351w swap or?

First post; long time lurker…. I picked up my 68 last spring with a supposedly “mild” built 302. I’m not happy with the overall power performance so I’d like start a slow build project while still being able to take drives.
Lots of searching seems to show 351w’s or stroking 302’s as the most popular options. I’m leaning more toward finding a local 351w block due to aftermarket parts options.
That being said, would any 351w block work? I don’t see many 60’s-70’s but there’s plenty of 80’s and 90’s.
I appreciate suggestions you could offer

I’m already planning a 3.55 gear upgrade


What is your end power goal for the car? This will also help answer the question if any 351 block will work or if you need to step it up to a dart block or if you may just be able to build a stout 347 out of your current engine to meet your power needs. I have a 500+ number in mind for mine which I plan to build a 427w out of my 351 block.

69 block is the best for the average Cougar build. Later year blocks lack fuel pump hole, and possibly “boss” for manual trans EQ bar pivot. Lots of great options avail for 351W. I do not suggest wasting $ on a 302/ stroker. You will need accessories for a Windsor, pullies, brackets ect. Trans will bolt up directly AOD, top loader, and a adapter for T5’s. I’ve got a 351 at 500+ hp VERY FUN!!

Thanks guys! I don’t have an end goal to be honest but I do know I don’t plan to get to that 5000+HP

I just picked up a 351W as well, and it has a 2v manifold. When I switch it to a 4v, will most all of them still fit under the hood or are there any to avoid? I don’t want to buy something online that looks great only to find the carb hit the bottom of my hood.

No clearance issues with an Edelbrock Performer in my 69 XR 7.

I’m not in a rush and have been looking for awhile but let’s say you have a choice between an early 70’s bare block(needs hot tanked at least) or a complete 93 out of a F150; both around the $200 range?
Essentially, is older better assuming only the block can be used in my car?

The older block may have some more metal to it, but the question comes up again, how much engine are you planning to build? A roller motor is a great up grade, in today’s world, as opposed to building a flat tappet cam. More aggressive profiles, easier on the valve train, and better economy. Also you should plan for transmission requirements, I.E., a shift kit and new torque converter to match what ever cam you get. The 3.55 rear gear to me would suggest sticking around a .500 ish lift cam. Edelbrock makes a top end kit, that works well. And I ran the air gap intake on my 351 in my 69 Cougar, and DID have clearance issues- Luckily I had already cut the hood for the scoop, but even with that it was very close to hitting.

Thanks for the info. I’ll be honest saying I don’t really understand what a roller is or consists of(I assumed it was a block that accommodated a roller cam but I really don’t know what that means either).

Long story short, I started and sold a 71 cutlass recently to buy the Cougar. Motor was solid so besides some carb tweaks I didn’t have to get into the motor. Before that, just 25 years of modern engine maintenance.

I won’t list all the apparent engine upgrades but tranny is a C-4 with a trans-go stage 2 shift kit. Current cam is a factory grind 289 HiPo

You can’t use a air-gap manifold on a 351 with a stock hood.
A roller motor just means that the cam uses roller lifters instead of flat tappet lifters, most any engine can be changed to a roller motor by changing the cam and lifters push rods and roller rockers.

Have a 69 351w with a Edelbrock Performer in my 68 with stock hood - it fits with a thin air cleaner and no carb spacer. I think anything beyond on a low riser like the Performer is going to be a tough fit.

I believe that 1993 was the first year for a roller 351W, or maybe 94. When planning your build, keep in mind that while you can retro fit a roller cam, in a flat tappet block. Having said that (I did this, myself) You are limited on camshaft choices. The roller block has a different bearing size to accommodate the roller cam. If you can source a roller motor, I think over all you will be happier. Also, on the clearance issue here is a shot from my 69- The oval air cleaner doesn’t fit I had to find a round one that I like-

That’s some very useful info. Thank you

I appreciate the info and pictures. Is that a late model roller block? High rise intake? I’ve been looking at a couple early 90’s 351 blocks which came out of F150’s so I’m not sure if that makes a difference.

I spent all night looking at camshaft choices - both the roller conversion options and the flat tappet options.

I’d like to add some aluminum GT40 or similar heads, and I have 3.55 gears on my AOD. I was planning to leave the stock pistons.

Is there a rule of thumb, do you go by RPM range, or is there math equation for lift/duration?

Shopping by camshaft description is terrible, “Hot cam for great power, rough idle.”

I need something that idles smooth enough it won’t shake my teeth out because in Houston traffic we spend a lot of time stuck sitting at idle.

I hear calling Comp Cams is your best option for choosing a cam for your specific application. Their customer service is supposed to be top notch even if it means getting a custom grind for your specific application and goals.

Mine is the stock block- and the intake is a ‘medium riser’. I bought a retrofit roller cam kit. It is less lift than what I wanted, but due to the heads that I bought, it was the best option at the time.
A quick guide that I think is close, is that lift specs, and duration, are like carb cfm numbers. Meaning that the ‘bigger’ you go, the higher in the power band you will have to live. Pretty much anything I will ever drive, especially at this point in my life will only ever visit 6500 RPM, certainly not spend any time there. If Idle quality is a concern in traffic, then you will want a roller block/ cam. Probably the best thing about the factory roller blocks is that you can run a noticeably more aggressive lift profile, with much less stress on the valve train. Plus the fact that roller cam’s aren’t as likely to fail, due to a lack of zinc in oil, makes it a no brainer. If you are starting from scratch, then a roller 351 is the way to go-
An audio clip of my engine, if you want to hear it-

I’d look into a rebuild of the 302 using a stroke parts assembly. That is a crankshaft, rods & pistons that when installed increases displacement. It’s best to have a machine shop do this & give you a short block, fully assembled.

The vehicle will handle better with the stock lighter weight engine & you can make a 351w fit, but it’s a tight squeeze. It’ll come real close to the shock towers. I’ve seen those installed. Obviously if you have to bang on the towers or even if more heat is transmitted–not good.

The other thing is that all your stock parts will go right back on & from the outside, it’ll look the same. Of course the camshaft can be changed to a roller & so can the rocker arms. Yes, it’s possible to figure out what length push rods you need yourself, but personally I’d just have the machine shop do that, get an assembled long block & be happy.

Of course, going with fuel injection can really make throttle response far more snappy & it’ll run a lot better. Low end torque will absolutely improve. That might be an easier alternative if the horsepower gained is sufficient. Best of all, you don’t even have to pull the engine, just have to have an oxygen sensor port welded in to your exhaust & if you weld, that’s a doable project. If not, any muffler shop can do that at a reasonable cost.

You’ll need to install a fuel return line to the fuel tank. There are parts that’ll let you drill a small hole in the tank & voila, a place to put the line. If you can get a fuel level switch with one preinstalled, it gets even easier or you might even be able to modify it so a return line will go there instead of the gas tank.

Biggest dimensional difference 351w to 302 is increased height. As far as width difference it is minimal- there is no shock tower interference or issue’s changing plugs. Not sure when my 68 got it’s 351w but it was there when I bought in 1980. My shock towers are perfect as an export brace drops on perfectly. Had cast iron manifolds for years and when I installed headers, I discovered they were the original 68 302 manifolds bolted to the 351w. Put a set of Doug’s Tri Y for 351w on and other than jacking up passenger side a couple inches were a bolt on with no hammering or banging. Have absolutely no issue’s with overheating even on long interstate runs. Car rides and handles fine. Hood clearance only place I’m careful.

I had Tri-Ys on my 66 289, and they worked great. My 351 came with manifolds on it, but I’ll probably add headers when I install since I’ll have to adjust the exhaust anyway.