308 Engine Rebuild & CIS to TWM Throttle Bodies Conversion Thread!

don't spose you can get them for 355s, can you?

 

D*m Chris,
That's really luck! You sure you're not Irish?

I've been figuring that neither of those heads was going to move a mm w/o a pulling plate.

While it's hard to tell from pix, most of those studs look really clean, & the corroded one doesn't look very bad. Don't go pulling any of them until one of us had had a close look. They way your luck is going, you probably won't need to replace any of them.

Still,wouldn't hurt to start applying PB Blaster at the base of the corroded ones, just in case.

Hope the other head looks as good!

The heads & cylinders look really clean!

Look at the sides of the cylinders, can you see fine criss-crossing scuff marks(good)?
Also look for marks going up & down the cylinder (bad).

 

In theory, the stud should not show any sign of corrosion because the aluminum should be the anode in the reaction and protect the steel….of course that means the aluminum corrodes (the white power) and binds the stud in the hole.

The studs I just pulled out of the 400 are perfect as far as corrosion goes, the original black oxide coating is still completely in tack. My QV engine was the same way.

 

Looks terrific - excellent work.
Can't wait to see the heads after they have been cleaned up.

 

The criss-crossing on the cylinder liners is really something. There are only a couple engines I can think of does one see criss-crossing still intact almost no matter the engine condition (911 3.0, 911 3.2 flat 6s).

Will you be honing the cylinders at all? By the look of it, a simple dimple honing to clean it up would be all it needs IMHO. Just enough of a rough surface so to help seat the new rings should do it.

 

I think he's going for pistons, so either a hone or bore job.

 

Thats typical, you would need a million miles to wear those off.

Those are the cross-hatching marks left from the honing stone when the liners were new. The angle of the cross-hatch is critical in that primarily it is to wear the rings to properly seal in the cylinders - this is what you are breaking in when you break in an engine. The angle if too steep one way or the other either causes too much friction and costs HP or doesnt break the rings in properly. Using a drill powered stone does the job but never as good as a proper machine like a CK-10 sunner hone. If you re-ring the engine but dont hone the cylinder the new rings will never seat and seal properly resulting in blow-by, oil consumption and lack of power.

 

Chris, your engine looks 4 times cleaner than mine, looking good.

 

Way to go Pizzaman!!

 

Hi Chris,

Good job!!!
How do you do it, 12hrs of tossing Pizza around and then working on her (308)??


I know you can't use your originals so
what are you doing for cams?

 

Yes we have Valves for the 355 List $69.00 USD, F-Chat Member price Less 30% $48.30 USD. each, Exhaust or Intake.

 

Chris,

She is looking good, the cylinder walls look excellent.
Keep up the good woork.

 

I would not go too extreme for a street application or the car will be a PIA to drive. P6 cams are very peaky and from what I have seen only make power between 4-8k. P6s will require at least 10:1 pistons to function properly as well. There are some posters on here that have so much cam experience, they can collectively tell you what each one of the above outlined profiles will drive like, but my opinion would be to go with the speis racing profile.

 

You have to select the compression ratio to match the cam profile. See what WEB offers for a street high performance grind and what they suggest for compression ratio. The cam and piston selection is the most important decision you will be making. You make the wrong one (like go for P6 cams) and you'll kick yourself everytime you drive the car. Make the right one and you'll be completely satisfied and always enjoy driving the car on the street or track.

 

I order I would pick them
Speis racing
.368 by 235
OEM 76-77
Diablo
P6

When you do pick, ask web for a compression recommendation. I’d guess 10:1 for all of them on the street

 

As said before, for the street, in very broad general terms, you want as much lift as you can get that maximizes head air velocity and flow without flipping a shim: this gives power across the entire band --and, you set the power band with the duration and overlap.

Personal opinion: the V-8s are already way over-exhausted, so to correct the intake/exhaust ratio, it is most cost efficient to do only the intake cams and keep the stock exhaust. Flame on!

So, depending on what your heads flow you set the lift based on as much as you can get without losing velocity, and not going unneccesarily beyond what the head will flow anyway. Another limit is the wear on the shim. Most of my learning on this is from a QV head WEB did. I do know that Kermit found in the 2v, unlike the the QV, flow continued to climb up a bit beyond .400 lift.

Tou'll be able to spin higher at the expense of low end with whopper durations, but for the street I think the Euro cam timings are good. I would agree with Mark that stock durations or maybe a bit ( 5-10 degrees) longer are best for the street which will lift the hp peak into the 7K range without much low end loss, assuming stock pistons. That said, in a 2v, I think you can be more aggressive than the Speis profile which is primarily aimed at QVs which do not need as large a change.

Now, if you go for higher compression, that will keep a good or improved low end allowing you to run more duration for top end flow and power.

I would ask Web to give me the max lift and add 10 degrees of duration over stock - 18 degrees more if you are increasing compression.

Just initial ramblings. Your motor is going to be very cool whatever you do.

 

You need to know the head specs before you can pick a cam. And the head guy needs to know how the car will be used before doing any port work. He would probably then have a recomendation of what cam he'd like you to have.

 

mk e is right on.

Additionally, Before you have the head work done & select a cam grind, you also need to tell the head guy what compression ratio pistons you will be using.

The cylinder's wear needs to be measured to verify that it's still within specs to determine if it needs to be re-bored oversize.

From appearances, there's a good chance that the compression problems were just stuck rings, and your cylinders would just need honing & not boring, but only measurement can tell.

Appearances can be deceiving tho, one area for concern is that dark ring at the top of each cylinder. It's an area that essentially has no wear. There will be a ridge between it & the worn area, the ridge must be measured, & most likely will have to be removed by light boring, otherwise it'll break the new top ring.

If the cylinder is within spec, then most likely your current pistons could be cleaned up, measured to verify that they are within spec, & new rings installed. ie: you wouldn't have to buy new pistons unless you want to spend $$ to increase compression.

If the cylinders must be bored oversize, then new pistons would be required & you might as well go for increased compression.

In either case, you need to decide on the piston compression ratio before work starts on the heads.

Your head guy will determine if you need new valve guides & seats. Of course increasing the valve size will require new seats.

BTW, my recommendation would be to use Vic (the guy that's doing mk e's & snj5's heads). From what I've seen he's got an excellent handle on what it takes to get F* heads to flow properly, & the flow bench to test it. He's been working with Webcam on their cam work as well. Also, mk e & snj5 know him & how he thinks & works, so would be able to better advise you & interpret his flow results, etc.

Another area that you need to have measured is the crankshaft's main, rod bearing surfaces, also main & connecting rod clearances to determine if the crankshaft needs to be reground, and/or if you need new bearings.

Oh, yes, the crankshaft thrust bearing clearance needs to be checked to determine if new thrust bearings are required. Whoever's doing your block work should do this as a matter of course, but make sure it's included in the initial quote.

Bottom line: Your block should be in the hands of whoever's going to be rebuilding it at the same time your heads are being worked on, & the block guy & head guy should be working together.

Whatever you do, be sure to keep very good records, copies of all receipts, etc. in case you, or a future owner has to have the engine worked on. They'll need to know exactly how it's different from a stock engine.

I'm sure there are other things you need to consider, so if you haven't already, now is the time to do your homework before you go further:
- Get a book on rebuilding overhead cam engines, it will give you a much better idea as to what else must be looked at.
- Read the engine rebuild sections of the F* workshop manuals, including the GT4 WSM.

If you try to go forward from here just based on just asking questions & Intuition, you're taking a big risk something critical will be overlooked or done in the wrong order & have to be redone because it changes something else. Questions only help if you know they need to be asked.