Been collectin parts. Still running good with next to no oil pressure. 6200lbs(?)78 250 supercab 4wd c6. Currently 33s 3.54. Eventually 35s 4.10 or 4.56, haven’t decided. Would like to continue to run 80 on the highway without spinning too high and not be working too hard off the line also.

want to do a build that has the potential to run on 87, if I can just pull some timing out when necessary and sacrifice power that’s fine(premium isn’t available everywhere). Plan to go full roller, no ideas on cam profile but do want torque down low, not planning on high rpm. Should I just call a cam manufacturer and let them suggest a grind?

unsure on heads/pistons. Was leaning towards trickflow heads, though this will mean a custom piston. Curious if I can keep compression down and still take advantage of proper quench. I’m sure stock head and tmi piston is easier but hoping for a better chamber. Warding off detonation is #1, I don’t want to sacrifice any more power than necessary.

have a Weiand intake and Holley 600 cfm. Plan on keeping stock manifolds. Going aftermarket ac also, sure tall valve covers will give me some issues too.

any thoughts?


Update build list
carb Holley 600cfm 80458-sa
intake Weiand 8010
scorpion stud mount rockers 1.73, I believe 1023BL
trickflow 72cc heads/valves
howards springs 98445
howards cam/link bar lifters CL233215-10
217/225@.050, .571/.577
Tmeyer cam bearings
hedman 89360 fenderwell exit headers
2.5 ss duals into
magnaflow 4x9x18 11246

 

What compression ratio are you shooting for ? You can't take a say.....10:1 motor and run it on 87. By the time you would back enough timing out and dump enough fuel in you would have a real pig on your hands that at the least would be difficult if not impossible to shut off if you have an automatic trans.

 

Thinking 9-9.5, whatever I can get to cooperate.

 

Roller cam is a good idea - then you din't have to worry about wiped out lobes & lifters.

Aluminum heads are a good idea as you can run more compression than the factory heads with big, open, detonation prone chambers. I'm not sure what you can really get away with, so much of it depends on your camshaft. Since you want a lot if low end, you won't be running a very big cam. I'm sure half a dozen cam companies would be able to help you out. TMeyer is a good resource too - lots of experience building solid 400s.

 

If you are looking to run 87octane then your dynamic compression have to be over 9:1 since the static compression is not that important but the dynamic which is the true factor to determine what octane to use with out getting any pinging. So your real mission is selecting the right cam.

 

I believe dcr would have to be under 8 to run 87 full time. I would rather set my static based on cam, then to try to correct dcr with a cam that is not on when I need it.

I did reach out to Tim Meyer as that’s what every thread says, but his response was that he is busy and only supports products sold on his website, which there isn’t any cams or heads.

 

Ok, suit yourself and get your DCR under 8 and you will end up with a pinging monster. Good luck, I’m out.

 

Keep leaning towards Trickflow heads, 72cc, as closed chamber heads are the only way to go to get an efficient combustion.

If you want an efficient quench, then yes, custom pistons are the first, and basically, only choice.

If you can find a reputable piston builder, ask if they can build you hyper-o-tec-tic pistons with a compression height of 1.71’’, a width of 4.03’’, and a 12cc D top dish, and post up the answer.

This is a D top dish :

https://www.summitracing.com/parts/u...-030/make/ford

This is a dish, which you don't want :

https://www.summitracing.com/parts/u...-030/make/ford

And you don't want flat tops either.

The above piston dimensions are not exact, but are close enough to give a piston builder a good idea of what you want.

 

You don't understand what you're talking about.. Please read up on what dynamic compression means. Lower means more octane tolerant not the opposite.

 

My apologies please...I don’t know what I was thinking. You are totally right. DCR have to be under 8 and not over to ovoid pinging on 87. It’s been a while and I got it all mixed up. I’m sorry for my silliness.On my build I ended up with 8.4 DCR and in summertime I can only use 93 otherwise It will ping on hard acceleration. But Im not regretting it since my cam gets me a great deal of low end torque from 1000 to 25000 rpm

 

It sounds to me like you've got it about right and having to run 93 in the summertime is a small price to pay for lots of low speed cylinder pressure and torque.

 

Here is a suggestion you might want to look into. Trick flow makes heads that have mid 72cc chambers. This might work great with Tim’s pistons. Something to check too is if Tim’s pistons match up to trick flows quench pad.

Not really engine related but don’t sell your 3.54 gears short. With 35” tires (most actually measure out at 34) you’ll be spinning 2800 or so at 80. 4.10 gears will put you at 3300 at 80. Once you get your engine built you’ll be blow away how much torque it makes and how it makes up for taller gears. My 79 F350 supercab 4x4 on 34” tires (325/60r18) with a C6 gets off the line really will with 3.54 gears and a 400 that’s not a built as yours is going to be. All my friends who have ever driven the truck can’t believe how quick it is off the line at stop lights and what not even with moderate throttle.

 

thanks. Looks like Tim’s step piston would not utilize a dual quench chamber. I’m sure they are used, but it’s an expensive way to build what looks inefficient

 

pretty much striking out on finding a custom hyper piston, everything I’m coming up with would be forged.

 

If you can get forged pistons made to your specifications, great !

I suggested hypers because they are cheaper, and would be suitable for your proposed build.

A 'zero deck' is an absolute must, and adding 12cc pistons and 72cc heads would give the engine a static compression ratio (SCR) of exactly 10 : 1.

13cc pistons would provide an SCR of 9.9 : 1.

The squish would be perfect (efficient) also.

Mention an SCR of 10 : 1 when talking to the piston supplier.

It wouldn't hurt to speak to cam manufacturers for their grind suggestions, and I for one, wouldn't mind knowing what results you get.

A custom ground cam could also be a consideration, but you can't choose a cam accurately until you know the EXACT engine specs. (10 : 1 etc could be used as a good example though.)