same problem with my son, he changed the head on his Toyota with little guidance...ran like crap with intake popping, it had a valve open, he didn't adjust the valves after the head gasket change.

Stick with the basics
Fuel
Air
Compression
Timing

What about voltage to the coil, are you still using the factory resistance wire.

[88Stanger]

Originally Posted by randy500

Check the firing order with this method...

1. Ignore the distributor and leave the cap on.
2. Number one cylinder is the front drivers side, remove the spark plug
3. With a helper you hold your finger tightly in the plug hole while the helper turns over the engine with a ratchet at the crank bolt.
4. When pressure builds on number one have the helper continue turning engine over until 8 degrees before TDC
5. Remove the distributor cap and determine which plug wire the rotor is pointing
6. Check firing order, distributor rotates clockwiise

A one person method to find TDC on number one is to attach a hose to a spark plug air pressure valve holder then you can turnover the engine with one hand while having your finger over the hose to feel pressure building in number 1 cylinder

I have a remote starter. So I have removed the spark plug from #1, using remote starter rotate engine and check #1. Done this. Also, take off valve cover and watch valves, as the intake valve closes, checked that also. Both slowed TDC is good.
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[88Stanger]

Originally Posted by randy500

And BTW, that cam is not too small for the static compression ratio unless its very advanced which is highly unlikely, forget about the fatal flaws and do the basics like timing and firing order

Agreed, but it seems all the "easy" or simple things have been tested that I know of, leaving me to ask here, otherwise I'm looking at the cam numbers. I am going to tear down the heads completely even though they are brand new and just check them for anything.
Posted via Mobile Device

[88Stanger]

[QUOTE=randy500;7977860]Could an intake valve be slightly open which would introduce flame to the intake and cause a backfire?
Check this with a vacuum gauge at idle the gauge should be steady, if it fluctuates quickly then an intake valve is open. Make sure the gauge you use is not highly dampened, some gauges have a tiny hole which restricts vacuum and smooths the gauge reading, I have a sun vac gauge that is useless as it has a hole which is about .010 in diameter or smaller

I have a brand new vacuum gauge without the hole that was registering very little movement. Steady as I know with maybe 1/2 lb difference, if that. It was low, 13 -14 lbs is all
Posted via Mobile Device

[88Stanger]

Originally Posted by randy500

Ported vacuum is actually and emissions thing, disconnect it and see how it acts, usually it doesn't matter but it can.
Check the firing order with the exact method I wrote otherwise you don't know if it's right or not. Just because multiple people checked it doesn't mean it right, do it yourself with the method I wrote and YOU will know for sure it's right.
The vac gauge test will be informative too and is a must,

I just had this same problem with my son, he changed the head on his Toyota with little guidance...ran like crap with intake popping, it had a valve open, he didn't adjust the valves after the head gasket change.

Stick with the basics
Fuel
Air
Compression
Timing

What about voltage to the coil, are you still using the factory resistance wire.

Posted via Mobile Device

[88Stanger]

Originally Posted by randy500

Ported vacuum is actually and emissions thing, disconnect it and see how it acts, usually it doesn't matter but it can.
Check the firing order with the exact method I wrote otherwise you don't know if it's right or not. Just because multiple people checked it doesn't mean it right, do it yourself with the method I wrote and YOU will know for sure it's right.
The vac gauge test will be informative too and is a must,

I just had this same problem with my son, he changed the head on his Toyota with little guidance...ran like crap with intake popping, it had a valve open, he didn't adjust the valves after the head gasket change.

Stick with the basics
Fuel
Air
Compression
Timing

What about voltage to the coil, are you still using the factory resistance wire.

Truck is complete rebuild from ground up. All new wiring,12v to the coil
I will do your idea for timing.
Posted via Mobile Device

[mikecaddy500]

are the pushrods the right length? if valves aren't closing all the way this will happen.

[geezer#99]

Have you confirmed timing tab/balancer is accurate using a piston stop?
How warmed up is your motor when you're wacking the throttle?
Where do you live in washington?

[HO455]

Is this a brand new engine build? Or did this issue just start happening?

[HO455]

Originally Posted by 88Stanger

Agreed, but it seems all the "easy" or simple things have been tested that I know of, leaving me to ask here, otherwise I'm looking at the cam numbers. I am going to tear down the heads completely even though they are brand new and just check them for anything.
Posted via Mobile Device

Before removing the heads I would pull the timing cover and verify your cam timing. At the same time check your push rod lengths. At this point it certainly sounds as if you have checked the basics. Did your camshaft get degreed when installed? It could be a mismachined keyway in the cam or the timing chain set.
Good luck

[88Stanger]

Originally Posted by mikecaddy500

are the pushrods the right length? if valves aren't closing all the way this will happen.

Talked with Howard's cams, they are comp cams 7.3 and Howard's agreed they are ok

[88Stanger]

Originally Posted by geezer#99

Have you confirmed timing tab/balancer is accurate using a piston stop?
How warmed up is your motor when you're wacking the throttle?
Where do you live in washington?

I have comfirmed that the timing tab is correct by doing a piston stop, also degreed in the cam to check all opening and closing numbers. All checked out perfectly.
Kennewick, Wa