I have a good running 1976 400 4bbl motor,175 hp, with 882 76cc heads,i want to install 3973370 64cc gm heads on it,3370 heads are 1969 Canadian 350 300 hp heads or American over the counter heads.they flow the same as 186 heads.IM installing a new oil pump,double roller chain & gear,cam & lifters,Edelbrock duel plane intake, 650 edelbrock carb,The original compression of the motor is 8.5-1 with 76cc heads, I need to know what the compression will be with 64cc heads on it,will it run on low octain gas,Im putting the motor in a 69 Acadian with a T350 trans & 308 gears & duel exhaust.this is a driver, not a race car, i won,t be reving over 4000 rpm.im not touching the short block,[no new pistons,no stroking,no after market heads, etc] just apgrading the top end cheap.The orig pistons have a 22cc dish.I want to know the compression ratio with 64cc heads & what would be a good cam for my application.better gas milage would help also.Thanks:welcome:
stk 400 sbc head replacement
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About 9.8:1. You're saying you don't want to get into the short block, but you may encounter some problems with detonation if you don't address the squish, depending on the cam used and the quality of fuel. As I remember, the piston is pretty far down in the hole on these motors and there is no good flat shelf on the crown to mate up with the underside of the cylinder head to form a good squish. With the stock static compression ratio, it won't be a problem, but when you begin raising the SCR, you need to pay attention to the squish.
400's have siamesed cylinders, which leaves blind corners in the cooling water jacket at 6 places on each block deck. If the motor is operating as a race motor, where revs will be above those used in city driving, the increased speed of the water pump impeller will be sufficient to speed the cycling of the coolant in the block to wash away any steam pockets that might form at these blind corners. But if this will be a street-driven motor, I would advise drilling steam holes in the cylinder heads according to this article from Greg's Garage....
Technical Articles at Greg's Engine & Machine
Some members of this forum recommend other procedures, but I favor doing it like the factory did it, by drilling steam holes in the new heads.
It's always best to counsel with a tech professional at your favorite cam grinder and get their recommendation, but here's an example of what I might use, after I addressed the squish issue....
Crane part #113941
Good low end and mid range torque and HP, good idle,
daily usage and off road, towing, performance and fuel
efficiency, marine applications: for 350+ cu.in. modified
engines with free flowing above water exhaust systems
for performance applications in light pleasure and ski
boats, including jet boats, 2600-3000 cruise RPM, 8.75 to
10.75 compression ratio advised, good w/plate nitrous
system. Good w/centrifugal or Roots supercharger, 8 lbs.
maximum boost w/8.5 maximum compression ratio
advised. (50 state legal, pre-computer, C.A.R.B. E.O.
D-225-18).
Grind number H-272-2
Operating range 1800-5600 rpm's
Crane lifter part # 99277-16
Duration @0.050" tappet lift 216/228
Duration @Advertised 272/284
Lobe separation angle 112
Timing events @0.050" 1/35/51/(3)
Valve lift 0.454"/0.480"
Dynamic compression ratio would be 8.67:1
My best bottom-line advice, if you won't get into the short block and address the squish issue, is to leave the motor alone and run what you have.
400's have siamesed cylinders, which leaves blind corners in the cooling water jacket at 6 places on each block deck. If the motor is operating as a race motor, where revs will be above those used in city driving, the increased speed of the water pump impeller will be sufficient to speed the cycling of the coolant in the block to wash away any steam pockets that might form at these blind corners. But if this will be a street-driven motor, I would advise drilling steam holes in the cylinder heads according to this article from Greg's Garage....
Technical Articles at Greg's Engine & Machine
Some members of this forum recommend other procedures, but I favor doing it like the factory did it, by drilling steam holes in the new heads.
It's always best to counsel with a tech professional at your favorite cam grinder and get their recommendation, but here's an example of what I might use, after I addressed the squish issue....
Crane part #113941
Good low end and mid range torque and HP, good idle,
daily usage and off road, towing, performance and fuel
efficiency, marine applications: for 350+ cu.in. modified
engines with free flowing above water exhaust systems
for performance applications in light pleasure and ski
boats, including jet boats, 2600-3000 cruise RPM, 8.75 to
10.75 compression ratio advised, good w/plate nitrous
system. Good w/centrifugal or Roots supercharger, 8 lbs.
maximum boost w/8.5 maximum compression ratio
advised. (50 state legal, pre-computer, C.A.R.B. E.O.
D-225-18).
Grind number H-272-2
Operating range 1800-5600 rpm's
Crane lifter part # 99277-16
Duration @0.050" tappet lift 216/228
Duration @Advertised 272/284
Lobe separation angle 112
Timing events @0.050" 1/35/51/(3)
Valve lift 0.454"/0.480"
Dynamic compression ratio would be 8.67:1
My best bottom-line advice, if you won't get into the short block and address the squish issue, is to leave the motor alone and run what you have.
400
On these 400 s the piston sits down in the hole .065 + or - the worst of all sbc,s How would you address the squish area with out changing pistons,if the motor was all stock,what cam would you use to help hp & mileage.i will change intake & carb, should i leave the 882 heads on it. just a driver not a race car. I thank you for replying, you are the man when it comes to camshaft info.
On these 400 s the piston sits down in the hole .065 + or - the worst of all sbc,s How would you address the squish area with out changing pistons,if the motor was all stock,what cam would you use to help hp & mileage.i will change intake & carb, should i leave the 882 heads on it. just a driver not a race car. I thank you for replying, you are the man when it comes to camshaft info.
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Thank you for the kind words, but as I try to say, always consult with a tech at your favorite cam grinder before you pull the trigger and order parts. I just try to get you into the general combination of parts that will work well together. Most of the fellows don't understand that all the components they bolt into the motor must be compatible with each other and compliment each other. No single part stands alone.
Many years ago, I was advised that most fellows would do well to choose the very first offering from the cam catalog if they are not going to completely go through the motor. Here's Isky's first offering......
Iskenderian part number 201256 (Supercam)
Best torque and economy in 327-400 cubic inch car and truck motors. Maximum static compression ratio advised, 9.5:1. Smooth idle, standard axle ratio, good vacuum.
RPM range 1500-4800
Valve lift 0.425/0.425
Duration @ 0.050" tappet lift 202*/202*
Duration @ advertised 256*/256*
Lobe separation angle 112*
Use Isky 222-HY lifters and 205-D valve springs
I would use an OEM cast iron Quadrajet intake manifold, mounting a rebuilt Quadrajet carburetor.
http://www.summitracing.com/parts/sum-210216/overview/
The tiny little primary throttle bores and venturis will produce excellent throttle response and fuel mileage if you keep your foot out of the secondaries. So the motor can breathe, I'd mount a 14" air cleaner base and a 4" thick filter element (stack two 2" ones if you can't find a 4", with a longer stud from Ace Hardware). On this mild motor, I don't think I'd fool with headers at all.
Many years ago, I was advised that most fellows would do well to choose the very first offering from the cam catalog if they are not going to completely go through the motor. Here's Isky's first offering......
Iskenderian part number 201256 (Supercam)
Best torque and economy in 327-400 cubic inch car and truck motors. Maximum static compression ratio advised, 9.5:1. Smooth idle, standard axle ratio, good vacuum.
RPM range 1500-4800
Valve lift 0.425/0.425
Duration @ 0.050" tappet lift 202*/202*
Duration @ advertised 256*/256*
Lobe separation angle 112*
Use Isky 222-HY lifters and 205-D valve springs
I would use an OEM cast iron Quadrajet intake manifold, mounting a rebuilt Quadrajet carburetor.
http://www.summitracing.com/parts/sum-210216/overview/
The tiny little primary throttle bores and venturis will produce excellent throttle response and fuel mileage if you keep your foot out of the secondaries. So the motor can breathe, I'd mount a 14" air cleaner base and a 4" thick filter element (stack two 2" ones if you can't find a 4", with a longer stud from Ace Hardware). On this mild motor, I don't think I'd fool with headers at all.
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17,613 Posts
The Isky cam I posted should work well with the low compression 882 heads.
400 sbc
I also have a 69 camaro Z28 winters aluminum intake that i want to put on it & a 600 edelbrock carb,the intake is corect date for the year of the car. & it looks good on the motor.The original 307 2bbl runs like a champ,but its a pig on fuel,17mpg at best, has anyone ever put 416 305ho heads on a 307, with a 4bbl & rv cam.orig heads on 307 are 70cc - 416 are 58 with begger valves.
I also have a 69 camaro Z28 winters aluminum intake that i want to put on it & a 600 edelbrock carb,the intake is corect date for the year of the car. & it looks good on the motor.The original 307 2bbl runs like a champ,but its a pig on fuel,17mpg at best, has anyone ever put 416 305ho heads on a 307, with a 4bbl & rv cam.orig heads on 307 are 70cc - 416 are 58 with begger valves.
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This thread is all over the place?
A 307 will burn less fuel than a 400. When you build an engine its all about matching the parts for the best combination. What techinspector is doing for you is a mathematical formula to maximize the efficiency of the piston to the cylinder head. He does this to make sure that the actual fit of the piston is as close to perfect as possible. He also has to figure in compression ratio and cylinder head configuration.The cylinder head configuration includes size of combustion chamber,shape of combustion chamber,size of cylinder,shape of piston,actual compression ratio of combination,then matches camshaft configuration including not only lift and duration of cam,but the lobe separation of the lobes related to each other (intake Vs exhaust) Using a mathematical formula he determines Dynamic Compression Ratio,this is how close the engine gets to actually filling the cylinder to full capacity ( all engines are less than 100% efficient)
This all needs to be done to certain tolerances,especially with lesser grade fuels, so as to have the engine burn the fuel efficiently,clean and COOL,with out detonation. The by product of his math is more power while burning less fuel and allowing the engine less stress therefore lasting longer and being more reliable.
EVERYTIME,,, you change the question,tech has to redo all the math to fit the new parts asked about. Tech is one of the best guys here when it comes to first,willing to help,sourcing parts,and attention to detail with actual numbers and parts lists included.
There are thousands of cam profiles,probably hundreds od cylinder heads,dozens of intakes and hundreds of fuel mixers (carbs,F.I.,propane mixers)
Im just saying,you have one of the best guys here helping,maybe list all the parts you have,what you want to do with what end result, and let him do the best with what you have.
That Nova should scoot and get decent mileage.
best of luck with the build.
A 307 will burn less fuel than a 400. When you build an engine its all about matching the parts for the best combination. What techinspector is doing for you is a mathematical formula to maximize the efficiency of the piston to the cylinder head. He does this to make sure that the actual fit of the piston is as close to perfect as possible. He also has to figure in compression ratio and cylinder head configuration.The cylinder head configuration includes size of combustion chamber,shape of combustion chamber,size of cylinder,shape of piston,actual compression ratio of combination,then matches camshaft configuration including not only lift and duration of cam,but the lobe separation of the lobes related to each other (intake Vs exhaust) Using a mathematical formula he determines Dynamic Compression Ratio,this is how close the engine gets to actually filling the cylinder to full capacity ( all engines are less than 100% efficient)
This all needs to be done to certain tolerances,especially with lesser grade fuels, so as to have the engine burn the fuel efficiently,clean and COOL,with out detonation. The by product of his math is more power while burning less fuel and allowing the engine less stress therefore lasting longer and being more reliable.
EVERYTIME,,, you change the question,tech has to redo all the math to fit the new parts asked about. Tech is one of the best guys here when it comes to first,willing to help,sourcing parts,and attention to detail with actual numbers and parts lists included.
There are thousands of cam profiles,probably hundreds od cylinder heads,dozens of intakes and hundreds of fuel mixers (carbs,F.I.,propane mixers)
Im just saying,you have one of the best guys here helping,maybe list all the parts you have,what you want to do with what end result, and let him do the best with what you have.
That Nova should scoot and get decent mileage.
best of luck with the build.
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1,684 Posts
Replacing the GM 882 76 cc heads with the 3973370 64 cc heads would be great for performance. With the 22cc dished pistons, C5248-.027 Cometic head gaskets, and the 3973370 heads would bump the static compression up to 9.426. Replacing the stock camshaft with a Howards 12571-12 hyd. flat tappet camshaft would give you a DCR of 8.255. The specs for the Howards cam is .440/.455 lift, 215/225 duration, and a 112 LSA. It has a basic operating range of 1200-5500 rpms. There are 2 sets of lifters that can be used with this cam part #91111 & #91116. I prefer the 91116 they are better. No this engine will not run on 87 octane gas, but neither did the 400 cid engine in 1972. Check out the emission sticker in post #13. Stock 400- Dished piston - Chevelle Tech.
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