Scott

Currently Texas requires testing going back 25 years. So your 1966 truck will only require safety inspection.

Your 89 Suburban will have to go on the chasis dyno for smog tests.

Jerry T

 

Really like your ride "Big Red"!! I'm building up the same kind of motor for my '84. '74 351w bored .030, Ported and polished '71 heads and a 270H Magnum cam.(Think it will have a nasty idle??) Roller rockers, all the good stuff. And a performer RPM with a #1407 750cfm carb. Basically was wondering what settings your running on your carb so I can have a basic idea of what i'll want to run.

Thanks!!

 

To: 1984_355w

I am running the stock calibration on the primaries and 1 stage rich on the secondaries.

Primaries: .113 Jets & #1453 Metering Rods
Secondaries: .110 Jets

I have a little stumble at about 5500 RPM on full acceleratoin that I think is a lean condition, and I think it may be that the original 5/16" fuel lines from the tank to the pump are too small.

I am using a new Holly 110GMH mechanical pump so I should not have a problem in that area.

I plan to change fuel tank to pump lines to 3/8" sometime soon.

I'm not sure about the 270H Magnum cam at idle. According to the Comp Cam book it says Mild Rough Idle.

One thing to watch for:
Compression Ratio. The stock pistons have a dish that must be deducted when calculating compression ratio. The heads that I used have a 69cc Combustion Chamber so my compression ratio ended up at 9:1.

I'm not sure about the heads that you are using, but some of the 351W's had very low compressions ratios.

Jerry T

 

I have speed pro forged pistons and with my early heads ('71 extreme port and polish job) they said 9.6 to 1. I think the chambers are like 59.9 cc's.

Thanks!!

 

Do these pistons have a dish (pocket) or are they flat tops?

If they are flat tops you will probably be up at 10.5:1.

You will need to run 91 octane fuel at 9.6:1 compressions ratio. I started using 89 octane and about 3000 miles later it started dieseling on shut down - a sign of carbon build up on the pistons.

I switched to 91 octane and the dieseling stopped.

 

Sorry I was off a bit. They have 9.19 to 1 compression ratio with a 13 cc dish. (I think) Summit said they would be fine on 87 octane fuel.

Thanks for all the help

 

Evan
My engine is 9:1 and I have to run 91 or better. I think this is true for most carburated engines without any computer management to eliminate pre-ignition.

Most of the new engine computers have knock sensors, O2 sensors, etc to manage the air/fuel ratio to eliminate pre-ignition.

I think you will need to run at least 89 octane. Be careful about advancing the timing too far.

After you get some miles on the engine and if you get some dieseling on shut doen, then it's probably time to move up to 91.

Good luck with yout build-up.

Jerry

 

Ok, thanks Just want to let you know you've been a great help in my engine build-up and it is MUCH appreciated.

 

Just failed a Texas emissions test today - high CO on the high speed test. I've a '94 w/ 6 cyl 4.9. Had a problem with the EGR valve previously, surging, rough running, changed the valve but when I put on the old position sensor, I did not notice that the small rubber gasket stuck to the old valve body. Check engine light immediately on and it took me a while to figure it out. Installed a new positioning sensor which of course had a new gasket. Got the light out but failed the test - had always passed easily in years past. While I was trying to get the check engine light off, I changed the O2 sensor, so it is new. Got a new EGR valve and new positioning sensor, also a new idle control valve. Cleaned the throttle body. Can't figure out what may be causing the high reading, and I do still have a rough idle and surge on acceleration, but nothing like before. I guess I'm going to try the changing oil and air filter, then test again. Can't imagine though what an oil change would do to reduce high CO.

 

Welcome to FTE.

You can/should start a new thread, not add to one that is 9 years old....

High CO--since the cat is supposed to change C0 into CO2, I suspect you have cat issues. Any reason to believe the cat was damaged or poisoned?

Do you have a readout from an old test? Maybe it was high but passable, and is now over the limit?

What about HC? How did it do there?

What else do they check, and did they give you a readout?

 

Hey 85e... Thanks for your reply. I am kinda new to FTE, haven't figured out how to post a new thread. I assume by "cat" you are referring to the catalytic converter, yes?
Will a faulty cat make the acceleration surge and turn on the check engine light after a few miles? Always had passing figures before, drove the vehicle quite a while with a bad EGR valve, possible screwed up the cat, is that likely?

 

Cat = catalytic converter.

A clogged or partially melted cat could cause those troubles.

Not sure if a bad EGR would lead to that--EGR is used to reduce combustion temps, which in turn cuts down on oxides of nitrogen. If the EGR problem caused misfires or a rich mixture that could have overheated the cat, that will cause the partial meltdown and clogging.

Do you have an oxygen sensor AFTER the cat?

This talks about how to check pressure, vacuum and temp to see what's happening with the cat:

How can I tell if my catalytic converter is... — Yahoo! Autos

 

There is an O2 sensor right before the cat, which I have replaced, and then there is a pipe connected to the exhaust pipe between the cat and the resonator that runs up toward the engine - is that the pipe that goes to the EGR valve? Anyway. there are two pipes running from the engine exhaust to the cat, then a pipe to the resonator (I think it's the resonator). That's all one piece - very expensive. Is it possible to just cut the old cat out of the system and clamp in a new one without replacing that whole piece?

I've got the truck in a shop that says they can connect it to an engine analyzer to tell if the cat is clogged or if something else is causing all the problems.

My problems started when the truck started running rough, surging on acceleration, and the check engine light came on periodically. All those symptoms said EGR valve so I replaced it. Ran a little better but the check engine light still came on now and then. I changed the O2 sensor and the idle air control valve. Better running but still some surging and check engine light. That's where I am now.

Emissions test data: (my reading/standard)

High speed HC 54/220 Pass
CO 1.3/1.2 Fail
CO2 13.2
O2 .4

Low speed HC 204/220 Pass
CO .36/1.2 Pass
CO2 14.4
O2 .5

NOx on both tests was 0.00

Sounds like you know what you're talking about with this truck - I sure appreciate your advice. This is a work truck for me and I hate to shell out big bucks for repairs that I can do myself, although replacing that cat looks like a knuckle-busting job.

 

You are so close on the CO, can't think of anything right now, gotta head out in a few min. for work.

Your cat can't be "dead" with those numbers. Something is just a little off methinks.

 

Check for vacuum leaks, check for pcv function.

This thing have air injection? Check that.