Has anyone had any experience getting a 400 to rev over about 5200? I'm on my second bullet and even with a hydralic roller cam thata as high as it wants to go. It has a performer dual plane and a 750 Demon carb, headers, port matching etc. Same limit as with a comp cams 278 cam. I tried an open 1" spacer but it wont idle with it. Maybe just too much stuff going round and round in there.


1977 Ford F-100
400m/c6
280,000 miles
Stock on the outside
modified/rebuilt everything

 

>Has anyone had any experience getting
>a 400 to rev over
>about 5200?

beartracks,

For an M-block, 5200 is pretty high, but I've seen them rev up to 6K with a similar intake setup and less carb than yours. I can rev my mostly stock 351M up to 5K (barely).

>even with a hydralic roller cam thata
>as high as it wants to go.

What are the specs on your cam?

Also, several more questions: What headers/exhaust? Any porting on the heads? What is your timing set at (static and total advance @ rpm)? What ignition system are you using?

>Same limit as with a comp cams 278
>cam.

I can understand that problem with a single-pattern cam. On the M-block, which likes a dual-pattern cam, single-pattern cams usually give you too much intake duration at low rpm and not enough exhaust duration at high rpm.

>I tried an open 1" spacer but it wont
>idle with it.

Assuming 100% volumetric efficiency, you could get by with a lot less carb. At 100% VE, a 650cfm carb should be good for up to about 5.7k rpm with a stock bore 400, a little less if you're overbored.

You may have to sacrifice some (maybe a lot of) idle quality to get a usable rpm range much past 5K rpm in this engine. I would suggest a single-plane intake, but that would probably cause the same kind of trouble you're having with the spacer. You may need to bump the idle speed up to keep it running.

BubbaF250

1980 F250 4x4 Custom, 351M/NP435/NP208/D44HD-TTB/D60-FF/3.55s 6750 GVW, Rust & White.

 

[font size="1" color="#FF0000"]LAST EDITED ON 06-Jun-01 AT 12:34 PM (EST)[/font][p]I've tried a 650 carb and it didn't work as well even at idle. heads are pocket ported and matched with rollers, stainless valves and stelite seats, intake port matched, open headers same rpm, cam is 218/224 at 50 with lift of .562/.586. It's balanced and having too much time on my hands I polished the rods and the crank.Close to 10:1 (175# static compression). 38 degrees total advance (without the vacuum added) and 24 at idle with the vacuum. Should be about 425 horsies but I'm always looking for a couple more. Should be good for high 14s (I think) at sea level. It'll shake your fillings out a 1/4 mile pass but I would like to embarass a couple of Camaros.:->
Heh, heh.


1977 Ford F-100
400m/c6
280,000 miles
Stock on the outside
modified/rebuilt everything

 

beartracks,

Everything you've got looks good to me. BTW, what heads are you using? Any milling or other mods besides the porting you mentioned? Just curious.

You didn't mention the ignition system, so I'd check that to make sure you're not cutting out or losing spark at high rpm. (You wouldn't have a rev limiter, would you?)

How about the fuel pump? Is it keeping up with demand at high rpm?

If you have fuel and spark, then based on your parts list, the weakest link has got to be that intake manifold. I've seen an M-block with a Performer EGR manifold run up to 6K, but that manifold was flow matched and ported extensively ($$$!). Unless you drop the coin to get that thing on a flow bench and have it tuned, I think it's marginal at anything over 5K or so. Even then, it's probably still marginal for what you really want to do.

I think it's time to start looking at something with a lot more plenum volume (more than you can get with just a spacer) and check out some single-plane intakes. Unfortunately, I don't have any experience with single-plane manifolds on the M-block, so I can't help you with any specific recommendations.

I have to mention that at the level of performance you seek, dyno tuning time can be well worthwhile (if you haven't done it already). I've seen good tuners get another 25-30% more power out of engines that the owners thought were maxed out.

Good luck.

BubbaF250

 

[font size="1" color="#FF0000"]LAST EDITED ON 07-Jun-01 AT 03:44 PM (EST)[/font][p][font size="1" color="#FF0000"]LAST EDITED ON 07-Jun-01 AT 02:58 PM (EST)[/font]

Bubba, it would be fun to play around with a single plane but I would have to adapt a Cleveland I'm afraid to find one. I'd also hate to lose the bottom end. (C-6 tranny with 2300 stall) I still pull 15.5 vacuum at 825rpm. It also gets driven almost every day and hauls the camper and boat to the lake from time to tome. I might try a smaller height open spacer. Ignition is Accel H.E.I. with super coil. 15psi electric pump with a return style regulator and line. The dyno was going to run $700 to start so I decided to quit throwing money at it. Oh well I guess you can't have everything but it's fun to try.

Oh yeah, the heads are 2v 71 Cleveland. Three angle, stock size valves. Valve train is all Crane.I think the 4v would be too much port size for the street. It's bored .060 over has Total Seal rings.


1977 Ford F-100
400m/c6
280,000 miles
Stock on the outside
modified/rebuilt everything

 

beartracks,

Even though no-one makes a single-plane manifold for the M-block anymore, I know Holley and Offenhauser used to make them. Now and then, they show up on ebay and such places. If you can get one cheap, it might worth experimenting.

You could also try a 4-hole spacer, as that would give you a little more plenum volume, and maybe less trouble with the idle.

As far as power goes, I believe 400hp is about the upper limit for a streetable truck M-block. If you were willing to dedicate the truck to non-towing/hauling duties, I'm sure you could do more. But your question was about the rpm limit you were hitting, and other than the intake issues, I'm stumped.

You may not be able to embarass Camaros (if they're paying attention), but I bet you could give them a good scare. ;-)

BubbaF250

 

Thanks for the thoughts. I might not quite out run a new Z28 or whatever they call em now but if I launch beside him with open headers he's likely to think the world is comming to an end and lift. :->


1977 Ford F-100
400m/c6
280,000 miles
Stock on the outside
modified/rebuilt everything

 

 

My first Ranchero was a 1973 with a 400/C6. It had 9.5:1 compression, headers, dual exhaust (with glass packs), Carter racing carb, Edelbrock intake, Crane cam, shift kit, etc. I was cruising down the highway at 60 mph and a guy came up in a 68 camaro and rode my tail for a while - then pulled along side for a few seconds to taunt me, then stomped on it to pass - all to impress his girl. He finished passing and then pulled back in, only doing maybe 65. They were surprised to see me pull alongside a few seconds later. I looked at them for a few seconds, dropped it into second and nailed it. From the look on their faces I think they had at first assumed the stock looking truck had a loud exhaust due to poor maintenance! He sheepishly dropped way back after that.

In the few years that I owned that Ranchero, I found out that people in sports cars really dislike being shown up by a stock looking truck! As far as redline - I typically did not take it much over 5000 (but may have that particular time). Also - the Carter carb made it sound like a GM product, which really confused Chevy fans as did the Ford air cleaner I had bolted to the middle of the plywood cover which covered the bed! Some people convinced themselves that I had a Toronado 455 mounted in the back!

Tom