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Old 02-26-2012, 09:57 PM
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Big block on my mind...

Heres the deal I have a 71 C10 350/350 turbo weekend driver no strip and have come across a good deal ($800) on a stock 1985 454 with 78,000 miles that is set-up for intake and carb. I am going to put a big block in this truck and I want to make 400 to 450 hp I know I can buy a turnkey for around 3k to 4k but I was wondering if I could make that hp with the stock bottom end by changing cam,heads ect and saving some coin?..Last option would be a short block build which way should I go any and all suggestions wanted!! Thanks

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Old 02-26-2012, 10:24 PM
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Quote:
Originally Posted by bigj7698
Heres the deal I have a 71 C10 350/350 turbo weekend driver no strip and have come across a good deal ($800) on a stock 1985 454 with 78,000 miles that is set-up for intake and carb. I am going to put a big block in this truck and I want to make 400 to 450 hp I know I can buy a turnkey for around 3k to 4k but I was wondering if I could make that hp with the stock bottom end by changing cam,heads ect and saving some coin?..Last option would be a short block build which way should I go any and all suggestions wanted!! Thanks
Chances are this engine will have "peanut port" heads, not known for big HP numbers. That said, they're good for the numbers you're looking to make- and at a low enough RPM to allow a decent rear gear ratio and no need for a loose torque converter, etc.

There is absolutely no need to swap heads or beef up the bottom end at this level. All you need is a sound engine w/good oil clearance and good ring seal. A recurved distributor is a must for ANY performance orientated engine. The exact timing figures will depend on the cam you end up using.

Car Craft did a test of a Demon Engines crate BBC 4-bolt 454 +0.030" (461 ci), Peanut Port heads (118cc chambers = 9.4:1 CR, stock valve sizes) w/a XE 268H Comp cam (.515"/.520" lift, 224/230 @0.050" duration on a 110 LSA), w/a Holley HP 750 carb and a (too-large) set of 2.25" dyno headers.

It made 446 HP @ 4900 RPM/542 TQ @ 3600 RPM. It made 490 ft/lbs @ 2500 RPM. There's no doubt the numbers would've been better w/a smaller primary header diameter, IMO.

More: http://www.carcraft.com/techarticles...d/viewall.html[/QUOTE]
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Old 02-27-2012, 04:45 AM
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Thanks Cobalt is there anything else you would do with this engine if it were you?
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Old 02-27-2012, 08:45 AM
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Quote:
Originally Posted by bigj7698
Thanks Cobalt is there anything else you would do with this engine if it were you?
That would depend on how it tested when I did a leak down and compression test along w/looking at the vacuum gauge readings.

If the engine tests as good as it should for having the mileage it is supposed to have, I wouldn't do much more than a cam and valve spring swap and a valve spring spacer kit to get rid of the exhaust valve rotators if it's equipped w/them, an intake w/a well-tuned carb, a performance timing curve in the distributor, and headers/dual exhaust.

A decent intake is available for the peanut port (PP for short) heads is the Weiand p/n 8122 Street Warrior- http://www.summitracing.com/parts/WND-8122/. Personally I wouldn't hesitate to use the Q-jet carb if it has one already.

A set of long tube headers will be needed for the best results, along w/a dual exhaust (=/> 2-1/2" diameter pipes w/mandrel bends). Using a connector between the two exhaust pipes aft of the collectors and before the mufflers will help the sound and might pick up the midrange a little to boot.
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Old 02-27-2012, 08:59 AM
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I don't mean to be a wet blanket, but a 85 454 was onlly rated at about 240 net Hp when new (assuming this is a standard truck motor) and, according to the web, had a compression ratio of 7.5 to 8.8 depending on the year with 7.8 being most likely. If thats true, it's good ways away from fresh 9.4 CR motor.

I don't know if you're talking 'gross' or 'net' when you say 400hp, but if it's net, picking up 160hp is going to require money. The heads are the biggest problem, and swapping them out can both increase your breathing and bump up the CR. Of course you'll want to match them to your intake/carb setup. I don't know if you'd come out that far 'ahead' money-wise when it's all said and done (I haven't priced BBC parts in over a decade) so I'd say do your homework.

Also, you mentioned the truck was setup for a 350/350. A big block is seriously heavier then a small block so you will likely need new springs. A stock TH350 will not last long behind a modified BBC, and probably not terribly long even behind a stock one with that punishing torque; trust me. My first hot rod was a 79 Camaro with a fresh, lightly modded 454 mated to an old TH350 and it chewed it up an spat it out shortly just after the 454's break in was over. The TH400 is, I am pretty sure, heavier then a TH350, so it makes the need for big-block springs all the more urgent. Finally there is the small money/time of getting the bracketry figured out.

Consider all the costs!

That being said; I'd do it again. I'd just start with 'at least' a stock TH400 though.
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Old 02-27-2012, 09:56 AM
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Thanks guys I am considering all my options..
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Old 02-27-2012, 01:59 PM
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HEY ...Nothing wrong with peanut port heads for a street machine! They have the good combustion chamber & for a street machine they are "quicker" then the big square port heads! ...They will need to be cleaned up ...hardened seats, brozen inserts in the guides, & gasket matching.
ONE issue you need to check, check and see if the crank is steel or cast iron!!! Obviously if your going for big HP then I'd spring for a steel crank!
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Old 02-27-2012, 02:14 PM
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If the short block is good then leave it alone. Pull the heads off, mill them .030" have a good valve job done and maybe bowl work. New springs and seals, new cam. Reassemble and go. Milling will boost your compression slightly and a vj and bowl work will help with low lift flow (small flat tappet cams need low lift flow).
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Old 02-27-2012, 02:25 PM
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Quote:
Originally Posted by 11echo
HEY ...Nothing wrong with peanut port heads for a street machine! They have the good combustion chamber & for a street machine they are "quicker" then the big square port heads! ...They will need to be cleaned up ...hardened seats, brozen inserts in the guides, & gasket matching.
ONE issue you need to check, check and see if the crank is steel or cast iron!!! Obviously if your going for big HP then I'd spring for a steel crank!
for a street machine, I would also want the peanut ports over a set of rect. port heads
however a set of oval ports (like some 049 or 781) would be best

what do you mean by big hp?
i'm no expert but from what i understand that cast crank can take 600-700 hp
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Old 02-27-2012, 02:39 PM
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PP heads all have hardened exhaust seats, the PP heads came along during the smog era (~1975-up), induction hardened seats were from around '73'ish -up. Unless the exhaust valve diameter was enlarged considerably, that is. Some HD applications might have used hardened seat inserts, although the PP heads I've seen didn't use them.
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Old 02-27-2012, 07:31 PM
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So if I decide to buy the 454 I can put a cam and lifters in it do some head work and get close to 400hp right.
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Old 02-27-2012, 08:48 PM
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yep 400 is ez

but when switching from a 350 to a 454 its not about 400 hp, its about how many ft lbs of torque
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Old 02-28-2012, 05:07 AM
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I did the same thing with my 70 c10. Came with a 350/th350 setup. I put in a 454/th400 from a 74 suburban.

If you want to run the later model brackets (1973+, long water pump) then you will have fan/radiator clearance issues. I ended up setting the engine back a few inches and moved the radiator forward about 1/2 inch.

mpg will drop 25% with a bbc compared to a sbc.

I bet your truck has a 3.08 gear open diff. Not the best for traction or cam with a lope. You need torque with that gear.

if I had to do it all over again, I would not do a bbc. MPG is really bad (8 city, 12 highway). It was fun but I wish I had put in a 406, or maybe an efi vortec 350 (factory roller cam) with a set of T3 turbos, or late model 5.3 which are very cheap.

You could even add efi and a set of turbos on your current 350. Think of boost this way, 7.5 psi of boost on a 350 will make it run like a 525 cid. (50% more hp and torque) with 7.5% of turbo boost).

In any case, your th350 will need to be modified or replaced with a th400 to handle the extra power. Also consider getting a limited slip diff.
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Old 08-20-2012, 08:00 PM
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I have been reading the post on here for awhile and seen some good and maybe just a little missed informed information on the 1985 PP 454cid.

I just put one in my 72 c10 Lb with a 88 700r4. I did move the motor back about 2'' just because I wanted to use a radiator from my 94 GMC.

Yes it has the 3.08 rear end now and looking for a 3.42 or 3.73.

Anyway my 454 was pulled from a 85 sub with about 80 some thousand miles on it. I had it put on the dino it came out 330hp 278tq I can remember what rpm.

Nothing has been added yet, I have a RPM performer intake for it but not sure what carb to use..

It drives awesome, it's dropped and sets about 7'' from the ground, went with flow exhaust that I had to wrap around the frame and stuff between the bed and the frame, fast 'n' loud...

Just saying it all fits with minimal mod...
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