Hey everybody, I said I'd keep you guys updated so here goes: I've stripped the engine down to bare block and main bearings (Going to get it boiled and honed tomorrow) so now for a relatively tricky question. One of the pistons cracked upon getting it out of the cylinder and I ended up with a nick in the cylinder wall, and a broken skirt on a piston. So I'm planning on getting new pistons, new rods*, a new mild cam, and new lifters to rebuild the engine into a mild performance engine that's streetable but fun when i want to step on it. My question is, what kind if pistons should i go with to increase compression to a sustainable amount (Maybe 9.5:1 or something around there?) and then what size cam would compliment that well? I have a standard bore, and standard crank (pretty much all original) but the original engine from 1974 had dished pistons. So I'm curious if i could go with flat top pistons or even domed pistons and be okay? Any thoughts? (Keep in mind im a very young mechanic working on this project in my garage, I have some experience since i used to work with my dad in a restoration shop for a few years, but i would appreciate any and all advice) *For those of you curious as to why im replacing the rods, it's because the person i got it from apparently built the engine with junkyard parts because the numbers that are stamped into the rods are completely off from where theyre supposed to be in the block. I have 2 rods marked #1 and two rods marked #6 and the rest of the rods are all mixed up between the cylinders. The only one that was the correct cylinder hole was #5. (I restamped them all just incase i have to use them again) But what kind of rods are good replacements?
Mixed up rods and std bore ? That's strange. I would expect it to be bored oversize too. You can go with flat tops, but pay attention to the pin height (also called the compression height) You want pistons with a 1.619-1.620 pin height to get them as close as possible to the deck at TDC. What are you looking for in a cam ? Lopey ? Good fuel mileage for an everyday driver ? What do you have in the drivetrain now ? Gears, transmission) The rod numbers really don't matter as long as they're all the same forgings. And they're installed in the correct orientation in relation to the crank journals. You should have C8OE rods in a 70's 302
That's actually what surprised me. There are no markings on the piston tops at all, so i figured it mustve been bored, but i guess not. It hasnt been undersized either. But thanks ford the advice with the rods. I'll try and put them back to how they were originally (i restamped them so i know where they were). But I want a semi-mild cam. (I'm looking at a mild cam with a 294 intake lift and 471 exhaust lift thats duration is running at 270* by 290*) I believe that should give me a decent bumpy-ish idle with good torque and power at lower RPM's if im correct? It looks like i have the original drive train. I believe it to be 3.20:1 in the rear end. Or 3:1 in the rear. I'm not too worried about gas mileage necessarily but i'd hope to keep it somewhere above 8 or 9 ish. If i get flat top pistons with that pin height, would that give me a decent 9.5:1 compression? And work well with the size cam I'm looking into? So far the best I've found on summit for pistons and rings is a compressions distance of 1.608. Will that be okay?
With your block (inless you have the decks milled to get rid of the extra .020 material there) you really need the tallest piston. With a small displacement engine, every little bit counts in computing the comp ratio. .010 is about 2.5 ccs added or subtracted to the compressed volume. That's about a quarter point in the ratio. I know the cam you're talking about, but never ran one myself, I've heard good things and bad things about it. Just from overall impressions, it's not one I'd run. What heads are you planning on using ?
highly doubtful you'll be able to find 1.62 pin heights for a Ford 302 as most are standardized to around 1.6 these days. You might find some 1.605's at the most but the ones to stay away from would be the dished versions with 1.585 pin heights since they will hurt the compression too much. Maybe try to find some 1.605 height pistons.. and then mill the heads about .020 - .030 and also try to find some slightly thinner head gaskets(around .038 thick) to ballpark around 9.3 - 9.4 SCR depending on what head volume you're starting out with. If you want any more than that?.. you'll need to start out with smaller combustion chambers(or mill about .050 off the lo-po smoggers you likely already have) and deck the block. But then you'll be into using premium only. If you just want a warmed over daily driver.. 9.5 should be more then enough and careful tuning will still allow you to run regular though. For cam.. and keeping with the warmed over theme.. look for something in the 260 advertised range(around 215 degree at .050) and about .450 lift. With complemetary parts.. you'll have healthy 270 horse motor in that light little car. Then add 3.25-3.50 gears to wake it up off the line even more.. and go have some fun. Mileage should be well into the teens when you keep your foot out of it.
It took me all of ten minutes searching Summit's website to come up with umpteen dozen 302 flat tops with a 1.605 pin height (matter of fact, that's the most popular P/H for 302 pistons) and a couple with 1.615 P/H and three part numbers for 1.619 P/H's: Speed Pro #ZL2488, ZLW2488 and Probe P/n P2488. All you have to do is look.
Wow.. you're really good at searching! Way to go out of your way to help the OP out here. I just quickly assumed he wanted some cheaper stockers or hypereutectics with tighter clearances and didn't think to search for those old outdated TRW's for him. Would be a good choice for adding more power down the road though. Jst be sure to warm it up a little longer, is all. PS. I just checked those Probe units out a bit closer and I'd surely pay the little extra to get those over the TRW's any day. Lighter, tighter, and better features by far. I was also surprised how expensive the shorter height KB Hyper's were too. Barely worth the savings nowadays. Although.. I do still think they are better for mild street motors due to less rock/blowby from tighter clearancing and less need to warm them up before getting on it.
I had actually been searching on summit for quite a long time and it seems I'll need to get it bored to find those pistons because the best I've found for a stock bore are 1.608. Will that be okay? I'll keep looking. Update: Ive found some with 1.619 pin height. Theyre Probe Brand. Any thoughts on these? What kind of rings go with them? But im planning on running either the stock heads (With the smog ports plugged ofcourse) or getting rebuilt cast iron heads. Aluminum is too expensive for me haha. But I'll look for a little more bumpy cam to go inside of it, and see if i can have the machine shop shave down the heads maybe .10 or .20. I dont mind running premium fuel but ive been told that 10:1 or higher is too much for stock cast iron heads. Is that true? If that's not the case then I'd gladly try and get the most i can for the buck. And as for the keeping my foot out of it.... I don't think that will happen too often. But I am hoping with the rebuild, gas mileage will be above what it used to get. (9 on the freeway if i was lucky) So then from what ive read so far, it seems the best ratio i could go with would be to shave down the heads .10-.20 then get a smaller compressed gasket (.38) and then get flat top pistons that have a pin height of 1.619 and a bumpier cam than one im looking at? Then try moving from 3:1 to 3.25-3.50 ratio in the back. With that piston set up, what would approximately be the compression ratio? About 9.5 or 10ish?
It all depends on the heads and their combustion chamber sizes. With a zero deck flat top piston and 53 cc heads, the ratio ends up at about 10.5 to 1 (the 68 302 4 bbl motor's ratio) 58 cc heads and it drops to about 10. 64 cc heads drops it to around 9.5 (just going off the top of my head here) My 331 has a 10.4 to 1 ratio and it'll accept nothing less than 92 octane before you hear the ping. But that's with the cam I'm running too. Everything comes into play as far as octane requirements (cam grind, compression, chamber shape, timing,etc) I've run a 10 to 1 390 with 89 octane, the roller 5.0 in my Ranger was fine on 87 in the winter, 89 in summer with around 9 to 1 and the stock Explorer cam. Just me, but I wouldn't worry about the gasket thickness, The best head gasket I've used yet is the O.E type expanded graphite that's about .043 thick. coat it with copper coat spray and never have to worry about blown gaskets from overheating. Shoot for as close to a zero deck as you can, then decide on what size chamber you need to get the comp ratio where you want it.
Okay, well took my engine to the shop today. Going to have it bored .030 over and undersized about .010. (Nick in the cylinder wall and very old crank) So ive found out the heads are from 1972 and have a combustion chamber size of 58.2cc's. Should I still have it shaved about .010? I was going to run .030 Probe pistons with a pin height of 1.619 with a Stage 2 cam shaft (278/290) for a lopey idle and more torque. Does this sound drive able so far?
Assuming your blocks decks are 8.226, and you're using 1.619 pistons, that puts them down in the hole about .017". With 58cc heads that gives you a 9.44 ratio. I would have them true up the decks by milling them, that will bump the comp ratio up some more, but still not be over 10 to 1. It's your money, your engine your call. The 9.5 to 10 to 1 ratio will compliment the cam if it's what I think it is. You really should have screw in studs put in those heads if you're serious about using them. Better heads would be a plus if you can afford it.
Okay, how much should I have them mill the heads? About .010? Or more? And I am planning on plugging the smog holes until I am able to buy new heads. The heads actually have casting numbers that start with D2. Is a 1972 head common for 1974?
I would mill the block, not the heads. Unless the heads need to be milled. Yes, it is common for Ford to use parts for several years, so D2 heads on a 74 would be normal. Ford used the E7TE heads for 11 years. The C8 302 rods were used for at least 22 years. If you're going to use those heads, then at least take a carbide porting bit anjd remove the Thermactor bumps from the inside of the exhaust ports. This takes about thirty minutes total to do all eight.
Okay. I'll ask them to mill the block. About .010 then should be good if the deck height is as you say it is? And okay. I'll drill those out of the heads and plug them with plugs and Teflon. I'm planning on putting shorty headers on so hopefully there won't be any exhaust leak.
