Engine Advise .... what to look for
- Thread starter ve3oky
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What motor is in the car now? Unless it's a 307, you'll need a set of frame mounts from a 307 car. While a '75 certainly isn't going to be anywhere near 500 horsepower as-is, it should still provide a nice kick. You'll also need to address the trans crossmember to work with a TH400 and shorten the driveshaft. I believe a later 200R4 crossmember will work if you elongate the holes.
Intragration said:
Ahh thanks for the heads up. Its got the 4.9L (301) in it now. I think the 75's are rated at 275HP .....as you said a nice boost for now and definitively up gradable to my 500 HP goal from what I'm reading and seeing online.
If the car has the 301 in it now, then that would be a Pontiac engine. You could stick with a Pontiac engine if you want. I believe that a 400 would bolt right in without changing the mounts, and even a 455 Pontiac should go in with minimal fuss. If you decide to go with an engine from another GM division (Chev Olds or Buick), then you're likely looking at changing engine mounts, possibly some wiring, fuel line location, accessory drive brackets, transmission mounts, driveshaft, etc. I'm sure that other people here can provide more info. Another thing to keep in mind-the factory rear axles in these cars weren't really designed for the kind of horsepower level that you're looking for. They can be upgraded if necessary, or you could go with a stronger axle, but as you change one thing (i.e. engine), then it affects other things. Just my $0.02. Good luck with your search
Is there much of any difference in the Pontiac 455 to the Olds?? Guess my main question is parts availability and any known issues with one or the other, again thanks all for the information and advise.
Doing a Pontiac motor would be cool too, since you don't seem to be looking for brand uniformity. The 307 mounts are easily available, but you've already got the Pontiac mounts... It's a good problem to have, lots of options. I'm not sure, but fan shroud may be something else to consider, since you already have a Pontiac motor. I believe there is a difference in mount location for Pontiac motors, it may be around '68-'70 where the change happened, if you went Pontiac you'd want to have a block with the same mount provisions as the 301.
As for differences, they're both obviously completely different motors. They're both reliable and there are parts available, not like for Chevy, but you don't need a ton of parts, just the right ones. I know Olds motors aren't considered the best for extended high-RPM usage, long stroke and slow oil drainback, but then there are guys with Olds 455s in their boats, it's not an insurmountable problem. Plus, a 455 doesn't NEED to rev that high, it makes it's power down low and lazy, that's why they're so much fun. I've HEARD that Pontiac 455s have some issues related to stroke length and geometry, but I don't think it's a deal-breaker. If I had a Grand Prix, I wouldn't hesitate to put a Pontiac 455 in it, but I'm a brand uniformity kind of guy.
Once you make your final decision on which way to go, it will be easier to come up with a plan. My advice would be to get a running motor/trans combo with all the accessories and brackets, that way you don't have to hunt around for everything. It's mostly all available, but some of it is harder to find and it's so much easier when you have it already. I'm excited to see what you end up doing.
As for differences, they're both obviously completely different motors. They're both reliable and there are parts available, not like for Chevy, but you don't need a ton of parts, just the right ones. I know Olds motors aren't considered the best for extended high-RPM usage, long stroke and slow oil drainback, but then there are guys with Olds 455s in their boats, it's not an insurmountable problem. Plus, a 455 doesn't NEED to rev that high, it makes it's power down low and lazy, that's why they're so much fun. I've HEARD that Pontiac 455s have some issues related to stroke length and geometry, but I don't think it's a deal-breaker. If I had a Grand Prix, I wouldn't hesitate to put a Pontiac 455 in it, but I'm a brand uniformity kind of guy.
Once you make your final decision on which way to go, it will be easier to come up with a plan. My advice would be to get a running motor/trans combo with all the accessories and brackets, that way you don't have to hunt around for everything. It's mostly all available, but some of it is harder to find and it's so much easier when you have it already. I'm excited to see what you end up doing.
Ok great. Took a quick look around and harder to find Pontiac 455's then Olds but like you said not impossible, they are out there and available. You all well definitively be kept in the project "loop" as all my previous knowledge is Dodge based (ducks) :wink:
I know of someone who is on another site that I'm on, that recently swapped a 400 Pontiac into his previously 301 equipped '78 Grand Prix, and he's very happy with the results. Its a relatively easy conversion too. Also, kep in mind that the MOE is on the lookout for older vehicles with swapped engines for emission compliance. In your case, you're going to have to keep all of the original emission controls that came with the car, or the engine, whichever is newer, or you could be risking a possible fine. As requested above, please keep us "in the loop". Thanks.
I had a 455 olds once in an 84 cutlass. There are plenty of engine recipes online that would meet your goal with a 455 olds or poncho. I have a soft spot for Oldsmobile so I will vote that if you are not interested in Chevy. The torque these engines make easily makes up for lack of horsepower. Honestly though, a rebuilt 455 olds with big valve C heads with a little massaging, 10 to 1 compression and a healthy cam will easily make 450-500hp with a dump truck full of torque. My 455 with big valve c heads, lunati bracket master cam and same compression would melt the 10.5 in mickey thompson slicks in any gear under 40 miles per hour. I don't know what the power output was but it was originally a toronado engine rated at 390hp, 500ftlbs of torque. Even with traction issues I could walk an LS1 f body with it. My power estimate was 450hp, 525 in torque. I am sure I was not too far off. What I am telling you here with my trip down memory lane is get a 455 olds. 😀
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