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455 Timing Question

  
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455 Timing Question

 
Freakytiki4u Freakytiki4u
New User | Posts: 8 | Joined: 05/10
Posted: 05/31/10
10:03 AM

I have a 1981 Trans Am with a newly rebuilt 455 in it. Initial timing is set to 12 degrees but under hard acceleration, or when the motor gets warmed up, the valves sound like they are going to come out of the engine. Any ideas? Can I idle the motor up a lil and advance the timing (without a timing light and see if it runs better under acceleration? I really don't want to hurt anything but I don't own a timing light.  

Pontiacman8 Pontiacman8
Moderator | Posts: 5771 | Joined: 02/08
Posted: 05/31/10
11:37 AM

Is the balancer new because if it is a old one it may be spun and that will give you a false timing reading.  
Engine builder,self taught auto body guy.
Horsepower sells engines and torque wins races

Pontiacman8
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Freakytiki4u Freakytiki4u
New User | Posts: 8 | Joined: 05/10
Posted: 05/31/10
12:42 PM

I am unsure as I purchased the car in its current state, having done none of the engine work myself. I would imagine the balancer to be new because of the extensive rebuilding of the power train but I could be wrong. When the car is cold, it runs great, no valve pinging at all, even under hard acceleration, but when it warms up, it pings badly.  

Pontiacman8 Pontiacman8
Moderator | Posts: 5771 | Joined: 02/08
Posted: 05/31/10
02:22 PM

Is it over heating?
What temperature is the engine running?  
Engine builder,self taught auto body guy.
Horsepower sells engines and torque wins races

Pontiacman8
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Freakytiki4u Freakytiki4u
New User | Posts: 8 | Joined: 05/10
Posted: 05/31/10
03:29 PM

When I first acquired the car it was running around 210 degrees F. I removed the 190 degree thermostat and installed a 160 degree and it gets to about 190 now. Not over heating.  

biggstepp biggstepp
User | Posts: 130 | Joined: 03/10
Posted: 05/31/10
07:38 PM

sounds like what i've been going thru, minus the pinging. i just bought a $25 timing lite, made a mark on the balancer at 36degrees, (2 1/8" for stock balancer) and checked it. my temp was around 210-220 on warm days, over the wknd i decided 2 bump it up, initial and total, now im almost at 20initial and 44total. runs a hair cooler power about the same, doesnt make sense, but no detonation or pinging. what octane gas do u run, if ur not running premium, that might be part of the problem when the engine is at temp. if temp isn't getting hot like it was, timing might be close, i had my timing set like your numbers but only run 93 octane.what heads do you have to determine your approximate compression ratio. sounds like your compression is high and running crummy gas  

Freakytiki4u Freakytiki4u
New User | Posts: 8 | Joined: 05/10
Posted: 06/01/10
11:06 AM

I always run highest octane possible and even added 108 Octane Booster. Still pings badly! Unsure of what heads but I'm trying to find out that info from the guy I bought the car from. Engine temp is lower now because I change to lower degree thermostat. I know how to change initial timing by rotating distributor but I do not know how to change total timing.  

biggstepp biggstepp
User | Posts: 130 | Joined: 03/10
Posted: 06/01/10
09:46 PM

that should change it as well, but without even a basic timing light who knows what even your initial timing is. if pinging is under acceleration, theres a good chance timing is too far advanced. disconnect and plug vacuum advance line, engine should still idle smooth. do you have a vacuum gauge? if so hook it up to constant vacuum, rotate distributor slightly til you have the highest vacuum reading. that will be your ideal start point. increase rpms and listen for detonation. if good reconnect vacuum advance and take it for a ride, put in 2nd and accelerate sharply but not to spin tires, listen for detonation, if still heard, turn timing down a hair until detonation isn't  heard. best bet is 2 buy a cheap timing light to see what your really at. the other possible cause would be your running really lean. hope this helps a lil more  

Pontiacman8 Pontiacman8
Moderator | Posts: 5771 | Joined: 02/08
Posted: 06/02/10
06:10 AM

+1  
Engine builder,self taught auto body guy.
Horsepower sells engines and torque wins races

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Pontiacman8 Pontiacman8
Moderator | Posts: 5771 | Joined: 02/08
Posted: 06/02/10
06:12 AM

To id the heads the casting number is on the center exhaust ports.  
Engine builder,self taught auto body guy.
Horsepower sells engines and torque wins races

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tuffnuff tuffnuff
Moderator | Posts: 2535 | Joined: 12/09
Posted: 06/02/10
08:32 AM

Icon QuoteFreakytiki4u:
I always run highest octane possible and even added 108 Octane Booster. Still pings badly! Unsure of what heads but I'm trying to find out that info from the guy I bought the car from. Engine temp is lower now because I change to lower degree thermostat. I know how to change initial timing by rotating distributor but I do not know how to change total timing.

Try this link, it will answer your HEI question with pics.

http://forums.highperformancepontiac.com/70/8193758/the-general-discussion/ok-total-timing-one-more-time/index.html

Grin  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

Opontee Opontee
Guru | Posts: 1422 | Joined: 07/09
Posted: 06/02/10
08:40 AM

Do you know what the cam spec's are? I aam thinking you might have to much (?) overlap and not bleeding enough cylinder pressure.  
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Freakytiki4u Freakytiki4u
New User | Posts: 8 | Joined: 05/10
Posted: 06/04/10
03:26 PM

I did manage to find out about the engine and internal parts. They are as follows.
• Engine – 1967 Catilina Vintage 455
• Heads – have been ported, new valves, Triple Angle Comp.
o Valve Job (Jaw-Cen), new seats, seals, springs and retainers and locks.
o Bore size is .40 over
• Pistons – Speed Pro Hypereutectic pistons
• New Soft Core Plugs
• Bores were heat & plate honed for new Moly Piston rings.
• Compression ration is 11:1
• Connecting rods have been reworked and polished
• Corners, pistons & rods were balanced, new rods & crank shaft bearings
• Cam, lifters, valve springs, retainers, timing chain & gears, intake manifold are Edelbrock Performer RPM.
• Carb – Edelbrock 850 CFM w/ electric choke
• Front and rear shocks are KYB
• Headers with Flow Master exhaust with H- Pipe
• Frame Connectors and traction ladder type bars
• Rear end is Posi Trac with 3:08 gear ratio

I did find in the Edlebrock book that came with the carb where the previous owner put the right jets in the carb so Im not sure how to stop the pinging from here. I use the best gas I can buy plus 108 octane Booster and it still pings bad when its at its normal temp of 190 degrees Fahrenheit.  

barneyformula barneyformula
Addict | Posts: 3304 | Joined: 01/07
Posted: 06/04/10
05:40 PM

You say you have 11:1 compression ratio, if that's true you will never get rid of the ping on pump gas even with octane booster. You need racing gas and nothing but. To run an iron headed engine on street pump gas (with a carb and distributor) you need a maximum of 9.5:1 CR. Anyone tells you different hasn't pulled a motor apart and found the ring lands in the pistons crushed, tops of the pistons looking like they were sandblasted, and the top 1/2 of the rod bearings and bottom half of the mains pounded out...YET!!!!
There is no magic potion or trick, it is simple, you need adequate octane for the compression ratio you are running or the engine will eventually detonate itself to death, even if you can't hear it, it's there pounding away at your expensive parts.
To start with, no 455's were built in 67. If you want to figure out what you have, you need to look for casting numbers and stamping numbers. On the block look next to the timing cover on the passenger side front of the block and at the rear next to the distributor. Post these numbers and we can ID it for you. On the heads, look on the top of the center exhaust port between the valve cover and the exhaust manifold or header, it's usually a 2 or 3 digit cast number.
The only ways to reduce your compression ratio is to either replace the cylinder heads with larger chamber iron heads (6X or 5C off a mid-late 70's 400 are popular and make decent power), replace the heads with Edelbrock aluminum heads (which will mean different headers) or rebuild the engine with dished pistons instead of flat-tops. The later iron heads are the lowest price option, the Edelbrocks are likely the most costly but you will make more power with them and replacing pistons means pulling the motor and a total teardown. This may not be what you wanted to hear but sometimes the cold, hard truth hurts and now you can make an informed decision.
Steve  
A little help... 'cause we don't all have to learn the hard way!

Brazil Brazil
Addict | Posts: 3892 | Joined: 06/09
Posted: 06/04/10
06:34 PM

For a clear explanation on timing, refer to this post:

http://forums.highperformancepontiac.com/70/8221033/the-general-discussion/initial-and-total-timing/index.html#8215781  

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