I have a distinct blow on the left bank exhaust pipe on a ‘74 Olds 455 ci.
The engine was rebuilt with .040 forged pistons, Erson high lift/duration roller cam with hydraulic lifters, Edelbrock heads, intake manifold and 750 c.f.m. carb.
Here’s what I checked out:
Cyl. Compression is 183- 197 psi.
New plugs installed
Checked 3 times the firing order with a Erson cam 7-4 swap. (counterclockwise rot.)
Switched out plug wire one at a time and checked for spark.
Checked ign. Timing from 4 deg BTDC to 22 deg BTDC. Runs best at 11 deg BTDC
No pre ignition problems with 93 Octane fuel.
Engine idle vacuum is between 13.5 and 14 inches of mercury (800 rpm).
No apparent vacuum leaks.
What to do next?
Remove left valve cover and check gapping for hydraulic lifters. (scorpion lifters)
Maybe a very tite valve guide is causing an exhaust valve to close slower.
Change out engine oil with Mobil 1 synthetic 10w-30.
Inspect valves with a scope thru the spark plug holes?
Check cyl. Exhaust port temps and compare. Look for higher temp than normal??
What else can I check before I remove the head?
Is it possible one exhaust cam lobe may be slightly off?

 

I don't understand your question. Blow-by is exhaust gasses "blowing by" the rings. The actual result is pressure build up in the block leading to smoking and/or blowing oil out of orifaces overcoming the PCV system.

A better description of symptoms please.

 

Have you done a compression test or a cylinder leak down test yet?

 

I have done a compression test as indicated. How do I perform a leak down test?
I am familiar with the term blow by past worn or broken piston rings. I indicated a blow by symptom at the left exhaust pipe, unconnected to the right exhaust pipe. I do not get the blow by sound from the right bank exhaust pipe. Does that clarify what I have tried to describe above? The idle otherwise sounds like a cam with considerable overlap. I cannot tell if the cylinders are performing at idle as they should except for the sound coming out of the left exhaust pipe. I do know that when I floor the throttle the engine has great acceleration/torque and the engine exhaust sounds like all cylinders are firing in proper sequence.

 

So your saying you have a miss in the left bank? You are sure your ign wires are setup for a 4/7 swap

 

Oops, sorry. I didn't see that you had good compression. I guess I'm blind.

If you decide to do a leak down test it will identify a bad intake/exhaust valve or rings. Here's a tool you can sometimes rent from a local auto parts store:


As Eric said though, you need to make sure your ignition is setup properly.

 

I indicated I checked 3 times for firing sequence to the cylinders for the Erson 7-4 swap or a 4-7 swap which ever comes first... (just jok'in). I think I've got it right. Thanks

 

With the engine running remove each spark plug wire and observe if there is a change in the way the engine runs. All cylinders should act the same with its wire removed.

 

If your only problem is an odd sound from the left exhaust pipe at idle then check under the car for exhaust leaks. Do you have an X pipe?

 

Exhaust pipes are not connected in any fashion. Mondello SS exhaust headers bolted and gasketed to 3 inch pipes with matching mufflers. No leaks.
I did the spark plug wire unhook routine with noticeable engine sound and shaking on all cylinders. I can do this test again to make sure there is not a slight change from one unhooked left bank cylinder to the other. Spark plug tips on left bank varied from clean tan to sooty black. No oil smoking on de acceleration. I plan to change out the Edelbrock quad with a 750 cfm holley double pumper. I'm not happy with engine pause and cutout from idle when I accelerate from a stoplight. It's like the engine is fuel starved until the secondary venturis open up. Very hard cranking to get it started when left overnite. It's like the carb drains completely dry... This is another problem to figure out!
I can send a movie with sound with my I-phone if I have an email address?

 

You can post a video on here.

 

I doubt what you're hearing is blow-by past the rings with those compression numbers being so close. The fact that the spark plugs are tan to sooty black tells me you have a dead cylinder. This is assuming you aren't sucking oil from a vacuum leak.
Do this simple test. Get yourself a cheap test light. The one with a ground clamp and a pointy probe with a light in it. The light is not important for this test. With the engine running ground the clamp and stab each spark plug wire boot that is on top of the distributor so that you contact the brass end of the wire. Each time you ground a wire there should be a noticeable drop in RPM and a rough idle noticed. If you don't notice anything on any wire you've found the culprit. So either the wire or the plug is bad in some way. It could also be inside the distributor but that is less likely. Good to check it anyway (cracked cap, carbon trailing, etc.) I'd be looking at that sooty plug, it's suspect.

 

post a sound clip of the engine and exhaust pipes
re check spark to each cylinder
possible leak down test to come prior to removing the left valve cover.

I'll be back...thanks guys!!

 

I bought this car in 11/2010 out of Orlando, Fl and I wound up doing a complete frame off rebuild including warming up a 74 Toronado 455. I've got thousands of picts. which will be another story....I digress.
I have a Melling hi vol. oil pump and a Summit Racing HEI distributor with a soft steel cam gear due to the Erson soft steel roller cam with lots of lift and duration.
Last suggestion was do a leak down test on each cyl. and no. 7 and 6 were the leakiest (the other 6 were 4-5%), and it was clear the new rings on 7 & 6 have not fully seated (compression tests keep indicating improved seating is occurring on all cyl as the engine breaks in).
I reset the lifter clearances on all 16 to 0 lash plus 1 half turn back off.

The brand new Edelbrock 4 barrel (bought in 2014)750cfm carb caused a serious fire way back when (remember this is a 7 year rebuild) due to floats sticking to the bottom due to fuel alcohol evaporation leaving water and corrosion at the bottom of both float chambers.
So, I have also replaced ign wires with new Taylor wires and I completely disassembled the Summit HEI distrib. I barely got the dist. out of the engine due to a very thin hard steel thrust washer in contact with the dist. gear, was completely worn out and came apart and jammed up the dist. as I tried to pull it out of the engine. Apparently the hi vol oil pump causes enough torque to force the distrib. gear upward with such pressure that the thrust washer literally wore out with just a couple hundred miles if that much.

Question: What's going on with my set up and do I need to find a distrib with a different type of thrust bearing above the distrib. gear??
I have 7 years of experience with this rebuild and I would do a lot of things differently starting with the purchase of this particular 69 442 Convert. It's beautiful and gets up and goes... boy.... what a project!! (time + $$$)

 

Get with cutlassefi, Mark, through a pm. He can help determine your distributor gear needs. Its what he does...
https://classicoldsmobile.com/forums...utlassefi.html

 

cutlassefi says:
try a different carb
distributor magnetic pickup setup change out

I have a holly double pumper I will setup.
The Summit blue print HEI does not fit a 455 properly, and I will deal with Summit on this issue. Solution?? I'll try a rebuilt 455 dist. from Cardone, points coil and all....and see if the dist. will not drift off advance setting (actual rotation in the block with clamp locked down) I'll swap out points with whatever you guys recommend if this distrib. works.
I have a Erson roller cam with a hi vol. Melling oil pump running 40 to 60 psi @ operating temp. Which dist. gear ya'all recommend. I have the .040 dia. hole in plug.
I installed an expensive vacuum pump to get 16 inches of mercury to operate the SSBC 4 wheel discs. Engine puts out 13 - 14 inches. The brakes are still weak and I can't do a panic stop (15 inch rims). (yes, I've plugged up all vacuum outlets for the measurement)
Anybody want to see the specs. on my installed roller cam? What's been your experience with distrib drift and thrust shim complete destruction with your olds 455? Cutlassefi have talked these issues out with me.....good advice...just asking ya'all..Thanx

 

Comparing the Summit HEI to a remanufactured points distrib. shows the Summit HEI to be 1/8th inch less dia at the clamp down flange and 1/16 inch less thick. also, the bottom end shaft is +1/8th inch longer from bottom gear to base of distrib. body. This extra length at the bottom end may cause the extreme pressure of the gear rubbing against the steel thrust washer causing it to completely disintegrate and jamb up the extraction of the Summit HEI when I first started my investigation.
I'll insert the points distrib and see if it locks down and appears to fit.

MSD components can be faulty and I'll want something better than points. Is there a trustworthy ignition system that's proven most trustworthy?

 

Did you explain to Mark you have a roller cam and were wanting to know which distributor gear to use?

 

Need to know more about the brakes, if you want them fixed. Vacuum is not usually the problem when you can't lock up the brakes. If you have a brake pressure gage you might want to check the pressure out of the master cylinder at full pressure.

In the old days, before power brakes, you could slam on the brakes and lock up the tires. People focus way to much on how much vacuum they have for the "power brakes"

Also if you did not get a big boost in vacuum to over 20 inches, with the addition of the electric you have a problem in the booster, or the pump, or how its connected in.

 

I have a SSBC master cyl hooked up to their 7 inch dual diaphragm booster and ssbc discs all around. Real good braking at 60 to 70 mph but seems really weak coming to a stop. I'll check the vacuum from the unit. I have not checked the hydraulic pressure.... don't have a gauge or the hookups.

On another subject, I'm sending back the Summit HEI distributor and got a refund on both the original 2013 installation and the new and unused. I'm going to use the original factory points distributor and convert to Pertronix Ignitor III Ignition system and a Flame Thrower III oil filled canister coil.
Cutlassefi discussed the conversion and did not recommend Pertronix setup.
He recommended the Crane bronze aluminum distributor gear for the roller cam and that's what I ordered. I would not recommend anyone buy the Summit HEI distributor after my experiences with my 455.

I am pleased with Summit's customer service. I got credit for both distributors, so I went with what they recommended for the conversion from points to digital.