I have a 1969 pontiac 400 w code block. I am building a low buck rod...looooow buck. Do i have to have the heads redone to run on pump gas? .....im not building a show winner or a race car
when i had mine redone (i did 3 of them) i had the heads done and i think all he did was harden the valve seating. its no big deal i bet you could get by without it reallly.
If the engine is older and the valve seats are already run on leaded gas then switching to unleaded usually doesn't hurt them because they are already work hardened from running. Its usually new seats that burn out on unleaded if they weren't hardened. You may want to watch the compression ratio, though, to avoid pinging.
Exactly, I used to run a high compression stock 400 with 93 octane and thing would ping like crazy in the summer time heat. You can solve alot of that with timing, but not all of it. If you have high compression heads (1970 or earlier) you might run into this problem. If you can find 4x or 6x heads, that will drop the compression. Do a search, there are Pontiac engine calculators online that will show you compression ratios of different year block and head combos.
Be mindful when buying the mid '70s 4X and 6X heads that, depending on whether they originally came on a 400 or 455, they were machined to different values at the factory, i.e. a pair that were originally on a 455 may have larger chamber volumes than a pair that came on a 400.
The answer is that it depends on several factors. There is no "W-code" block. Get the 2-letter code off the front of the block below the passenger cylinder head, the 4 digit/letter code by the distributor hole, and the number off of the heads which is more than likely cast in the center exhaust ports. That way we can tell what block, displacement , CR- etc. A mild compression motor will not require hardened exhaust seats if tuned properly, as many others have already stated. A 428 with domed pistons and #62 heads is on the strong side of 11.0-1.
Thanks for the advice guys, exactly what i was looking for..im sure im mistaken on the block code...i think one of the letters is W...i will check it out, i couldnt remember...lol...Thanks again... maybe have some pics up soon..
it's probably worth a few bucks to add the harden't valve seat--assuming it's not a super high milage engine on the brink of death already
I haven't heard of anyone induction hardening valve seats in the field. Doesn't mean it isn't done, I just never heard of anyone, short of the manufacturers, doing it. Adding inserts, but not hardening the actual seats. Exhausts need hardened seats more than intakes, and a lot of builders add the hardened seats to them only. If you're not going to grind unhardened seats that have been run on leaded fuel, you're probably safe running unleaded, at least for a while. If you're doing a full on valve grind, adding hardened seat inserts will definitely reduce or eliminate seat pounding and recession. All of this is provided you run a low enough static compression, high enough octane, and adjust the timing to prevent detonation. Factory Pontiacs used nothing higher than flat top pistons to promote frame travel and produce the best power, adjusting compression ratio for a particular year and displacement by varying chamber volume, piston dish or lack of, and the size and depth of valve clearance eye brows. If you're on a budget (everyone is except the government these days) and working on a Pontiac, get yourself a copy of Jim Hand's book. Without doubt, the biggest bang for your buck of anything spent to put your Pontiac powered car together.
I thought all you guys knew the hardened seat thing w/ unleaded gas was a myth started by the tooth fairy....
Hey guys, just went out to the garage and blew the dust off the old 400 and turns out the block code is YB (Told you it was a W lol. Under the block code is the stamped numbers 102727. The heads have GM on one exhast port, the middle ports say 4 and 5 upside down (unless you stand on your head) and the other port has a G on it. Might not be looking in the right spot but i was freezing my cubes off. Again...this is awesome. Thanks guys, im gonna check out the links provided. Double checked again, i checked on it when i bought it like 5 years ago and everything i can tell shows its a 1969 265hp 2bbl 400ci. idk....i really want to just freshen up the gaskets and run it.....i have a 46 chevy truck (cab) that i want to put together just so i can get my fix. I have a Bagged pickup already but no more high dollar builds for awhile...Getting married soon so that's where all the real cash is goin'. I just need somthing to grind on....Finished projects just arent as fun as the ones in my head.
According to the Wallace site, 45 heads were '69 pontiac 400's with 1.96 intake valves, 1.66 exhausts and an 8.6 compression ratio. I'm running a pair of 46's which are almost the same as yours [69, 400] but have 10 to one C.R.
8.6 compression ratio sounds pretty low.....thus making me think that the motor would run pretty well on the unleaded stuff. Assuming its in good running condition otherwise, which i believe it to be. Probably going to start tearing it down for fresh gaskets and a good inspection.
are the heads 990 castings? I'm running a 55 Nailhead on pump gas and I've never done anything to the heads...four full summers so far.
I had a 64 imperial with 413 i ran 94 octaine when it could be found. also i used lead replacement treatment in it at least every 2nd tankfull eventually went to lucas fuel treatment with upper cyl lube and it ran JUST FINE!
The good news is that it's definitley a 400 block. While it does have lo-po heads, you can improve performance easily and cheaply with a Summit house-brand cam, 4bbl intake, different factory heads, headers, etc., when the time comes. Practically any Pontiac head will bolt on, and if you're not hung up on numbers for the "good heads", you should be able to find some decent performers pretty cheaply as well. Factory 4-bbl intakes are great performers and they are cheap and readily available. One thing to note, is that the Pontiac used a nylon coated timing gear for noise reduction purposes on the lower performance 400s. You'll want to check and see if this one still does, because the nylon has this nasty little habit of chipping off and clogging the oil pump. Change the timing set and clean or replace the oil pump and pick-up.
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