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Old 04-11-2007, 01:41 PM
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Big block questions, help please???

Ok i have never built a motor before, I know a little and I am learning a lot from you guys and some speed shop friends of mine. This is what I have, 1967 swb chevy p/u. 390 gears, 700r tranny, currently a small block. I recently found an untouched 454, don't have numbers with me right now, I remember it was a mid seventies not a tall deck. Got a deal I think, hooker headers, block with pistons still hung, balancer, all sheet metal, rebuildeable edelbrock 750, and my choice of 3 sets of heads, no intake though. I have no idea what to look for on these heads to see what is a good choice. I did find most of you want the heads that end with 049 or 781 so I will look for this when I go to pick up the parts. Now my question, I am wanting to build 400 to 450 reliable horsepower that I don't have to worry about, the small block I have is just running about 260 hp in my 4000lb beast and just isn't cutting it. I would like to know the best and hopefully cheapest way to do this. I only have a few hundred dollars here and there to spend on this project and would like to get the big block in as quick as possible. I was wondering if that edelbrock is going to be able to do that big block justice? I am also worried about the 700r I believe it is a stock 86 caprice transmission, it has been behind a big block before and no problems but I don't know the specs on it. Any answers would be really appreciated, thanks guys, and just to let you small block guys know up front, I do like small blocks but I am not interested in building one right now.

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Old 04-11-2007, 02:13 PM
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If you can get a set of 781 or 049 heads, 400-450 hp is not too hard. I assume that you will be using to stock valves, which will make things a little harder, but I think it is still do able. Below is a combo with a very mild cam and those heads with 2.19 1.88 valves.

http://www.compcams.com/Community/Ar...ID=-1989283802

454
7.9:1 compression (as far as I can tell)
220 @.050 .500 lift 115 lsa hyd flat tappet
049 heads with 2.19 1.88 vavles
dual plane intake

made 419 hp 473 ft lbs

One thing I don't really understand about this is that they said it was detonating without 100 octane. I guess anything can detonate if the situation is right for it, but it still seems weird with 7.9:1 compression. I would look at a similar set up with something like the comp xe268h cam (224 230 @.050 .515 .520 lift 110 lsa).

Adam
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Old 04-11-2007, 03:16 PM
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Ok i got the casting number, it is 361959. I don't know if the heads are different from year to year as this number spanned 1973 to 1985 from what I have read but one choice is the stock heads for this. Does anyone know if they are decent or should I just start over?
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Old 04-11-2007, 03:22 PM
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ok even though I don't have the casting numbers a little research showed that the heads I can get are the 781. Now what is the best thing to do for these heads to get horsepower and reliability.
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Old 04-11-2007, 04:07 PM
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I'm sorry to say that a couple hundred dollars here and there is not going to cut it. A 1000.00 for a cheap basic rebuild. And 200.00 for an intake that can make 400 hp. Plus you will need dual 2.5 inch exhaust and a long list of other items that will nickle and dime you to death(fuel pump, hoses, plugs, wires, oil, filter, antifreeze, gaskets, belts, ect).

You will also have trouble with the later style (73 and up) BBC brackets with the 67 body. The later style brackets stick the fan out way too far due the long water pump. I had to move my BBC motor back 1.5 inches and make custom raditor mounts to make room for a BBC with newer brakets on my 70 truck. Also, an electric cooling fan will not cool your 454. Plus a good one cost another 200.

For 400 hp you will need 8.75 to 9.25:1 cr and a cam with 220 to 230 degrees of duration at 0.050" and headers. A cam this size will need a 2500 stall converter. I doubt a stock 700r will hold up to that.

3.90 gear in a 67 truck? Are you sure? The closest to that size that came in those trucks is a 3.73 or 4.11. 3.73 were very common in 6 cylinder trucks. Pull your cover and read the stamped ratio on the ring gear.

Don't worry about casting numbers. They mean nothing after you put in new pistons and a cam. Yes, get the 781's or the 049's. 820's are good also and have smaller chambers which will make higher compression with the stock mid 70's smogger pistons. Plus 820's flow great on the exhaust side due to a very un-shrouded chambers at the exhaust valve. Stock smogger compression is about 7.5:1 using 781 heads (120-123cc). Cr will jump to around 8.2 with the 820's (110 to 112cc) which is a good thing if you aren't planning on changing out the pistons.

Also, be ready for some terrible gas mileage. Amazing how much gas a BBC can suck down. A setup like yours could get 6 or 8 mpg in the city, depending how you drive it. I know, I had a 350 in my 70 1/2 ton and installed a 454. Mileage went down a lot. I now get 7 to 9 city and 11 to 12 with my bbc and got 10 to 12 city and 14 to 16 with the 350. About a 1/3 less mpg with the BBC.

I know you don't want a sbc, but you should reconsider. A 400hp/450ftlb 406 sbc can be built for the same money and will bolt right in and deliver much better mpg. Don't under estimate the amount of work and money involved to do a sbc to bbc conversion.
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Old 04-11-2007, 05:14 PM
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I am aware that I am not going to rebuild this motor and put it in my truck in a week. I have a few extra hundred here and there and will have to save up for the big stuff I realize that, which is why I need the best way to do it the first time. I don't want to have to do this four different times before I get it done. I got the first big expense out of the way the majority of the motor for $800. I'm not sure about the gears just going by what my cousin had told me, hadn't checked for myself. I know they're low, and this was a 6 cylinder 3 on the tree to begin with.
Thanks for the heads up on the brackets, my cousin that had this truck before me pulled the big block out of it, ill ask him how he had it set up. If you could let me know how you set up your radiator brackets, moving the motor back wouldn't be a bad thing, balance it out a little more. I know a lot of people like them but, I just don't trust electric fans I will probably never use one I like to know that as long as the motor is turning it is being cooled.
I'm not against buying a new set of heads if the 781's won't work but I know they are expensive and I would like to use the ones I have if at all possible.
Is there any way to beef up that 700r easily, if not do I just need to go to the ol tried and true 400 and some higher gears?
I don't think anyone who has ever thought about using a big block has ever let gas mileage be a determining factor or they would have ran away screaming.
It is too late to reconsider I already bought the big block and I am going to build it. The 350 is weak but it was rebuilt well and will last as long as I need be to finish the big block, but as I am sure you know if you already have one anticipating the power of that big block is hard to put off.
I was planning on building a 350 out of a 88 chevy pick up i bought to put in the '67 actually but I went to my cousins house a couple weeks ago and went for a ride in the 1971 chevelle he put the 454 in that used to be in this truck and let's just say I won't accept anything less now.
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Old 04-12-2007, 08:51 AM
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I understand, I just needed to get that information to you so you know what you are getting into.

781 heads are really good but the chambers are big (120 to 123cc). They just need a piston with a dome to work with a bigger cam. A 10cc dome will get the compression up to 8.5 and a 25cc dome will get it up to 9.5:1. If you are looking for 400 to 450 hp then some more compression would be nice. Yes, you can make 450hp with 8.5:1 cr but the low speed torque will be down. Better to use as much cr as pump gas can handle. However, bbc are more detonation prone as compared to sbc. For similar setups, about 0.5:1 less cr should be with bbc as compared to sbc's.

BBC's also eat cams. Especially with todays engine oil. Make sure to use diesel engine oil for break in and from now on. I also recommend to use a cam with slightly softer ramps. So, avoid the xtreme series compcams. An old school, compcam 280H (230/230) or a summit brand will live much longer. Also set the springs up a little lighter.

Use 8.75 to 9.25:1 and 2000 to 2300 stall with a compcam 270H for 400-425hp, or 9:0 to 9.5:1 and 2400 to 2600 stall with a compcam 280H for 425 to 450hp.

700r's take about 1200.00 to rebuild and beef up. Converters are also expensive for the 700r's if you get the locking version. I use a th400 and later plan to install a gear vendor OD. Even with my 3.08 gear I'm wanting more OD. Does about 3K rpm at 80mph with 28 inch tires.

I like the new style brackets better. Puts the alternator on the passenger side and the belts are much shorter. I used a 2 core alum summit racing radiator with a home made fan shroud. I just cut off all the radiator brackets from the radiator support and mounted the radiator right up to the radiator support. For weight transfer, moving the engine back 1.5 inches is like moving the battery from the front corner to the inside the cab. But using the older style brackets with the short water pump and the stock radiator and fan shroud would make the job much easier.


So, build a 9.25 to 9.5:1 468 (0.060+ 454) with 781 or 049 heads and a compcam 280H. Use small tube headers, 2.5 inch exhaust, aerochamber mufflers, performer rpm intake, holley 850 carb, th400, 2500 stall, 3.73 rear with a LSD center section.

You should also look into lowering springs from Classic Enterprises. I did a 4/6 drop on my truck. See my photo album.

Good luck with your project.
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Old 04-12-2007, 09:27 AM
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I think the standard ratio for that 6 was 3:73, but optional gears were a 3:07. The 3:73 worked great with a 700r4, either with a 6 or a very built smallblock we put in later. The 6 with that setup was a little weak on power if you hit a big hill on the higway,(in OD with the converter still locked) but the 350 didn't feel those hills. I would think the 3:73 would be really nice for a big block with the 700r4.


Doom & gloom: I've been saving a 396 for many years for a possible streetrod transplant, but gas is going up 10 cents a week lately
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Old 04-12-2007, 11:13 AM
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Quote:
Originally Posted by 454C10
So, build a 9.25 to 9.5:1 468 (0.060+ 454) with 781 or 049 heads and a compcam 280H. Use small tube headers, 2.5 inch exhaust, aerochamber mufflers, performer rpm intake, holley 850 carb, th400, 2500 stall, 3.73 rear with a LSD center section.

Good luck with your project.
I agree, this combo should work well.

Adam
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Old 04-12-2007, 02:10 PM
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That combo will work, but why restrict yourself to the expensive gas? I built a 454 with a 218/224 cam, stock 049 heads, flat tops for 8.5:1, edelbrock intake, headers, and a stock HEI. Makes 390-400 all day on 86 octane.
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Old 04-13-2007, 02:52 PM
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Quote:
Originally Posted by 454C10
So, build a 9.25 to 9.5:1 468 (0.060+ 454) with 781 or 049 heads and a compcam 280H. Use small tube headers, 2.5 inch exhaust, aerochamber mufflers, performer rpm intake, holley 850 carb, th400, 2500 stall, 3.73 rear with a LSD center section.


I have been thinking about building this exact combo for a while. How much affect would 3.55 gears have on it because that is what I already have?
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Old 04-13-2007, 03:29 PM
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A 3.55 gear should be OK in a car under 4000 pounds using a 454 with that 280H cam. Anything over 4000 pounds will slow the engine down a little with 3.55 gears, but not that badly. Just not ideal. A compcam 270H is also a good running cam, makes more low rpm torque, better idle, decent mpg, and works well with a 3.55 gear and fair with a stock converter.
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Old 04-14-2007, 10:55 AM
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thanks for all your help guys I will let you know how it is going when I get the project underway.
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Old 04-14-2007, 11:30 AM
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Quote:
Originally Posted by 454C10
...
You will also have trouble with the later style (73 and up) BBC brackets with the 67 body. The later style brackets stick the fan out way too far due the long water pump. I had to move my BBC motor back 1.5 inches and make custom raditor mounts to make room for a BBC with newer brakets on my 70 truck. Also, an electric cooling fan will not cool your 454. Plus a good one cost another 200.
...
I must have "lucked out".

I have been reading that lots of people have had mounting bracket and header interference problems with 60 - 72 trucks and BBC engines.

I swapped the entire front suspension clip fom a mid-70's C10 into my 66 with just MINOR modifications (see my journal ... entry #'s 10, 11, 12)

The engine is on the frame, the stock 6-cylinder rad is in it's original location, (journal entry #41) and the (Hedman 69111) headers already have the paint burnt off of them.

Now before anyone says "Original 6-cylinder radiator!!!" ... Yes, I will be getting a special 3-row dimpled core rad built that is going to cost me $600.00. You should expect to have to "beef up" your cooling system, too ... big blocks generate a lot of heat.

That being said though ... the engine was broken in using the 6-cyl rad. I took it to the rad shop to have them estimate the upgrade, and they cleaned it out for me for free while it was there ... bonus! The engine was run for about 90 minutes or so, and the temp never got over about 210. This was inside a shop with the doors open. Ambient temperature was a cool 40F or so.

Last edited by 66GMC; 04-14-2007 at 11:36 AM.
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Old 04-14-2007, 07:51 PM
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Thanks for the info, I am putting a 1972 front end under my '67 as well. I have a friend who put one under his '66 Chevy he said they didn't change the suspension until '68 and it should bolt right up to my current setup just like his. He even found it for me, good friend huh.
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