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Tips

Rebuliding 1974 2.5L, N. American version.

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Went through the same exercise a couple of years ago when I had the head off my '73. I was reasonably certain my head had been milled sometime in the past. I had no idea how much. I calculated compression using an old time hot-rodders trick by measuring the volume of the head:

Leave the valves in, place the head upside down on a bench. Using a good liquid measuring device (graduated cylinder, etc - I ended up using a large syringe) fill the cavity in the head for a single cyl. Use the head volume measured with the cylinder volume (bore*stroke) to get the compression ratio. Don't forget to add the head gasket thickness.

Stock '73 compression was 7.75:1, mine calculated at 9.5:1. Because I had a bit more taken off when I had the head faced, I'm now at around 9.6:1.

Best of luck.
 
Oh heck. I'l have to check the casting number when the shop opens back up. Thats a good start, though. Thnx
 
Hello, $700 may sound steep however, I have been racing Spitfires & GT6s for 12+ years and I believe that person was refering to roller rockers. As far as rocker ratio and cams I would suggest only buying a new cam not a regrind. I have had several regrinds in my 6cyl go bad (welded lobes comeing apart and when you buy a regrind there is no garentee on what your buying). My 6 cyl is a full race motor 12:1, high lift cam, HD valve springs, complete balanced, lots of head porting, etc. The roller rockers I have seen are 1.55:1 & 1.65:1 ratios. The 1.65 is not recommended unless your going with a stock cam (it can be very harsh on the rest of the valve train). If you use the stock rockers do not have the valve stems ground. The Hardening process is only surface deep. This I learnd the hard way. I use 1.55:1 roller rockers with a bushed shaft from Quantum Mechanics in Monroe, CT and a high lift new cam (don't remember spec haven't had to change it in 4 years)from Cambridge Motorsports in England. The BL competion manual is very useful for engine modification. I bought a complete set on ebay & see them there quite often. Good luck.
 
Alright, I should be able to crank the little turd up tomorrow=). The coolant passages in the block, head(before hot-tanking), and waterpump all looked like crap. What kind of flush can I use that isn't going to eat the radiator as it cleans? I hope the rust isn't holding this thing together. Any other first start tips would be helpful.
 
When I removed my cylinder head to repair damage caused by a valve dropping into cylinder #3 (caused by broken valve spring) I noticed two of my exhaust valves were cracked from excessive heat, so I decided to order the stelite stainless steel exhaust valves from the moss catalog, the exhaust are the only ones offered by them, because they take more abuse than the intake valves. I have a 9.5/1 compression. Cam is stock with .250 lift (tr250) everything else is stock except headers, K&N filters, and alloy valve cover. Your stock conecting rods should do fine for your street motor, just make sure you mark on each rod cap with an arrow showing direction of front of engine and number of cylinder the rod came out of also with a punch mark the cap on the side with another mark on the conecting rod so that the cap and rod go back together the exact way they came off. Your machine shop will install the new pistons on the rods. The rings are easy to put on the pistons, Ask the guys at the machine shop, you may need to check ring gaps by placing each ring about 2 1/2 inches down into cylinder and using a feeler gauge check the gap between the ends making sure each is in spec. With the oil ring going on the bottom grooves, and compression rings going on the top two grooves. Shift your ring gaps to different locations on your piston before installing piston into cylinder. Use plenty of oil on cylinder walls. Put small lengths of fuel line hose over studs on connecting rods so that crank shaft journal is protected. Wipe off connecting rod bearing surface with lacquer thinner removing any oil, this keeps you from spinning your bearing, Then install your new bearing and put engine assembly grease on bearing surface. Make sure your piston ring compressor is tight covering all the rings slip leading edge of piston into cylinder making sure correct side of rod faces front of engine. This all only covers installing each piston and rod assembly and of course the crank shaft should already be in place with the new main bearings installed first into the block adding engine assembly grease on each bearing surface and gently lowering crankshaft into block. Each main bearing cap should have been marked the same way as the rods and caps according to its location and direction of front of engine, and when reinstalling with new bearing and assembly grease snug each bearing cap bolt and when applying the specified torque to each cap bolt finishing one cap at a time spin your crankshaft to make sure there is no binding by the particular cap your tightening. Just a brief explanation of crank shaft and piston and rod assembly, it really is easy once you've done it a few times. Just remember keep the entire assembly area very clean and allway keep a clean plastic sheet covering engine to keep dirt out when not working on it. Dirt is your engines enemy.
 
Started it up to day and it ran like a top. The carbs need a little tuning, but the engine ran MUCH smoother and sounded great. Rabid Dolphin>TR6 =)
 
Ok, I'm late if you did the initial start-up. My suggestions would be to definetly manually prime the oil pump & engine to insure good lubrication on a dry motor. Cam break-in should be done at varying rpm's between 2,000-2,500 rpm's for 20 minutes. Drive the car for a short time & dump the oil & filter. I always recomend a magnetic drain plug.
Nows the time to document & record engine baselines like compression, valve adjustments spec's. Compression should improve as the rings seat, so this number will change, it's nice to compare stat's. You'll need to re-adjust the valves & re-torque the head bolts after 5 hours of run time. No low rpm lumbering under load for a while.
For me, nothing compares to the start-up of a fresh engine, it's like giving birth for a guy /ubbthreads/images/graemlins/smirk.gif
 
Well we didn't manually prie the pump, but we did turn the engine over for a good thirty seconds using the starter with no sparkplugs in. Oil pressure jumped right up to ~70psi upon ignition. This was just a bottom end rebuild so the cam should be fine. Getting the baselines is a good idea.
 
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