First motor rebuild, need some solid advice, please help

[Fusion]

Hello, my name is Joe and I own a 1979 Trans Am, 4-speed, 400 engine with 6X heads. I bought it from a private buyer and I have driven it for 3 years. I am not exactly sure what is done to the motor, but I am assuming it has around 350-375 horse.
I plan on doing a motor rebuild this spring. I want to achieve somewhere in the neighborhood of 450-500 horsepower, while still being able to drive all day with no major overheating. It has 3.73 gears in the rear, a Centerforce II clutch, the frame is tied, and I have a super T-10(i think) 4 speed.
I know a fair bit about motors and whatnot, but I really need some advice on what parts to buy and match. Are there any good motor kits out there that would match up to my motor? I really didnt want to get new heads.

Here's my question: I was really hoping someone that knows a lot about this stuff could give me some advice on good cam/piston ring/piston/bore/etc parts. I think maybe over email or ICQ would be a good place, since we wouldnt have to clutter up this messageboard. I would really appreciate it if someone would reply or email me at ecke0048@tc.umn.edu or icq me at 6851742

Thanks a lot guys, you're the best
Joe (Fusion)



[This message has been edited by Fusion (edited 03-16-2000).]

[Fusion]

Hello, my name is Joe and I own a 1979 Trans Am, 4-speed, 400 engine with 6X heads. I bought it from a private buyer and I have driven it for 3 years. I am not exactly sure what is done to the motor, but I am assuming it has around 350-375 horse.
I plan on doing a motor rebuild this spring. I want to achieve somewhere in the neighborhood of 450-500 horsepower, while still being able to drive all day with no major overheating. It has 3.73 gears in the rear, a Centerforce II clutch, the frame is tied, and I have a super T-10(i think) 4 speed.
I know a fair bit about motors and whatnot, but I really need some advice on what parts to buy and match. Are there any good motor kits out there that would match up to my motor? I really didnt want to get new heads.

Here's my question: I was really hoping someone that knows a lot about this stuff could give me some advice on good cam/piston ring/piston/bore/etc parts. I think maybe over email or ICQ would be a good place, since we wouldnt have to clutter up this messageboard. I would really appreciate it if someone would reply or email me at ecke0048@tc.umn.edu or icq me at 6851742

Thanks a lot guys, you're the best
Joe (Fusion)



[This message has been edited by Fusion (edited 03-16-2000).]

[Will]

Joe, why not clutter up this board? That's what it's here for! ;-) You can achieve your goals with iron heads. If the engine in the car is original and it was originally a 4-speed car then you most likely have a W72 400 with the 6X-4 heads, but check the heads to be sure. The identifying "4" or "8" is stamped into a small machined pad just below the valvecover rail near the left end of the head as you view it from the exhaust side. If you have the 6X-4 heads for sure, then you can do a little milling on block & heads and get your compression ratio up into the 9:1 range which will allow you to choose a good cam. Get the heads street ported if that's in your budget and go with a cam that has between 222 and 230 duration @ .050" and get as much lift as you can. Make sure when the heads are being built that they are setup with long enough valves or that the spring seats are machined to allow the use of a good spring for high lifts (Comp Cams #995 spring is a good example). Using a cam at the small end of that range (222 - 224 duration) with 1.65 rockers and Rhodes lifters will make for a relatively tame engine that will really scream in the 2800-5800 RPM range. Plan the rest of your components around that RPM range and you'll be set. Unfortunately your manifold choices will be limited unless you want to bolt the shaker scoop to your hood. If you can find a Holley Street Dominator at a swap meet or from some other source that would probably be your best choice and you shouldn't have to modify the shaker scoop to use that manifold as it's stock height and accepts a Q-jet. As for engine kits, the standard TRW forged piston kit like what's available from Summit Racing is all you'll need (along with proper machine work) to achieve your performance goal. Good luck!

[Paul Spotts]

very good advice Will. The motor should be the TA 6.6 The blocks were casting #481988XX and are very good blocks. To add on what Will said - I would increase the exhaust valves to 1.77 with the port work. I have done several of these heads and they are as good as the older heads. The 4 speed will be tough to make the car hook up with street tires. Also keep the car at the factory height and leaf spring rate.

Also - a ported torker I will allow the shaker to fit. The torker I needs a lot of plenum work to allow mid range and top end with a Q-jet as the corners of the intake plemum are restrictive. I also increase both the heads and intake to RAIV port configuration.


[This message has been edited by Paul Spotts (edited 03-17-2000).]

[Fusion]

First off, thanks a lot for responding Will and Paul. Will, do you think I will lose power steering and brakes if I go too crazy on the cam? Also, what do you mean when you say a "tame engine" but will scream in the 2800-5800 rpm range? I guess I am probably looking for more on the 450 side of the horsepower range I stated. Also, just curiously, what would this cost me, considering I bought the car with the heads already ported and polished (don't know the exact specs /infopop/emoticons/icon_frown.gif ) One other thing, what do you think a 4 speed 1979 trans am with 3.73 gears and BFG street drag radials would run in the 1/4 mile with a good launch??


thanks again

Joe (Fusion)

[Will]

Fusion, yes, if you go "too crazy" on the cam, you'll lose enough vacuum to affect your power brakes unless you crank the idle way up, which causes other problems. The thing is, you should be shooting for a particular performance goal and not some imaginary horsepower number. Horsepower is only part of the equation, torque is where it's at with a Pontiac, and torque over a broad RPM range. What I meant by a tame engine is one that idles at 800 RPM or less with enough vacuum to run your power brakes and that won't rattle the fenders off. By "scream in the 2800-5800 RPM range" I meant an engine that makes enough power in that range to really push you back in the seat and put a permanent grin on your face as you slam through the gears. Low 13s or high 12s with that combo should not be too difficult IF you can get that good launch. Launching a 4-speed is tricky. My '72 Formula is running a Comp Xtreme 274 cam with Rhodes lifters (and still only pulls 12" vacuum at a "choppy" 800 RPM idle), lightly ported #13 heads on a dished-piston 400 (9.27:1 CR), Rhodes lifters, Performer intake (NOT the RPM, but I have a Street Dominator ready to go on), 800 Q-jet that's jetted too lean (another thing to be fixed next time out), headers, 2.5" Flowmaster exhaust, 3000 Coan stall, TH400 trans, and 3.23 rear gears. With really heavy 15x10 steel wheels on all four corners, 265/50-15 up front and 305/50-15 street radials out back and a total weight with me in the driver's seat of 3640 lbs I've so far run a best of 13.65 at 102.3 with a 2.1 sec. 60' in cool dry air. My best launch so far has netted a 2.0 60'. There's more in this combo and I really want to run in the low 13s on street tires with those 3.23 gears. With drag radials and your vastly superior gearing, you should be able to best me easily. I've had some simulations run on a dyno program and it looks like I would actually be better off as far as average torque production goes with a slightly smaller cam and the 1.65 rockers I mentioned, but you can probably get away with a larger cam since you have a 4-speed and steeper gears and take advantage of increased top-end power. Just don't go too big on the cam or you'll actually lose power. You should see if you can get those heads flow-tested. It's easy to screw up the flow on a Pontiac head if the porter doesn't know what he's doing and takes out too much material in the wrong places. Finally, as for cost, I really don't know. What condition is the engine in now? If it's strong and has good compression and ported heads and all that, then why rebuild it? What intake does it have, what exhaust? Have you tuned the distributor at all? What cam is in it (if you don't know, then how does it idle - what RPM and how much vacuum plus how "rough"). You might not need to do anything more than swap cams and maybe put an intake or good exhaust or whatever on it to get where you want to be.

[Fusion]

Ok, here's the lowdown. When I say I want about 450 horsepower, the reason I stated that value is because that i what i thought i would need to get my car into the 12's with street tires. Right now my car runs a 13.73@ 102.9mph with a 2.242 60' time with a decent start on my 295 60 R 15 BFG street drag radials. The heads are supposedly ported and polished, but to what extent, I have no idea, can I bring them to someone and have them tell me how much they are ported? I have no knowledge of my cam specs or vacuum, but I would venture to say that the idle is "medium" at about 900 rpm. I believe my carb is ****ty (800 cfm Holley), so i'll have to get a new one (any recommendations?), and if all possible I would like to not bore the motor out. The two main reasons I want to rebuild my motor are: to get into the 12's, and secondarily to stop it from puffing smoke at high rpm shifts(enough to be annoying and embarrassing) and thirdly so i can polish up the engine compartment and rewire some stuff. So I figured I would at bare minimum put new rings in, and a little wilder cam. How much compression should I have? You are right I really don't care about the exact horsepower number, just the times. I want the car to be streetable as well. And to answer your other questions, yes the distributor is tuned, it has 3" hooker comp headers leading to full 3" duals and flow-through mufflers, with an edelbrock aluminum intake (i think performer). How much (roughly) horsepower does a 1979 trans am with street tires, 4-speed and 3.73 gears need to get into the 12's? If I do need the heads ported, how much does a decent port job cost? Sorry to bombard you with all these questions, I just need some guidance to get this Pontiac where it belongs, out on the street kicking some Chevy ass.


thanks

Joe (Fusion)

[slobrd]

By all means go with a wider lobe seperation cam. My experience is that the variable duration lifters are almost a sure bet when going for the 12's with your combination. My sugestion for the cam is a lobe seperation of 112 at least. When Taylor put together the 500 horse 400 in a recent article I read, the cam was on a 112 LSA. This will even out your idle somewhat as compared to a tighter lobe seperation but it will keep you moving strong at the end of the track. The summit grind 224 243 on a 114 seperation sounds perfect but I personally don't go for the low dollar units. I figure there isn't a good reason to buy a cheap cam if you want to run in the 12's.
Pontiac saw great success with the 068 in the 400's with deep gears. But to get you desired performance I'd try to mimic the effective duration of the 068 cam at idle. At idle using the rhoads lifters (10 to 12 degrees less than the cam is rated at). This will magnify the operating range of the cam. On top of the effect of wide lobe seperation you'll effectively have more cam at the end of the track because of the increased duration effect of the lifters and still have the necessary low end to get the car moving.

[Will]

Joe, you are actually pretty close to where you want to be. Your MPH is good but your 60' times are too high. If you can get those 60' times down to 2.0 or less, you'll shave almost a half-second off your ET. Practice those launches! I know on my car I have to baby it off the line and then ease into the throttle to keep from blowing the tires off, but I still managed to cut a 2.0 sec. 60' on regular street radials (admittedly in the 305/50-15 size). As for what you need to do to make more power, a lot is going to depend on what you've got now. I really don't think an 068 or equivalent cam has enough duration to get you where you want to be. The 068 only has 212 @ .050" on the intake and you'll need at least 10 more degrees than that, if not 15 or 20. As Slobrd said, get a cam with a 112 lobe separation angle and run Rhoads lifters on it and you'll get a very broad power range with a good idle. The wider LSA will help extend your upper RPM power too. Ditch the Performer manifold, it's killing you above 5000. Go with one of the manifolds recommended above. The Performer RPM would be the best choice but you'll have to bolt your scoop to your hood since it's too tall. If you go through your engine to cure the smoking problems and get your heads checked out, then get the block zero decked and have the heads shaved down .060" and you'll end up with somewhere close to 9.5:1 compression, which should be plenty. I don't know what to say about your carb other than that it seems a bit big. Why do you believe it's bad? Maybe it just needs a rebuild. It's not a double-pumper is it? If I was you I'd start by freshening up the engine, finding out for sure whether your heads flow well or not (get them flow tested), put a different intake manifold on and change cams to something in the range recommended above with a 112 LSA and Rhoads lifters. Once that's all done, 12s should be a real possibility for you, and that 450 horsepower is probably fairly accurate.

[AG]

Fusion, If the engine is worn and you want the maximum power that you can get out of it I would bore it and use file fit rings for good ring seal. The correct piston to wall clearance and tightly gapped rings could be worth 25 Hp. If your heads have some porting, get a good valve job, SS valves, bronze guide liners properly honed and CC 995 springs (cut the seats for proper installed height). My .060" 400 in a 3900 lb '65 GTO does 12.8 at 108mph and is a mild rebuild. 62 heads cleaned up, performer intake, RAIV cam w/Rhoads lifters, 3.55 rear, 2500 stall auto, 750 cfm carb and junk three tube headers.

[Fusion]

AG, thanks for responding. I wasn't sure that I wanted to bore the motor out, since I really really don't want any chances of overheating problems. I was thinking about getting the block honed, what do you think about that process?

And Will, do you mind emailing me or posting your email address, I would love to email you when I actually start rebuilding if I have any little questions (which I will, hehe)

Joe (Fusion)

[AG]

Fusion, What is the bore now? Honing is fine if you don't have excessive taper in the bore, you'll need a dial bore gauge or have a shop check it out. The specified clearance for a set of TRW L2262F pistons is a minimum of .0025", and I don't see any need to go beyond .0035" for your application. If you end up with a piston to wall clearance of .006 or greater say with a .002-.004" taper, then you will not get a good ring gap and you'll have too much wall clearance (might experience a little more piston slap). So check out the condition of your bore and decide. My engine is bored .060" and it does not run excessively hot, maybe 195-200 on the highway on a 100F day worst case, but it is something to consider. Also, depending on your deck height, you might want to deck it to zero which will help your CR and detonation resistance (probably won't have to worry about that with 9-9.5 CR). My CR is 10.3:1 measured and I always use 108 octane at the track.

[Fusion]

As far as I know, it is standard bore right now. How much does it cost (roughly) to have a shop tell me what shape my cylinders are in and then hone the walls? Another question about valve springs: what do I look for in a valve spring?? I thought I should replace them as long as I am dismantling the heads. Also, while the block and heads are off, should I pay to have them "dipped", and what would the cost roughly be?

Thanks

Joe (Fusion)

[Fusion]

Ok, here's another question: I really want to keep my shaker on my air cleaner, and not attached to the hood. I assume that I would have to use a quadrajet carburator in order to make my shaker fit...My question is: how big of cfm sizes to quadrajets come in, and are the hard to tune?? I have heard bad things about quadrajets (i'm sure you all have heard the term quadrajunk), so would I be better off buying a edelbrock or holley carb?? Right now I am running a Holley carb (800 cfm I believe) and I am running the shaker, even though I had to dent the air cleaner to fit it. If I bought an edelbrock 750, would I be able to fit an air cleaner so fit my shaker??

[Will]

Fusion, you can e-mail me at willbaker@home.com any time. Since your aircleaner has already been "modified" to fit a Holley, you can pretty much use any carb you want except an AFB/Edelbrock carb as they are too wide for the factory drop-base aircleaners to fit over them. Q-jets are great carbs IF you get one that's in good shape and is tuned properly for your engine. They come in two flavors, 750cfm and 800cfm. Many of the late '70s Q-jets are 800cfm variety. The Edelbrock Performer RPM carb is an 800 cfm Q-jet, you might want to go that route if you don't mind the expense as you're getting a brand-new carb that way. Buying used Q-jets is somewhat perilous unless you know what to look for. All to often people overtighten the two big bolts that mount the front of the carb to the manifold and this warps the airhorn and if they really tighten them down it can warp the carb body too. Many rebuilt Q-jets that you buy at the local parts store have been butchered into worthlessness by the rebuilders as they stuff generic parts into them and will modify the carb bodies to make these parts fit. If you don't have the inclination to spend some time learning the ins & outs of Q-jets and scouring the wrecking yards or swap meets for a good one, I'd suggest you buy either a new Edelbrock Performer RPM or stick with a Holley unless you find a knowledgeable Q-jet specialist who can set you up. Hmm.. part of what I wrote might be confusing.. The regular Edelbrock carbs are Carter AFB clones and will NOT fit under your stock aircleaner base. The Edelbrock Performer RPM and Q-jet replacements are new Q-jets and will fit fine. You hear the term "Quadrajunk" all the time because guys get a car with a worn out Q-jet on it, don't know how to rebuild or tune it, so they throw it away and slap a Holley on and all of a sudden the engine runs better. Well, duh! That's like calling all 455s junk because you bought a car that has a worn out one in it, you couldn't make it run good, so you tossed it in favor of a GM Goodwrench 350 that's brand new. I don't know what you mean by "dipped." A good hot-tanking to clean the grime off them is all that's needed. Check with your local machine shops on prices as prices can vary a lot. As for your valvesprings, match them to the cam you plan to use. If you use longer than stock valves, chances are you can install the Comp #995 springs without machining the spring pockets in the heads but you will also then need custom length pushrods. At their recommended installed height of 1.700", they can accept up to .600" lift and I seriously doubt you need to go that radical with the cam to get your performance goals.

[AG]

Fusion, A V8 hone is $50 usually, measuring the bores will be hourly rate. If you really don't want to bore the block, then reuse the old pistons if there isn't too much wear on the skirts. I really can't see buying new pistons if you don't bore it, you'll have a sloppy set-up if you put standard pistons in a worn stock bore. As Will said, you must match the springs to your cam. If you use the CC 995 springs, you can use up to a .640" lift cam. If you are using a cam with .450" or under lift, then just use stock replacement springs and you won't have to worry about installed height. If you use the 995 springs, then I would get the spring pads machined for the 1.700" installed height and you don't have to get the pushrod length measured if you used taller valves.

[KEN CROCIE]

Re: the CFM question.The 79 Q-jet on your car is an 800CFM unit.ALL (and man do I hate to say that around a Pontiac!)1975 and later Pontiac Q jets are 800 cfm units-even the350s and 301s.You will need to tweek the sec.stop tab to get full opening of the air valve for the full 800 cfm.