BBC Heads which to look for

[tilley52]

Hello, i have a 1990 GMC Suburban 7.4 TBI, it has always been a dog. I have had of for a couple years and it never had the grunt and torque of other older 454's that i have had, I have had the heads off because when i bought it it had lost a timing chain and ran valves into pistons. I noticed at that time how small the rect. ports on the heads were, they seem VERY small and restricitve. Well its time for a rebuild now and i want to change the heads and try and make a little more grunt for towing, any ideas what i need to look for for casting numbers, i dont mind having to change the manifold to an oval port if needed, seems lots of people are saying 049 casting. keep in mind it will need to smog thanks in advance

[TAWL_BOY]

049 and 781s are the large oval ports.

[b454rat]

I was told that you can't use the 049 or 781s on TBI motors. Why I don't know, just what I've been told. But something sorta doesn't make any sense, the motor that was in my 89 was out of an early 70s truck, never ran the heads, so dunno what they were. BUt my 89 had balls, even with 40" boggers and 3.73 gears, would still shit n git. I don't think they had the peanut ports back in the 70s.....

[rockhog]

Im running some closed chamber 063's on my 89 shortblock. With the smaller chamber it brings the comp ratio up to around 9 to 1. Your current comp ratio is around 7.8 to 1 or so.

[trkklr77]

049 are perfect and a DIRECT BOLT IN!!!

the post 92ish motors are when the started to change things around again. a 90 is still a gen 4/ IV and all older head will swap straight on.

a real nice up grade would be to ge the 049s, and a edlbrock efi replacment intake.

neither will affect your smog in any way and the intake is designed to legaly replace your iron brick ass pos.

the later heads [73-91] are small OVAL ports [not rect] and are called peanut ports. yeah they suck for high hp but in the end are some what benifical in that the small port increase air velocity and it does work, well mhe at best. you have to remember that from 73-91 454 are rated at 215hp, that why it doesnt feel like bbc's of old.

[Grumpy_old_fart]

Originally Posted by trkklr77

049 are perfect and a DIRECT BOLT IN!!!

the post 92ish motors are when the started to change things around again. a 90 is still a gen 4/ IV and all older head will swap straight on.

a real nice up grade would be to ge the 049s, and a edlbrock efi replacment intake.

neither will affect your smog in any way and the intake is designed to legaly replace your iron brick ass pos.

the later heads [73-91] are small OVAL ports [not rect] and are called peanut ports. yeah they suck for high hp but in the end are some what benifical in that the small port increase air velocity and it does work, well mhe at best. you have to remember that from 73-91 454 are rated at 215hp, that why it doesnt feel like bbc's of old.

most peanut port heads started around 77 or 78, and there were 049 and 781 castings available up in different years... . dont go by anything but the casting numbers to identify them.

049 and 781 castings are what you want.

049 castings had larger 122 cc chambers, and had a better exhaust port. available from 73-84.

781 castings had 119 cc chambers, and a slightly smaller exhaust port. available from 73-85.

both castings can be angle milled for more compression, but not a huge amount.

you can also find some 99 cc closed chamber heads that have shrouded valves. these may not have the port flow into the cylinder, but with the longer stroke, they almost make up for it. You can run them with a flat top and get 9:1 or 9.3:1 compression. sure beats the 7.8:1 compression of the smog era engines.

702 casting number heads have a 98 cc chamber, oval ports, and generally 2.065 intake and 1.72 exhaust valves. these can go to 2.19 x 1.88, but they are shrouded a lot by the bathtub shaped closed chamber.

for info on bbc cylinder heads go to www.mortec.com edit: shit, the sites down, but googles got a cache for it, under mortec.com/bbc.html

i copied and pasted the info to a spreadsheet so I can keep it on my computer here for reference.

[TAWL_BOY]

I'm going to look at a motor this weekend and if a get it I'm selling a set of 781 rebuilt heads with a 3 angle valve job and new springs and valves.

[offroadjunkie]

man you guys would love the class im in... im taking a engine reconditioning class at the local junior college and my teacher is a master machinist, he has given me so much one on one time that through discussion we have decided to run 305 heads on my 350 block to increase compression because i plan to run propane. With some of the stuff he has shown the students im sure he would be able to make your, or any 454, gain about 30hp just by a little machine work. He has an s10 sleeper with a 383 running a mean cam, dynos at 432hp at wheels on pump gas, and he let me drive it the other day and even highway gears you still burn rubber on a 12 inch wide tire. Sorry to get off topic just thought it was interesting.

[Grumpy_old_fart]

Originally Posted by offroadjunkie

man you guys would love the class im in... im taking a engine reconditioning class at the local junior college and my teacher is a master machinist, he has given me so much one on one time that through discussion we have decided to run 305 heads on my 350 block to increase compression because i plan to run propane. With some of the stuff he has shown the students im sure he would be able to make your, or any 454, gain about 30hp just by a little machine work. He has an s10 sleeper with a 383 running a mean cam, dynos at 432hp at wheels on pump gas, and he let me drive it the other day and even highway gears you still burn rubber on a 12 inch wide tire. Sorry to get off topic just thought it was interesting.

burning rubber on a 12 inch tire with a 383 is purely a function of having an S10.

there is no weight over the rear tires. there is no traction. so, whats he braggin about? I thought the idea was to get the tire to STICK to the road so you could accelerate like mad.

[K30_dump]

Hello all,

While on the topic, I have a quick question on the peanut port heads. They are some of the best heads for low-end grunt, right? I know they die off early, but that doesn't really confront me. I have a set of the 346236 peanut ports on my 454 and plan to run them in my K30 project. I was also considering some closed-chamber heads though for more compression. Looking for strictly low-end grunt in my heavy dually dump. Anyway, just curious if anyone has any input. Again, don't really care if they die off at 4k+ rpm, just want lots of bottom end torque.

Thanks,

Joe

P.S. - Anyone have a rough idea how many points of compression are gained per amount milled on a 120cc head?

[Grumpy_old_fart]

0-.125" angle milling will make combustion Chambers that are 108cc. the problem with that is that you may be getting close to the seats, or making the deck thin by taking an 1/8 inch off of one side. of course, all of the bolts will be a little crooked so you will have to spot face the bolt holes on the top side to get them to torque right.

[trkklr77]

Originally Posted by K30_dump

Hello all,

While on the topic, I have a quick question on the peanut port heads. They are some of the best heads for low-end grunt, right? I know they die off early, but that doesn't really confront me. I have a set of the 346236 peanut ports on my 454 and plan to run them in my K30 project. I was also considering some closed-chamber heads though for more compression. Looking for strictly low-end grunt in my heavy dually dump. Anyway, just curious if anyone has any input. Again, don't really care if they die off at 4k+ rpm, just want lots of bottom end torque.

Thanks,

Joe

P.S. - Anyone have a rough idea how many points of compression are gained per amount milled on a 120cc head?

so you dont care if the heads behave exactly as you expected but just want them to do exactly what they are designed to do????????

your post is a run around onto it self, they are best for a dump truck that wont need to spin fast or may stupid hp. if you put some 049's on it you wont lose anything. i had the exact same peanuts, i swaped on some stock 049's and it was a huge improvement, but mine is a go fast street truck.


and "30hp just by a little machine work" is just the tip of the iceburg, you get a die grinder into any set of bbc heads and you will pull in some much freaking power you wont need alums for a long time.

[K30_dump]

Originally Posted by trkklr77

so you dont care if the heads behave exactly as you expected but just want them to do exactly what they are designed to do????????

your post is a run around onto it self, they are best for a dump truck that wont need to spin fast or may stupid hp. if you put some 049's on it you wont lose anything. i had the exact same peanuts, i swaped on some stock 049's and it was a huge improvement, but mine is a go fast street truck.


and "30hp just by a little machine work" is just the tip of the iceburg, you get a die grinder into any set of bbc heads and you will pull in some much freaking power you wont need alums for a long time.

Hello,

Thanks for the reply. I don't claim to be an engine expert, I just wanted a confirmation that the peanut port heads do have a niche, which may happen to be low-end grunt. I have heard this before, but have never ran a set of these heads and was curious to see if anyone has run these and can confirm this. Didn't mean to post a "run around". Anyway, thanks for the help.

Joe