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swb-big boy 01-05-2013 07:09 AM

need skilled info
ok im a new guy been reading alot on 781s im building a 79' 454 looking for a good setup on my 85'swb its gonna be a weekend show off .my run the strip few times.( its got comp lifter n cam package 292/ lookun to build a dependable street motor and i live across from drag strip .im needing info on rebuilding my heads but not lookin to replace my bottom end.was thinkin of uping the valve size like i read but dont want to over do it
.im 26 this is my first build.:drool: i need to know what to tell the shop to do to the heads. please help:confused:

vinniekq2 01-05-2013 07:19 AM

If you do a little porting on the exhaust side,bowl work and install 2.19 intakes and 1.88 exhaust valves you will make very good power.This is not over doing anything. I did similar work to my oval heads when I had my 1980 Camaro. worth the money

swb-big boy 01-05-2013 08:26 AM

ok, cool i live se of dallas any good shop u recomend? 01-05-2013 08:36 AM

Here is basic for big valve 049-781 heads.

Clean, check for cracks/warp.
Check valve guides for wear. If worn, repair with bronze liners.
Shorten guides and cut for performance seals.
Serdi cut intake seats for 2.19 valves.
Bowl hog to blend.
Serdi cut exhaust seats for 1.88 valve.
Bowl hog to blend.
two angles on valves
Install rotator eliminators.
Install valve seals.
10 degree +.100 retainers
Set springs to spec height.

I just did six of these heads for inventory last week.

For economy sake. Comp Products has a good price for aftermkt seals and a special on valves on the broom sheet.
Good prices on springs.

I bought hundreds of stock length stainless 2.19 and 1.88 valves. On a deal, several years ago. If you can buy +.100 valves reasonable, use them rather than the +.100 retainers. These heads, stock, have short valve springs.

If a mild cam with single springs. You can save money by not cutting guides and use 455 Buick valve seals. Also TSC stores sell a gold colored 5/8" washer in bulk hardware. That, when used in pairs, work good as rotator eliminator.

Heep guide to valve stem reasonably tight. Loose guides along with large valve heads= dropped valves. A historic BBC problem.

cdminter59 01-05-2013 08:40 AM

need skilled info
I know you said you don't want to replace your bottom end. But the chambers on the 781 heads are at least 118cc. So it would be nice to know if the pistons are flat top or domed. For an example KB pistons have three different size domes -12cc, -25.5cc and -43cc. With the 781 heads you would need a -12cc dome to have a 9.173 compression ratio which would be ideal with pump gas. The compression ratio with a flat top piston would be 8.233 a little on the low side.

swb-big boy 01-05-2013 04:59 PM

well im not sure of miles on it i believe its stock pistons i guess they r flat top they have s mall circle in the center. i have a set of luntine:confused:double springd that i got with all of the parts. how do i know if the springs r the rite ones to use?

cdminter59 01-05-2013 07:58 PM

need skilled info
I am sorry but you have a set of dished pistons in the bottom end. If you were to use the 781 heads you would have a compression ratio of 7.487. With this setup you will need to use a RV cam. Something like X4 254H. You will have good low end and mid-range power. The engine would have around 369 hp @ 4500 rpms and 510 lbs torque @ 2500 rpms. This will be fine for shows but not the track. BTW it would be your best interest to sell all the COMP .550/292 camshaft parts.

swb-big boy 01-05-2013 11:18 PM

have n second thoughts on the bb .im running a 87'block n heads now its a 355 im really thinking about just makin it tbi or tpi (i love the throttle response) its fresh maybe 2k miles on motor. its got comp cam n lifter setup.I have never been a fan of runnin a 750 holley double pumper was told its to much for my motor ??? can i make close to 500hp with the sb? whats better tpi/tbi??

vinniekq2 01-05-2013 11:26 PM

big difference between a 500 hp 355 and a 500 hp 460

yes you can make 500 hp

swb-big boy 01-06-2013 12:19 AM

so whats better tpi/tbi?

swb-big boy 01-06-2013 12:36 AM

when u say diff u talkin ft lbs
and waight. i got 355 and 454 not 460

cdminter59 01-06-2013 01:05 AM


Originally Posted by vinniekq2 (Post 1631167)
big difference between a 500 hp 355 and a 500 hp 460

yes you can make 500 hp

Vinnie, I think you had better explain to him what it will take and cost for a 500hp tbi or tpi engine if he didn't want to rebuild the BBC.

swb-big boy 01-06-2013 11:26 AM

only reason for second guess n is 355 is fresh and is alot less weight.yes what more could it take to make near 500hp? :confused:

swb-big boy 01-06-2013 11:35 AM

one more stupid ?? the 87' heads on the small block that have the valve covers that mount with bolts in center of the covers .. r they considered vortec heads???

vinniekq2 01-06-2013 01:24 PM

the 454 bored 030 is 460
a 500 HP 454 would be a mild build that revs 5800 to 6000 RPM making over 500 pounds torque. A 350 would need closer to 6800 rpm to make 500 hp and would require cylinder heads that flow 280 cfm, a roller cam(rough idle) big carb or modified fuel injection. The 350 would be a beast and expensive to build with moderate street manners. the torque would likely be 50-70 pounds less.
If you raced the engines against each other the performance would be close with a slight edge most likely to the 454.The small block 350 would need more gear to be close in performance.The small block is a lot lighter and easier to fit an engine bay,if that matters.
I use a small block for weight savings and handling.
what do you need/want

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