Vortec Head Swap.....

[musclecarmatt]

Hey guys...well i'm thinking of doing vortec head swap on my .040 350 in my car....already got the heads and vortec intake got stored up from troutman while back...was planning on vortec 383 build but looks like thats going wait for another year and the with the autocross season coming up in few months got other stuff i wanna do to the car....here's the current specs:


Current Specs:
73 .010 Block 350 2 bolt
bored .040 over
factory 76cc heads 1.94 1.50 valve
Edelbrock Performer Intake
Holley 670 carb
Perfomance HEI 50,000 coil/dyna-module
Moroso ultra 40 race wires
Accel race plugs
1 5/8 headers...2.5 inch flowmaster dumped
Close to "Stock" Cam
about 80,000 on bottom end

I was thinkin about bumping up my cam to maybe comp cam Xe 268H and swapping out the factory crap heads to vortecs with edelbrock Rpm air gap.....the vortec heads i believe are the 64 cc 1.94 1.50 valve heads...cant remember the casting off hand....the main reason for swap is to free up some hp and make her breath alittle better...
Would this swap be benefit?.and would it bump up compression too much for the bottom end?

Matt

[anthonys 69]

You didn’t give enough information to give you exact # but if your running flat top pistons no valve relieve. .016’’ deck clearance 0.025’’ head gasket thickness your compression with 76 cc combustion chamber is 9.65 to1. And with a 64 cc combustion chamber would go up to 11.08 to 1. of course you probable have some valve relieve and maybe a slight dish which make a big difference. Just changing the head gasket thickness by 0.010’’ to 0.035 changes the compression ratio to 10.8 to 1. im going to be running edelbrock etec 200 cylinder heads they have very good flow #s.

[musclecarmatt]

You didn’t give enough information to give you exact # but if your running flat top pistons no valve relieve. .016’’ deck clearance 0.025’’ head gasket thickness your compression with 76 cc combustion chamber is 9.65 to1. And with a 64 cc combustion chamber would go up to 11.08 to 1. of course you probable have some valve relieve and maybe a slight dish which make a big difference. Just changing the head gasket thickness by 0.010’’ to 0.035 changes the compression ratio to 10.8 to 1. im going to be running edelbrock etec 200 cylinder heads they have very good flow #s.

its got flat tops...wow..around 11:1 compression that be alot on that stock bottom end...........hmmmm

[SLO_Z28]

its got flat tops...wow..around 11:1 compression that be alot on that stock bottom end...........hmmmm

It will be fine. This is the same build that any number of magazines has done, and is EASILY good for 400/425.

[musclecarmatt]

It will be fine. This is the same build that any number of magazines has done, and is EASILY good for 400/425.

only thing i have is pushing that amount of compression with stock pistons...and 80,000 mile rings.......cause high compression motors are more tempmental then lower compression motors?....

[anthonys 69]

just go for the 383 build. you wont be sorry. just a side not cast vortec heads are known for cracking so get them checked.

[shep]

I wouldn't worry about the compression as long as you don't run crap gas or try to run a bunch of timing it will be fine. I don't know the specs on that cam you listed but if it is over .500 you will need to either run the upgraded bee hive springs or cut the heads to use the older style oil seals.

[MonzaRacer]

Part Number Cylinder Head Volume
58.0cc 64.0cc 68.0cc 76.0cc
P2256F-030 11.03 10.26 9.81 9.03
P2256F-040 11.07 10.30 9.85 9.07
P2256F-060 11.16 10.38 9.93 9.14
This should give basic idea in increases.

[novaderrik]

you can run higher compression with vortecs than any other iron small block heads- that's the main benefit of the heads and the thing that keeps them competitive with even the newer aftermarket cylinder heads that have come out in the 15 years since they came out.
i was running just over 10:1 in the 355 in my Nova on 87 octane without any detonation issues except on really hot days- so i just ran 89 octane in the hot months.
when i first built that motor, i used the cheap thick head gaskets that came in a McCord engine gasket set just so i could get it together and in the car- it would ping like crazy on even 93 octane with the timing pulled way back. i drove it like that for 2 years and just assumed that's how it was supposed to be.. i decided to go thru the motor and look things over when i took the car apart one winter to rebuild the suspension.. i used some .015 thick Mr Gasket head gaskets when i put it back together and all the detonation issues were gone. i asked the machinist that did all the machine work for me when i originally built the engine, and he told me that i was at right around 9:1 when it rattled and a little over 10:1 after i put it back together- he thought i was going to have to run race gas or switch over to that new miracle fuel called "E85".. he was shocked when i came back and told him how much better and cooler it ran on the cheaper gas.. this was in '03 and it was the first time he'd ever heard of anyone using those heads on a true street car, but he had put tons of those heads on all out circle track engines since they first hit the streets in the summer of '95.

[musclecarmatt]

sweet deal....probably start on the swap after first of the year....i got the fel-pro high performance gaskets .015 thick.........top off the swap with edelbrock RPM air-gap and comp cam 270H..

[JWilson]

I have the XE268H and an Edelbrock Performer (hoping to keep the stock hood) with my 355 & Vortecs. It was my dirt track engine back in the day, so I had all of the stuff except the cam and intake. It has 2-valve relief flat tops with a decked block. I have it in the car and hope to drive it this afternoon. I'll post my opinion. Good luck with your build, and that is a good looking 2nd gen!

[JWilson]

Just to update....indefinite delay. Coolant in the cylinders as a result of pinholes in #3 and #6 cylinder walls. Kinda have to step back and figure out what to do next.