DJackson1357

Greetings all, this is my first post on these forums after lurking here for a while.

I'm currently going through a set of Edelbrock heads that I purchased about a year ago. The previous owner looks like they started to port around the pushrod area, but the work doesn't look very good. I was going to smooth out / clean up that area, then do some work in the bowl area and call them good.

Does anyone have a good recommendation for the valve to throat ratio on the Edelbrocks? I've seen numbers of 92% posted in the ProComp porting thread from February, 89.5% from an old Mondello article, 90% as the general rule, and I think 88-89% was mentioned in the cast iron head porting thread. Is there much difference between 90% and 92%? Should the exhaust throat % be smaller than intake?

Following the clean up the heads will get a good valve job and probably back cut intake valves.

The heads will be going on the 455 in my dad's 85 Delta 88. The rest of the engine is unknown pistons (180 PSI cranking compression), generic 214/224 camshaft, Edelbrock Performer intake, repop W/Z manifolds and a full 2.5" exhaust with X pipe. The rest of the combo will stay the same with the Edelbrock heads.

Any help is appreciated. Thanks!

cutlassefi

Welcome!!!
90% is about right but there are others here that can confirm that one way or another.
But I will tell you that the guys that do all my headwork, Champion Race heads, tell me that the stock intake valve is too small to begin with. On all the Edelbrocks I've been using I have the intake valve size increased to 2.125 right off the bat. An otherwise stock Edelbrock head with the 2.125 intake flows 271@.600. Not bad for no work.

Any reason for the generic cam? There are better inexpensive grinds out there for your build. And you'd be better served to put more lift in it. Otherwise those heads will be wasted imo.

Thanks!

TripDeuces

The 90% figure will work just fine. 90% is the general figure so you can use that for the exhaust valve ratio also.

joe_padavano

Mark,

That's great info. What size exhaust are you using with that intake? No problems with clearances with the stock valve centerlines? Thanks.

cutlassefi

Hey joe,
No problems whatsoever. I'm using the supplied 1.68 exhaust.
The guys at Champion recommended that change right away. It helps flow all the way thru, from .100 to .650 lift. After that it plateaus. The stock port will only handle so much at that point.

DJackson1357

From what you and Joe mentioned I'll shoot for 90% on the intake and exhaust. I appreciate the input. The 2.125" valve sounds like a good deal, but not sure if I want to spend the extra money on the valves. Will have to think on that one.

The generic 214/224 came in the engine when I purchased it. Basically picked up a whole car to get a rebuilt 455 and TH-400. Then the TH-400 blew up. I swapped the engine into my dad's Delta and pretty much left everything as is minus pulling the heads to check everything.

The Edelbrocks are going on because I got a what I think is a good deal on them ($900 assembled with head bolts, pushrods, and rockers) and they might help a few issues I have. The C heads on there were cracked and repaired, the crossover isn't filled and I can't run any more than 32 degrees of total timing without pinging. I figure the Edelbrocks will fix all those issues in one shot.

PM sent regarding the camshaft.