Re: Removal and rebuilding of a Twincam
Posted: Sun Jul 05, 2020 12:58 pm
Now finally into the assembly, which is the bit I like as its clean and interesting work compared to pulling an old engine apart
Lapped in the valves. The replacement QED race valve I got for the damaged No. 4 inlet was the same profile but unfortunately they have shortened the stem so too short for the head and springs I am using , also shorter than the common race valve length of 101 mm, why did they change it ?? I hunted through my spares and found a suitable used inlet, crack tested and checked it for stem wear and all was good so will reuse it. Inlet seats 1.0 mm wide and on the very edge of the 1.625 inch valve and the seats bored and porting to match. Exhaust seats 1.5 mm wide on the edge of the 1.4 inch valves and seats bored and porting to match.
New Tony Ingram light blue stripe race springs and other components ready for final clean and assembly. Decided not to reuse the existing or new QED red race springs as the Tony Ingram ones are nearly identical in install height and spring rates and are made of what appears to be a better steel grade so thought I would give them a try. They are also a bit cheaper with current exchange rates.
Valves and spring packs all fitted. I do hate fitting the split collets, sometimes it takes 30 seconds and other times it can take 10 minutes. Good thing there are only 8 valves!!. I get quicker as I go along as the adjustment of how much spring compression is needs is key, to much and the collet falls out , to little and you cant get it in, just right and it slips in, rotates to the bottom and stays while you fit the second one and release the compressor. New retainer to replace the damaged one from No.4 inlet Tony Ingram has changed the design of his titanium retainers slightly but he sent me one to his older design to match the other 7, nice service.
You will note the cleaned exhaust valves are still black on the face from the carbon adsorbed into the surface of the stainless steel. The inlet valves run cooler and dont stain the same.
The studs all go back into the head now. The brackets on the middle two inlets are for the dual throttle springs required by the race regulations here, they mount on extended carb studs.
Pulling the plugs out of the end of the cams and cleaning the oil passage in the cams, lots of metal in there from the bearing failure and filter by passing.
Cams mounted for trial shim fit , I use old bearings at this stage and non nyloc nuts as it may be coming on and off a couple of times, though if I got my measurements right, hopefully the first shims fit is spot on... HA Ha HA I wish !
Ran out of time so have to wait until next weekend to bolt it down and check the clearances.
cheers
Rohan
Lapped in the valves. The replacement QED race valve I got for the damaged No. 4 inlet was the same profile but unfortunately they have shortened the stem so too short for the head and springs I am using , also shorter than the common race valve length of 101 mm, why did they change it ?? I hunted through my spares and found a suitable used inlet, crack tested and checked it for stem wear and all was good so will reuse it. Inlet seats 1.0 mm wide and on the very edge of the 1.625 inch valve and the seats bored and porting to match. Exhaust seats 1.5 mm wide on the edge of the 1.4 inch valves and seats bored and porting to match.
New Tony Ingram light blue stripe race springs and other components ready for final clean and assembly. Decided not to reuse the existing or new QED red race springs as the Tony Ingram ones are nearly identical in install height and spring rates and are made of what appears to be a better steel grade so thought I would give them a try. They are also a bit cheaper with current exchange rates.
Valves and spring packs all fitted. I do hate fitting the split collets, sometimes it takes 30 seconds and other times it can take 10 minutes. Good thing there are only 8 valves!!. I get quicker as I go along as the adjustment of how much spring compression is needs is key, to much and the collet falls out , to little and you cant get it in, just right and it slips in, rotates to the bottom and stays while you fit the second one and release the compressor. New retainer to replace the damaged one from No.4 inlet Tony Ingram has changed the design of his titanium retainers slightly but he sent me one to his older design to match the other 7, nice service.
You will note the cleaned exhaust valves are still black on the face from the carbon adsorbed into the surface of the stainless steel. The inlet valves run cooler and dont stain the same.
The studs all go back into the head now. The brackets on the middle two inlets are for the dual throttle springs required by the race regulations here, they mount on extended carb studs.
Pulling the plugs out of the end of the cams and cleaning the oil passage in the cams, lots of metal in there from the bearing failure and filter by passing.
Cams mounted for trial shim fit , I use old bearings at this stage and non nyloc nuts as it may be coming on and off a couple of times, though if I got my measurements right, hopefully the first shims fit is spot on... HA Ha HA I wish !
Ran out of time so have to wait until next weekend to bolt it down and check the clearances.
cheers
Rohan