Bainzy Posted March 1, 2013 Share Posted March 1, 2013 Would it still be worthwhile installing a TR5 profile cam in a Spitfire 1500, without upping the compression? It'd be going in a standard engine but with a tubular exhaust manifold and wasted spark ignition + efi.Only reason I ask is that the cylinder head being prepared for it won't be ready for ages, and it seems a shame to have it sat here unused. Quote Link to comment Share on other sites More sharing options...
CHRIS211083 Posted March 1, 2013 Share Posted March 1, 2013 I wouldnt. I think you will get idle problems and a loss of torque.Just my own opinion. Fit the head and cam at the same time.Chris. Quote Link to comment Share on other sites More sharing options...
That Man Posted March 1, 2013 Share Posted March 1, 2013 You'll need to remove the head to change the cam anyways, so i'd wait untill you have your other haed done Quote Link to comment Share on other sites More sharing options...
TimW Posted March 1, 2013 Share Posted March 1, 2013 2402 wrote:I wouldnt. I think you will get idle problems and a loss of torque.Just my own opinion. Fit the head and cam at the same time.Chris.not with EFI you wont. I have a TR5 profile in my GT6 with a standard head and have loads of torque. Quote Link to comment Share on other sites More sharing options...
Bainzy Posted March 1, 2013 Author Share Posted March 1, 2013 Whats your GT6's static compression with that head Tim? 9:1? Quote Link to comment Share on other sites More sharing options...
TimW Posted March 1, 2013 Share Posted March 1, 2013 1381 wrote:Whats your GT6's static compression with that head Tim? 9:1? Fook knows!!Standard head and decked (previously recessed) block with flat-top pistons180psi on a compression tester not that that means anything!! Quote Link to comment Share on other sites More sharing options...
CHRIS211083 Posted March 1, 2013 Share Posted March 1, 2013 Tim his car isnt running efi yet!!!! (come on Brainzy) However that would clear it up im sure but for the price of a skim? £36-45pound im sure it would be better at 10-1 comp. As staited the head must come off anyway???Chris. Quote Link to comment Share on other sites More sharing options...
Nick Jones Posted March 1, 2013 Share Posted March 1, 2013 339 wrote:Fook knows!!Standard head and decked (previously recessed) block with flat-top pistons180psi on a compression tester not that that means anything!!Decking enough to remove the recesses will raise the CR alot. More than the equivalent thickness from the head as you get the full cylinder area.Assuming 0.025" recesses (some are more like 0.030) I reckon you'll pick up roughly .75 of a ratio to go up from 9.5:1 to 10.25:1Nick Quote Link to comment Share on other sites More sharing options...
Bainzy Posted March 1, 2013 Author Share Posted March 1, 2013 Haha true Chris but it's not running carbs either! Has all the EFI parts ready to start up when I fix a leaking o-ring and do up all the coolant hoses with clips when they arrive. That's literally all I have between now and it's first startup.Yeah I'm thinking your CR might be quite high Tim. You've had it decked, but also isn't the 2.5 litre engine higher compression than 9:1 anyway at 9.5:1? I guess I could skim the head but it'd be a bit pointless spending £40 on it when the new one is getting prepared. Might just leave the cam off until I have it done, as that'll give me an incentive to crack on with porting the short side radius. If I had a depth gauge that I trusted for taking off the 2mm from the ports I'd probably start it next week, I just didn't really feel confident with the DIY one I'd made. Quote Link to comment Share on other sites More sharing options...
bob dunn Posted March 4, 2013 Share Posted March 4, 2013 Just do it !! Quote Link to comment Share on other sites More sharing options...
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