Chasz86 Posted June 12, 2020 Share Posted June 12, 2020 So while I have the head stripped for my Na-t build I have been thinking whether it necessary to replace valve springs, I'm only going for 400, but have built most of the rest of the engine to take 600bhp. Costs are spiralling and would rather save the £400 for any other out lays that may arise. I would like to replace seals, de-carb, re-lap and reinstall with original springs and retainers. Engine has unknown mileage looks to be around 100k+. Has been sitting in a shed for 2/3 years. What's people's thoughts? Quote Link to comment Share on other sites More sharing options...
Chasz86 Posted June 12, 2020 Author Share Posted June 12, 2020 Here are some pics Quote Link to comment Share on other sites More sharing options...
Dan8 Posted June 12, 2020 Share Posted June 12, 2020 (edited) Now buddy If your planning raising the rev limit and changing cams and chasing some power but to be honest think it’s over engineering it for that power and if you not getting any machining done /multi angle / valve seats and all that I wouldn’t bother mate as long as there all seated and lapped and shimmed to correct spec and valve lash ok I would imagine it would be fine mate Edited June 12, 2020 by Dan8 (see edit history) Quote Link to comment Share on other sites More sharing options...
Noz Posted June 12, 2020 Share Posted June 12, 2020 Cams aren't needed for 600hp and are overkill really. Mine revs to 7200. Stock springs. Need bottom end doing as well really if you want a safe block above 600. Thus. 600 is a good goal on a stock refreshed head. Mine hardly ran for 5 years. Banged out 1.5 bar 7200 rpm at 600 fine. If you want 700 at any point. Do cams and springs now. Quote Link to comment Share on other sites More sharing options...
Dan8 Posted June 12, 2020 Share Posted June 12, 2020 That’s reassuring to know Noz as I just refreshing the head and leaving it as is there some great figures you got What RPM and power do the rod bolts need changing at Quote Link to comment Share on other sites More sharing options...
Chasz86 Posted June 12, 2020 Author Share Posted June 12, 2020 Cheers i was hoping to keep stock, spent so much already the budget build is running away with me. Watch updates on the build thread! Quote Link to comment Share on other sites More sharing options...
Luxluc Posted June 12, 2020 Share Posted June 12, 2020 With 400bhp, I would keep them Quote Link to comment Share on other sites More sharing options...
Chasz86 Posted June 12, 2020 Author Share Posted June 12, 2020 Sweet. keep it is. Money that can be well spent somewhere else. Quote Link to comment Share on other sites More sharing options...
Noz Posted June 13, 2020 Share Posted June 13, 2020 (edited) That’s reassuring to know Noz as I just refreshing the head and leaving it as is there some great figures you got What RPM and power do the rod bolts need changing at A decent bottom end 'should' be fine upto 800hp without racing. But then even at 6-700 that's quite the margin and things can be unexpected with their failure. Online reading tells us 600 is common ground for abused and driven daily setups. Above that stuff does seem to go wrong. I think 7-800 is crazy without a build. But. It has been done quite a bit in the US. I wouldn't call it reliable though. And no one ever races with that hp. I mean I'm taking 650whp+ However. I've slightly lower compression on two cylinders since being at 600 on a stock bottom end. Noticed when looking for some smoke and found a turbo oil leak. So though it could not drop any further. Sometimes stuff just wears out. I'm personally considering a rebuild just to be safe. I may have never noticed it unless looking. Some people have hit 400 and spun a bearing. I'd use the hp as a target. Rather than rpm. I try not to think about rpm too much. As it should really be power dependant which in line will predict your cam usage. Remember mate. Rpm limit going up means your power band is higher due to cams and that means losing lower down rpm usage! There should be no other reason to raise the rev limit in my opinion. Other than to chase the power band (or in a drag situation where shifting isn't worth it and you want a little more in the lower gears, seen that before too). Edited June 13, 2020 by Noz (see edit history) Quote Link to comment Share on other sites More sharing options...
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