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need help identify pistons


1968 327 replacement,truck engine.piston number is 3796494.cant find any info on it.What im looking for is the pluc cc' measurement to use for calculating compression as I have a set of 58 cc' heads and don't want to be too high. thanks percy why are the rods red?IMG_3326.JPGIMG_3316.JPGIMG_3324.JPGIMG_3324.JPG



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I can't find the cc, but I did find this info. If all else fails, you might have to do the old syringe trick...

  

327 piston numbers.jpg

 

327 piston Mahle.jpg

 

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My name is ___ but you can call me Vern

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Crankshaft journal diameter changed in 1968 to a large journal diameter. 1967 was the last year for the small journal. Are you wanting to use a 58cc head from a 305 high output engine with the 1.84 intake valve ? You will raise the compression but not have a good breathing head. With a dished piston I would recommend using a 1996-1998 Vortec 350 head 64 cc. . there are plenty around and fairly priced although the matching intake manifold is expensive. 1968 was also the first year the heads had the 3 bolt holes for mounting the accessories. The 58cc head does not even come close to the flow of a vortec head.

I guess it all depends on what parts you have available and what you are going to use the engine for. Every 327 car engine I have ever rebuilt always had a flat top with 4 valve reliefs that varied the compression with the cylinder head cc even a 210 hp 327 2V had flat top pistons. The high compression 327 engine had a pop up piston 350 hp.

You can tell it was a truck engine by the double roller crankshaft gear and with some luck it may have a forged steel crankshaft .

Al


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Yes Al ,that is EXACTLY what im planning on doing. Reason being those heads came with the one year only GM aluminum intake that had the Electric Quadrajet ,so I can bolt a normal carb on there.just want a stock running engine to cruise around in.Didnt realize the head gasket effects it so much,.im thinking I should put the thick one on to knock it down but don't want to if I don't have to. and yes its steel crank # on it is 4577

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Those 327 truck engines (bigger than one ton trucks) are usually 8.5 to 1 compression ratio. I dont think that you will have problems with too much compression. I think the flat top piston in the car application are 9.5.

Paul

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The HO 305 heads are a good street head for want you want to do. The 1981- 1986 Chevrolet L69 305 pickup truck engines had the same heads along with flat top pistons and lots of them had the aluminium intake manifolds with electric choke Quadrajet. What is the casting no. on the heads you are going to use as the truck heads had better flow than the 305 HO heads used on Monte Carlo SS. The truck 305 engines were 9.5 compression with a flat top piston and a thin steel head gasket with the small chamber 58 cc head so you will have no problem using the recessed pistons with either the thin or composite heads gaskets. The gaskets might make 1/4 point difference in compression. The cylinder head cc.volumne makes the big difference in compression along with piston configuration.

The 700 R4 transmissions from that era of truck is also a better transmission than the car transmission to use in stock form. The truck trannys have a higher shift point and a higher stall torque converter built in from GM than the car transmissions.

The L69 305 was used in a lot of 2 wheel drive pickup trucks.

Al

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Prefecta your correct.engines from big truck 2-3 ton. Casting on the 305 heads is 14101081 throttle body .center bolt valve covers. the 2 middle bolts on each side are on a different angle. I believe the intake is off of a van as they used those heads with a quadrajet with electric choke and a solenoid in 1987 and didn't put throttle body until the next year.valves are 1.84 /1.50. Cam that was in the engine said 6930X so, 3896930 which is the 3896929 cam they used in everything from 195-300 horse.from what ive read.Id swear you've been looking in my shed Al.the truck 700r4 is sitting there,it sat behind a diesel tho so it has 6 bolts on the torque converter.Some say its basically same trans just put gas converter.some say leave that one. I have to research that more

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The six bolt converter will fit some flywheels. The stall speed may be a bit lower than a gas engine, but I have pulled out blown 6.2 diesels and put in 350 gas engines and the trans worked fine. Sometimes you can only use three converter bolts, never had a problem. These were 400 trans but if youre just doing a driver I would try the 700 trans and converter, it would probably be ok.

Paul



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flatop wrote:

Prefecta your correct.engines from big truck 2-3 ton. Casting on the 305 heads is 14101081 throttle body .center bolt valve covers. the 2 middle bolts on each side are on a different angle. I believe the intake is off of a van as they used those heads with a quadrajet with electric choke and a solenoid in 1987 and didn't put throttle body until the next year.valves are 1.84 /1.50. Cam that was in the engine said 6930X so, 3896930 which is the 3896929 cam they used in everything from 195-300 horse.from what ive read.Id swear you've been looking in my shed Al.the truck 700r4 is sitting there,it sat behind a diesel tho so it has 6 bolts on the torque converter.Some say its basically same trans just put gas converter.some say leave that one. I have to research that more


 I'll tell you a story about 700-R4, diesel vs. gas. At our dealership in the 90's we changed a lot of those transmissions, as failure rate in those days was pretty high (they seem to be much better now).  We ordered rebuilts from GM and they come in that nice plastic case (we called them coffins) and it wasn't uncommon for at least a couple of coffins to be sitting on the floor waiting for the truck(s) to come in and get a new trans. 

I recall a time when a 350 powered pickup came in, we put the new trans in and as always with the GM reman units it worked great. Sent the customer down the road. Likely 4-5 days later, another pickup came in, a diesel. When we went to put the trans in, we realized it was a transmission for a 350, not a diesel. And suddenly it his us. When we checked, yup, we put the diesel trans into the gas truck. So, we put the gas trans in the diesel. Same result, worked great, we couldn't tell the difference. From then on we were less concerned about interchange!

I know someone may come on here and tell me I'm wrong but experience with them has been it works fine.  



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Prefectca wrote:

Those 327 truck engines (bigger than one ton trucks) are usually 8.5 to 1 compression ratio. I dont think that you will have problems with too much compression. I think the flat top piston in the car application are 9.5.

Paul


Going from memory they ran 8:1 in trucks with dished pistons, probably 75cc heads. With flat tops they were about 8.55:1 with same 75cc heads (1967-8 327/210), 9:1 with 69cc heads (1969 327/210 and 327/235) and 9.8:1 with 64cc heads (1967-8 327/275). GM rounded up in compression to the nearest 0.25:1 hence why you see 8.75:1 on 1967-8 327/210hp, 10:1 on 1967-8 327/275hp etc. If you stuck a set of 64cc heads on those dished pistons you'd be in the region of 9.2-9.3:1 with factory head gaskets, take 0.1 or so off for aftermarket type gaskets. 58cc heads will bump you up to closer to 10:1. If you want small chamber heads why not use some alloy LT1 heads, or even the cast iron version? These in stock 1.95/1.5 valve form flow essentially as good as an old 2.02/1.6 fuelie. They are pretty good heads, just watch the oddball valve stem lengths if replacing valves (read about it at alexsparts.com).



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