# upgrades to the 400ci



## ltcbear (Dec 7, 2011)

I'm proud new owner of a 69. The engine has been rebuilt about 4000 miles ago with excellent components. It is a YS block 9790071 bored .040 over #62 heads forged pistons, polished rods, stainless valves etc. Also has electronic ignition. Has stock Rochester 4 bbl and manifold. Don't think the carb has been rebuilt. I would like to do some cost effective upgrades to the engine (under $1000) and would appreciate some ideas. Not interested in racing, just a nice street machine.


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## Instg8ter (Sep 28, 2010)

if built right with the 62 heads it should be around 360-400 HP now depending on the cam choice, tell us the specs if you have them. A 2.5" dual exhaust with "X" pipe and RA manifolds will help wake it up and sound good. Get the carb and tuning dialed in. Find out what your rear gear is, may have a highway gear it it, but with the torque you should have it should still pin you back in your seat when you stand on it.


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## BearGFR (Aug 25, 2008)

That's almost exactly what the beast was before I started in on it 25 or so years ago...

The most common factory rear gear ratio in that year was 3.23:1. Inst8ter's right, if the motor's fresh and running good it's going to be plenty strong like it is. If it has the more common 'open' rear end then it's already soing to be severely 'traction challenged'.

Your biggest concern is going to be the heads. Those 62's with their chamber size and everything else "nominal" for Pontiacs is going to put you right at 9.9:1 compression. The standard cam in the YS didn't have a whole lot of seat to seat timing, so it's going to be a struggle to keep it from detonating and destroying itself on any readily available pump gas today.

$1000 isn't a lot to work with to try to correct that. You said it was rebuilt 4000 miles ago. Do you have details on exactly which rods and pistons were used? Which head gaskets? That would help...

Assuming for the moment that everything is "stock", your first priority needs to be on "upgrades" that will help keep the engine from destroying itself on today's gas.
The cheapest most direct path for you (again assuming everything is stock) would be as follows:
1) dished pistons to drop static compression down to less than 9.5:1
2) forged aftermarket rods (factory rods have always been the weak link)
3) a little "more" cam (including lifters, springs, etc, 7/16" rocker studs, poly-locks) but don't go crazy
4) good exhaust (repro ram air manifolds or headers, depending on your tolerance for pain )

None of the so called "high performance" aftermarket manifolds or carburetors will perform as well as what you already have, so don't waste money on them. If the carb is the original carb, you should find #7029268 stamped on the side.

Again, all of that was with the assumption that all your stuff is stock. Can you give us more detail on the engine build?

Bear


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## ltcbear (Dec 7, 2011)

I appreciate the input. I'm a novice eager to learn. I'll tell you what I know, but there's a few things I'm not sure about. The original build list from 2002 goes like this: YS Block bored .040 over, #62 heads(pocket ported), cast four barrel intake, forged pistons, polished rods, stainless valves, ARP head bolts, ARP intake bolts, crane push rods, solid crower cam, solid crower lifters, crower springs, new cam and engine bearings, new piston pins, screw in studs, erson full roller roller(fulcrum & tip) rockers with a 1.65 ratio, edelbrock true dual roller timing chain, crane retainers, high volume oil pump, carter street super pump, MSD pro-billet distributor, MSD 6AL ignition box w/rev limiter, MSD super conductor plkug wires, MSD blaster 2 coil, bosch platinum dpark plugs, windage tray that has been modified for improved oil flow, chrome high profile Moroso valve covers, Chrome Moroso air cleaner. The compression ratio at that time was 9.75:1.

This was the engine as delivered to the owner previous to the guy I bought the car from. The guy I bought the car from who owned it for 10 years said there was a problem with the oil pressure that had to do with some screws or plugs on the back of the engine. Anyway, he had the engine gone through shortly after he bought it and had hydraulic lifters put in and the cam replaced, new bearings and I guess whatever they felt it needed at the time. This is where I'm in a gray area. He can't find the paperwork on that engine work and is a little foggy on exactly what was done. He did say he wished he had gotten an upgraded intake manifold and maybe a new carberator and air cleaner set up.

Overall I am happy with the car. If I can figure out how to post a picture I'll do so later. It has flow master exhaust system that sounds awesome, and the engine runs well. I'm feeling a little miss when I'm cruising, but I suspect that may be timing. It's hard to start when cold. Takes a lot of pumping. Don't know what I've got for rear gear ratio. It is posi-traction, but there's no tag on it anywhere.

By the way, Bear I loved that picture of you and your son with the engine which was a thing of beauty.


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## Instg8ter (Sep 28, 2010)

sounds like you have all the right parts and at 9:75/1 should feed it 94 octane. cam card would help determine what the HP and Torque are and define where it comes on in the power band. is the idle choppy or smooth? i would start with timing, carb (quadrajet may need a re-build) and tuning and go from there. After that if its still not as peppy as you like. Cam will be the biggest upgrade to change the attitude of the engine.


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## ALKYGTO (Mar 29, 2010)

:agree , might also look into a torque converter upgrade if you're running an automatic. I also say if it ain't broke, don't fix it. If the rods are polished and have good bolts they'll probably be fine as long as you keep the rev's under 5500. You might also want to check the valvesprings and see if they are still viable....


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## MITYGTO (Jun 10, 2011)

Solid lifter cams are typically pretty stout. Cam specs as already mentioned would be helpful. You may have way more cam than the heads and exhaust manifolds can support. Not going to be able to upgrade heads and stay in budget. I would agree that a gear change will give you the most bang for the buck. As already suggested, start by having the carb rebuilt and tune the motor. At 9.75 to 1 you are in detonation country on pump gas when tuned to factory specs. Is this a daily driver? Octane booster may help as well. Detonation can be both audible and inaudible so be careful here.


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## ltcbear (Dec 7, 2011)

Thanks again for the input/comments. Some of the questions I can't answer yet, but I'll fill in what I know. Once I get it started, it seems to idle smooth. It's not a daily driver. It's a fair weather driver. As for the cam, exact info on pistons and rods, I have to do some more research. The previous owner's wife is in the hospital so I don't want to bug him right now. My mechanic brother said the rear end gears felt like maybe 3.5's. 

As for the carburetor, I'm having a little trouble deciphering the code stamped on it. The numbers are 17054905 and then 2676 under that. If I'm reading it right it's a 1976-79 model for a Chevrolet with manual tranny built on the 267th day of 1976, but I'm confused with the "49". So the carbueretor may be a good starting point. I've picked Jim Hand's book on building max performance Pontiac V-8's and asked for a couple of more for Christmas to try to get a little better educated. I'm open to any other recommended reading ideas.:confused


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## Instg8ter (Sep 28, 2010)

also a good book on re-building the rochester if you are gonna tackle it yourself, or you can send it out to cliff rugles (who i think wrote the book) or another competent shop. That will be money well spent in either case and should tell you where you stand with he motor once you get it back on and set the timing correctly. If you have a rough idle your cam may not come on til later in the powerband 2000-2500 rpm and pull up to 6000 n wich case your foots too light....


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