The motor in question is a 1974 350sbc. Recently, i replaced the head gaskets with newer gaskets sporting an EGR block off. After buttoning it all up, the motor didnt respond well with the original timing (marked on the distributor prior to removal) as it idles rough occaisionally missing. After retarding the timing via the distributor cap, the motor idled nicely but under hard acceleration would bogg out almost as though it were not receiving an adequete fuel supply. Again, let me express that these problems arose only AFTER the installation of head gaskets with EGR block offs!?! any ideas on what could potentially causing these symptoms? any and all help would be greatly appreciated. Diém
Even though it is some work I would be tempted to switch the gaskets out to some earlier style ones without the blockoffs. Being that it is the only thing you did diffferently than before????? Also check timing and fuel supply, you never know when you have had something apart. Later
No such thing as head gaskets with EGR passages, so I assume your are talking about intake gaskets? I would check for an intake vacuum leak first. And you need to set the timing correctly.... Put a vacuum gauge on the motor if you have it and see what it tells you.....
Firstly, thanks for the correction trannyman as i meant intake gasket but wrote head gaskets. secondly scrap, thanks for the redundant input; youve been no help. greaser, going back to intake gaskets without blockoffs solves nothing because i need the egr ports to be blocked off! The vacuum reads 20"Hg at idle, after retarding the timing via the distributor. So now it idles nicely, but at higher rpms the motor is laggish still. any valuable input is greatly appreciated. thanks. Diém
Since you only replaced the intake gaskets and the only thing you had to move was the gaskets and distributor I would start with the timing. Are you using a timing light and what are you setting the initial timing at? Double check the plug wires for the right firing order both at the cap and the plugs. You may also have had a gasket slip which could cause a vacuum leak.
Good stuff here. With it running and the air cleaner off (any open vacuum ports plugged), place your hand over the carb air horn. If the idle smooths out and picks up, you have a vacuum leak. If so, spray something like carb cleaner down the intake rails, base of the carb, etc. If that fails, think about the distributor being dropped in 1 tooth off. Bob
There is no such thing as an EGR block-off on a SBC intake gasket. I assume you are talking about the exhaust cross-over that is designed to heat the carb and prevent it from icing (along with other cold drivabilty issues). The intake gaskets have what is called a passage restrictor. You can completely block off the cross-over passage, but I wouldn't except for a race only application. I don't know if that helps you or not...
with 20" of vacuum at idle I wouldn't think you have a leak. If all you swapped was the gaskets you will probably still need to block off the egr valve. If it bogs on heavy acceleration and not light acceleration, If it's a 4bbl with vacuum secondaries, holley or q-jet it could be that the secondaries are opening to fast. Vacuum advance on distributor? checking initial with that hooked up to the wrong port could cause the timing to be way off at higher rpm. Also as a side note: I fixed my friends car that had almost the same problem. He had been working on it for months. Turns out he had an aftermarket distributor in the car that would actually retard the timing the faster the rpm got. Drove him nuts, the only way I found it was with a timing light with the dial on it.
Yea bob, just heard that trick with the carb spray a few days ago but havent tried it; just the same thank you. As for trannyman, you seem to be the only one with reliable knowledge and no signs of inconsideracy, much obliged. Loudpedal, really? you have the audacity to question my integrity over calling someone out on redundant input? you yourself simply told me useless 'historical info'; clearly youre opinion is just as useless. dont waste your time or mine with pointless trash talk via a public forum; im only here for mechanical advice.
Dude, Verbal Kint called you out, not me. Can you hit your ass with both hands? You are clueless. FUCK YOU.
As a student of all things mechanical myself I find I learn more when I talk less, listen more and check the attitude at the door. YMMV BTW someone "repeating" or agreeing with earlier advice is not "useless". Good Luck
Lot of misconceptions about what EGR does. It doesn't rob horsepower. Really no need to block it off, but if using aftermarket carburation/ignition, it probably isn't necessary, either. If using stock, emissions type carb and distributor, keep it, and be sure it's passages are clear and it's working properly. Basically, what it was used for was to dilute air fuel mixture, to prevent high combustion chamber temps, leading to detonation, on cars that were running on the edge of being "too lean" for emission control. In most cases, it only "came on" during low RPM, high load conditions, like cruising along the highway.
onebabydeparted<SCRIPT type=text/javascript> vbmenu_register("postmenu_4781597", true); </SCRIPT> You seem to have quite an attitude,I went back and looked at some of your other posts, same attitude in some of those. You do reliaze that a lot of time just replying ditto is to keep the thread on the first page and makes its easier to find and having multiple people agreeing should help you even more not less. You may get people telling you to try different things cause working on cars is not so cut and dried. I am assuming you are a youngin since you are a student. You have gotten some really good advice here, if you keep the attitude the advice will not be so good if you get any.
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