Hey guys. I just purchased a 1967 GS 400 & was wondering how I can boost the horsepower. I would like to exceed 400 horsepower. -Can this be done with this motor? -If so how? -Money wise is it even worth it? I would like to get the most horsepower from the stock motor & keep the #'s matching. Any help or advice is much appreciated. Thanks ---------- Post added at 10:57 PM ---------- Previous post was at 10:55 PM ---------- It is a true #'s matching car so I don't want to ruin the motor. I have thought of rebuilding a 455 the way I would like it, but that's going to be down the road a ways. I was thinking that I could purchase a couple of used cylinder heads and port them, while keeping the original heads original and in storage. If I were to do this, how much extra hp are we talking. Is it even worth the trouble. Second: what would be the best cylinder head to purchase. Can I use a 455 stage 1 head, is a 1967 430 cylinder head a better option, or should I just purchase another set of GS 400 cylinders heads and port them, or would it be ok to port the original cylinder heads. ---------- Post added at 10:59 PM ---------- Previous post was at 10:57 PM ---------- Looks like 430 heads might be my best option to play around with since the oiling is the same (or would i be better off with 455 heads) or I can drop a few grand with TA. Any other suggestions to get more power without modifying the motor. Also if I were to buy a new 455 motor what years would be the best. I found a complet 455 with code for 72-75 & heads from 74 plus the valve covers, HEI, carter AFB competition series carb, & TH400 trans all for $500. Is this a good deal, or will I end up getting rid of almost everything to make it better. Also what iriginsl cylinder head years are the best.
I would suggest leaving the 400 alone and build a 455. The 455 Stage 1 head with the larger valves will not work on the 400. So the options are to use a 430 ported head or a TA head set up with the factory size valve. If you use the TA head, then the smaller valve configuration will not be what you want if you decide to use them on a 455 later on. Then you will need a higher performing cam and a set of headers. You will need the original carb setup to run with the new equipment or replace it so it stays in stock form. The distributor can be recurved. If you want to save a lot of weight then replace the stock intake manifold with a TA or Edelbrock that can be used on the 455 later. At this point you have the original heads, cam & lifters, carb, intake and exhaust manifolds sitting in storage waiting to be installed back on the 400 when you build the 455. As you already know the 455 will give you a lot more power for the dollar invested so save yourself a lot of extra work and just do the 455 and swap out the 400. Then store the numbers matching 400 as an untouched unit. Paul
I agree with Paul, build the engine you want the first time. I would not worry about keeping it numbers matching.
It'd be easier to make a recomendation with a clear goal in mind. Are you going to the track and looking for a specific 1/4 mile time or is this for a street machine. Daily driver? Cruiser? The most cost effective way to reach the 400HP benchmark would be the 455 route. It is however possible with your 400 block and heads with porting of the heads, intake, exhaust manifolds (or better yet headers), cam and optimized timing and fuel delivery. When you get that far into it, you'll have to start considering a torque converter and possibly gear change to take full advantage of the changes you've made. Oiling system upgrades can't be overlooked either. If you want some extra performance now while you save and plan for a future 455 build, you can look at your rear gears, trans, torque converter, cam and home done port job for a substantial increase in the seat of the pants feel. All of these (except the porting) can be used with your future 455.
Ok. So if i plan on leaving the 400 in place right now while I save & plan for the 455 what would be the best options for rear gears, trans, & torque converter? For the most part I'm just looking for a really powerful/fast street car. I would like to still be able to drive it on the freeway without it sounding like its going to blow up. -Is the stock trans a viable option for this or should I get something else? -what should I do with the rear gears to obtain what Im looking for? -what types of torque converters are out there that are compatible with my car/trans & what would be my best option? -what companies websites can I look at/are the best? Thanks, Josh
why not bore the 400 out to 430 size and then the stage 1 head will work just fine? the 400 and 430 block are the same, the 430 just has a larger bore.
First order of business would be finding out what you already have. Check to see what gears are in there now. You can pull the cover off the diff or lift the rear end off the ground and turn the rear wheels while watching the drivshaft. The ratio of turn of the driveshaft vs rear wheels will tell you what gears you have. A 3.42 would be good for a strong street runner. http://taperformance.com/ http://trishieldperformance.com/ Here are a couple of good websites to browse till you get a clear direction. TA is the leader in aftemarket support for Buicks. Tri-Shield is owned by Jim Weise who also owns/ operates this board. He is one of the leading authorities on Buicks. I'd start with recurving the distributor as outlined in the timing sticky. Rebuild the Q-jet, gears and shift kit for the trans. After that it'd be time for cylinder head work, cam and torque converter, but you have to choose if you're doing the work to the exsisting 400 or looking for a 430/455.
