[Chris/75]

Okay, my boss just gave me an 454 4 bolt main block that has been bored and has new cam bearings aswell as new freeze plugs installed.But this engine has been sitting in storage for 5 or 6 years since all of that had been done. He gave me a set of heads aswell that havent been touched yet and im not sure if they came of this block or not. My boss doesnt know much about the history of this 454 block or the heads, someone gave it to him years ago in the condition they are now. The #s on the block indicate it is from 1978.Its a 4 bolt main so i assume it came from a truck or maybe a Suburban, dont know. The heads are a set of oval ports # 3993820. I would like to know if there a decent head for a street machine. Id like to build this 454 for my 70 Chevelle someday and would consider using them.They have 113.06 combustion chambers with 2.06/1.72 valves. Ive read a little about them in my Chevrolet By The Numbers book, and it says that these heads are a oval port design that are identical to the #3931063 except these 820 heads are a open-chamber design and the intake and exhaust seats are redesigned and the spark plug seat is now tapered. Just wanted to know if any of you big block guys know anything about these heads and if they may be worth using for a mild street setup.Maybe install bigger valves with a little head work,mild cam, good intake,good ignition and ofcourse a set of headers. Or should i look for a set of 049s or 781s?...

 

[Rmchevelle]

I used the search function (very useful tool on this site) at the top and found this: http://www.chevelles.com/forums/showthread.php?t=106565&highlight=820

There are several other old threads to be found if you use the search tool.

Rod

 

[71malibu406]

the 820's are worth using. there isn't much difference between them and 049/781's, imo. you can actually get a little better compression ratio with the 820's and not have to have as much dome on the pistons. i know several who have used them before in performance applications and they did very well.

 

[Guest]

Read the link one post up.

pdq67

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[Hi-po SS 454]

These heads were on the 1971 454 365 hp engine and some 402's. With the stock flat top pistons on that engine it was 8.5 compression ratio using those heads. I have learned its a good head, but you will have to deal with low compression with stock flat tops..

 

[66rat]

820's are good heads. We put a set on my son's .030 over 427. At 10.25 compression and a small solid flat tappet cam the car went a best of 7.60 (1/8th mile) in his all steel 72 Chevelle. That's equal to high 11's in the quarter. We cleaned them up, did a little DIY home porting, polished the chambers and installed the bigger valves.

Rob

 

[Chris/75]

Thanks! Looks like i may use them. Thanks again!

 

[TNTRacing2]

I have a 3700lb camaro.

454 with the 3993820 heads. They were ported with 2.25/1.88 valves. 11:1 compression. victor jr intake. 830hp carb. solid roller 260 duration 680 lift. 4200 stall. 4.30 gear. 26X10 slicks. 1.75" headers with 3" exhaust. Run 1.49 60' times, 6.90's at 99 mph in the 1/8 mile.

They are a pretty good head..

 

[ddeennis]

i have had those heads on the race car with 14.5 to 1 comp, 268 @.050 roller cam with .685 lift, tunnel ram and so forth good for 10's with my own porting and 2.19 /1.88 valves, after all the work and new valves with just a slight mill to make sure flat i had 108 cc chambers...............