351 Cleveland vs. 351M/400- which is better ?

I hear a lot of people dissing the 351M/400 family of engines- but IMO they are only a raised deck Cleveland with a larger 3"main bearing.

What's the deal ?

I see no reason why a 400 would not be a good street or race buildup- how "bad" can 50 more cubes be, with the same top end equipment ?

Every time I hear someone knocking a 400 for being a slug- it makes no sense to me.

Any opinions and info welcome !

 

The 351c was a decent motor stock. The 351m and 400 were big performers. They came along too late and were "smogged out". maybe good for a truck. I don't know what it would take to get good compression out of a 400.

I was just looking at a Ford Performance book next to the computer. It's quote : "The 351-m is, unfortunately, a hermaphrodite-a compromise at best. So we won't discuss it here as a performance engine."

sounds like fight'in words.

 

a stock 4 barrel 351 cleveland will out perform a mild built m400 anyday.a nice big cam in a 4/b cleveland will make a nice runner.most of the performance in the cleveland is in the 4 barrel heads.they will out flow most of any of the aftermarket heads that any company make,bone stock.the ports in a 4 b/ cleveland are big enough for you to stick 4 of your finger in them up to your knuckle.i use to run one with a 550 lift cam,tunnel ram w/ 2 600 holley's and a top loader behind it .it was a runner and a half.I've never seen a 400 that would run even with a cam an intake,cc of the head stinks and the pistons are less than a performance piece.no compression.as for the 2 barrel head cleveland I'm not sure how they would perform.if you go with the clevland stay with the 4 barrel version.2 b/ & 4 b. heads are different.it doesn't matter about the extra cubes if the engine just can't push out the power.it all has to work together.

 

The M heads are not perfomers to speak of but with a set of clevlands the whole deal changes.
One of the things i have learned in engine building is follow your heart. If you want a strong 400 M and you think it can be done , go ahead and try it. No one will work harder at your dream than you. People who are neg are a dime a dozen and most never built didley squat anyway.
Just to encourage you here is a 400 mopar I stroked to 426 cubes built by hand in my shop in my spare time for my friend G Wager.We even made our own pistons from a discarded set of forged 440 units. We never asked anyone if it could be done, we just built it. Cost was so low I wont mention it. No one would believe it anyway so it is pointless to mention it.
What did it run? 10.64 in an all steel 82 Mirada race car.
Best of luck with your project. Go fer it!!

 

encouragement

 

The 351M/400 were poor performers in stock trim, with restrictive intakes and poor cam timing, but there is no reason that can't be fixed with a rebuild. The stock 2 barrel heads are fine for a mild engine, although the open chambers are prone to detonation. 4 barrel heads can be adapted.

Here is a link with some basic M info
http://www.home.earthlink.net/~bubbaf250/

This is a long thread on a truck build, He put together a mild 400 that made 351 hp, 473 ft-lb on the dyno
http://www.pirate4x4.com/forum/showthread.php?t=415703&page=12

 

I run a mild 400 in my 58. It worked out to be a good street engine,not much low end but put it to the floor at 60 and man its gone. probably the 3.0 gear helps that. The only bad thing is it burns alot of gas.

 

thanks for all the replies to the thread

I run a 400M in my parts-chaser, etc. truck

I've owned a pair of Cleveland closed-chamber 4V heads, but sold them after checking them out.

Why not just drop 4V Cleveland heads on the 400- or put the larger C valves in the M heads.

I've built a ton of engines in my life, over 60 different motors- Ford-Buick-Chevy-Mopar-Pontiac-Olds-both small and big blocks of various makes. Been doing this now since 1982.

But the one thing I could never understand, is why Ford guys knock the Ford 351M/400. Being a GM guy, I've taken 455 Pontiac low compression engines with 2-barrel carbs, and warmed them over with heads/intake/4bbl/headers/cam/converter/gearing and made tire shredders out of them.

For some reason, no one wants to do that with a Ford 400.

Well if I was racing that engine, I sure as hell would not opt for a 351 over a 400, and give up 50 free cubes ! That's like running a 400 Pontiac, instead of a 455 Pontiac on the street. Same motor- why not enjoy the extra CID.

I guess my question was more "rhetorical" (did I spell that right ?).

The few that did embrace the 400 did well with it. Here's a guy that runs 9's with one.

http://www.dragtimes.com/Ford-EXP-Timeslip-8574.html

So I emailed the guy, this is what he said:

I had thought for years that this would make a good combo but had been talked out of it. I finally built one anyway. The first combo used 4v closed chamber heads with some filling of the intake ports and internal porting of the exhaust(along with plates to fill the bottom of the port). With a tunnel ram, (2)stage3 barry grant 660s, an engle flat tappet cam, flat top pistons and stock rods and crank, it ran a best of 6.05 @ 112mph shifting at 7000 rpm, in the 1/8th at sea level. That ET would equate to an approx. 9.5 sec 1/4 mile et. The flat top pistons with the closed chamber heads gave approx 12.2 to 1 compression.
I ran that combination for about 5 years then decided to pump it up a little.

13.7 to 1 compression
aluminum rods (6.967")
stroke stock crank 4.125"
.040" overbore
roller cam 286, 296, @ .50 with .750 lift w/110 cl
spayed 4 bolt main caps (showed evidence of cap walk with 2 bolt)
self made hi-port plates for exhaust side of the heads.
same intake and carbs.

The et posted on dragtimes was the first time out with the new motor , 900 feet elevation and we were dialing in a new four-link setup. I feel certain that it would have run 5.70s if I could have made another pass after making adjustments. I was also shortshifting at 7000. The cam mfg recommended a 76-7700 rpm shift point with this combo.
Since then I've gotten myself into an upcoming match race situation with my brother (53 willys w/blown 427 alky) and in preparation, have changed mine over to a dual Ron's Toilet alky injection system. I haven't made a pass with it yet, but if the change in it's sound is any indicator, it's going to be interesting!!
The biggest aggravation in using 400m and 4v head combo is the intake manifold situation. I used modified weiand spacers for a while but finally made my own and had them welded to the manifold.
The extra cubic inches is just what the 4v heads need to make them work and really turns the 400m into a mid-range torque monster when properly built. I'd love to see more people use them so maybe some aftermarket intakes might become available.
I ported the heads myself but have never had them flowed.
I wouldn't overbore more that .040 at this compression without filling the block.
As far as max rpm,,, the crank is the limiting factor. With the lightweight pistons and aluminum rods, I don't plan to spin it beyond 75-7600. Good crank prep is very important especially when using a cast crank.

 

The 351M/400 came out in the smog years when Ford wasn't making anything of interest to performance guys, so they get ignored compared to the Clevelands. It's like the Hemi & the Poly in the 50s. If the Hemi hadn't existed the Poly would have been a great engine, as it is the Poly is viewed as a source of blocks to make into Hemis! People also poo-pooed the 455 S/D cuz it had only 7.9 comp. ratio.

 

I have a 351M I rebuilt in my old beater truck. I put a mild cam in it and removed all the smog pump crap. Then added holley 2barrel carb. It will get up and go. I just wanted a nice running v8 and thats what I got. It will spin the tires and even give some kids in their tuners a suprise. I have had three of these engines and this one I rebuilt is the best so far. I had a stock rebuilt 351 cleveland with a stock 2 barrel and it would flat out run!
I have gotten past the I need all this speed equipment and headers and $800 carbs and have more fun running stock rebuilt lightly modified stone reliable engines.
If your not racing for money every weekend that changes everything.

 

The biggest problem with the 400's (the hardcore fans of it get pissy when you call it a 400m) is the stock numbers are so bad, who would brag about making 160hp with a 400ci engine.

The main problem with them is the low compresssion ratio, but a set of flat-top piston can put it up to 9.5:1 with stock heads. And with the Australian 302 heads you can get it up over 12:1. There is also not a lot of aftermarket performace parts for the 400 (ie only 2 intake manifolds that are made for it) but some of the Cleveland parts fit with adapters.

I think it's mainly an image problem, there's just no enough 400s that have been done up for people to see they can be more than a gas-guzzling smog block. Personally I think it's got a lot of potential, in fact I'm doing one as my first engine build up and I'm looking at 360hp/450ft-lb with just changing the pistons, intake, and cam.

If anyone is looking at doing one check out these guys for parts, http://www.tmeyerinc.com/ they have high-compression pistons and most of the other performance parts, even a 434ci stroker kit for the 400s.

 

There are a couple of issues to consider with the 351M/400 which tend to make people shy away from them...rightly or wrongly. All the issues can be worked around, but for the average guy it doesn't seem worth it. If a person does his homework & is prepared to go through some hassle, the 400 can be a very surprising engine & well worth it. They are not exactly a high deck 351C, though.

1) The 351M & 400 both (except for the '71 400s, first year) all have pistons that sit a min. of .030 down in the hole at TDC. With the average .040-.045 composition gasket, they have no quench (or much compression, for that matter) & are prone to detonate, especially with some miles on them. Finally, as of about two years ago, Tim Meyer is making (having made) both hypereutectic & forged pistons with increased compression height to solve this. You can also use 351C pistons, but you need to bush the connecting rods.

2) Truthfully, unless it's just a stock rebuild, you are better off converting the 351M to a 400. It's the same parts you would machine or replace in a rebuild anyway.

3) The whole issue of 2V vs. 4V is controversial anyway. Without going there....the '71-'74 400 heads & 351C 2V heads are functionally identical. It is possible to rework them nicely for a street engine, although STRICT attention needs to be paid to deck height, compression, etc., as the 2V open chamber heads have little quench surface anyway. '75-up heads for the 351M & 400 have exhaust port issues (relocated water jacket) & aren't a great choice.

A lot of people push the Aussie Cleveland heads as the cure-all for the 400 or 351C 2v. They have the 2V ports but closed chambers (all US 2V heads are open chamber). However, the Aussie head has very small chambers, as it was designed for the Aussie 302C, and it is difficult to hold compression down for a street 400...& a max-effort race 400 would use 4v or aftermarket heads anyway.

The 351C 4V heads, open or closed chamber, will work, but as the e-mail mentioned, you have to use intake spacers. The Weiand spacers are no longer available new, & were for 2V ports anyway. Price Motorsports makes spacers for a 400 with 4V heads...they are pricey (bad joke) & take a while to get. However, when using them, you can use ANY 351C 4V intake, including the FunnelWeb, Blue Thunder, Holley Strip Dominator, etc.

4) There are no real good intake manifolds for a 400 with 2V heads. The two common ones are the Weiand & the Edelbrock Performer, both really designed for low rpm, heavy vehicle use...which is what the 351M/400 were intended for in the first place, in trucks & heavy cars like the LTD. This may, or may not, be an issue...depends on what a person wants.

5) The 351M & 400 have unique motor mount bosses which are not like the SBF, Cleveland, FE, BBF, etc., so mounts must be fabbed. Not a big deal.

6) They also have the BBF (370-429-460) trans case pattern. This more or less mandates the C6 & this, along with the additional width/height makes them more difficult to swap into many Ford cars. Not an issue in older Fords.

7) It is possible...with searching...to find a bellhousing that has the BBF block pattern, but the C4 trans case. I happen to have one. They are found in '77-'79 Rancheros with the 351M/C4, & perhaps other vehicles. Going rate is about $100-$150. JW, among others, makes this in an aftermarket version, about $400.

8) There are a VERY FEW 400 blocks that have the SBF trans case, & motor mount bosses for both the 400 & the SBF (some of the bosses are not drilled from the factory). They are found in early '70s station wagons with the 400 & FMX trans. Quite rare, quite expensive, as they are prized by Pantera owners to match the Pantera transaxle to build strokers.

9) There is a truck puller in WI who built two 400s, a 434 & IIRC a 427, for class racing. The 434 made over 700hp, on a dyno...& he did pretty well. He spent a lot of money, too. He changed classes (or the class rules changed) and switched to the BBF. Says that, all things considered, he wouldn't do it again.

10) Certain 400 blocks are prone to cracking. If you want the details I'll dig 'em up.

I guess the point I'm trying to make is that anything is possible. Some of these items may not apply to you. If you want a very healthy street engine, with lots of torque, it's a great choice, especially in a truck. Cores are very cheap. If ya wanna go racing, in a mid '60s or later Ford, maybe not as easy, or cheap.

 

somebody hit the nail there- methinks too many read the factory HP rating and think the 351/400 engine is no good

the Weiand tunnel ram will fit the M blocks, with intake port to intake manifold spacers- they'd be easy to make using a gasket as a template and sheet aluminum or mild steel

The Aussie aluminum blocks and Funnel Web intake will also fit with spacers on the intake per above.

And that Aussie stuff is even better than the original USA Cleveland parts

check it out- for picture reference and description only- this is an old auction that is over already

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&ih=018&sspagename=STRK%3AMEWA%3AIT&viewitem=&item=280039219288&rd=1,1

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&ih=018&sspagename=STRK%3AMEWA%3AIT&viewitem=&item=280039217645&rd=1,1

imagine these puppies on a stroked 400M block with headers and a solid flat tappet cam- reason tells me, how bad can aluminum canted valve heads be ?? things that make you go hmmmmm.....

 

great info- thanks- it's good to know the foibles of this engine family before diving in- let me add a few things- a few years ago, I recovered what we thought was a 400M from street rod project that was broken up- the block had the correct casting number for a 400, that should have been "400 only" casting- when we took it to the machine shop to be machined, it turned out to be the shorter stroke 351M crank- in a coded 400 block

there is a few other open plenum intakes for the 351M/400- I saw both Holley Street Dominator and Edelbrock Streetmaster, both open plenum intakes, for the raised deck M block- on Ebay- both were labelled as "351m/400", they are out of production but still in circulation- the Street Dom went for nearly $180+. Edelbrock and Weiand also both make new dual plane intakes today for just under $200.

the piston deck height really isn't an issue- unless someone is stuck on dumping an original motor in a car and not rebuilding it- I would zero deck any pump gas street motor regardless- the last Pontiac 455 I did, required dishing the pistons 30 cc to get the CR down to 9:1- so basically if we're want to make an omelett, we have to break a few eggs...easy fix. The pistons in the hole .030" would only require the block be decked that amount to zero it, or get pistons to fit as mentioned above.

IMO the spacers seem to be the missing link to making this engine worthwhile- being able to use any Cleveland intake would be great- as they are plentiful and available new. Big port motors are a ball to drive on the street- part throttle response goes down slightly, but the engine will still freak at WOT if geared/convertered properly- and ends up having a "huge" sound with bigger port heads- due to more airflow through the engine- definitely a cool factor !

The M blocks use the 429/460 bellhousing bolt pattern, with a few exceptions, if my info is correct. There are a lot of big car/truck trannies around that will work. Truck bellhousings should be quite common though for the M blocks- I have 2 of them, one in my truck, another "lent out" to a relative to eventually put his M block in his '68 Cougar.

cracking blocks, now THAT'S a problem. But one thing I like about the 400M is, it will make comparable power to the 460 Ford, but in a lighter/more compact package. The motor mount deal is a bummer, because that means screwing around and doing a mock up with block/trans in the car and bolted to the crossmember, then setting it on the frame rails to see where/how to get it in there. That can end up being more of a PITA than anything.

 

seem to have read that the '73 400 (some,all?) have the SBF bell pattern.

 

that never bothered the chevy guys! they'll build a good performing lightweight 406 sbc that makes lots of power cheap.

Kind of strange that the 400 ford uses such a tall block, while the 351c or windsor can be stroked (using the 400 crank!) and use production intakes and stuff and get the cubes

 

If anybody gets the motivation to build up a good 351m motor from this thread. I got one connected to a good C6 tranny sitting in my pickup truck for cheap, but you gotta take the truck too. PM me for details if interested.

 

Nothing "wrong" with a 351/400m or a 351 Cleveland...they're just the victims of poor timing, arriving just in time for the "smog years" and poor publicity.

The Cleveland made a brief stab at street glory in the form of the legendary Boss 351 Mustangs before being choked down and de-tuned until they were finally discontinued in 1974. However, they continue to shine on the NASCAR circut as the basis for the engines used in Ford 'stock cars' to this day.

For most street applications, the 4v Cleveland heads were just too much, with the best budget-minded results coming from running a mild cam and an aftermarket intake on the 2v heads that allowed the use of a Holley or Carter 4v carb. Good headers and exhaust system plumbing helped a bunch, too...as the Cleveland, like most other Ford V8s of the time, suffered from poor exhaust flow. This came about because Ford had to make these engines fit into their chassis which utilized shock towers, so the exhaust ports were somewhat compromised while the intake ports flowed well. A dual pattern cam is STRONGLY recommended for most Ford V8s...especially 351C, 351/400M and 429/460 engines, as they suffered the most from the poor exhaust port designs.

The 351/400M engines are torquey brutes, but as several others have pointed out, they are low compression smog motors in stock form, and not very impressive in anything other than a truck or van as produced by Ford! They, like almost ANY other engine, are completely unaware of what name is one their valve covers and will respond to basic, sensible performance mods.

One 'drawback' is that they aren't light by any means. The big block bellhousing pattern used on the 351/400M also generally require a heavy, power soaking (but very rugged!) C6 transmission, unless you can locate the one-year-only C4 bellhousing that allows the use of a C4 transmission behind a 351/400M...but the 429/460 guys scoop those up pretty quick at swap meets and on e-bay...so ya gotta be quick and more than a little lucky to score one!!!

Now, if you REALLY want to make for a super-heavy drivetrain, you can run a cast iron FMX automatic...but I wouldn't recommend that at all!!!

TopLoader four speeds bolt right up to 351/400M engines using the same bellhousing as a 429 or 460 four speed application would require, so you aren't limited to automatic trannys by any means, even though the vast majority of 351/400Ms come backed by automatics in OEM applications.

Overall, the 351/400M is an odd motor to mess with for any hot rod application, and doing so will cost ya some bucks...but they will run just fine if you take your time and build 'em right...and they'll keep on chuggin' for years! If you want to be DIFFERENT, that's a good way to do it!!

 

most likely Ford upped the deck height on the M to fit the stroke increase- the 351M came out later and was actually a destroked 400 using a 351W crank and bearings- and to fit a longer connecting rod and keep R/S ratio as high as possible

one thing is really odd about that engine family- the 351M/400 has a 6.58" rod length- the 351C has a 5.78" rod length

the engine with the best R/S ratio for extended high-rpm use, like the high banks of Daytona or Talladega, is the lowly 351M with 2-barrel carb, the truck motor....

what were those Ford engineers smoking ??

 

what's the weight difference for an M compared to a C?

 

According to this site, the 351/400M weighs the same as a small block Chevy (575lbs), with the Cleveland being listed at 550lbs! I find that hard to believe...if you've ever hefted a stock cast iron intake manifold or stock heads off of a 400M!!! Anyone got some engines laying around an accurate scale?? Ha Ha!!

http://www.241computers.com/ford/ContentExpress20-30-38.html

 

Also ford smog engines have a timing gear 7 degrees retarded. That is almost the first thing to cure. people have forgotten about that in recent times.
Some engines you can buy the earlier set up. it is easy to forget about this so many years after the fact but it is how they got a lot of the motors into line for smog and it is what killed the power for awhile

 

According to a Ford production table for 1971, all actual weights, not estimated:

351C 2V 556 lb
351C 4v 571 lb
400 2V 596 lb
460 4v 668 lb

This includes accessories like starter, alt., etc., & set up for an automatic trans...i.e. a flexplate, not a flywheel. Also, certain car models have slightly different engine weights than others, depending on vehicle requirements.

An Internet commonly mentioned weight diff. between the 400 & 460 is 140 lb. for a bare, complete engine with no accessories...but I don't know where that came from, and I have no personal proof. I doubt the 400 accessories are 70 lb. heavier than a 460's. This argument usually comes from those trying to prove the 400's advantage over the 460. Believe or disbelieve as you like.

 

Here's some good info on the 351/400M
http://www.projectbronco.com/
Go to the technical section.
They can be made to go, and they are pretty sturdy. Just came out at a bad time, and no performance version. All 351/400M have heads like a 2V Cleveland, which are usually perfect for a street motor.

 

this thread is getting good.the only thing wrong with your thinking is a mild built cleveland will out run a mild built m400 anyday.anyone that has messed with both will tell you so.you are talking about apples and oranges.now I do agree 100% that if you do all those things that the guy listed you will out perform the 4v/cleveland.but is it worth the effort and the high cost.if you want to get crazy and spend a mint to get the 400 to run like a scared rabbit.it will do it.but what if you took all that extra money and tossed it at a v4 cleveland?you could take the extra cash to get the 400 to run. but a 144 mini blower on the 351 and would more than likely smoke the 400.and you could drive it every day not so radical that you couldn't afford to drive it like the 400 would be.those 49 extra cubes are not worth spending the money on to make it a good runner.my thoughts anyway.

 

I value everyones opinion and your post has my attention- point taken- but I'd have to disagree with you on that one- I'm skeptical- here's why-I've built Pontiac 350's and 400's with identical heads, intake, carb, cam- actually moved the stuff from one engine to the other, and put it in the same heavy car '72 Lemans 3800 lbs. w/driver- you can feel 50 cubes difference right off the reel, esp. at street driving speeds in a heavy car. It was glaringly obvious the 400 made more power. Then we took those same heads, intake, carb, cam and moved them onto a Pontiac 455, and back into the same car- again a huge torque increase.

I think the problem is, no one ever did that with a 351C and 400M back to back in the same car with identical top end parts. Reason being if a 351C resides in a car now, the 400M won't just bolt in- so it's impossible without time consuming mods to motor mounts and bellhousing/trans change. I'd wager it's the rarest engine swap in the world, taking a C-out, and putting an M-in, if it's ever been done at all, in the same vehicle. Most likely if a 351C comes out, a 351W, FE, or 429/460 goes in. Or the heads, intake, cam are not the same- so that would not be a valid comparison.

There's rules in professional racing, the most important being CID limit- and for a good reason- if someone was able to use a 50 CID larger engine in a class dictated by engine size, they'd drive around everyone in the class- be it NASCAR or drag racing. I'm sure if someone snuck in a 405 small block into a NASCAR race car, instead of the 355 dictated by the rules, that car would be hard to run with.

The only way I could see the 351C making more power, would be if it was geared deeper and turned higher rpms. But with the exact same intake, carb, headers, heads, cam, in the same car, the bigger engine would make more power- it would show up on the dyno too. Both engines have the same bore size, one just has more CID.

If the 400M had a smaller bore than the 351C, then I would also agree with you- because then the smaller bore would be shrouding the airflow a bit. Case in point- Olds made (2) different late-60's Rocket V-8 400 CID engines- one had a smallish 3.87" bore size and 4.125" stroke. The other had a large bore and shorter stroke, 4" x 3.98". The latter oversquare 400 with larger bore engine ran better.

see it here

http://www.442.com/oldsfaq/ofe400.htm#E400%20400CIDEngineDetail

oddly enough, that oversquare Olds 400 that is touted as a "great" engine, had very similar dimensions to the Ford 400M- and the M has much better cylinder heads than the Olds to boot. The motor mounts, intake availability, and transmission pattern are the only hurdles I see with the 400M. Being the 351W guys put the 400M crank in the W motor as a stroker kit, how bad can it be in the M motor ?

I would agree that "perhaps" the 351C could outrun an equally built 351M- due to the larger main bearing on the latter and increased bearing friction, and longer heavier rods and crank not revving as quickly. But the longer rod in the 351M can also be seen as an advantage with the 2V heads, so that too would be a toss up. I think the M engines were just neglected from lack of development, that's all.

 

lol. last one then I'll shut up.I agree with you at some points.I'm a Pontiac nut.I have two 455 and a few 400 sitting in the garage with dust on them waiting for the right car.if you take the heads off the 400 poncho and put them on a 455 it boost the compression way up.thats where the power is coming from.the thing about it is,is everything on a 326 all the way to a 455 is a bolt on.no machine work no spacers and the same trans bolts up.you can't say the same for the 351C to a 400 ford.it just seems like a lot of cash to pitch at a 400 in order to do what you want it to do.spacers machine work aftermarket stuff.if you are after the cubes go to a 460 and build it with the same amout of cash as you would the m 400 it will run.as for the more cubes the better.I agree to a point,but it matter how it's built everything must match in order for it to run it's best.I have out ran big blocks of different makes with a built 355 small black chev.I also had a built 400 poncho in a 69 Goat that would out run my built 462 poncho.it matter how they are built.I'm not trying to stop you from building what you want.I'd like to see the results if it gets done.it just doesn't seem cost effective to me.

 

i reread your post and want to add that I know stock to stock the more cubes you have the more power you will make in some cases.thats not what I mean I was refering to building a mild to wild engine would you get that much more out of the extra 49 cubes ?would it be worth the cost.i don't think so.and I still think a 351 c would still out perform a m400 stock or even with performance cam change on both

 

Also note the 4 jet motor had two type of heads one closed chamber high compresson and an open chamber head.