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Discussion Starter #1
I've got the 400 in my Rnchero running really well and it pulls hard right up to about 4700 RPM but right there it just seems to be hitting a mechanical barrier that is keeping it from going any higher. I still have bit more tuning to do but I was just wondering if this was normal or if the motor should be able to spin higher without reaching this sort of mechanical limit?
 

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My nephew had a 78 F150 with a 400 and I think it quit at around 5000 rpms. It had a good dual exhaust on it which may have helped some. I'm not sure what else had been done to it. I think it was fairly stock.
 

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Discussion Starter #3
400 stock spec bottom end (yes, awful dished pistons)

'71 casting Cleveland 2v heads machined for 2.19"in/1.71"ex valves, 5 angle valve job, machined for 7/16" studs and guide plates, 1.73 ratio harland sharpe roller rockers.

Edlebrock 351m/400 Street Mster intake

Generic RV cam: Camshaft - RV - Duration (I) 204 .050" (E) 214
Adv Dur (I) 270 (E) 280
Valve Lift (I) .484 (E) .510
Lobe Sep (I) 107 (E) 117
Pwr Range 1,500 - 4,000

Speed Demon 650 DP modified with annular boosters and Quik Fuel metering blocks

Ignition: Mallory unilite dizzy (all mechanical) and holley promaster resin filled coil 55,000 volt output

Exhaust: 351c 2v headers going through 2 1/4" pipe with an H pipe.
 

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Do you have good aftermarket valve springs?
 

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Discussion Starter #6

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If you sit in neutral and slowly raise RPMs, does it rev-limit as well? Have you checked for proper mechanical timing advance vs RPM with a light?

David
PS: Don't do damage over-revving. Do a controlled rev increase. I wouldn't pass 52-5300. And, hey, it's a 4k rpm cam. Pushing 5k won't do you any good anyway.
 

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PS: Don't do damage over-revving. Do a controlled rev increase. I wouldn't pass 52-5300. And, hey, it's a 4k rpm cam. Pushing 5k won't do you any good anyway.
LMAO, Very good point! If it's a cam designed for the 4K range then of course it's going to hit a wall past that point.... I should have paid closer attention.
 

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Discussion Starter #9
Running out of cam would certainly make sense, I forgot about the RPM range for it, lol.
 

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Ive got a similar engine in my chero. But my cam is 228 @ .050 .544 lift. Also, edelbrock heads performer rpm air gap intake, speed demon 750 mech secondaries, same headers, 2.5 exhaust.

I set the rev limiter @ 6100 rpm and it shows zero signs of slowing down when it slams aginst the rev limiter. The first issue is absolutely your cam, the second issue is that intake. I cant prove it, but i talked to several engine builders about that intake, and they all told me that i was better off sticking with the newer edelbrock performer 400 intake, which is what i had befor the rpm air gap, with similar results on the top end, just not as potent.
 

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I have a 78 F150 4x4 w/400. Pocket ported heads 4V 351C valves Crane hi speed towing cam and Offy dual plane intake 750 Holley. Easly hits 6K pulls real hard.
Issue is valve springs these engines are heavy. I use more seat pressure than some companys recomend because of this. 120# seat pressure might be max for a mild small block but with big block valves 120 to 140 is recomended by some companys. Side note on 351M and 400 anything over 6K you better go with aftermarket push rods as factory ones tend to bend after that point.
 
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