Don Terrill’s Speed-Talk

I'm trying to help my cousin decide on a good flowing head for his 350 SBC. He likes the idea of aluminum, but price is a factor, so I suspect iron may be considered.. His current heads are 74 cc and that's what he needs, that produces 10 1/4 compression and it's a street pump gas engine with a 230* @ .050 cam.

SKeown

Vortecs, can't beat them for price, ccs may need adjustment.
Dart Iron eagles in the paper here 1 season used, $500.00, buyer beware!
Craiglist, bunch of "ported" 882/3s for all kinds of prices.
What are the motors parameters? Like how many ponies, rpms, requirements?

Dart SS Vortec

I know the runners are quite large for a 350 BUT I would suggest the EngineQuest part #cc220ds. They are a straight plug, 220 cc runner, 72cc chamber and when I tested them they flowed about 255 cfm @ .600" IIRC. I think they are about $300-$350 each bare. J.Rob

Brodix IK200 best bang for the buck. $1100 +/- assembled. Call a Brodix dealer you might be able to get them for around a grand.

http://www.brodix.com/heads/ik.html

I would use the IK180's on a 350, for a street application. TB

How is he getting 10.25 to 1 CR. using 74 cc heads??

A blue printed '67 350SS engine with 4-notch flat-tops, 64 cc double-humps and stock .020" thick steel shim headgaskets created 10.25 to 1 CR. back then.

What's he got, 12 to 1 pistons in it??

pdq67

What is His Budget ???? Best Bang for the Buck could be very different at $500.00 or $1200.00

ItalianJohnny wrote:What is His Budget ???? Best Bang for the Buck could be very different at $500.00 or $1200.00

Good point. I assumed (there is that word again) that he was looking for entry level iron or aluminum heads with a 74cc chamber. Vortecs and iron darts have smaller chambers than this. The IK heads come with a 64 or 70 cc chamber but can be had with up to a 75cc chamber with the cnc chamber option which costs around $150 and if it's like the RR heads picks up the flow substantially as well. Just a touch over a grand for fully assembled heads that flow as well as the IK's is a very good deal in my book but if they aren't in the budget or if the budget is substantially more then there are a lot of other choices.

Pdq67 makes a good observation about the compression ratio though but without knowing the whole combo I can only go by "budget head" and "74cc" I personally would run the 200cc IK's even on a 350, they aren't that much head and they would work just fine with that duration/rpm range. IMHO.

I went through the engine a while back, what I can tell you is after checking piston & head volume it ended up at 10 1/4 to 1 compression after decking the block and .015 shim gaskets. It has a Comp 230* hydraulic cam & springs, Weind single plain w/ 750 Holley and headers. I figure $1,200 max for complete heads ready to run for his cam. Naturaly he would like them to be aluminum. I have a mid 10 second AMX with ported oem irons myself.

SKeown

Yeah are you so stuck on just 10.2 to 1 ? Run the brodix which is a great head for the money .Get it in the 70 cc chamber and go with it.... You will be just fine on pump gas I promise !! With the aluminum head you can get away with higher compression on pump gas. I have a 383 that is 11.5 to 1 pump gas motor and has no problems at that.

The Brodix IK200 @ 70 cc's sound interesting. The engine is in a 56 Chevy that will be going to the strip and see 6000 rpm operation. I understand they are aluminum and will have suitable springs for his use?

Does everyone feel this is a logical choice, or what?

SKeown

Tony B wrote:I would use the IK180's on a 350, for a street application. TB

DITTO; you don't need a bigger port for 350 with a low RPM camshaft

As pdq67 suggested, if you have a 74cc head on a 355 with flat top pistons, you'll end up with around 9:1 compression (.040" head to piston clearance). If you have 11:1 pistons in there, you should be around the 9.75:1 area. I'd recheck my compression figures unless you are running 12:1 pistons.

JoePorting wrote:As pdq67 suggested, if you have a 74cc head on a 355 with flat top pistons, you'll end up with around 9:1 compression (.040" head to piston clearance). If you have 11:1 pistons in there, you should be around the 9.75:1 area. I'd recheck my compression figures unless you are running 12:1 pistons.

Okay, now I'm starting to question the heads chamber volumes, I'm going on George's recollection there, it's been about 18 months. I do know I calculated the compression at about 10.2:1 with flat tops & .040 P-H cearance.

I'll describe what I remember about the heads and maybe some of you Chevy guys can decipher what they are, I remember George said they were common truck heads, the same as on his Blazer. I recall the four center bolt holes were horrizontal rather than at an angle like the rest. The intake ports had a weird shape at the opening and the rockers were self alligning.

SKeown