Nickelplate Posted July 31 Share Posted July 31 One issue with the 351M, 400 Fords and also the 400 SBC, was heat. All of these engines have "siamesed" cylinders in order to fit the large bore into the block constraints. The Ford engines are (bore first then stroke) 351C 4.0 X 3.5 = 351.8592 ci, 351M is the same, 400 4.0 X 3.98. Chevrolet 400 4.125 X 3.75 = 400.92216 ci was in a block originally designed for the 283 3.875 X 3.0 = 283.0386 ci (265 didn't have an oil filter provision, might have gotten one later). On the shorter stroke 351M the siamesed cylinders didn't seem to be an issue, and even the Ford 400 didn't have a bad heat problem, the Chevrolet 400 possibly had one. Biggest issue with the Ford engines, the 400 was built to replace the 390, which by 1970 was reduced to a 2 barrel only, and was a mid 1950s design and was going to have problems with the upcoming emission requirements, they were set up so lean they barely ran, and the huge ports of the Cleveland heads didn't help. The 351M and 400 were built to share their back of block bolt pattern with the 385 family (429/460) but in a shorter package. This allowed Ford to use the existing 385 family transmission or clutch housings reducing the number of different parts. The unfortunate problem with both the 351M and 400 was the lack of power and horrible fuel economy. Ford spent three years (1980-1982) building trucks with the 400 being the biggest availble engine. It hurt them badly in the towing market after having the 460 available from 1975-1979. Since the new body and chassis introduced for the 1980 model year was toughted as being smaller frontage for better economy, there almost wasn't room for the 460 due to it's size. When I sent Gary a picture of Darth's engine compartment, his first question was "how high up did they have to drop it from to get it in?". He knows now, and I think he understands why I don't want headers on Darth. To add a little trivia, there was actually a 351m and 400 casting t had bolt holes for the big pattern and the sbf pattern! Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted July 31 Share Posted July 31 To add a little trivia, there was actually a 351m and 400 casting t had bolt holes for the big pattern and the sbf pattern! D3AE-B blocks were one year wonders to allow the FMX tranny to bolt to the 400. My buddy Joey had a Cougar with one, and a bunch of Pantera's went to them if the class allowed the displacement. No holes in the outside pattern... Link to comment Share on other sites More sharing options...
Nickelplate Posted August 1 Share Posted August 1 I had a buddy in Florida who owned two Pantera and a gold head E-type Jag. Somehow all of them died of neglect when he hopped on the crazy train. (this is the same guy who got his AMX stuck so high in a tree he needed to hire a crane and a tree surgeon to recover it!) Wild times! Sometimes it seems like good cars are wasted on contemporary owners. It's only the people decades later that truly appreciate them after most of them are rusted away lol Link to comment Share on other sites More sharing options...
viven44 Posted August 1 Share Posted August 1 Sometimes it seems like good cars are wasted on contemporary owners. It's only the people decades later that truly appreciate them after most of them are rusted away lol Watched this interesting video on Vacuum advance that showed up randomly on my feed Gary and Jim were explaining a couple days ago on a thread why ported vacuum might be better for an automatic... It makes sense that ported vacuum would offer an advantage and provide that additional timing when needed... But this brings a question... regarding no EGR and pinging on stock distributor.... if I am not using EGR and I am hooked up to manifold vacuum full time that means the distributor is at full vacuum advance all the time at idle... and as i accelerate, the distributor would actually 'vacuum-retard' timing on part throttle.. so thats a safeguard against pinging, right ?? Link to comment Share on other sites More sharing options...
FordFETruck Posted August 1 Share Posted August 1 Watched this interesting video on Vacuum advance that showed up randomly on my feed Gary and Jim were explaining a couple days ago on a thread why ported vacuum might be better for an automatic... It makes sense that ported vacuum would offer an advantage and provide that additional timing when needed... But this brings a question... regarding no EGR and pinging on stock distributor.... if I am not using EGR and I am hooked up to manifold vacuum full time that means the distributor is at full vacuum advance all the time at idle... and as i accelerate, the distributor would actually 'vacuum-retard' timing on part throttle.. so thats a safeguard against pinging, right ?? I've run it both ways on my truck and run manifold vacuum on the truck. I have noticed no difference whatsoever how it takes off under light throttle or drives ported vs manifold other than it idles smoother throughout all of the AFR and weather conditions with the additional timing at idle. That being said I've tried manifold vac on other cars with automatics and bigger camshafts and it didn't work too well. Worked fine until the rpm drop from park to drive or reverse takes the vacuum advance away from the vacuum drop then the idle speed would drop too fast to recover. Stock vacuum levels though with small camshafts never had any issues. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted August 1 Share Posted August 1 Watched this interesting video on Vacuum advance that showed up randomly on my feed Gary and Jim were explaining a couple days ago on a thread why ported vacuum might be better for an automatic... It makes sense that ported vacuum would offer an advantage and provide that additional timing when needed... But this brings a question... regarding no EGR and pinging on stock distributor.... if I am not using EGR and I am hooked up to manifold vacuum full time that means the distributor is at full vacuum advance all the time at idle... and as i accelerate, the distributor would actually 'vacuum-retard' timing on part throttle.. so thats a safeguard against pinging, right ?? Vacuum advance goes away as the throttle opens, but mechanical increases with Rpm, up to whatever limit you set. Link to comment Share on other sites More sharing options...
viven44 Posted August 2 Share Posted August 2 I've run it both ways on my truck and run manifold vacuum on the truck. I have noticed no difference whatsoever how it takes off under light throttle or drives ported vs manifold other than it idles smoother throughout all of the AFR and weather conditions with the additional timing at idle. That being said I've tried manifold vac on other cars with automatics and bigger camshafts and it didn't work too well. Worked fine until the rpm drop from park to drive or reverse takes the vacuum advance away from the vacuum drop then the idle speed would drop too fast to recover. Stock vacuum levels though with small camshafts never had any issues. Cam choice is a good point... stock cam is what I was thinking.. I haven't experienced that big drop in idle in my trucks. Jim, yes mechanical would increase... but comparing ported and manifold vaccum scenarios, both would have that mechanical advance + vacuum advance... but if I understand correctly, overall advance would be lower in manifold vacuum on part throttle, correct ? hence less likely to ping without EGR ? Link to comment Share on other sites More sharing options...
salans7 Posted August 2 Share Posted August 2 Cam choice is a good point... stock cam is what I was thinking.. I haven't experienced that big drop in idle in my trucks. Jim, yes mechanical would increase... but comparing ported and manifold vaccum scenarios, both would have that mechanical advance + vacuum advance... but if I understand correctly, overall advance would be lower in manifold vacuum on part throttle, correct ? hence less likely to ping without EGR ? I didn't necessarily do anything to it aside from pushing it around, but I did have all of the dead and dying tree limbs/trees above it cut down so that there's a much lesser chance of the truck getting nailed by falling limbs. I mainly had them come out to trim two dead trees and one weak branch that were close to my house to reduce the risk of trees hitting my house (Florida things). But since they were here with the fancy equipment, I had them trim along the back fence line as well. Everything visible in the photo points away from my truck so I didn't bother having them cut the rest but may change my mind if I still see stuff flying towards my trucks. With that being said, I can now park two of my trucks together on the concrete. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted August 2 Share Posted August 2 Cam choice is a good point... stock cam is what I was thinking.. I haven't experienced that big drop in idle in my trucks. Jim, yes mechanical would increase... but comparing ported and manifold vaccum scenarios, both would have that mechanical advance + vacuum advance... but if I understand correctly, overall advance would be lower in manifold vacuum on part throttle, correct ? hence less likely to ping without EGR ? I don't think anything would be different once the throttle blade is above the transfer ports. There may be some small pressure drop because of Bernoulli effect in the venturi of the carb. Fluid dynamics is challenging to model in a complex shape like a carburetor where you have venturi, boosters, transfers, the throttle blade, the choke plate on top is also going to be changing as it's spring warms up... (complex for me to visualize, pretty simple once you model it in CAD, if you have enough processor power) Link to comment Share on other sites More sharing options...
Gary Lewis Posted August 2 Author Share Posted August 2 But this brings a question... regarding no EGR and pinging on stock distributor.... if I am not using EGR and I am hooked up to manifold vacuum full time that means the distributor is at full vacuum advance all the time at idle... and as i accelerate, the distributor would actually 'vacuum-retard' timing on part throttle.. so thats a safeguard against pinging, right ?? Be careful with the terminology. There were actually distributors with two vacuum ports - one for advance and one for retard. I don't think you have one of those, but that's where my mind went when you said "vacuum retard". But to answer the question I'd say "Probably not". The vacuum advances that came with engines with EGR had full advance with not much vacuum. So unless you really get into the throttle heavy you'll probably still have full advance. That's where the adjustment comes in. You turn the Allen wrench to put more preload on the spring so it takes more vacuum to get full advance. And you keep doing that until the pinging stops. Link to comment Share on other sites More sharing options...
Recommended Posts