2v 400 cast heads, decked .010.
KB flattops, 0 deck.

How much valve lift can 2v heads take before clearance might become an issue?

 

There is no way to know for sure, you have to check it. Anyone that tells you different, don't take their advise. You make your own luck in engine building. Double check everything, leave nothing to chance.

 

I've got a Crane 529541 roller with .562 and .586 lift with no problems. I don't remember what the actual clay check measurements were but there was lots of clearance. I also don't have any spring bind problems.Engine and head surfaces were decked.
Marc is right on about checking everything.

 

Well im already short blocked. So claying without rings would be no easy chore.

 

Since you already have your heads on, you could and pull the valve spring, replace with a weaker 'checker' spring that you can depress manually, and do a brute force method of measuring PV clearance. You'll want to do a sweep of 15-20 degrees before and after TDC, and with any luck all of your PV clearances will be well greater than 0.100". HTH

 

Short block does not have heads on, thats long block.

 

And old mechanic told me i can check clearance with soft wire like the one to weld copper pipe with a torch. Just put inside spark plug hole and turn engine. The soft wire get crush between piston and valve and then mesure the crush wire.

 

BrutalBronco idea is a good one- if the spring is light enough you should be able to depress it manually and measure the clearance.

 

Did my 400 with KB flattops and a comp cams 265DEH, valve lift is .510 and .526. Heads are 2V open chamber 78cc. The pistons even pop out some hundreds over the deck, had no problems with piston-to-valve clearance.

Watch for your SCR/DCR, what are your plans for cam ?

 

Voodoo Hyd Cam - Ford 351C-400M 250/256

Product Description

Hydraulic. The best torque cam for 351-400 applications. Expect strong low to mid range horsepower and torque gains. Excellent for RV type vehicles, pleasure boats or towing applications.

• Advertised Duration (Int/Exh): 250/256
• Duration @ .050 (Int/Exh): 207/213
• Gross Valve Lift (Int/Exh): .503/.524
• LSA/ICL: 112/108
• Valve Lash (Int/Exh): Hyd/Hyd
• RPM Range: 1000-5200
• Includes: Cam Only

Part Number: 10320700
Previoius Part Number: 62500
Jobber Price: $143.73


29 degree overlap on 112 LSA should compliment the ECC-IV very well on a 351C. Torque and fuel economy are my main goals. Cruising and utility pulling. I will rarely see above 4k rpms, I have been told I drive like a grandpa at age 33. ZF tranny has 5.72 first gear and .76 OD 5th gear.

 

I took the liberty, given the specs in this thread, to calculate the approximate Dynamic compression ratio on the kb-silvolite compression calculator. United Engine & Machine Co. Incorporated

Assuming that: the bore is 4.030", the heads being milled now have a combustion chamber of 76cc, and that the voodoo cam is installed at the 108 ICL, I felt compelled to reply that the DCR is approaching 8.8:1, and has the potential to present a detonation/octane sensitivity issue with the iron heads. I believe you'll need to run 89 octane, and possibly more in higher elevations.

 

Bronco is right, please also look for the casting number of your heads, there is a make #D5AE-A2A with only 74.5 cc !

I have those and ended up with a DCR of 8.8. Because I didn´t wanted to change the cam I went with 0.080" head gaskets, much better.

 

I recently spoke with a racing guy who have 2100hp race engine. He said the way he check it was to remove the head and with clay over the piston and spread oil over the head and piston for not sticking solution and turn the engine by hand with the head retorqued then took cisors to cut the exedent and mesure. He told me the gaskets are way cheaper than a motor job! lol. He was talking about 90, 000 $ engine that run low 7's sec.

 

The plasticene/clay method is THE ultimate method of checking clearance.But it does come down to time V cost and how close you think you are. Most of the time it is when you are pushing the boundaries and are trying to find issues after valve pocket mods or nonstandard hi-top pistons (for example).

 

For as much money as I have dumped into this rebuild, paying for higher octane fuel does no bother me. The 2v heads have a fairly deep pocket. In all reality i could clay the heads w/o a head gasket. Flat tops came out of the block, and I'm not going for crazy stupid valve lift. True there is a big difference between stock and the lunati cam. There should still be gobs of room w/o a head gasket, then just have to add compressed gasket thickness.